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201. APOGEE Chemical Abundances of the Sagittarius Dwarf Galaxy

Author: Hasselquist, Sten, Shetrone, Matthew, Smith, Verne, Holtzman, Jon, McWilliam, Andrew, Fernández-Trincado, J. G., Beers, Timothy C., Majewski, Steven R., Nidever, David L., Tang, Baitian, Tissera, Patricia B., Alvar, Emma Fernández, Prieto, Carlos Allende, Almeida, Andres, Anguiano, Borja, Battaglia, Giuseppina, Carigi, Leticia, Inglada, Gloria Delgado, Frinchaboy, Peter, García-Hernández, D. A., Geisler, Doug, Minniti, Dante, Placco, Vinicius M., Schultheis, Mathias, Sobeck, Jennifer, Villanova, Sandro, Hasselquist, Sten, Shetrone, Matthew, Smith, Verne, Holtzman, Jon, McWilliam, Andrew, Fernández-Trincado, J. G., Beers, Timothy C., Majewski, Steven R., Nidever, David L., Tang, Baitian, Tissera, Patricia B., Alvar, Emma Fernández, Prieto, Carlos Allende, Almeida, Andres, Anguiano, Borja, Battaglia, Giuseppina, Carigi, Leticia, Inglada, Gloria Delgado, Frinchaboy, Peter, García-Hernández, D. A., Geisler, Doug, Minniti, Dante, Placco, Vinicius M., Schultheis, Mathias, Sobeck, Jennifer, and Villanova, Sandro
Abstract: The Apache Point Observatory Galactic Evolution Experiment (APOGEE) provides the opportunity to measure elemental abundances for C, N, O, Na, Mg, Al, Si, P, K, Ca, V, Cr, Mn, Fe, Co, and Ni in vast numbers of stars. We analyze the chemical abundance patterns of these elements for 158 red giant stars belonging to the Sagittarius dwarf galaxy (Sgr). This is the largest sample of Sgr stars with detailed chemical abundances and the first time C, N, P, K, V, Cr, Co, and Ni have been studied at high-resolution in this galaxy. We find that the Sgr stars with [Fe/H] $\gtrsim$ -0.8 are deficient in all elemental abundance ratios (expressed as [X/Fe]) relative to the Milky Way, suggesting that Sgr stars observed today were formed from gas that was less enriched by Type II SNe than stars formed in the Milky Way. By examining the relative deficiencies of the hydrostatic (O, Na, Mg, and Al) and explosive (Si, P, K, and Mn) elements, our analysis supports the argument that previous generations of Sgr stars were formed with a top-light IMF, one lacking the most massive stars that would normally pollute the ISM with the hydrostatic elements. We use a simple chemical evolution model, flexCE to further backup our claim and conclude that recent stellar generations of Fornax and the LMC could also have formed according to a top-light IMF., Comment: 14 pages, 12 figures, accepted for publication in ApJ
Published: 2017
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202. The age-metallicity structure of the Milky Way disk

Author: Mackereth, J. Ted, Bovy, Jo, Schiavon, Ricardo P., Zasowski, Gail, Cunha, Katia, Frinchaboy, Peter M., Perez, Ana E. Garcia, Hayden, Michael R., Holtzman, Jon, Majewski, Steven R., Meszaros, Szabolcs, Nidever, David L., Pinsonneault, Marc, Shetrone, Matthew D., Mackereth, J. Ted, Bovy, Jo, Schiavon, Ricardo P., Zasowski, Gail, Cunha, Katia, Frinchaboy, Peter M., Perez, Ana E. Garcia, Hayden, Michael R., Holtzman, Jon, Majewski, Steven R., Meszaros, Szabolcs, Nidever, David L., Pinsonneault, Marc, and Shetrone, Matthew D.
Abstract: The measurement of the structure of stellar populations in the Milky Way disk places fundamental constraints on models of galaxy formation and evolution. Previously, the disk's structure has been studied in terms of populations defined geometrically and/or chemically, but a decomposition based on stellar ages provides a more direct connection to the history of the disk, and stronger constraint on theory. Here, we use positions, abundances and ages for 31,244 red giant branch stars from the SDSS-APOGEE survey, spanning $3 < R_{\mathrm{gc}} < 15$ kpc, to dissect the disk into mono-age and mono-[Fe/H] populations at low and high [$\alpha$/Fe]. For each population, with $\Delta \mathrm{age} < 2$ Gyr and $\Delta \mathrm{[Fe/H]} < 0.1$ dex, we measure the structure and surface-mass density contribution. We find that low [$\alpha$/Fe] mono-age populations are fit well by a broken exponential, which increases to a peak radius and decreases thereafter. We show that this profile becomes broader with age, interpreted here as a new signal of disk heating and radial migration. High [$\alpha$/Fe] populations are well fit as single exponentials within the radial range considered, with an average scale length of $1.9\pm 0.1$ kpc. We find that the relative contribution of high to low [$\alpha$/Fe] populations at $R_0$ is $f_\Sigma = 18\% \pm 5\%$; high [$\alpha$/Fe] contributes most of the mass at old ages, and low [$\alpha$/Fe] at young ages. The low and high [$\alpha$/Fe] populations overlap in age at intermediate [Fe/H], although both contribute mass at $R_{0}$ across the full range of [Fe/H]. The mass weighted scale height $h_Z$ distribution is a smoothly declining exponential function. High [$\alpha$/Fe] populations are thicker than low [$\alpha$/Fe], and the average $h_Z$ increases steadily with age, between 200 and 600 pc., Comment: Submitted to MNRAS. Revised version following comments from the referee. 24 Pages, 18 Figures
Published: 2017
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203. Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe

Author: Blanton, Michael R., Bershady, Matthew A., Abolfathi, Bela, Albareti, Franco D., Prieto, Carlos Allende, Almeida, Andres, Alonso-García, Javier, Anders, Friedrich, Anderson, Scott F., Andrews, Brett, Aquino-Ortíz, Erik, Aragón-Salamanca, Alfonso, Argudo-Fernández, Maria, Armengaud, Eric, Aubourg, Eric, Avila-Reese, Vladimir, Badenes, Carles, Bailey, Stephen, Barger, Kathleen A., Barrera-Ballesteros, Jorge, Bartosz, Curtis, Bates, Dominic, Baumgarten, Falk, Bautista, Julian, Beaton, Rachael, Beers, Timothy C., Belfiore, Francesco, Bender, Chad F., Berlind, Andreas A., Bernardi, Mariangela, Beutler, Florian, Bird, Jonathan C., Bizyaev, Dmitry, Blanc, Guillermo A., Blomqvist, Michael, Bolton, Adam S., Boquien, Médéric, Borissova, Jura, Bosch, Remco van den, Bovy, Jo, Brandt, William N., Brinkmann, Jonathan, Brownstein, Joel R., Bundy, Kevin, Burgasser, Adam J., Burtin, Etienne, Busca, Nicolás G., Cappellari, Michele, Carigi, Maria Leticia Delgado, Carlberg, Joleen K., Rosell, Aurelio Carnero, Carrera, Ricardo, Cherinka, Brian, Cheung, Edmond, Chew, Yilen Gómez Maqueo, Chiappini, Cristina, Choi, Peter Doohyun, Chojnowski, Drew, Chuang, Chia-Hsun, Chung, Haeun, Cirolini, Rafael Fernando, Clerc, Nicolas, Cohen, Roger E., Comparat, Johan, da Costa, Luiz, Cousinou, Marie-Claude, Covey, Kevin, Crane, Jeffrey D., Croft, Rupert A. C., Cruz-Gonzalez, Irene, Cuadra, Daniel Garrido, Cunha, Katia, Damke, Guillermo J., Darling, Jeremy, Davies, Roger, Dawson, Kyle, de la Macorra, Axel, De Lee, Nathan, Delubac, Timothée, Di Mille, Francesco, Diamond-Stanic, Aleks, Cano-Díaz, Mariana, Donor, John, Downes, Juan José, Drory, Niv, Bourboux, Hélion du Mas des, Duckworth, Christopher J., Dwelly, Tom, Dyer, Jamie, Ebelke, Garrett, Eisenstein, Daniel J., Emsellem, Eric, Eracleous, Mike, Escoffier, Stephanie, Evans, Michael L., Fan, Xiaohui, Fernández-Alvar, Emma, Fernandez-Trincado, J. G., Feuillet, Diane K., Finoguenov, Alexis, Fleming, Scott W., Font-Ribera, Andreu, Fredrickson, Alexander, Freischlad, Gordon, Frinchaboy, Peter M., Galbany, Lluís, Garcia-Dias, R., García-Hernández, D. A., Gaulme, Patrick, Geisler, Doug, Gelfand, Joseph D., Gil-Marín, Héctor, Gillespie, Bruce A., Goddard, Daniel, Gonzalez-Perez, Violeta, Grabowski, Kathleen, Green, Paul J., Grier, Catherine J., Gunn, James E., Guo, Hong, Guy, Julien, Hagen, Alex, Hahn, ChangHoon, Hall, Matthew, Harding, Paul, Hasselquist, Sten, Hawley, Suzanne L., Hearty, Fred, Hernández, Jonay I. Gonzalez, Ho, Shirley, Hogg, David W., Holley-Bockelmann, Kelly, Holtzman, Jon A., Holzer, Parker H., Huehnerhoff, Joseph, Hutchinson, Timothy A., Hwang, Ho Seong, Ibarra-Medel, Héctor J., Ilha, Gabriele da Silva, Ivans, Inese I., Ivory, KeShawn, Jackson, Kelly, Jensen, Trey W., Johnson, Jennifer A., Jones, Amy, Jönsson, Henrik, Jullo, Eric, Kamble, Vikrant, Kinemuchi, Karen, Kirkby, David, Kitaura, Francisco-Shu, Klaene, Mark, Knapp, Gillian R., Kneib, Jean-Paul, Kollmeier, Juna A., Lacerna, Ivan, Lane, Richard R., Lang, Dustin, Law, David R., Lazarz, Daniel, Goff, Jean-Marc Le, Liang, Fu-Heng, Li, Cheng, LI, Hongyu, Lima, Marcos, Lin, Lihwai, Lin, Yen-Ting, de Lis, Sara Bertran, Liu, Chao, Lizaola, Miguel Angel C. de Icaza, Long, Dan, Lucatello, Sara, Lundgren, Britt, MacDonald, Nicholas K., Machado, Alice Deconto, MacLeod, Chelsea L., Mahadevan, Suvrath, Maia, Marcio Antonio Geimba, Maiolino, Roberto, Majewski, Steven R., Malanushenko, Elena, Malanushenko, Viktor, Manchado, Arturo, Mao, Shude, Maraston, Claudia, Marques-Chaves, Rui, Masters, Karen L., McBride, Cameron K., McDermid, Richard M., McGrath, Brianne, McGreer, Ian D., Peña, Nicolás Medina, Melendez, Matthew, Merloni, Andrea, Merrifield, Michael R., Meszaros, Szabolcs, Meza, Andres, Minchev, Ivan, Minniti, Dante, Miyaji, Takamitsu, More, Surhud, Mulchaey, John, Müller-Sánchez, Francisco, Muna, Demitri, Munoz, Ricardo R., Myers, Adam D., Nair, Preethi, Nandra, Kirpal, Nascimento, Janaina Correa do, Negrete, Alenka, Ness, Melissa, Newman, Jeffrey A., Nichol, Robert C., Nidever, David L., Nitschelm, Christian, Ntelis, Pierros, O'Connell, Julia E., Oelkers, Ryan J., Oravetz, Audrey, Oravetz, Daniel, Pace, Zach, Padilla, Nelson, Palanque-Delabrouille, Nathalie, Palicio, Pedro Alonso, Pan, Kaike, Parikh, Taniya, Pâris, Isabelle, Park, Changbom, Patten, Alim Y., Peirani, Sebastien, Pellejero-Ibanez, Marcos, Penny, Samantha, Percival, Will J., Perez-Fournon, Ismael, Petitjean, Patrick, Pieri, Matthew M., Pinsonneault, Marc, Pisani, Alice, Poleski, Radosław, Prada, Francisco, Prakash, Abhishek, Queiroz, Anna Bárbara de Andrade, Raddick, M. Jordan, Raichoor, Anand, Rembold, Sandro Barboza, Richstein, Hannah, Riffel, Rogemar A., Riffel, Rogério, Rix, Hans-Walter, Robin, Annie C., Rockosi, Constance M., Rodríguez-Torres, Sergio, Roman-Lopes, A., Román-Zúñiga, Carlos, Rosado, Margarita, Ross, Ashley J., Rossi, Graziano, Ruan, John, Ruggeri, Rossana, Rykoff, Eli S., Salazar-Albornoz, Salvador, Salvato, Mara, Sánchez, Ariel G., Aguado, David Sánchez, Sánchez-Gallego, José R., Santana, Felipe A., Santiago, Basílio Xavier, Sayres, Conor, Schiavon, Ricardo P., Schimoia, Jaderson da Silva, Schlafly, Edward F., Schlegel, David J., Schneider, Donald P., Schultheis, Mathias, Schuster, William J., Schwope, Axel, Seo, Hee-Jong, Shao, Zhengyi, Shen, Shiyin, Shetrone, Matthew, Shull, Michael, Simon, Joshua D., Skinner, Danielle, Skrutskie, M. F., Slosar, Anže, Smith, Verne V., Sobeck, Jennifer S., Sobreira, Flavia, Somers, Garrett, Souto, Diogo, Stark, David V., Stassun, Keivan, Stauffer, Fritz, Steinmetz, Matthias, Storchi-Bergmann, Thaisa, Streblyanska, Alina, Stringfellow, Guy S., Suárez, Genaro, Sun, Jing, Suzuki, Nao, Szigeti, Laszlo, Taghizadeh-Popp, Manuchehr, Tang, Baitian, Tao, Charling, Tayar, Jamie, Tembe, Mita, Teske, Johanna, Thakar, Aniruddha R., Thomas, Daniel, Thompson, Benjamin A., Tinker, Jeremy L., Tissera, Patricia, Tojeiro, Rita, Toledo, Hector Hernandez, de la Torre, Sylvain, Tremonti, Christy, Troup, Nicholas W., Valenzuela, Octavio, Valpuesta, Inma Martinez, Vargas-González, Jaime, Vargas-Magaña, Mariana, Vazquez, Jose Alberto, Villanova, Sandro, Vivek, M., Vogt, Nicole, Wake, David, Walterbos, Rene, Wang, Yuting, Weaver, Benjamin Alan, Weijmans, Anne-Marie, Weinberg, David H., Westfall, Kyle B., Whelan, David G., Wild, Vivienne, Wilson, John, Wood-Vasey, W. M., Wylezalek, Dominika, Xiao, Ting, Yan, Renbin, Yang, Meng, Ybarra, Jason E., Yèche, Christophe, Zakamska, Nadia, Zamora, Olga, Zarrouk, Pauline, Zasowski, Gail, Zhang, Kai, Zhao, Gong-Bo, Zheng, Zheng, Zhou, Zhi-Min, Zhu, Guangtun B., Zoccali, Manuela, Zou, Hu, Blanton, Michael R., Bershady, Matthew A., Abolfathi, Bela, Albareti, Franco D., Prieto, Carlos Allende, Almeida, Andres, Alonso-García, Javier, Anders, Friedrich, Anderson, Scott F., Andrews, Brett, Aquino-Ortíz, Erik, Aragón-Salamanca, Alfonso, Argudo-Fernández, Maria, Armengaud, Eric, Aubourg, Eric, Avila-Reese, Vladimir, Badenes, Carles, Bailey, Stephen, Barger, Kathleen A., Barrera-Ballesteros, Jorge, Bartosz, Curtis, Bates, Dominic, Baumgarten, Falk, Bautista, Julian, Beaton, Rachael, Beers, Timothy C., Belfiore, Francesco, Bender, Chad F., Berlind, Andreas A., Bernardi, Mariangela, Beutler, Florian, Bird, Jonathan C., Bizyaev, Dmitry, Blanc, Guillermo A., Blomqvist, Michael, Bolton, Adam S., Boquien, Médéric, Borissova, Jura, Bosch, Remco van den, Bovy, Jo, Brandt, William N., Brinkmann, Jonathan, Brownstein, Joel R., Bundy, Kevin, Burgasser, Adam J., Burtin, Etienne, Busca, Nicolás G., Cappellari, Michele, Carigi, Maria Leticia Delgado, Carlberg, Joleen K., Rosell, Aurelio Carnero, Carrera, Ricardo, Cherinka, Brian, Cheung, Edmond, Chew, Yilen Gómez Maqueo, Chiappini, Cristina, Choi, Peter Doohyun, Chojnowski, Drew, Chuang, Chia-Hsun, Chung, Haeun, Cirolini, Rafael Fernando, Clerc, Nicolas, Cohen, Roger E., Comparat, Johan, da Costa, Luiz, Cousinou, Marie-Claude, Covey, Kevin, Crane, Jeffrey D., Croft, Rupert A. C., Cruz-Gonzalez, Irene, Cuadra, Daniel Garrido, Cunha, Katia, Damke, Guillermo J., Darling, Jeremy, Davies, Roger, Dawson, Kyle, de la Macorra, Axel, De Lee, Nathan, Delubac, Timothée, Di Mille, Francesco, Diamond-Stanic, Aleks, Cano-Díaz, Mariana, Donor, John, Downes, Juan José, Drory, Niv, Bourboux, Hélion du Mas des, Duckworth, Christopher J., Dwelly, Tom, Dyer, Jamie, Ebelke, Garrett, Eisenstein, Daniel J., Emsellem, Eric, Eracleous, Mike, Escoffier, Stephanie, Evans, Michael L., Fan, Xiaohui, Fernández-Alvar, Emma, Fernandez-Trincado, J. G., Feuillet, Diane K., Finoguenov, Alexis, Fleming, Scott W., Font-Ribera, Andreu, Fredrickson, Alexander, Freischlad, Gordon, Frinchaboy, Peter M., Galbany, Lluís, Garcia-Dias, R., García-Hernández, D. A., Gaulme, Patrick, Geisler, Doug, Gelfand, Joseph D., Gil-Marín, Héctor, Gillespie, Bruce A., Goddard, Daniel, Gonzalez-Perez, Violeta, Grabowski, Kathleen, Green, Paul J., Grier, Catherine J., Gunn, James E., Guo, Hong, Guy, Julien, Hagen, Alex, Hahn, ChangHoon, Hall, Matthew, Harding, Paul, Hasselquist, Sten, Hawley, Suzanne L., Hearty, Fred, Hernández, Jonay I. Gonzalez, Ho, Shirley, Hogg, David W., Holley-Bockelmann, Kelly, Holtzman, Jon A., Holzer, Parker H., Huehnerhoff, Joseph, Hutchinson, Timothy A., Hwang, Ho Seong, Ibarra-Medel, Héctor J., Ilha, Gabriele da Silva, Ivans, Inese I., Ivory, KeShawn, Jackson, Kelly, Jensen, Trey W., Johnson, Jennifer A., Jones, Amy, Jönsson, Henrik, Jullo, Eric, Kamble, Vikrant, Kinemuchi, Karen, Kirkby, David, Kitaura, Francisco-Shu, Klaene, Mark, Knapp, Gillian R., Kneib, Jean-Paul, Kollmeier, Juna A., Lacerna, Ivan, Lane, Richard R., Lang, Dustin, Law, David R., Lazarz, Daniel, Goff, Jean-Marc Le, Liang, Fu-Heng, Li, Cheng, LI, Hongyu, Lima, Marcos, Lin, Lihwai, Lin, Yen-Ting, de Lis, Sara Bertran, Liu, Chao, Lizaola, Miguel Angel C. de Icaza, Long, Dan, Lucatello, Sara, Lundgren, Britt, MacDonald, Nicholas K., Machado, Alice Deconto, MacLeod, Chelsea L., Mahadevan, Suvrath, Maia, Marcio Antonio Geimba, Maiolino, Roberto, Majewski, Steven R., Malanushenko, Elena, Malanushenko, Viktor, Manchado, Arturo, Mao, Shude, Maraston, Claudia, Marques-Chaves, Rui, Masters, Karen L., McBride, Cameron K., McDermid, Richard M., McGrath, Brianne, McGreer, Ian D., Peña, Nicolás Medina, Melendez, Matthew, Merloni, Andrea, Merrifield, Michael R., Meszaros, Szabolcs, Meza, Andres, Minchev, Ivan, Minniti, Dante, Miyaji, Takamitsu, More, Surhud, Mulchaey, John, Müller-Sánchez, Francisco, Muna, Demitri, Munoz, Ricardo R., Myers, Adam D., Nair, Preethi, Nandra, Kirpal, Nascimento, Janaina Correa do, Negrete, Alenka, Ness, Melissa, Newman, Jeffrey A., Nichol, Robert C., Nidever, David L., Nitschelm, Christian, Ntelis, Pierros, O'Connell, Julia E., Oelkers, Ryan J., Oravetz, Audrey, Oravetz, Daniel, Pace, Zach, Padilla, Nelson, Palanque-Delabrouille, Nathalie, Palicio, Pedro Alonso, Pan, Kaike, Parikh, Taniya, Pâris, Isabelle, Park, Changbom, Patten, Alim Y., Peirani, Sebastien, Pellejero-Ibanez, Marcos, Penny, Samantha, Percival, Will J., Perez-Fournon, Ismael, Petitjean, Patrick, Pieri, Matthew M., Pinsonneault, Marc, Pisani, Alice, Poleski, Radosław, Prada, Francisco, Prakash, Abhishek, Queiroz, Anna Bárbara de Andrade, Raddick, M. Jordan, Raichoor, Anand, Rembold, Sandro Barboza, Richstein, Hannah, Riffel, Rogemar A., Riffel, Rogério, Rix, Hans-Walter, Robin, Annie C., Rockosi, Constance M., Rodríguez-Torres, Sergio, Roman-Lopes, A., Román-Zúñiga, Carlos, Rosado, Margarita, Ross, Ashley J., Rossi, Graziano, Ruan, John, Ruggeri, Rossana, Rykoff, Eli S., Salazar-Albornoz, Salvador, Salvato, Mara, Sánchez, Ariel G., Aguado, David Sánchez, Sánchez-Gallego, José R., Santana, Felipe A., Santiago, Basílio Xavier, Sayres, Conor, Schiavon, Ricardo P., Schimoia, Jaderson da Silva, Schlafly, Edward F., Schlegel, David J., Schneider, Donald P., Schultheis, Mathias, Schuster, William J., Schwope, Axel, Seo, Hee-Jong, Shao, Zhengyi, Shen, Shiyin, Shetrone, Matthew, Shull, Michael, Simon, Joshua D., Skinner, Danielle, Skrutskie, M. F., Slosar, Anže, Smith, Verne V., Sobeck, Jennifer S., Sobreira, Flavia, Somers, Garrett, Souto, Diogo, Stark, David V., Stassun, Keivan, Stauffer, Fritz, Steinmetz, Matthias, Storchi-Bergmann, Thaisa, Streblyanska, Alina, Stringfellow, Guy S., Suárez, Genaro, Sun, Jing, Suzuki, Nao, Szigeti, Laszlo, Taghizadeh-Popp, Manuchehr, Tang, Baitian, Tao, Charling, Tayar, Jamie, Tembe, Mita, Teske, Johanna, Thakar, Aniruddha R., Thomas, Daniel, Thompson, Benjamin A., Tinker, Jeremy L., Tissera, Patricia, Tojeiro, Rita, Toledo, Hector Hernandez, de la Torre, Sylvain, Tremonti, Christy, Troup, Nicholas W., Valenzuela, Octavio, Valpuesta, Inma Martinez, Vargas-González, Jaime, Vargas-Magaña, Mariana, Vazquez, Jose Alberto, Villanova, Sandro, Vivek, M., Vogt, Nicole, Wake, David, Walterbos, Rene, Wang, Yuting, Weaver, Benjamin Alan, Weijmans, Anne-Marie, Weinberg, David H., Westfall, Kyle B., Whelan, David G., Wild, Vivienne, Wilson, John, Wood-Vasey, W. M., Wylezalek, Dominika, Xiao, Ting, Yan, Renbin, Yang, Meng, Ybarra, Jason E., Yèche, Christophe, Zakamska, Nadia, Zamora, Olga, Zarrouk, Pauline, Zasowski, Gail, Zhang, Kai, Zhao, Gong-Bo, Zheng, Zheng, Zhou, Zhi-Min, Zhu, Guangtun B., Zoccali, Manuela, and Zou, Hu
Abstract: We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratio in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially-resolved spectroscopy for thousands of nearby galaxies (median redshift of z = 0.03). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between redshifts z = 0.6 and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGN and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5-meter Sloan Foundation Telescope at Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5-meter du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in July 2016., Comment: Published in Astronomical Journal
Published: 2017
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204. IN-SYNC. V. Stellar kinematics and dynamics in the Orion A Molecular Cloud

Author: Da Rio, Nicola, Tan, Jonathan C., Covey, Kevin R., Cottaar, Michiel, Foster, Jonathan B., Cullen, Nicholas C., Tobin, John J., Kim, Jinyoung S., Meyer, Michael R., Nidever, David L., Stassun, Keivan G., Chojnowski, S. Drew, Flaherty, Kevin M., Majewski, Steve, Skrutskie, Michael F., Zasowski, Gail, Pan, Kaike, Da Rio, Nicola, Tan, Jonathan C., Covey, Kevin R., Cottaar, Michiel, Foster, Jonathan B., Cullen, Nicholas C., Tobin, John J., Kim, Jinyoung S., Meyer, Michael R., Nidever, David L., Stassun, Keivan G., Chojnowski, S. Drew, Flaherty, Kevin M., Majewski, Steve, Skrutskie, Michael F., Zasowski, Gail, and Pan, Kaike
Abstract: The kinematics and dynamics of young stellar populations enable us to test theories of star formation. With this aim, we continue our analysis of the SDSS-III/APOGEE IN-SYNC survey, a high resolution near infrared spectroscopic survey of young clusters. We focus on the Orion A star-forming region, for which IN-SYNC obtained spectra of $\sim2700$ stars. In Paper IV we used these data to study the young stellar population. Here we study the kinematic properties through radial velocities ($v_r$). The young stellar population remains kinematically associated with the molecular gas, following a $\sim10\:{\rm{km\:s}}^{-1}$ gradient along filament. However, near the center of the region, the $v_r$ distribution is slightly blueshifted and asymmetric; we suggest that this population, which is older, is slightly in foreground. We find evidence for kinematic subclustering, detecting statistically significant groupings of co-located stars with coherent motions. These are mostly in the lower-density regions of the cloud, while the ONC radial velocities are smoothly distributed, consistent with it being an older, more dynamically evolved cluster. The velocity dispersion $\sigma_v$ varies along the filament. The ONC appears virialized, or just slightly supervirial, consistent with an old dynamical age. Here there is also some evidence for on-going expansion, from a $v_r$--extinction correlation. In the southern filament, $\sigma_v$ is $\sim2$--$3$ times larger than virial in the L1641N region, where we infer a superposition along the line of sight of stellar sub-populations, detached from the gas. On the contrary, $\sigma_v$ decreases towards L1641S, where the population is again in agreement with a virial state., Comment: 14 pages, 13 figures, ApJ accepted
Published: 2017
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205. SMASH - Survey of the MAgellanic Stellar History

Author: Nidever, David L., Olsen, Knut, Walker, Alistair R., Vivas, A. Katherina, Blum, Robert D., Kaleida, Catherine, Choi, Yumi, Conn, Blair C., Gruendl, Robert A., Bell, Eric F., Besla, Gurtina, Munoz, Ricardo R., Gallart, Carme, Martin, Nicolas F., Olszewski, Edward W., Saha, Abhijit, Monachesi, Antonela, Monelli, Matteo, de Boer, Thomas J. L., Johnson, L. Clifton, Zaritsky, Dennis, Stringfellow, Guy S., van der Marel, Roeland P., Cioni, Maria-Rosa L., Jin, Shoko, Majewski, Steven R., Martinez-Delgado, David, Monteagudo, Lara, Noel, Noelia E. D., Bernard, Edouardo J., Kunder, Andrea, Chu, You-Hua, Bell, Cameron P. M., Santana, Felipe, Frechem, Joshua, Medina, Gustavo E., Parkash, Vaishali, Seron, Jacqueline, Hayes, Christian, Nidever, David L., Olsen, Knut, Walker, Alistair R., Vivas, A. Katherina, Blum, Robert D., Kaleida, Catherine, Choi, Yumi, Conn, Blair C., Gruendl, Robert A., Bell, Eric F., Besla, Gurtina, Munoz, Ricardo R., Gallart, Carme, Martin, Nicolas F., Olszewski, Edward W., Saha, Abhijit, Monachesi, Antonela, Monelli, Matteo, de Boer, Thomas J. L., Johnson, L. Clifton, Zaritsky, Dennis, Stringfellow, Guy S., van der Marel, Roeland P., Cioni, Maria-Rosa L., Jin, Shoko, Majewski, Steven R., Martinez-Delgado, David, Monteagudo, Lara, Noel, Noelia E. D., Bernard, Edouardo J., Kunder, Andrea, Chu, You-Hua, Bell, Cameron P. M., Santana, Felipe, Frechem, Joshua, Medina, Gustavo E., Parkash, Vaishali, Seron, Jacqueline, and Hayes, Christian
Abstract: The Large and Small Magellanic Clouds (LMC and SMC) are unique local laboratories for studying the formation and evolution of small galaxies in exquisite detail. The Survey of the MAgellanic Stellar History (SMASH) is an NOAO community DECam survey of the Clouds mapping 480 square degrees (distributed over ~2400 square degrees at ~20% filling factor) to ~24th mag in ugriz with the goal of identifying broadly distributed, low surface brightness stellar populations associated with the stellar halos and tidal debris of the Clouds. SMASH will also derive spatially-resolved star formation histories covering all ages out to large radii from the MCs that will further complement our understanding of their formation. Here, we present a summary of the survey, its data reduction, and a description of the first public Data Release (DR1). The SMASH DECam data have been reduced with a combination of the NOAO Community Pipeline, PHOTRED, an automated PSF photometry pipeline based mainly on the DAOPHOT suite, and custom calibration software. The attained astrometric precision is ~15 mas and the accuracy is ~2 mas with respect to the Gaia DR1 astrometric reference frame. The photometric precision is ~0.5-0.7% in griz and ~1% in u with a calibration accuracy of ~1.3% in all bands. The median 5 sigma point source depths in ugriz bands are 23.9, 24.8, 24.5, 24.2, 23.5 mag. The SMASH data already have been used to discover the Hydra II Milky Way satellite, the SMASH 1 old globular cluster likely associated with the LMC, and very extended stellar populations around the LMC out to R~18.4 kpc. SMASH DR1 contains measurements of ~100 million objects distributed in 61 fields. A prototype version of the NOAO Data Lab provides data access, including a data discovery tool, SMASH database access, an image cutout service, and a Jupyter notebook server with example notebooks for exploratory analysis., Comment: 23 pages, 12 figures. Revised and slightly reorganized based on referee's comments. Accepted for publication in AJ
Published: 2017
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206. IN-SYNC III: The dynamical state of IC 348 - A super-virial velocity dispersion and a puzzling sign of convergence

Author: Cottaar, Michiel, Covey, Kevin R., Foster, Jonathan B., Meyer, Michael R., Tan, Jonathan C., Nidever, David L., Chojnowski, S. Drew, da Rio, Nicola, Flaherty, Kevin M., Frinchaboy, Peter M., Majewski, Steve, Skrutskie, Michael F., Wilson, John C., and Zasowski, Gail
Subjects: Astrophysics - Solar and Stellar Astrophysics, Astrophysics::Solar and Stellar Astrophysics, FOS: Physical sciences, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: Most field stars will have encountered the highest stellar density and hence the largest number of interactions in their birth environment. Yet the stellar dynamics during this crucial phase are poorly understood. Here we analyze the radial velocities measured for 152 out of 380 observed stars in the 2-6 Myr old star cluster IC 348 as part of the SDSS-III APOGEE. The radial velocity distribution of these stars is fitted with one or two Gaussians, convolved with the measurement uncertainties including binary orbital motions. Including a second Gaussian improves the fit; the high-velocity outliers that are best fit by this second component may either (1) be contaminants from the nearby Perseus OB2 association, (2) be a halo of ejected or dispersing stars from IC 348, or (3) reflect that IC 348 has not relaxed to a Gaussian velocity distribution. We measure a velocity dispersion for IC 348 of $0.72 \pm 0.07$ km s$^{-1}$ (or $0.64 \pm 0.08$ km s$^{-1}$ if two Gaussians are fitted), which implies a supervirial state, unless the gas contributes more to the gravitational potential than expected. No evidence is found for a dependence of this velocity dispersion on distance from the cluster center or stellar mass. We also find that stars with lower extinction (in the front of the cloud) tend to be redshifted compared with stars with somewhat higher extinction (towards the back of the cloud). This data suggests that the stars in IC 348 are converging along the line of sight. We show that this correlation between radial velocity and extinction is unlikely to be spuriously caused by the small cluster rotation of $0.024 \pm 0.013$ km s$^{-1}$ arcmin$^{-1}$ or by correlations between the radial velocities of neighboring stars. This signature, if confirmed, will be the first detection of line-of-sight convergence in a star cluster(...), Comment: online data available at http://www.astro.ufl.edu/insync/perseus.html
Published: 2015
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207. The LSST Data Management System

Author: Jurić, Mario, Kantor, Jeffrey, Lim, K-T, Lupton, Robert H., Dubois-Felsmann, Gregory, Jenness, Tim, Axelrod, Tim S., Aleksić, Jovan, Allsman, Roberta A., AlSayyad, Yusra, Alt, Jason, Armstrong, Robert, Basney, Jim, Becker, Andrew C., Becla, Jacek, Bickerton, Steven J., Biswas, Rahul, Bosch, James, Boutigny, Dominique, Kind, Matias Carrasco, Ciardi, David R., Connolly, Andrew J., Daniel, Scott F., Daues, Gregory E., Economou, Frossie, Chiang, Hsin-Fang, Fausti, Angelo, Fisher-Levine, Merlin, Freemon, D. Michael, Gee, Perry, Gris, Philippe, Hernandez, Fabio, Hoblitt, Joshua, Ivezić, Željko, Jammes, Fabrice, Jevremović, Darko, Jones, R. Lynne, Kalmbach, J. Bryce, Kasliwal, Vishal P., Krughoff, K. Simon, Lang, Dustin, Lurie, John, Lust, Nate B., Mullally, Fergal, MacArthur, Lauren A., Melchior, Peter, Moeyens, Joachim, Nidever, David L., Owen, Russell, Parejko, John K, Peterson, J. Matt, Petravick, Donald, Pietrowicz, Stephen R., Price, Paul A., Reiss, David J., Shaw, Richard A., Sick, Jonathan, Slater, Colin T., Strauss, Michael A., Sullivan, Ian S., Swinbank, John D., Van Dyk, Schuyler, Vujčić, Veljko, Withers, Alexander, and Yoachim, Peter
Subjects: FOS: Physical sciences, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract: The Large Synoptic Survey Telescope (LSST) is a large-aperture, wide-field, ground-based survey system that will image the sky in six optical bands from 320 to 1050 nm, uniformly covering approximately $18,000$deg$^2$ of the sky over 800 times. The LSST is currently under construction on Cerro Pach\'on in Chile, and expected to enter operations in 2022. Once operational, the LSST will explore a wide range of astrophysical questions, from discovering "killer" asteroids to examining the nature of Dark Energy. The LSST will generate on average 15 TB of data per night, and will require a comprehensive Data Management system to reduce the raw data to scientifically useful catalogs and images with minimum human intervention. These reductions will result in a real-time alert stream, and eleven data releases over the 10-year duration of LSST operations. To enable this processing, the LSST project is developing a new, general-purpose, high-performance, scalable, well documented, open source data processing software stack for O/IR surveys. Prototypes of this stack are already capable of processing data from existing cameras (e.g., SDSS, DECam, MegaCam), and form the basis of the Hyper-Suprime Cam (HSC) Survey data reduction pipeline., Comment: 10 pages, 3 figures, to appear in the Proceedings of ADASS XXV
Published: 2015
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208. Imprints of radial migration on the Milky Way’s metallicity distribution functions

Author: Loebman, Sarah R., Debattista, Victor P, Nidever, David L., Hayden, Michael R., Holtzman, Jon A., Clarke, Adam J., Roškar, Rok, Valluri, Monica, Loebman, Sarah R., Debattista, Victor P, Nidever, David L., Hayden, Michael R., Holtzman, Jon A., Clarke, Adam J., Roškar, Rok, and Valluri, Monica
Abstract: Recent analysis of the SDSS-III/Apache Point Observatory Galactic Evolution Experiment (APOGEE) Data Release 12 stellar catalog has revealed that the Milky Way’s (MW) metallicity distribution function (MDF) changes shape as a function of radius, transitioning from being negatively skewed at small Galactocentric radii to positively skewed at large Galactocentric radii. Using a high-resolution, N-body+SPH simulation, we show that the changing skewness arises from radial migration—metal-rich stars form in the inner disk and subsequently migrate to the metal-poorer outer disk. These migrated stars represent a large fraction (>50%) of the stars in the outer disk; they populate the high-metallicity tail of the MDFs and are, in general, more metal-rich than the surrounding outer disk gas. The simulation also reproduces another surprising APOGEE result: the spatially invariant high-[α/Fe] MDFs. This arises in the simulation from the migration of a population formed within a narrow range of radii (3.2 ±1.2 kpc) and time (8.8 ± 0.6 Gyr ago), rather than from spatially extended star formation in a homogeneous medium at early times. These results point toward the crucial role radial migration has played in shaping our MW.
Published: 2016

209. The Thirteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-IV Survey MApping Nearby Galaxies at Apache Point Observatory

Author: SDSS Collaboration, Albareti, Franco D., Prieto, Carlos Allende, Almeida, Andres, Anders, Friedrich, Anderson, Scott, Andrews, Brett H., Aragon-Salamanca, Alfonso, Argudo-Fernandez, Maria, Armengaud, Eric, Aubourg, Eric, Avila-Reese, Vladimir, Badenes, Carles, Bailey, Stephen, Barbuy, Beatriz, Barger, Kat, Barrera-Ballesteros, Jorge, Bartosz, Curtis, Basu, Sarbani, Bates, Dominic, Battaglia, Giuseppina, Baumgarten, Falk, Baur, Julien, Bautista, Julian, Beers, Timothy C., Belfiore, Francesco, Bershady, Matthew, de Lis, Sara Bertran, Bird, Jonathan C., Bizyaev, Dmitry, Blanc, Guillermo A., Blanton, Michael, Blomqvist, Michael, Bolton, Adam S., Borissova, J., Bovy, Jo, Brandt, William Nielsen, Brinkmann, Jonathan, Brownstein, Joel R., Bundy, Kevin, Burtin, Etienne, Busca, Nicolas G., Chavez, Hugo Orlando Camacho, Diaz, M. Cano, Cappellari, Michele, Carrera, Ricardo, Chen, Yanping, Cherinka, Brian, Cheung, Edmond, Chiappini, Cristina, Chojnowski, Drew, Chuang, Chia-Hsun, Chung, Haeun, Cirolini, Rafael Fernando, Clerc, Nicolas, Cohen, Roger E., Comerford, Julia M., Comparat, Johan, Cousinou, Marie-Claude, Covey, Kevin, Crane, Jeffrey D., Croft, Rupert, Cunha, Katia, da Costa, Luiz, Ilha, Gabriele da Silva, Darling, Jeremy, Davidson Jr., James W., Dawson, Kyle, De Lee, Nathan, de la Macorra, Axel, de la Torre, Sylvain, Machado, Alice Deconto, Delubac, Timothee, Diamond-Stanic, Aleksandar M., Donor, John, Downes, Juan Jose, Drory, Niv, Bourboux, Helion du Mas des, Du, Cheng, Dwelly, Tom, Ebelke, Garrett, Eigenbrot, Arthur, Eisenstein, Daniel J., Elsworth, Yvonne P., Emsellem, Eric, Eracleous, Michael, Escoffier, Stephanie, Evans, Michael L., Falcon-Barroso, Jesus, Fan, Xiaohui, Favole, Ginevra, Fernandez-Alvar, Emma, Fernandez-Trincado, J. G., Feuillet, Diane, Fleming, Scott W., Font-Ribera, Andreu, Freischlad, Gordon, Frinchaboy, Peter, Fu, Hai, Gao, Yang, Garcia-Hernandez, D. A., Perez, Ana E. Garcia, Garcia, Rafael A., Garcia-Dias, R., Gaulme, Patrick, Ge, Junqiang, Geisler, Douglas, Marin, Hector Gil, Gillespie, Bruce, Girardi, Leo, Goddard, Daniel, Chew, Yilen Gomez Maqueo, Gonzalez-Perez, Violeta, Grabowski, Kathleen, Green, Paul, Grier, Catherine J., Grier, Thomas, Guo, Hong, Guy, Julien, Hagen, Alex, Hall, Matt, Harding, Paul, Harley, R. E., Hasselquist, Sten, Hawley, Suzanne, Hayes, Christian R., Hearty, Fred, Hekker, Saskia, Toledo, Hector Hernandez, Ho, Shirley, Hogg, David W., Holley-Bockelmann, Kelly, Holtzman, Jon A., Holzer, Parker H., Hu, Jian, Huber, Daniel, Hutchinson, Timothy Alan, Hwang, Ho Seong, Ibarra-Medel, Hector J., Ivans, Inese I., Ivory, KeShawn, Jaehnig, Kurt, Jensen, Trey W., Johnson, Jennifer A., Jones, Amy, Jullo, Eric, Kallinger, T., Kinemuchi, Karen, Kirkby, David, Klaene, Mark, Kneib, Jean-Paul, Kollmeier, Juna A., Lacerna, Ivan, Lane, Richard R., Lang, Dustin, Laurent, Pierre, Law, David R., Goff, Jean-Marc Le, Leauthaud, Alexie, Li, Cheng, Li, Ran, Li, Chen, Li, Niu, Liang, Fu-Heng, Liang, Yu, Lima, Marcos, Lin, Lihwai, Lin, Lin, Lin, Yen-Ting, Long, Dan, Lucatello, Sara, MacDonald, Nicholas, MacLeod, Chelsea L., Mackereth, J. Ted, Mahadevan, Suvrath, Maia, Marcio Antonio-Geimba, Maiolino, Roberto, Majewski, Steven R., Malanushenko, Olena, Mallmann, Nicolas Dullius, Manchado, Arturo, Maraston, Claudia, Marques-Chaves, Rui, Valpuesta, Inma Martinez, Masters, Karen L., Mathur, Savita, McGreer, Ian D., Merloni, Andrea, Merrifield, Michael R., Meszaros, Szabolcs, Meza, Andres, Miglio, Andrea, Minchev, Ivan, Molaverdikhani, Karan, Montero-Dorta, Antonio D., Mosser, Benoit, Muna, Demitri, Myers, Adam, Nair, Preethi, Nandra, Kirpal, Ness, Melissa, Newman, Jeffrey A., Nichol, Robert C., Nidever, David L., Nitschelm, Christian, O'Connell, Julia, Oravetz, Audrey, Padilla, Nelson, Palanque-Delabrouille, Nathalie, Pan, Kaike, Parejko, John, Paris, Isabelle, Peacock, John A., Peirani, Sebastien, Pellejero-Ibanez, Marcos, Penny, Samantha, Percival, Will J., Percival, Jeffrey W., Perez-Fournon, Ismael, Petitjean, Patrick, Pieri, Matthew, Pinsonneault, Marc H., Pisani, Alice, Prada, Francisco, Prakash, Abhishek, Price-Jones, Natalie, Raddick, M. Jordan, Rahman, Mubdi, Raichoor, Anand, Rembold, Sandro Barboza, Reyna, A. M., Rich, James, Richstein, Hannah, Ridl, Jethro, Riffel, Rogerio, Riffel, Rogemar A., Rix, Hans-Walter, Robin, Annie C., Rockosi, Constance M., Rodriguez-Torres, Sergio, Rodrigues, Thaise S., Roe, Natalie, Lopes, A. Roman, Roman-Zuniga, Carlos, Ross, Ashley J., Rossi, Graziano, Ruan, John, Ruggeri, Rossana, Runnoe, Jessie C., Salazar-Albornoz, Salvador, Salvato, Mara, Sanchez, Ariel G., Sanchez, Sebastian F., Sanchez-Gallego, Jose R., Santiago, Basilio Xavier, Schiavon, Ricardo, Schimoia, Jaderson S., Schlafly, Eddie, Schlegel, David J., Schneider, Donald P., Schoenrich, Ralph, Schultheis, Mathias, Schwope, Axel, Seo, Hee-Jong, Serenelli, Aldo, Sesar, Branimir, Shao, Zhengyi, Shetrone, Matthew, Shull, Michael, Aguirre, Victor Silva, Skrutskie, M. F., Slosar, Anže, Smith, Michael, Smith, Verne V., Sobeck, Jennifer, Somers, Garrett, Souto, Diogo, Stark, David V., Stassun, Keivan G., Steinmetz, Matthias, Stello, Dennis, Bergmann, Thaisa Storchi, Strauss, Michael A., Streblyanska, Alina, Stringfellow, Guy S., Suarez, Genaro, Sun, Jing, Taghizadeh-Popp, Manuchehr, Tang, Baitian, Tao, Charling, Tayar, Jamie, Tembe, Mita, Thomas, Daniel, Tinker, Jeremy, Tojeiro, Rita, Tremonti, Christy, Troup, Nicholas, Trump, Jonathan R., Unda-Sanzana, Eduardo, Valenzuela, O., Bosch, Remco van den, Vargas-Magana, Mariana, Vazquez, Jose Alberto, Villanova, Sandro, Vivek, M., Vogt, Nicole, Wake, David, Walterbos, Rene, Wang, Yuting, Wang, Enci, Weaver, Benjamin Alan, Weijmans, Anne-Marie, Weinberg, David H., Westfall, Kyle B., Whelan, David G., Wilcots, Eric, Wild, Vivienne, Williams, Rob A., Wilson, John, Wood-Vasey, W. M., Wylezalek, Dominika, Xiao, Ting, Yan, Renbin, Yang, Meng, Ybarra, Jason E., Yeche, Christophe, Yuan, Fang-Ting, Zakamska, Nadia, Zamora, Olga, Zasowski, Gail, Zhang, Kai, Zhao, Cheng, Zhao, Gong-Bo, Zheng, Zheng, Zhou, Zhi-Min, Zhu, Guangtun, Zinn, Joel C., Zou, Hu, SDSS Collaboration, Albareti, Franco D., Prieto, Carlos Allende, Almeida, Andres, Anders, Friedrich, Anderson, Scott, Andrews, Brett H., Aragon-Salamanca, Alfonso, Argudo-Fernandez, Maria, Armengaud, Eric, Aubourg, Eric, Avila-Reese, Vladimir, Badenes, Carles, Bailey, Stephen, Barbuy, Beatriz, Barger, Kat, Barrera-Ballesteros, Jorge, Bartosz, Curtis, Basu, Sarbani, Bates, Dominic, Battaglia, Giuseppina, Baumgarten, Falk, Baur, Julien, Bautista, Julian, Beers, Timothy C., Belfiore, Francesco, Bershady, Matthew, de Lis, Sara Bertran, Bird, Jonathan C., Bizyaev, Dmitry, Blanc, Guillermo A., Blanton, Michael, Blomqvist, Michael, Bolton, Adam S., Borissova, J., Bovy, Jo, Brandt, William Nielsen, Brinkmann, Jonathan, Brownstein, Joel R., Bundy, Kevin, Burtin, Etienne, Busca, Nicolas G., Chavez, Hugo Orlando Camacho, Diaz, M. Cano, Cappellari, Michele, Carrera, Ricardo, Chen, Yanping, Cherinka, Brian, Cheung, Edmond, Chiappini, Cristina, Chojnowski, Drew, Chuang, Chia-Hsun, Chung, Haeun, Cirolini, Rafael Fernando, Clerc, Nicolas, Cohen, Roger E., Comerford, Julia M., Comparat, Johan, Cousinou, Marie-Claude, Covey, Kevin, Crane, Jeffrey D., Croft, Rupert, Cunha, Katia, da Costa, Luiz, Ilha, Gabriele da Silva, Darling, Jeremy, Davidson Jr., James W., Dawson, Kyle, De Lee, Nathan, de la Macorra, Axel, de la Torre, Sylvain, Machado, Alice Deconto, Delubac, Timothee, Diamond-Stanic, Aleksandar M., Donor, John, Downes, Juan Jose, Drory, Niv, Bourboux, Helion du Mas des, Du, Cheng, Dwelly, Tom, Ebelke, Garrett, Eigenbrot, Arthur, Eisenstein, Daniel J., Elsworth, Yvonne P., Emsellem, Eric, Eracleous, Michael, Escoffier, Stephanie, Evans, Michael L., Falcon-Barroso, Jesus, Fan, Xiaohui, Favole, Ginevra, Fernandez-Alvar, Emma, Fernandez-Trincado, J. G., Feuillet, Diane, Fleming, Scott W., Font-Ribera, Andreu, Freischlad, Gordon, Frinchaboy, Peter, Fu, Hai, Gao, Yang, Garcia-Hernandez, D. A., Perez, Ana E. Garcia, Garcia, Rafael A., Garcia-Dias, R., Gaulme, Patrick, Ge, Junqiang, Geisler, Douglas, Marin, Hector Gil, Gillespie, Bruce, Girardi, Leo, Goddard, Daniel, Chew, Yilen Gomez Maqueo, Gonzalez-Perez, Violeta, Grabowski, Kathleen, Green, Paul, Grier, Catherine J., Grier, Thomas, Guo, Hong, Guy, Julien, Hagen, Alex, Hall, Matt, Harding, Paul, Harley, R. E., Hasselquist, Sten, Hawley, Suzanne, Hayes, Christian R., Hearty, Fred, Hekker, Saskia, Toledo, Hector Hernandez, Ho, Shirley, Hogg, David W., Holley-Bockelmann, Kelly, Holtzman, Jon A., Holzer, Parker H., Hu, Jian, Huber, Daniel, Hutchinson, Timothy Alan, Hwang, Ho Seong, Ibarra-Medel, Hector J., Ivans, Inese I., Ivory, KeShawn, Jaehnig, Kurt, Jensen, Trey W., Johnson, Jennifer A., Jones, Amy, Jullo, Eric, Kallinger, T., Kinemuchi, Karen, Kirkby, David, Klaene, Mark, Kneib, Jean-Paul, Kollmeier, Juna A., Lacerna, Ivan, Lane, Richard R., Lang, Dustin, Laurent, Pierre, Law, David R., Goff, Jean-Marc Le, Leauthaud, Alexie, Li, Cheng, Li, Ran, Li, Chen, Li, Niu, Liang, Fu-Heng, Liang, Yu, Lima, Marcos, Lin, Lihwai, Lin, Lin, Lin, Yen-Ting, Long, Dan, Lucatello, Sara, MacDonald, Nicholas, MacLeod, Chelsea L., Mackereth, J. Ted, Mahadevan, Suvrath, Maia, Marcio Antonio-Geimba, Maiolino, Roberto, Majewski, Steven R., Malanushenko, Olena, Mallmann, Nicolas Dullius, Manchado, Arturo, Maraston, Claudia, Marques-Chaves, Rui, Valpuesta, Inma Martinez, Masters, Karen L., Mathur, Savita, McGreer, Ian D., Merloni, Andrea, Merrifield, Michael R., Meszaros, Szabolcs, Meza, Andres, Miglio, Andrea, Minchev, Ivan, Molaverdikhani, Karan, Montero-Dorta, Antonio D., Mosser, Benoit, Muna, Demitri, Myers, Adam, Nair, Preethi, Nandra, Kirpal, Ness, Melissa, Newman, Jeffrey A., Nichol, Robert C., Nidever, David L., Nitschelm, Christian, O'Connell, Julia, Oravetz, Audrey, Padilla, Nelson, Palanque-Delabrouille, Nathalie, Pan, Kaike, Parejko, John, Paris, Isabelle, Peacock, John A., Peirani, Sebastien, Pellejero-Ibanez, Marcos, Penny, Samantha, Percival, Will J., Percival, Jeffrey W., Perez-Fournon, Ismael, Petitjean, Patrick, Pieri, Matthew, Pinsonneault, Marc H., Pisani, Alice, Prada, Francisco, Prakash, Abhishek, Price-Jones, Natalie, Raddick, M. Jordan, Rahman, Mubdi, Raichoor, Anand, Rembold, Sandro Barboza, Reyna, A. M., Rich, James, Richstein, Hannah, Ridl, Jethro, Riffel, Rogerio, Riffel, Rogemar A., Rix, Hans-Walter, Robin, Annie C., Rockosi, Constance M., Rodriguez-Torres, Sergio, Rodrigues, Thaise S., Roe, Natalie, Lopes, A. Roman, Roman-Zuniga, Carlos, Ross, Ashley J., Rossi, Graziano, Ruan, John, Ruggeri, Rossana, Runnoe, Jessie C., Salazar-Albornoz, Salvador, Salvato, Mara, Sanchez, Ariel G., Sanchez, Sebastian F., Sanchez-Gallego, Jose R., Santiago, Basilio Xavier, Schiavon, Ricardo, Schimoia, Jaderson S., Schlafly, Eddie, Schlegel, David J., Schneider, Donald P., Schoenrich, Ralph, Schultheis, Mathias, Schwope, Axel, Seo, Hee-Jong, Serenelli, Aldo, Sesar, Branimir, Shao, Zhengyi, Shetrone, Matthew, Shull, Michael, Aguirre, Victor Silva, Skrutskie, M. F., Slosar, Anže, Smith, Michael, Smith, Verne V., Sobeck, Jennifer, Somers, Garrett, Souto, Diogo, Stark, David V., Stassun, Keivan G., Steinmetz, Matthias, Stello, Dennis, Bergmann, Thaisa Storchi, Strauss, Michael A., Streblyanska, Alina, Stringfellow, Guy S., Suarez, Genaro, Sun, Jing, Taghizadeh-Popp, Manuchehr, Tang, Baitian, Tao, Charling, Tayar, Jamie, Tembe, Mita, Thomas, Daniel, Tinker, Jeremy, Tojeiro, Rita, Tremonti, Christy, Troup, Nicholas, Trump, Jonathan R., Unda-Sanzana, Eduardo, Valenzuela, O., Bosch, Remco van den, Vargas-Magana, Mariana, Vazquez, Jose Alberto, Villanova, Sandro, Vivek, M., Vogt, Nicole, Wake, David, Walterbos, Rene, Wang, Yuting, Wang, Enci, Weaver, Benjamin Alan, Weijmans, Anne-Marie, Weinberg, David H., Westfall, Kyle B., Whelan, David G., Wilcots, Eric, Wild, Vivienne, Williams, Rob A., Wilson, John, Wood-Vasey, W. M., Wylezalek, Dominika, Xiao, Ting, Yan, Renbin, Yang, Meng, Ybarra, Jason E., Yeche, Christophe, Yuan, Fang-Ting, Zakamska, Nadia, Zamora, Olga, Zasowski, Gail, Zhang, Kai, Zhao, Cheng, Zhao, Gong-Bo, Zheng, Zheng, Zhou, Zhi-Min, Zhu, Guangtun, Zinn, Joel C., and Zou, Hu
Abstract: The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) began observations in July 2014. It pursues three core programs: APOGEE-2, MaNGA, and eBOSS. In addition, eBOSS contains two major subprograms: TDSS and SPIDERS. This paper describes the first data release from SDSS-IV, Data Release 13 (DR13), which contains new data, reanalysis of existing data sets and, like all SDSS data releases, is inclusive of previously released data. DR13 makes publicly available 1390 spatially resolved integral field unit observations of nearby galaxies from MaNGA, the first data released from this survey. It includes new observations from eBOSS, completing SEQUELS. In addition to targeting galaxies and quasars, SEQUELS also targeted variability-selected objects from TDSS and X-ray selected objects from SPIDERS. DR13 includes new reductions of the SDSS-III BOSS data, improving the spectrophotometric calibration and redshift classification. DR13 releases new reductions of the APOGEE-1 data from SDSS-III, with abundances of elements not previously included and improved stellar parameters for dwarf stars and cooler stars. For the SDSS imaging data, DR13 provides new, more robust and precise photometric calibrations. Several value-added catalogs are being released in tandem with DR13, in particular target catalogs relevant for eBOSS, TDSS, and SPIDERS, and an updated red-clump catalog for APOGEE. This paper describes the location and format of the data now publicly available, as well as providing references to the important technical papers that describe the targeting, observing, and data reduction. The SDSS website, http://www.sdss.org, provides links to the data, tutorials and examples of data access, and extensive documentation of the reduction and analysis procedures. DR13 is the first of a scheduled set that will contain new data and analyses from the planned ~6-year operations of SDSS-IV., Comment: Full information on DR13 available at http://www.sdss.org. Comments welcome to spokesperson@sdss.org. To be published in ApJS
Published: 2016
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210. The Stellar Density Profile of the Distant Galactic Halo

Author: Slater, Colin T., Nidever, David L., Munn, Jeffrey A., Bell, Eric F., Majewski, Steven R., Slater, Colin T., Nidever, David L., Munn, Jeffrey A., Bell, Eric F., and Majewski, Steven R.
Abstract: We use extensive gravity-sensitive DDO 51 photometry over 5100 square degrees, combined with SDSS broadband photometry, to select a catalog of $\sim 4,000$ giant stars covering a large fraction of the high Galactic latitude sky and reaching out to $\sim 80$ kpc in the Galactic halo. This sample of bright and unbiased tracers enables us to measure the radial profile and 3D structure of the stellar halo to large distance which had previously only been measured with sparse tracers or small samples. Using population synthesis models to reproduce the observed giant star luminosity function, we find that the halo maintains a $r^{-3.5}$ profile from $30$ to $80$ kpc with no signs of a truncation or sharp break over this range. The radial profile measurement is largely insensitive to individual halo substructure components, but we find that attempting to measure the shape of the halo is overwhelmed by the Sagittarius stream such that no ellipsoidal shape is a satisfactory description in this region. These measurements allow us to begin placing the Milky Way in context with the growing sample of external galaxies where similar halo profile measurements are available, with the goal of further linking the properties of stellar halos to the accretion histories that formed them., Comment: Accepted to ApJ
Published: 2016
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211. SMASH 1: a very faint globular cluster disrupting in the outer reaches of the LMC?

Author: Martin, Nicolas F., Jungbluth, Valentin, Nidever, David L., Bell, Eric F., Besla, Gurtina, Blum, Robert D., Cioni, Maria-Rosa L., Conn, Blair C., Kaleida, Catherine C., Gallart, Carme, Jin, Shoko, Majewski, Steven R., Martinez-Delgado, David, Monachesi, Antonela, Mñoz, Ricardo R., Noël, Noelia E. D., Olsen, Knut, Olszewski, Edward W., Stringfellow, Guy S., van der Marel, Roeland P., Vivas, A. Katherina, Walker, Alistair R., Zaritsky, Dennis, Martin, Nicolas F., Jungbluth, Valentin, Nidever, David L., Bell, Eric F., Besla, Gurtina, Blum, Robert D., Cioni, Maria-Rosa L., Conn, Blair C., Kaleida, Catherine C., Gallart, Carme, Jin, Shoko, Majewski, Steven R., Martinez-Delgado, David, Monachesi, Antonela, Mñoz, Ricardo R., Noël, Noelia E. D., Olsen, Knut, Olszewski, Edward W., Stringfellow, Guy S., van der Marel, Roeland P., Vivas, A. Katherina, Walker, Alistair R., and Zaritsky, Dennis
Abstract: We present the discovery of a very faint stellar system, SMASH 1, that is potentially a satellite of the Large Magellanic Cloud. Found within the Survey of the MAgellanic Stellar History (SMASH), SMASH 1 is a compact ($r_h = 9.1^{+5.9}_{-3.4}$ pc) and very low luminosity (M_V = -1.0 +/- 0.9, $L_V=10^{2.3 +/- 0.4}$ Lsun) stellar system that is revealed by its sparsely populated main sequence and a handful of red-giant-branch candidate member stars. The photometric properties of these stars are compatible with a metal-poor ([Fe/H]=-2.2) and old (13 Gyr) isochrone located at a distance modulus of ~18.8, i.e. a distance of ~57 kpc. Situated at 11.3$^\circ$ from the LMC in projection, its 3-dimensional distance from the Cloud is ~13 kpc, consistent with a connection to the LMC, whose tidal radius is at least 16 kpc. Although the nature of SMASH 1 remains uncertain, its compactness favors it being a stellar cluster and hence dark-matter free. If this is the case, its dynamical tidal radius is only <19 pc at this distance from the LMC, and smaller than the system's extent on the sky. Its low luminosity and apparent high ellipticity ($\epsilon=0.62^{+0.17}_{-0.21}$) with its major axis pointing toward the LMC may well be the tell-tale sign of its imminent tidal demise., Comment: 7 pages, 4 figures, 1 table. Accepted for publication in ApJL. v2: corrected figure 4 in which rh for globular clusters were miscalculated. The updated figure reflect the published version of the paper
Published: 2016
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212. Chemical abundance gradients from open clusters in the Milky Way disk: results from the APOGEE survey

Author: Cunha, Katia, Frinchaboy, Peter M., Souto, Diogo, Thompson, Benjamin, Zasowski, Gail, Prieto, Carlos Allende, Carrera, Ricardo, Chiappini, Cristina, Donor, John, Garcia-Hernandez, Anibal, Perez, Ana Elia Garcia, Hayden, Michael R., Holtzman, Jon, Jackson, Kelly M., Johnson, Jennifer A., Majewski, Steven R., Meszaros, Szabolcs, Meyer, Brianne, Nidever, David L., O'Connell, Julia, Schiavon, Ricardo P., Schultheis, Mathias, Shetrone, Matthew, Simmons, Audrey, Smith, Verne V., Zamora, Olga, Cunha, Katia, Frinchaboy, Peter M., Souto, Diogo, Thompson, Benjamin, Zasowski, Gail, Prieto, Carlos Allende, Carrera, Ricardo, Chiappini, Cristina, Donor, John, Garcia-Hernandez, Anibal, Perez, Ana Elia Garcia, Hayden, Michael R., Holtzman, Jon, Jackson, Kelly M., Johnson, Jennifer A., Majewski, Steven R., Meszaros, Szabolcs, Meyer, Brianne, Nidever, David L., O'Connell, Julia, Schiavon, Ricardo P., Schultheis, Mathias, Shetrone, Matthew, Simmons, Audrey, Smith, Verne V., and Zamora, Olga
Abstract: Metallicity gradients provide strong constraints for understanding the chemical evolution of the Galaxy. We report on radial abundance gradients of Fe, Ni, Ca, Si, and Mg obtained from a sample of 304 red-giant members of 29 disk open clusters, mostly concentrated at galactocentric distances between ~8 - 15 kpc, but including two open clusters in the outer disk. The observations are from the APOGEE survey. The chemical abundances were derived automatically by the ASPCAP pipeline and these are part of the SDSS III Data Release 12. The gradients, obtained from least squares fits to the data, are relatively flat, with slopes ranging from -0.026 to -0.033 dex/kpc for the alpha-elements [O/H], [Ca/H], [Si/H] and [Mg/H] and -0.035 dex/kpc and -0.040 dex/kpc for [Fe/H] and [Ni/H], respectively. Our results are not at odds with the possibility that metallicity ([Fe/H]) gradients are steeper in the inner disk (R_GC ~7 - 12 kpc) and flatter towards the outer disk. The open cluster sample studied spans a significant range in age. When breaking the sample into age bins, there is some indication that the younger open cluster population in our sample (log age < 8.7) has a flatter metallicity gradient when compared with the gradients obtained from older open clusters., Comment: 4 pages, 3 figures, To appear in Astronomische Nachrichten, special issue "Reconstruction the Milky Way's History: Spectroscopic surveys, Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J. Montalb\'an, and M. Steffen, AN 2016 (in press)"
Published: 2016
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213. Chemical tagging with APOGEE: Discovery of a large population of N-rich stars in the inner Galaxy

Author: Schiavon, Ricardo P., Zamora, Olga, Carrera, Ricardo, Lucatello, Sara, Robin, A. C., Ness, Melissa, Martell, Sarah L., Smith, Verne V., Hernandez, D. A. Garcia, Manchado, Arturo, Schoenrich, Ralph, Bastian, Nate, Chiappini, Cristina, Shetrone, Matthew, Mackereth, J. Ted, Williams, Rob A., Meszaros, Szabolcs, Prieto, Carlos Allende, Anders, Friedrich, Bizyaev, Dmitry, Beers, Timothy C., Chojnowski, S. Drew, Cunha, Katia, Epstein, Courtney, Frinchaboy, Peter M., Perez, Ana E. Garcia, Hearty, Fred R., Holtzman, Jon A., Johnson, Jennifer A., Kinemuchi, Karen, Majewski, Steven R., Muna, Demitri, Nidever, David L., Nguyen, Duy Cuong, O'Connell, Robert W., Oravetz, Daniel, Pan, Kaike, Pinsonneault, Marc, Schneider, Donald P., Schultheis, Matthias, Simmons, Audrey, Skrutskie, Michael F., Sobeck, Jennifer, Wilson, John C., Zasowski, Gail, Schiavon, Ricardo P., Zamora, Olga, Carrera, Ricardo, Lucatello, Sara, Robin, A. C., Ness, Melissa, Martell, Sarah L., Smith, Verne V., Hernandez, D. A. Garcia, Manchado, Arturo, Schoenrich, Ralph, Bastian, Nate, Chiappini, Cristina, Shetrone, Matthew, Mackereth, J. Ted, Williams, Rob A., Meszaros, Szabolcs, Prieto, Carlos Allende, Anders, Friedrich, Bizyaev, Dmitry, Beers, Timothy C., Chojnowski, S. Drew, Cunha, Katia, Epstein, Courtney, Frinchaboy, Peter M., Perez, Ana E. Garcia, Hearty, Fred R., Holtzman, Jon A., Johnson, Jennifer A., Kinemuchi, Karen, Majewski, Steven R., Muna, Demitri, Nidever, David L., Nguyen, Duy Cuong, O'Connell, Robert W., Oravetz, Daniel, Pan, Kaike, Pinsonneault, Marc, Schneider, Donald P., Schultheis, Matthias, Simmons, Audrey, Skrutskie, Michael F., Sobeck, Jennifer, Wilson, John C., and Zasowski, Gail
Abstract: Formation of globular clusters (GCs), the Galactic bulge, or galaxy bulges in general, are important unsolved problems in Galactic astronomy. Homogeneous infrared observations of large samples of stars belonging to GCs and the Galactic bulge field are one of the best ways to study these problems. We report the discovery by APOGEE of a population of field stars in the inner Galaxy with abundances of N, C, and Al that are typically found in GC stars. The newly discovered stars have high [N/Fe], which is correlated with [Al/Fe] and anti-correlated with [C/Fe]. They are homogeneously distributed across, and kinematically indistinguishable from, other field stars in the same volume. Their metallicity distribution is seemingly unimodal, peaking at [Fe/H]~-1, thus being in disagreement with that of the Galactic GC system. Our results can be understood in terms of different scenarios. N-rich stars could be former members of dissolved GCs, in which case the mass in destroyed GCs exceeds that of the surviving GC system by a factor of ~8. In that scenario, the total mass contained in so-called "first-generation" stars cannot be larger than that in "second-generation" stars by more than a factor of ~9 and was certainly smaller. Conversely, our results may imply the absence of a mandatory genetic link between "second generation" stars and GCs. Last, but not least, N-rich stars could be the oldest stars in the Galaxy, the by-products of chemical enrichment by the first stellar generations formed in the heart of the Galaxy., Comment: 29 pages, 9 Figures. Submitted to MNRAS, revised after second referee pass
Published: 2016
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214. Chemical tagging can work: Identification of stellar phase-space structures purely by chemical-abundance similarity

Author: Hogg, David W., Casey, Andrew R., Ness, Melissa, Rix, Hans-Walter, Foreman-Mackey, Daniel, Hasselquist, Sten, Ho, Anna Y. Q., Holtzman, Jon A., Majewski, Steven R., Martell, Sarah L., Meszaros, Szabolcs, NIdever, David L., Shetrone, Matthew, Hogg, David W., Casey, Andrew R., Ness, Melissa, Rix, Hans-Walter, Foreman-Mackey, Daniel, Hasselquist, Sten, Ho, Anna Y. Q., Holtzman, Jon A., Majewski, Steven R., Martell, Sarah L., Meszaros, Szabolcs, NIdever, David L., and Shetrone, Matthew
Abstract: Chemical tagging promises to use detailed abundance measurements to identify spatially separated stars that were in fact born together (in the same molecular cloud), long ago. This idea has not yielded much practical success, presumably because of the noise and incompleteness in chemical-abundance measurements. We have succeeded in substantially improving spectroscopic measurements with The Cannon, which has now delivered 15 individual abundances for ~100,000 stars observed as part of the APOGEE spectroscopic survey, with precisions around 0.04 dex. We test the chemical-tagging hypothesis by looking at clusters in abundance space and confirming that they are clustered in phase space. We identify (by the k-means algorithm) overdensities of stars in the 15-dimensional chemical-abundance space delivered by The Cannon, and plot the associated stars in phase space. We use only abundance-space information (no positional information) to identify stellar groups. We find that clusters in abundance space are indeed clusters in phase space. We recover some known phase-space clusters and find other interesting structures. This is the first-ever project to identify phase-space structures at survey-scale by blind search purely in abundance space; it verifies the precision of the abundance measurements delivered by The Cannon; the prospects for future data sets appear very good., Comment: accepted for publication in the ApJ
Published: 2016
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215. Detailed Chemical Abundances in the r-Process-Rich Ultra-Faint Dwarf Galaxy Reticulum 2

Author: Roederer, Ian U., Mateo, Mario, Bailey III, John I., Song, Yingyi, Bell, Eric F., Crane, Jeffrey D., Loebman, Sarah, Nidever, David L., Olszewski, Edward W., Shectman, Stephen A., Thompson, Ian B., Valluri, Monica, Walker, Matthew G., Roederer, Ian U., Mateo, Mario, Bailey III, John I., Song, Yingyi, Bell, Eric F., Crane, Jeffrey D., Loebman, Sarah, Nidever, David L., Olszewski, Edward W., Shectman, Stephen A., Thompson, Ian B., Valluri, Monica, and Walker, Matthew G.
Abstract: The ultra-faint dwarf galaxy Reticulum 2 (Ret 2) was recently discovered in images obtained by the Dark Energy Survey. We have observed the four brightest red giants in Ret 2 at high spectral resolution using the Michigan/Magellan Fiber System. We present detailed abundances for as many as 20 elements per star, including 12 elements heavier than the Fe group. We confirm previous detection of high levels of r-process material in Ret 2 (mean [Eu/Fe]=+1.69+/-0.05) found in three of these stars (mean [Fe/H]=-2.88+/-0.10). The abundances closely match the r-process pattern found in the well-studied metal-poor halo star CS22892-052. Such r-process-enhanced stars have not been found in any other ultra-faint dwarf galaxy, though their existence has been predicted by at least one model. The fourth star in Ret 2 ([Fe/H]=-3.42+/-0.20) contains only trace amounts of Sr ([Sr/Fe]=-1.73+/-0.43) and no detectable heavier elements. One r-process enhanced star is also enhanced in C (natal [C/Fe]=+1.1). This is only the third such star known, which suggests that the nucleosynthesis sites leading to C and r-process enhancements are decoupled. The r-process-deficient star is enhanced in Mg ([Mg/Fe]=+0.81+/-0.14), and the other three stars show normal levels of alpha-enhancement (mean [Mg/Fe]=+0.34+/-0.03). The abundances of other alpha and Fe-group elements closely resemble those in ultra-faint dwarf galaxies and metal-poor halo stars, suggesting that the nucleosynthesis that led to the large r-process enhancements either produced no light elements or produced light-element abundance signatures indistinguishable from normal supernovae., Comment: Accepted for publication in the Astronomical Journal. 12 pages, 6 figures, 8 tables
Published: 2016
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216. Companions to APOGEE Stars I: A Milky Way-Spanning Catalog of Stellar and Substellar Companion Candidates and their Diverse Hosts

Author: Troup, Nicholas W., Nidever, David L., De Lee, Nathan, Carlberg, Joleen, Majewski, Steven R., Fernandez, Martin, Covey, Kevin, Chojnowski, S. Drew, Pepper, Joshua, Nguyen, Duy T., Stassun, Keivan, Nguyen, Duy Cuong, Wisniewski, John P., Fleming, Scott W., Bizyaev, Dmitry, Frinchaboy, Peter M., García-Hernández, D. A., Ge, Jian, Hearty, Fred, Meszaros, Szabolcs, Pan, Kaike, Prieto, Carlos Allende, Schneider, Donald P., Shetrone, Matthew D., Skrutskie, Michael F., Wilson, John, Zamora, Olga, Troup, Nicholas W., Nidever, David L., De Lee, Nathan, Carlberg, Joleen, Majewski, Steven R., Fernandez, Martin, Covey, Kevin, Chojnowski, S. Drew, Pepper, Joshua, Nguyen, Duy T., Stassun, Keivan, Nguyen, Duy Cuong, Wisniewski, John P., Fleming, Scott W., Bizyaev, Dmitry, Frinchaboy, Peter M., García-Hernández, D. A., Ge, Jian, Hearty, Fred, Meszaros, Szabolcs, Pan, Kaike, Prieto, Carlos Allende, Schneider, Donald P., Shetrone, Matthew D., Skrutskie, Michael F., Wilson, John, and Zamora, Olga
Abstract: In its three years of operation, the Sloan Digital Sky Survey (SDSS-III) Apache Point Observatory Galactic Evolution Experiment (APOGEE-1) observed $>$14,000 stars with enough epochs over a sufficient temporal baseline for the fitting of Keplerian orbits. We present the custom orbit-fitting pipeline used to create this catalog, which includes novel quality metrics that account for the phase and velocity coverage of a fitted Keplerian orbit. With a typical RV precision of $\sim100-200$ m s$^{-1}$, APOGEE can probe systems with small separation companions down to a few Jupiter masses. Here we present initial results from a catalog of 382 of the most compelling stellar and substellar companion candidates detected by APOGEE, which orbit a variety of host stars in diverse Galactic environments. Of these, 376 have no previously known small separation companion. The distribution of companion candidates in this catalog shows evidence for an extremely truncated brown dwarf (BD) desert with a paucity of BD companions only for systems with $a < 0.1-0.2$ AU, with no indication of a desert at larger orbital separation. We propose a few potential explanations of this result, some which invoke this catalog's many small separation companion candidates found orbiting evolved stars. Furthermore, 16 BD and planet candidates have been identified around metal-poor ([Fe/H] $< -0.5$) stars in this catalog, which may challenge the core accretion model for companions $>10 M_{Jup}$. Finally, we find all types of companions are ubiquitous throughout the Galactic disk with candidate planetary-mass and BD companions to distances of $\sim6$ and $\sim16$ kpc, respectively., Comment: 27 pages, 14 figures,Published in AJ 02/26/2015. Full catalog available will be available as a FITS binary table with published version, and is currently avaliable on Filtergraph at https://filtergraph.com/apOrbitPub
Published: 2016
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217. VARIABLE STARS in the FIELD of the HYDRA II ULTRA-FAINT DWARF GALAXY

Author: Vivas, Anna Katherina, Olsen, Knut A. G., Blum, Robert D., Nidever, David L., Walker, Alistair R, Martin, Nicolas F, Besla, Gurtina, Gallart, Carme, van der Marel, R P, Majewski, S, Conn, Blair, Vivas, Anna Katherina, Olsen, Knut A. G., Blum, Robert D., Nidever, David L., Walker, Alistair R, Martin, Nicolas F, Besla, Gurtina, Gallart, Carme, van der Marel, R P, Majewski, S, and Conn, Blair
Abstract: We report the discovery of one RR Lyrae star in the ultra-faint satellite galaxy Hydra II based on time series photometry in the g, r and i bands obtained with the Dark Energy Camera at Cerro Tololo Inter-American Observatory, Chile. The association of the RR Lyrae star discovered here with Hydra II is clear because is located at 42″ from the center of the dwarf, well within its half-light radius of 102″. The RR Lyrae star has a mean magnitude of i= 21.30 ± 0.04 which is too faint to be a field halo star. This magnitude translates to a heliocentric distance of 151 ± 8 kpc for Hydra II; this value is ∼13%larger than the estimate from the discovery paper based on the average magnitude of several blue horizontal branch star candidates. The new distance implies a slightly larger half-light radius of 76+12 -10pc and a brighter absolute magnitude of Mv = -5.1 ± 0.3, which keeps this object within the realm of the dwarf galaxies. A comparison with other RR Lyrae stars in ultra-faint systems indicates similar pulsational properties among them, which are different to those found among halo field stars and those in the largest of the Milky Way satellites. We also report the discovery of 31 additional short period variables in the field of view (RR Lyrae, SX Phe, eclipsing binaries, and a likely anomalous cepheid) which are likely not related with Hydra II
Published: 2016

218. CHEMICAL TAGGING CAN WORK: IDENTIFICATION OF STELLAR PHASE-SPACE STRUCTURES PURELY BY CHEMICAL-ABUNDANCE SIMILARITY

Author: Hogg, David W., primary, Casey, Andrew R., additional, Ness, Melissa, additional, Rix, Hans-Walter, additional, Foreman-Mackey, Daniel, additional, Hasselquist, Sten, additional, Ho, Anna Y. Q., additional, Holtzman, Jon A., additional, Majewski, Steven R., additional, Martell, Sarah L., additional, Mészáros, Szabolcs, additional, Nidever, David L., additional, and Shetrone, Matthew, additional
Published: 2016
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219. THE STELLAR DENSITY PROFILE OF THE DISTANT GALACTIC HALO

Author: Slater, Colin T., primary, Nidever, David L., additional, Munn, Jeffrey A., additional, Bell, Eric F., additional, and Majewski, Steven R., additional
Published: 2016
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220. SMASH 1: A VERY FAINT GLOBULAR CLUSTER DISRUPTING IN THE OUTER REACHES OF THE LMC?

Author: Martin, Nicolas F., primary, Jungbluth, Valentin, additional, Nidever, David L., additional, Bell, Eric F., additional, Besla, Gurtina, additional, Blum, Robert D., additional, Cioni, Maria-Rosa L., additional, Conn, Blair C., additional, Kaleida, Catherine C., additional, Gallart, Carme, additional, Jin, Shoko, additional, Majewski, Steven R., additional, Martinez-Delgado, David, additional, Monachesi, Antonela, additional, Muñoz, Ricardo R., additional, Noël, Noelia E. D., additional, Olsen, Knut, additional, Stringfellow, Guy S., additional, van der Marel, Roeland P., additional, Vivas, A. Katherina, additional, Walker, Alistair R., additional, and Zaritsky, Dennis, additional
Published: 2016
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221. Chemical tagging with APOGEE: discovery of a large population of N-rich stars in the inner Galaxy

Author: Schiavon, Ricardo P., primary, Zamora, Olga, additional, Carrera, Ricardo, additional, Lucatello, Sara, additional, Robin, A. C., additional, Ness, Melissa, additional, Martell, Sarah L., additional, Smith, Verne V., additional, García-Hernández, D. A., additional, Manchado, Arturo, additional, Schönrich, Ralph, additional, Bastian, Nate, additional, Chiappini, Cristina, additional, Shetrone, Matthew, additional, Mackereth, J. Ted, additional, Williams, Rob A., additional, Mészáros, Szabolcs, additional, Allende Prieto, Carlos, additional, Anders, Friedrich, additional, Bizyaev, Dmitry, additional, Beers, Timothy C., additional, Chojnowski, S. Drew, additional, Cunha, Katia, additional, Epstein, Courtney, additional, Frinchaboy, Peter M., additional, García Pérez, Ana E., additional, Hearty, Fred R., additional, Holtzman, Jon A., additional, Johnson, Jennifer A., additional, Kinemuchi, Karen, additional, Majewski, Steven R., additional, Muna, Demitri, additional, Nidever, David L., additional, Nguyen, Duy Cuong, additional, O'Connell, Robert W., additional, Oravetz, Daniel, additional, Pan, Kaike, additional, Pinsonneault, Marc, additional, Schneider, Donald P., additional, Schultheis, Matthias, additional, Simmons, Audrey, additional, Skrutskie, Michael F., additional, Sobeck, Jennifer, additional, Wilson, John C., additional, and Zasowski, Gail, additional
Published: 2016
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222. CHEMICAL TAGGING IN THE SDSS-III/APOGEE SURVEY: NEW IDENTIFICATIONS OF HALO STARS WITH GLOBULAR CLUSTER ORIGINS

Author: Martell, Sarah L., primary, Shetrone, Matthew D., additional, Lucatello, Sara, additional, Schiavon, Ricardo P., additional, Mészáros, Szabolcs, additional, Prieto, Carlos Allende, additional, Hernández, D. A. García, additional, Beers, Timothy C., additional, and Nidever, David L, additional
Published: 2016
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223. ASPCAP: THE APOGEE STELLAR PARAMETER AND CHEMICAL ABUNDANCES PIPELINE

Author: García Pérez, Ana E., primary, Prieto, Carlos Allende, additional, Holtzman, Jon A., additional, Shetrone, Matthew, additional, Mészáros, Szabolcs, additional, Bizyaev, Dmitry, additional, Carrera, Ricardo, additional, Cunha, Katia, additional, García-Hernández, D. A., additional, Johnson, Jennifer A., additional, Majewski, Steven R., additional, Nidever, David L., additional, Schiavon, Ricardo P., additional, Shane, Neville, additional, Smith, Verne V., additional, Sobeck, Jennifer, additional, Troup, Nicholas, additional, Zamora, Olga, additional, Weinberg, David H., additional, Bovy, Jo, additional, Eisenstein, Daniel J., additional, Feuillet, Diane, additional, Frinchaboy, Peter M., additional, Hayden, Michael R., additional, Hearty, Fred R., additional, Nguyen, Duy C., additional, O’Connell, Robert W., additional, Pinsonneault, Marc H., additional, Wilson, John C., additional, and Zasowski, Gail, additional
Published: 2016
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224. THE STELLAR POPULATION STRUCTURE OF THE GALACTIC DISK

Author: Bovy, Jo, primary, Rix, Hans-Walter, additional, Schlafly, Edward F., additional, Nidever, David L., additional, Holtzman, Jon A., additional, Shetrone, Matthew, additional, and Beers, Timothy C., additional
Published: 2016
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225. VARIABLE STARS IN THE FIELD OF THE HYDRA II ULTRA-FAINT DWARF GALAXY

Author: Vivas, A. Katherina, primary, Olsen, Knut, additional, Blum, Robert, additional, Nidever, David L., additional, Walker, Alistair R., additional, Martin, Nicolas F., additional, Besla, Gurtina, additional, Gallart, Carme, additional, Marel, Roeland P. van der, additional, Majewski, Steven R., additional, Kaleida, Catherine C., additional, Muñoz, Ricardo R., additional, Saha, Abhijit, additional, Conn, Blair C., additional, and Jin, Shoko, additional
Published: 2016
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226. COMPANIONS TO APOGEE STARS. I. A MILKY WAY-SPANNING CATALOG OF STELLAR AND SUBSTELLAR COMPANION CANDIDATES AND THEIR DIVERSE HOSTS

Author: Troup, Nicholas W., primary, Nidever, David L., additional, Lee, Nathan De, additional, Carlberg, Joleen, additional, Majewski, Steven R., additional, Fernandez, Martin, additional, Covey, Kevin, additional, Chojnowski, S. Drew, additional, Pepper, Joshua, additional, Nguyen, Duy T., additional, Stassun, Keivan, additional, Nguyen, Duy Cuong, additional, Wisniewski, John P., additional, Fleming, Scott W., additional, Bizyaev, Dmitry, additional, Frinchaboy, Peter M., additional, García-Hernández, D. A., additional, Ge, Jian, additional, Hearty, Fred, additional, Meszaros, Szabolcs, additional, Pan, Kaike, additional, Prieto, Carlos Allende, additional, Schneider, Donald P., additional, Shetrone, Matthew D., additional, Skrutskie, Michael F., additional, Wilson, John, additional, and Zamora, Olga, additional
Published: 2016
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227. DETAILED CHEMICAL ABUNDANCES IN THEr-PROCESS-RICH ULTRA-FAINT DWARF GALAXY RETICULUM 2

Author: Roederer, Ian U., primary, Mateo, Mario, additional, III, John I. Bailey, additional, Song, Yingyi, additional, Bell, Eric F., additional, Crane, Jeffrey D., additional, Loebman, Sarah, additional, Nidever, David L., additional, Olszewski, Edward W., additional, Shectman, Stephen A., additional, Thompson, Ian B., additional, Valluri, Monica, additional, and Walker, Matthew G., additional
Published: 2016
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228. MAGELLAN/M2FS SPECTROSCOPY OF TUCANA 2 AND GRUS 1

Author: Walker, Matthew G., primary, Mateo, Mario, additional, Olszewski, Edward W., additional, Koposov, Sergey, additional, Belokurov, Vasily, additional, Jethwa, Prashin, additional, Nidever, David L., additional, Bonnivard, Vincent, additional, III, John I. Bailey, additional, Bell, Eric F., additional, and Loebman, Sarah R., additional
Published: 2016
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229. IN-SYNC. IV. THE YOUNG STELLAR POPULATION IN THE ORION A MOLECULAR CLOUD

Author: Rio, Nicola Da, primary, Tan, Jonathan C., additional, Covey, Kevin R., additional, Cottaar, Michiel, additional, Foster, Jonathan B., additional, Cullen, Nicholas C., additional, Tobin, John J., additional, Kim, Jinyoung S., additional, Meyer, Michael R., additional, Nidever, David L., additional, Stassun, Keivan G., additional, Chojnowski, S. Drew, additional, Flaherty, Kevin M., additional, Majewski, Steve, additional, Skrutskie, Michael F., additional, Zasowski, Gail, additional, and Pan, Kaike, additional
Published: 2016
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230. IMPRINTS OF RADIAL MIGRATION ON THE MILKY WAY’S METALLICITY DISTRIBUTION FUNCTIONS

Author: Loebman, Sarah R., primary, Debattista, Victor P., additional, Nidever, David L., additional, Hayden, Michael R., additional, Holtzman, Jon A., additional, Clarke, Adam J., additional, Roškar, Rok, additional, and Valluri, Monica, additional
Published: 2016
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231. Evidence for an Interaction in the Nearest Starbursing Dwarf Galaxy IC 10

Author: Nidever, David L., Ashley, T. L., Slater, C., Ott, J., Johnson, M. C., Bell, E. F., Stanimirovic, S., Putman, M. E., Majewski, S., Simpson, C. E., Burton, W., Juette, E., Oosterloo, T., and Kapteyn Astronomical Institute
Subjects: Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: Using deep 21-cm HI data from the Green Bank Telescope we have detected an ~18.3 kpc-long gaseous extension associated with the starbursting dwarf galaxy IC 10. The newly-found feature stretches 1.3 deg to the northwest and has a large radial velocity gradient reaching to ~65 km/s lower than the IC 10 systemic velocity. A region of higher column density at the end of the extension that possesses a coherent velocity gradient 10 km/s across ~26 arcmin) transverse to the extension suggests rotation and may be a satellite galaxy of IC 10. The HI mass of IC 10 is 9.5x10^7 (d/805 kpc)^2 Msun and the mass of the new extension is 7.1x10^5 (d/805 kpc)^2 Msun. An IC 10-M31 orbit using known radial velocity and proper motion values for IC 10 show that the HI extension is inconsistent with the trailing portion of the orbit so that an M31-tidal or ram pressure origin seems unlikely. We argue that the most plausible explanation for the new feature is that it is the result of a recent interaction (and possible late merger) with another dwarf galaxy. This interaction could not only have triggered the origin of the recent starburst in IC 10, but could also explain the existence of previously-found counter-rotating HI gas in the periphery of the IC 10 which was interpreted as originating from primordial gas infall.
Published: 2014

232. DETERMINING AGES OF APOGEE GIANTS WITH KNOWN DISTANCES

Author: Feuillet, Diane K., primary, Bovy, Jo, additional, Holtzman, Jon, additional, Girardi, Léo, additional, MacDonald, Nick, additional, Majewski, Steven R., additional, and Nidever, David L., additional
Published: 2016
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233. ASPCAP: The Apogee Stellar Parameter and Chemical Abundances Pipeline

Author: Pérez, Ana E. García, Prieto, Carlos Allende, Holtzman, Jon A., Shetrone, Matthew, Mészáros, Szabolcs, Bizyaev, Dmitry, Carrera, Ricardo, Cunha, Katia, García-Hernández, D. A., Johnson, Jennifer A., Majewski, Steven R., Nidever, David L., Schiavon, Ricardo P., Shane, Neville, Smith, Verne V., Sobeck, Jennifer, Troup, Nicholas, Zamora, Olga, Bovy, Jo, Eisenstein, Daniel J., Feuillet, Diane, Frinchaboy, Peter M., Hayden, Michael R., Hearty, Fred R., Nguyen, Duy C., O'Connell, Robert W., Pinsonneault, Marc H., Weinberg, David H., Wilson, John C., Zasowski, Gail, Pérez, Ana E. García, Prieto, Carlos Allende, Holtzman, Jon A., Shetrone, Matthew, Mészáros, Szabolcs, Bizyaev, Dmitry, Carrera, Ricardo, Cunha, Katia, García-Hernández, D. A., Johnson, Jennifer A., Majewski, Steven R., Nidever, David L., Schiavon, Ricardo P., Shane, Neville, Smith, Verne V., Sobeck, Jennifer, Troup, Nicholas, Zamora, Olga, Bovy, Jo, Eisenstein, Daniel J., Feuillet, Diane, Frinchaboy, Peter M., Hayden, Michael R., Hearty, Fred R., Nguyen, Duy C., O'Connell, Robert W., Pinsonneault, Marc H., Weinberg, David H., Wilson, John C., and Zasowski, Gail
Abstract: The Apache Point Observatory Galactic Evolution Experiment (APOGEE) has built the largest moderately high-resolution (R=22, 500) spectroscopic map of the stars across the Milky Way, and including dust-obscured areas. The APOGEE Stellar Parameter and Chemical Abundances Pipeline (ASPCAP) is the software developed for the automated analysis of these spectra. ASPCAP determines atmospheric parameters and chemical abundances from observed spectra by comparing observed spectra to libraries of theoretical spectra, using chi-2 minimization in a multidimensional parameter space. The package consists of a fortran90 code that does the actual minimization, and a wrapper IDL code for book-keeping and data handling. This paper explains in detail the ASPCAP components and functionality, and presents results from a number of tests designed to check its performance. ASPCAP provides stellar effective temperatures, surface gravities, and metallicities precise to 2%, 0.1 dex, and 0.05 dex, respectively, for most APOGEE stars, which are predominantly giants. It also provides abundances for up to 15 chemical elements with various levels of precision, typically under 0.1 dex. The final data release (DR12) of the Sloan Digital Sky Survey III contains an APOGEE database of more than 150,000 stars. ASPCAP development continues in the SDSS-IV APOGEE-2 survey., Comment: 19 pages,11 figures - Submitted to The Astronomical Journal
Published: 2015
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234. IN-SYNC IV - The Young Stellar Population in the Orion A Molecular Cloud

Author: Da Rio, Nicola, Tan, Jonathan C., Covey, Kevin R., Cottaar, Michiel, Foster, Jonathan B., Cullen, Nicholas C., Tobin, John J., Kim, Jinyoung S., Meyer, Michael R., Nidever, David L., Stassun, Keivan G., Chojnowski, S. Drew, Flaherty, Kevin M., Majewski, Steve, Skrutskie, Michael F., Zasowski, Gail, Pan, Kaike, Da Rio, Nicola, Tan, Jonathan C., Covey, Kevin R., Cottaar, Michiel, Foster, Jonathan B., Cullen, Nicholas C., Tobin, John J., Kim, Jinyoung S., Meyer, Michael R., Nidever, David L., Stassun, Keivan G., Chojnowski, S. Drew, Flaherty, Kevin M., Majewski, Steve, Skrutskie, Michael F., Zasowski, Gail, and Pan, Kaike
Abstract: We present the results of the SDSS APOGEE INfrared Spectroscopy of Young Nebulous Clusters program (IN-SYNC) survey of the Orion A molecular cloud. This survey obtained high resolution near infrared (NIR) spectroscopy of about 2700 young pre-main sequence stars throughout the region, acquired across five distinct fields spanning 6deg field of view (FOV). With these spectra, we have measured accurate stellar parameters (T_eff, log g, v sin i) and extinctions, and placed the sources in the Hertzsprung-Russel Diagram (HRD). We have also extracted radial velocities for the kinematic characterization of the population. We compare our measurements with literature results for a sub-sample of targets in order to assess the performances and accuracy of the survey. Source extinction shows evidence for dust grains that are larger than those in the diffuse interstellar medium (ISM): we estimate an average R_V=5.5 in the region. Importantly, we find a clear correlation between HRD inferred ages and spectroscopic surface-gravity inferred ages. This clearly indicates a real spread of stellar radii at fixed temperature, and together with additional correlations with extinction and with disk presence, strongly suggests a real spread of ages large than a few Myr. Focussing on the young population around NGC1980 iota Ori, which has previously been suggested to be a separate, foreground, older cluster, we confirm its older (5Myr) age and low A_V, but considering that its radial velocity distribution is indistinguishable from the Orion A's population, we suggest that NGC1980 is part of Orion A's star formation activity. Based on their stellar parameters and kinematic properties, we identify 383 new candidate members of Orion A, most of which are diskless sources in areas of the region poorly studied by previous works., Comment: ApJ accepted
Published: 2015
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235. Magellan/M2FS Spectroscopy of Tucana 2 and Grus 1

Author: Walker, Matthew G., Mateo, Mario, Olszewski, Edward W., Koposov, Sergey E., Belokurov, Vasily, Jethwa, Prashin, Nidever, David L., Bonnivard, Vincent, Bailey III, John I., Bell, Eric F., Loebman, Sarah R., Walker, Matthew G., Mateo, Mario, Olszewski, Edward W., Koposov, Sergey E., Belokurov, Vasily, Jethwa, Prashin, Nidever, David L., Bonnivard, Vincent, Bailey III, John I., Bell, Eric F., and Loebman, Sarah R.
Abstract: We present results from spectroscopic observations with the Michigan/Magellan Fiber System (M2FS) of $147$ stellar targets along the line of sight to the newly-discovered `ultrafaint' stellar systems Tucana 2 (Tuc 2) and Grus 1 (Gru 1). Based on simultaneous estimates of line-of-sight velocity and stellar-atmospheric parameters, we identify 8 and 7 stars as probable members of Tuc 2 and and Gru 1, respectively. Our sample for Tuc 2 is sufficient to resolve an internal velocity dispersion of $8.6_{-2.7}^{+4.4}$ km s$^{-1}$ about a mean of $-129.1_{-3.5}^{+3.5}$ km s$^{-1}$ (solar rest frame), and to estimate a mean metallicity of [Fe/H]= $-2.23_{-0.12}^{+0.18}$. These results place Tuc 2 on chemodynamical scaling relations followed by dwarf galaxies, suggesting a dominant dark matter component with dynamical mass $2.7_{-1.3}^{+3.1}\times 10^6$ $\mathrm{M}_{\odot}$ enclosed within the central $\sim 160$ pc, and dynamical mass-to-light ratio $1900_{-900}^{+2200}$ $\mathrm{M}_{\odot}/L_{V,\odot}$. For Gru 1 we estimate a mean velocity of $-140.5_{-1.6}^{+2.4}$ km s$^{-1}$ and a mean metallicity of [Fe/H]=$-1.42_{-0.42}^{+0.55}$, but our sample does not resolve Gru 1's velocity dispersion. The radial coordinates of Tuc 2 and Gru 1 in Galactic phase space suggest that their orbits are among the most energetic within distance $\leq 300$ kpc. Moreover, their proximity to each other in this space arises naturally if both objects are trailing the Large Magellanic Cloud., Comment: replaced with ApJ-accepted version, all spectra and data products (including samples from posterior PDFs) are available at http://www.andrew.cmu.edu/user/mgwalker/tuc2gru1_dataproducts.tar.gz
Published: 2015
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236. Imprints of radial migration on the Milky Way's metallicity distribution functions

Author: Loebman, Sarah R., Debattista, Victor P., Nidever, David L., Hayden, Michael R., Holtzman, Jon A., Clarke, Adam J., Roskar, Rok, Valluri, Monica, Loebman, Sarah R., Debattista, Victor P., Nidever, David L., Hayden, Michael R., Holtzman, Jon A., Clarke, Adam J., Roskar, Rok, and Valluri, Monica
Abstract: Recent analysis of the SDSS-III/APOGEE Data Release 12 stellar catalogue has revealed that the Milky Way's metallicity distribution function (MDF) changes shape as a function of radius, transitioning from being negatively skewed at small Galactocentric radii to positively skewed at large Galactocentric radii. Using a high resolution, N-body+SPH simulation, we show that the changing skewness arises from radial migration - metal-rich stars form in the inner disk and subsequently migrate to the metal-poorer outer disk. These migrated stars represent a large fraction (> 50%) of the stars in the outer disk; they populate the high metallicity tail of the MDFs and are, in general, more metal-rich than the surrounding outer disk gas. The simulation also reproduces another surprising APOGEE result: the spatially invariant high-[alpha/Fe] MDFs. This arises in the simulation from the migration of a population formed within a narrow range of radii (3.2+/-1.2 kpc) and time (8.8+/-0.6 Gyr ago), rather than from spatially extended star formation in a homogeneous medium at early times. These results point toward the crucial role radial migration has played in shaping our Milky Way., Comment: 5 pages, 5 figures, published in ApJ Letters
Published: 2015
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237. Determining Ages of APOGEE Giants with Known Distances

Author: Feuillet, Diane K, Bovy, Jo, Holtzman, Jon, Girardi, Leo, MacDonald, Nick, Majewski, Steven R, Nidever, David L, Feuillet, Diane K, Bovy, Jo, Holtzman, Jon, Girardi, Leo, MacDonald, Nick, Majewski, Steven R, and Nidever, David L
Abstract: We present a sample of local red giant stars observed using the New Mexico State University 1 m telescope with the APOGEE spectrograph, for which we estimate stellar ages and the age distribution from the high-resolution spectroscopic stellar parameters and accurate distance measurements from Hipparcos. The high-resolution (R ~ 23,000), near infrared (H-band, 1.5-1.7 micron) APOGEE spectra provide measurements of the stellar atmospheric parameters (temperature, surface gravity, [M/H], and [alpha/M]). Due to the smaller uncertainties in surface gravity possible with high-resolution spectra and accurate Hipparcos distance measurements, we are able to calculate the stellar masses to within 40%. For red giants, the relatively rapid evolution of stars up the red giant branch allows the age to be constrained based on the mass. We examine methods of estimating age using both the mass-age relation directly and a Bayesian isochrone matching of measured parameters, assuming a constant star formation history (SFH). To improve the prior on the SFH, we use a hierarchical modeling approach to constrain the parameters of a model SFH from the age probability distribution functions of the data. The results of an alpha dependent Gaussian SFH model shows a clear relation between age and [alpha/M] at all ages. Using this SFH model as the prior for an empirical Bayesian analysis, we construct a full age probability distribution function and determine ages for individual stars. The age-metallicity relation is flat, with a slight decrease in [M/H] at the oldest ages and a ~ 0.5 dex spread in metallicity. For stars with ages < 1 Gyr we find a smaller spread, consistent with radial migration having a smaller effect on these young stars than on the older stars., Comment: 14 page, 18 figures, accepted to ApJ with minor revisions, full electronic table of data available upon publication
Published: 2015
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238. The stellar population structure of the Galactic disk

Author: Bovy, Jo, Rix, Hans-Walter, Schlafly, Edward F., Nidever, David L., Holtzman, Jon A., Shetrone, Matthew, Beers, Timothy C., Bovy, Jo, Rix, Hans-Walter, Schlafly, Edward F., Nidever, David L., Holtzman, Jon A., Shetrone, Matthew, and Beers, Timothy C.
Abstract: The spatial structure of stellar populations with different chemical abundances in the Milky Way contains a wealth of information on Galactic evolution over cosmic time. We use data on 14,699 red-clump stars from the APOGEE survey, covering 4 kpc <~ R <~ 15 kpc, to determine the structure of mono-abundance populations (MAPs)---stars in narrow bins in [a/Fe] and [Fe/H]---accounting for the complex effects of the APOGEE selection function and the spatially-variable dust obscuration. We determine that all MAPs with enhanced [a/Fe] are centrally concentrated and are well-described as exponentials with a scale length of 2.2+/-0.2 kpc over the whole radial range of the disk. We discover that the surface-density profiles of low-[a/Fe] MAPs are complex: they do not monotonically decrease outwards, but rather display a peak radius ranging from ~5 kpc to ~13 kpc at low [Fe/H]. The extensive radial coverage of the data allows us to measure radial trends in the thickness of each MAP. While high-[a/Fe] MAPs have constant scale heights, low-[a/Fe] MAPs flare. We confirm, now with high-precision abundances, previous results that each MAP contains only a single vertical scale height and that low-[Fe/H], low-[a/Fe] and high-[Fe/H], high-[a/Fe] MAPs have intermediate (h_Z~300 to 600 pc) scale heights that smoothly bridge the traditional thin- and thick-disk divide. That the high-[a/Fe], thick disk components do not flare is strong evidence against their thickness being caused by radial migration. The correspondence between the radial structure and chemical-enrichment age of stellar populations is clear confirmation of the inside-out growth of galactic disks. The details of these relations will constrain the variety of physical conditions under which stars form throughout the MW disk., Comment: Code available at https://github.com/jobovy/apogee-maps
Published: 2015
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239. The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

Author: Majewski, Steven R., Schiavon, Ricardo P., Frinchaboy, Peter M., Prieto, Carlos Allende, Barkhouser, Robert, Bizyaev, Dmitry, Blank, Basil, Brunner, Sophia, Burton, Adam, Carrera, Ricardo, Chojnowski, S. Drew, Cunha, Katia, Epstein, Courtney, Fitzgerald, Greg, Perez, Ana E. Garcia, Hearty, Fred R., Henderson, Chuck, Holtzman, Jon A., Johnson, Jennifer A., Lam, Charles R., Lawler, James E., Maseman, Paul, Meszaros, Szabolcs, Nelson, Matthew, Nguyen, Duy Coung, Nidever, David L., Pinsonneault, Marc, Shetrone, Matthew, Smee, Stephen, Smith, Verne V., Stolberg, Todd, Skrutskie, Michael F., Walker, Eric, Wilson, John C., Zasowski, Gail, Anders, Friedrich, Basu, Sarbani, Beland, Stephane, Blanton, Michael R., Bovy, Jo, Brownstein, Joel R., Carlberg, Joleen, Chaplin, William, Chiappini, Cristina, Eisenstein, Daniel J., Elsworth, Yvonne, Feuillet, Diane, Fleming, Scott W., Galbraith-Frew, Jessica, Garcia, Rafael A., Garcia-Hernandez, D. Anibal, Gillespie, Bruce A., Girardi, Leo, Gunn, James E., Hasselquist, Sten, Hayden, Michael R., Hekker, Saskia, Ivans, Inese, Kinemuchi, Karen, Klaene, Mark, Mahadevan, Suvrath, Mathur, Savita, Mosser, Benoit, Muna, Demitri, Munn, Jeffrey A., Nichol, Robert C., O'Connell, Robert W., Robin, A. C., Rocha-Pinto, Helio, Schultheis, Matthias, Serenelli, Aldo M., Shane, Neville, Aguirre, Victor Silva, Sobeck, Jennifer S., Thompson, Benjamin, Troup, Nicholas W., Weinberg, David H., Zamora, Olga, Majewski, Steven R., Schiavon, Ricardo P., Frinchaboy, Peter M., Prieto, Carlos Allende, Barkhouser, Robert, Bizyaev, Dmitry, Blank, Basil, Brunner, Sophia, Burton, Adam, Carrera, Ricardo, Chojnowski, S. Drew, Cunha, Katia, Epstein, Courtney, Fitzgerald, Greg, Perez, Ana E. Garcia, Hearty, Fred R., Henderson, Chuck, Holtzman, Jon A., Johnson, Jennifer A., Lam, Charles R., Lawler, James E., Maseman, Paul, Meszaros, Szabolcs, Nelson, Matthew, Nguyen, Duy Coung, Nidever, David L., Pinsonneault, Marc, Shetrone, Matthew, Smee, Stephen, Smith, Verne V., Stolberg, Todd, Skrutskie, Michael F., Walker, Eric, Wilson, John C., Zasowski, Gail, Anders, Friedrich, Basu, Sarbani, Beland, Stephane, Blanton, Michael R., Bovy, Jo, Brownstein, Joel R., Carlberg, Joleen, Chaplin, William, Chiappini, Cristina, Eisenstein, Daniel J., Elsworth, Yvonne, Feuillet, Diane, Fleming, Scott W., Galbraith-Frew, Jessica, Garcia, Rafael A., Garcia-Hernandez, D. Anibal, Gillespie, Bruce A., Girardi, Leo, Gunn, James E., Hasselquist, Sten, Hayden, Michael R., Hekker, Saskia, Ivans, Inese, Kinemuchi, Karen, Klaene, Mark, Mahadevan, Suvrath, Mathur, Savita, Mosser, Benoit, Muna, Demitri, Munn, Jeffrey A., Nichol, Robert C., O'Connell, Robert W., Robin, A. C., Rocha-Pinto, Helio, Schultheis, Matthias, Serenelli, Aldo M., Shane, Neville, Aguirre, Victor Silva, Sobeck, Jennifer S., Thompson, Benjamin, Troup, Nicholas W., Weinberg, David H., and Zamora, Olga
Abstract: The Apache Point Observatory Galactic Evolution Experiment (APOGEE), one of the programs in the Sloan Digital Sky Survey III (SDSS-III), has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the Milky Way. After a three year observing campaign on the Sloan 2.5-m Telescope, APOGEE has collected a half million high resolution (R~22,500), high S/N (>100), infrared (1.51-1.70 microns) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. This paper describes the motivations for the survey and its overall design---hardware, field placement, target selection, operations---and gives an overview of these aspects as well as the data reduction, analysis and products. An index is also given to the complement of technical papers that describe various critical survey components in detail. Finally, we discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstrations, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity and abundance patterns across the Galaxy and as a function of age, to new views of the interstellar medium, the chemistry of star clusters, and the discovery of rare stellar species. As part of SDSS-III Data Release 12, all of the APOGEE data products are now publicly available., Comment: Submitted to The Astronomical Journal: 50 pages, including 38 figures, 4 tables, and 5 appendices
Published: 2015
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240. Rapid Rotation of Low-Mass Red Giants Using APOKASC: A Measure of Interaction Rates on the Post-main-sequence

Author: Tayar, Jamie, Ceillier, Tugdual, García-Hernández, D. A., Troup, Nicholas W., Mathur, Savita, García, Rafael A., Zamora, O., Johnson, Jennifer A., Pinsonneault, Marc H., Mészáros, Szabolcs, Prieto, Carlos Allende, Chaplin, William J., Elsworth, Yvonne, Nidever, David L., Salabert, David, Schneider, Donald P., Serenelli, Aldo, Shetrone, Matthew, Stello, Dennis, Tayar, Jamie, Ceillier, Tugdual, García-Hernández, D. A., Troup, Nicholas W., Mathur, Savita, García, Rafael A., Zamora, O., Johnson, Jennifer A., Pinsonneault, Marc H., Mészáros, Szabolcs, Prieto, Carlos Allende, Chaplin, William J., Elsworth, Yvonne, Nidever, David L., Salabert, David, Schneider, Donald P., Serenelli, Aldo, Shetrone, Matthew, and Stello, Dennis
Abstract: We investigate the occurrence rate of rapidly rotating ($v\sin i$$>$10 km s$^{-1}$), low-mass giant stars in the APOGEE-Kepler (APOKASC) fields with asteroseismic mass and surface gravity measurements. Such stars are likely merger products and their frequency places interesting constraints on stellar population models. We also identify anomalous rotators, i.e. stars with 5 km s$^{-1}$$<$$v\sin i$$<$10 km s$^{-1}$ that are rotating significantly faster than both angular momentum evolution predictions and the measured rates of similar stars. Our data set contains fewer rapid rotators than one would expect given measurements of the Galactic field star population, which likely indicates that asteroseismic detections are less common in rapidly rotating red giants. The number of low-mass moderate (5-10 km s$^{-1}$) rotators in our sample gives a lower limit of 7% for the rate at which low-mass stars interact on the upper red giant branch because single stars in this mass range are expected to rotate slowly. Finally, we classify the likely origin of the rapid or anomalous rotation where possible. KIC 10293335 is identified as a merger product and KIC 6501237 is a possible binary system of two oscillating red giants., Comment: 39 pages, 8 figures, 4 tables. Accepted for publication in the Astrophysical Journal. For a brief video discussing key results from this paper see http://youtu.be/ym_0nV7_YqI . The full table 1 is available at http://www.astronomy.ohio-state.edu/~tayar/tab1_full.txt
Published: 2015
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241. The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III

Author: Alam, Shadab, Albareti, Franco D., Prieto, Carlos Allende, Anders, F., Anderson, Scott F., Andrews, Brett H., Armengaud, Eric, Aubourg, Éric, Bailey, Stephen, Bautista, Julian E., Beaton, Rachael L., Beers, Timothy C., Bender, Chad F., Berlind, Andreas A., Beutler, Florian, Bhardwaj, Vaishali, Bird, Jonathan C., Bizyaev, Dmitry, Blake, Cullen H., Blanton, Michael R., Blomqvist, Michael, Bochanski, John J., Bolton, Adam S., Bovy, Jo, Bradley, A. Shelden, Brandt, W. N., Brauer, D. E., Brinkmann, J., Brown, Peter J., Brownstein, Joel R., Burden, Angela, Burtin, Etienne, Busca, Nicolás G., Cai, Zheng, Capozzi, Diego, Rosell, Aurelio Carnero, Carrera, Ricardo, Chen, Yen-Chi, Chiappini, Cristina, Chojnowski, S. Drew, Chuang, Chia-Hsun, Clerc, Nicolas, Comparat, Johan, Covey, Kevin, Croft, Rupert A. C., Cuesta, Antonio J., Cunha, Katia, da Costa, Luiz N., Da Rio, Nicola, Davenport, James R. A., Dawson, Kyle S., De Lee, Nathan, Delubac, Timothée, Deshpande, Rohit, Dutra-Ferreira, Letícia, Dwelly, Tom, Ealet, Anne, Ebelke, Garrett L., Edmondson, Edward M., Eisenstein, Daniel J., Escoffier, Stephanie, Esposito, Massimiliano, Fan, Xiaohui, Fernández-Alvar, Emma, Feuillet, Diane, Ak, Nurten Filiz, Finley, Hayley, Finoguenov, Alexis, Flaherty, Kevin, Fleming, Scott W., Font-Ribera, Andreu, Foster, Jonathan, Frinchaboy, Peter M., Galbraith-Frew, J. G., García-Hernández, D. A., Pérez, Ana E. García, Gaulme, Patrick, Ge, Jian, Génova-Santos, R., Ghezzi, Luan, Gillespie, Bruce A., Girardi, Léo, Goddard, Daniel, Gontcho, Satya Gontcho A, Hernández, Jonay I. González, Grebel, Eva K., Grieb, Jan Niklas, Grieves, Nolan, Gunn, James E., Guo, Hong, Harding, Paul, Hasselquist, Sten, Hawley, Suzanne L., Hayden, Michael, Hearty, Fred R., Ho, Shirley, Hogg, David W., Holley-Bockelmann, Kelly, Holtzman, Jon A., Honscheid, Klaus, Huehnerhoff, Joseph, Jiang, Linhua, Johnson, Jennifer A., Kinemuchi, Karen, Kirkby, David, Kitaura, Francisco, Klaene, Mark A., Kneib, Jean-Paul, Koenig, Xavier P., Lam, Charles R., Lan, Ting-Wen, Lang, Dustin, Laurent, Pierre, Goff, Jean-Marc Le, Leauthaud, Alexie, Lee, Khee-Gan, Lee, Young Sun, Licquia, Timothy C., Liu, Jian, Long, Daniel C., López-Corredoira, Martín, Lorenzo-Oliveira, Diego, Lucatello, Sara, Lundgren, Britt, Lupton, Robert H., Mack III, Claude E., Mahadevan, Suvrath, Maia, Marcio A. G., Majewski, Steven R., Malanushenko, Elena, Malanushenko, Viktor, Manchado, A., Manera, Marc, Mao, Qingqing, Maraston, Claudia, Marchwinski, Robert C., Margala, Daniel, Martell, Sarah L., Martig, Marie, Masters, Karen L., McBride, Cameron K., McGehee, Peregrine M., McGreer, Ian D., McMahon, Richard G., Ménard, Brice, Menzel, Marie-Luise, Merloni, Andrea, Mészáros, Szabolcs, Miller, Adam A., Miralda-Escudé, Jordi, Miyatake, Hironao, Montero-Dorta, Antonio D., More, Surhud, Morice-Atkinson, Xan, Morrison, Heather L., Muna, Demitri, Myers, Adam D., Newman, Jeffrey A., Neyrinck, Mark, Nguyen, Duy Cuong, Nichol, Robert C., Nidever, David L., Noterdaeme, Pasquier, Nuza, Sebastián E., O'Connell, Julia E., O'Connell, Robert W., O'Connell, Ross, Ogando, Ricardo L. C., Olmstead, Matthew D., Oravetz, Audrey E., Oravetz, Daniel J., Osumi, Keisuke, Owen, Russell, Padgett, Deborah L., Padmanabhan, Nikhil, Paegert, Martin, Palanque-Delabrouille, Nathalie, Pan, Kaike, Parejko, John K., Park, Changbom, Pâris, Isabelle, Pattarakijwanich, Petchara, Pellejero-Ibanez, M., Pepper, Joshua, Percival, Will J., Pérez-Fournon, Ismael, Pérez-Ràfols, Ignasi, Petitjean, Patrick, Pieri, Matthew M., Pinsonneault, Marc H., de Mello, Gustavo F. Porto, Prada, Francisco, Prakash, Abhishek, Price-Whelan, Adrian M., Raddick, M. Jordan, Rahman, Mubdi, Reid, Beth A., Rich, James, Rix, Hans-Walter, Robin, Annie C., Rockosi, Constance M., Rodrigues, Thaíse S., Rodríguez-Rottes, Sergio, Roe, Natalie A., Ross, Ashley J., Ross, Nicholas P., Rossi, Graziano, Ruan, John J., Rubiño-Martín, J. A., Rykoff, Eli S., Salazar-Albornoz, Salvador, Salvato, Mara, Samushia, Lado, Sánchez, Ariel G., Santiago, Basílio, Sayres, Conor, Schiavon, Ricardo P., Schlegel, David J., Schmidt, Sarah J., Schneider, Donald P., Schultheis, Mathias, Schwope, Axel D., Scóccola, C. G., Sellgren, Kris, Seo, Hee-Jong, Shane, Neville, Shen, Yue, Shetrone, Matthew, Shu, Yiping, Sivarani, Thirupathi, Skrutskie, M. F., Slosar, Anže, Smith, Verne V., Sobreira, Flávia, Stassun, Keivan G., Steinmetz, Matthias, Strauss, Michael A., Streblyanska, Alina, Swanson, Molly E. C., Tan, Jonathan C., Tayar, Jamie, Terrien, Ryan C., Thakar, Aniruddha R., Thomas, Daniel, Thompson, Benjamin A., Tinker, Jeremy L., Tojeiro, Rita, Troup, Nicholas W., Vargas-Magaña, Mariana, Vazquez, Jose A., Verde, Licia, Viel, Matteo, Vogt, Nicole P., Wake, David A., Wang, Ji, Weaver, Benjamin A., Weinberg, David H., Weiner, Benjamin J., White, Martin, Wilson, John C., Wisniewski, John P., Wood-Vasey, W. M., Yèche, Christophe, York, Donald G., Zakamska, Nadia L., Zamora, O., Zasowski, Gail, Zehavi, Idit, Zhao, Gong-Bo, Zheng, Zheng, Zhou, Xu, Zhou, Zhimin, Zhu, Guangtun, Zou, Hu, Alam, Shadab, Albareti, Franco D., Prieto, Carlos Allende, Anders, F., Anderson, Scott F., Andrews, Brett H., Armengaud, Eric, Aubourg, Éric, Bailey, Stephen, Bautista, Julian E., Beaton, Rachael L., Beers, Timothy C., Bender, Chad F., Berlind, Andreas A., Beutler, Florian, Bhardwaj, Vaishali, Bird, Jonathan C., Bizyaev, Dmitry, Blake, Cullen H., Blanton, Michael R., Blomqvist, Michael, Bochanski, John J., Bolton, Adam S., Bovy, Jo, Bradley, A. Shelden, Brandt, W. N., Brauer, D. E., Brinkmann, J., Brown, Peter J., Brownstein, Joel R., Burden, Angela, Burtin, Etienne, Busca, Nicolás G., Cai, Zheng, Capozzi, Diego, Rosell, Aurelio Carnero, Carrera, Ricardo, Chen, Yen-Chi, Chiappini, Cristina, Chojnowski, S. Drew, Chuang, Chia-Hsun, Clerc, Nicolas, Comparat, Johan, Covey, Kevin, Croft, Rupert A. C., Cuesta, Antonio J., Cunha, Katia, da Costa, Luiz N., Da Rio, Nicola, Davenport, James R. A., Dawson, Kyle S., De Lee, Nathan, Delubac, Timothée, Deshpande, Rohit, Dutra-Ferreira, Letícia, Dwelly, Tom, Ealet, Anne, Ebelke, Garrett L., Edmondson, Edward M., Eisenstein, Daniel J., Escoffier, Stephanie, Esposito, Massimiliano, Fan, Xiaohui, Fernández-Alvar, Emma, Feuillet, Diane, Ak, Nurten Filiz, Finley, Hayley, Finoguenov, Alexis, Flaherty, Kevin, Fleming, Scott W., Font-Ribera, Andreu, Foster, Jonathan, Frinchaboy, Peter M., Galbraith-Frew, J. G., García-Hernández, D. A., Pérez, Ana E. García, Gaulme, Patrick, Ge, Jian, Génova-Santos, R., Ghezzi, Luan, Gillespie, Bruce A., Girardi, Léo, Goddard, Daniel, Gontcho, Satya Gontcho A, Hernández, Jonay I. González, Grebel, Eva K., Grieb, Jan Niklas, Grieves, Nolan, Gunn, James E., Guo, Hong, Harding, Paul, Hasselquist, Sten, Hawley, Suzanne L., Hayden, Michael, Hearty, Fred R., Ho, Shirley, Hogg, David W., Holley-Bockelmann, Kelly, Holtzman, Jon A., Honscheid, Klaus, Huehnerhoff, Joseph, Jiang, Linhua, Johnson, Jennifer A., Kinemuchi, Karen, Kirkby, David, Kitaura, Francisco, Klaene, Mark A., Kneib, Jean-Paul, Koenig, Xavier P., Lam, Charles R., Lan, Ting-Wen, Lang, Dustin, Laurent, Pierre, Goff, Jean-Marc Le, Leauthaud, Alexie, Lee, Khee-Gan, Lee, Young Sun, Licquia, Timothy C., Liu, Jian, Long, Daniel C., López-Corredoira, Martín, Lorenzo-Oliveira, Diego, Lucatello, Sara, Lundgren, Britt, Lupton, Robert H., Mack III, Claude E., Mahadevan, Suvrath, Maia, Marcio A. G., Majewski, Steven R., Malanushenko, Elena, Malanushenko, Viktor, Manchado, A., Manera, Marc, Mao, Qingqing, Maraston, Claudia, Marchwinski, Robert C., Margala, Daniel, Martell, Sarah L., Martig, Marie, Masters, Karen L., McBride, Cameron K., McGehee, Peregrine M., McGreer, Ian D., McMahon, Richard G., Ménard, Brice, Menzel, Marie-Luise, Merloni, Andrea, Mészáros, Szabolcs, Miller, Adam A., Miralda-Escudé, Jordi, Miyatake, Hironao, Montero-Dorta, Antonio D., More, Surhud, Morice-Atkinson, Xan, Morrison, Heather L., Muna, Demitri, Myers, Adam D., Newman, Jeffrey A., Neyrinck, Mark, Nguyen, Duy Cuong, Nichol, Robert C., Nidever, David L., Noterdaeme, Pasquier, Nuza, Sebastián E., O'Connell, Julia E., O'Connell, Robert W., O'Connell, Ross, Ogando, Ricardo L. C., Olmstead, Matthew D., Oravetz, Audrey E., Oravetz, Daniel J., Osumi, Keisuke, Owen, Russell, Padgett, Deborah L., Padmanabhan, Nikhil, Paegert, Martin, Palanque-Delabrouille, Nathalie, Pan, Kaike, Parejko, John K., Park, Changbom, Pâris, Isabelle, Pattarakijwanich, Petchara, Pellejero-Ibanez, M., Pepper, Joshua, Percival, Will J., Pérez-Fournon, Ismael, Pérez-Ràfols, Ignasi, Petitjean, Patrick, Pieri, Matthew M., Pinsonneault, Marc H., de Mello, Gustavo F. Porto, Prada, Francisco, Prakash, Abhishek, Price-Whelan, Adrian M., Raddick, M. Jordan, Rahman, Mubdi, Reid, Beth A., Rich, James, Rix, Hans-Walter, Robin, Annie C., Rockosi, Constance M., Rodrigues, Thaíse S., Rodríguez-Rottes, Sergio, Roe, Natalie A., Ross, Ashley J., Ross, Nicholas P., Rossi, Graziano, Ruan, John J., Rubiño-Martín, J. A., Rykoff, Eli S., Salazar-Albornoz, Salvador, Salvato, Mara, Samushia, Lado, Sánchez, Ariel G., Santiago, Basílio, Sayres, Conor, Schiavon, Ricardo P., Schlegel, David J., Schmidt, Sarah J., Schneider, Donald P., Schultheis, Mathias, Schwope, Axel D., Scóccola, C. G., Sellgren, Kris, Seo, Hee-Jong, Shane, Neville, Shen, Yue, Shetrone, Matthew, Shu, Yiping, Sivarani, Thirupathi, Skrutskie, M. F., Slosar, Anže, Smith, Verne V., Sobreira, Flávia, Stassun, Keivan G., Steinmetz, Matthias, Strauss, Michael A., Streblyanska, Alina, Swanson, Molly E. C., Tan, Jonathan C., Tayar, Jamie, Terrien, Ryan C., Thakar, Aniruddha R., Thomas, Daniel, Thompson, Benjamin A., Tinker, Jeremy L., Tojeiro, Rita, Troup, Nicholas W., Vargas-Magaña, Mariana, Vazquez, Jose A., Verde, Licia, Viel, Matteo, Vogt, Nicole P., Wake, David A., Wang, Ji, Weaver, Benjamin A., Weinberg, David H., Weiner, Benjamin J., White, Martin, Wilson, John C., Wisniewski, John P., Wood-Vasey, W. M., Yèche, Christophe, York, Donald G., Zakamska, Nadia L., Zamora, O., Zasowski, Gail, Zehavi, Idit, Zhao, Gong-Bo, Zheng, Zheng, Zhou, Xu, Zhou, Zhimin, Zhu, Guangtun, and Zou, Hu
Abstract: The third generation of the Sloan Digital Sky Survey (SDSS-III) took data from 2008 to 2014 using the original SDSS wide-field imager, the original and an upgraded multi-object fiber-fed optical spectrograph, a new near-infrared high-resolution spectrograph, and a novel optical interferometer. All the data from SDSS-III are now made public. In particular, this paper describes Data Release 11 (DR11) including all data acquired through 2013 July, and Data Release 12 (DR12) adding data acquired through 2014 July (including all data included in previous data releases), marking the end of SDSS-III observing. Relative to our previous public release (DR10), DR12 adds one million new spectra of galaxies and quasars from the Baryon Oscillation Spectroscopic Survey (BOSS) over an additional 3000 sq. deg of sky, more than triples the number of H-band spectra of stars as part of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE), and includes repeated accurate radial velocity measurements of 5500 stars from the Multi-Object APO Radial Velocity Exoplanet Large-area Survey (MARVELS). The APOGEE outputs now include measured abundances of 15 different elements for each star. In total, SDSS-III added 2350 sq. deg of ugriz imaging; 155,520 spectra of 138,099 stars as part of the Sloan Exploration of Galactic Understanding and Evolution 2 (SEGUE-2) survey; 2,497,484 BOSS spectra of 1,372,737 galaxies, 294,512 quasars, and 247,216 stars over 9376 sq. deg; 618,080 APOGEE spectra of 156,593 stars; and 197,040 MARVELS spectra of 5,513 stars. Since its first light in 1998, SDSS has imaged over 1/3 of the Celestial sphere in five bands and obtained over five million astronomical spectra., Comment: DR12 data are available at http://www.sdss3.org/dr12. 30 pages. 11 figures. Accepted to ApJS
Published: 2015
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242. Abundances, Stellar Parameters, and Spectra From the SDSS-III/APOGEE Survey

Author: Holtzman, Jon A., Shetrone, Matthew, Johnson, Jennifer A., Prieto, Carlos Allende, Anders, Friedrich, Andrews, Brett, Beers, Timothy C., Bizyaev, Dmitry, Blanton, Michael R., Bovy, Jo, Carrera, Ricardo, Cunha, Katia, Eisenstein, Daniel J., Feuillet, Diane, Frinchaboy, Peter M., Galbraith-Frew, Jessica, Perez, Ana E. Garcia, Hernandez, D. Anibal Garcia, Hasselquist, Sten, Hayden, Michael R., Hearty, Fred R., Ivans, Inese, Majewski, Steven R., Martell, Sarah, Meszaros, Szabolcs, Muna, Demitri, Nidever, David L., Nguyen, Duy Cuong, O'Connell, Robert W., Pan, Kaike, Pinsonneault, Marc, Robin, Annie C., Schiavon, Ricardo P., Shane, Neville, Sobeck, Jennifer, Smith, Verne V., Troup, Nicholas, Weinberg, David H., Wilson, John C., Wood-Vasey, W. M., Zamora, Olga, Zasowski, Gail, Holtzman, Jon A., Shetrone, Matthew, Johnson, Jennifer A., Prieto, Carlos Allende, Anders, Friedrich, Andrews, Brett, Beers, Timothy C., Bizyaev, Dmitry, Blanton, Michael R., Bovy, Jo, Carrera, Ricardo, Cunha, Katia, Eisenstein, Daniel J., Feuillet, Diane, Frinchaboy, Peter M., Galbraith-Frew, Jessica, Perez, Ana E. Garcia, Hernandez, D. Anibal Garcia, Hasselquist, Sten, Hayden, Michael R., Hearty, Fred R., Ivans, Inese, Majewski, Steven R., Martell, Sarah, Meszaros, Szabolcs, Muna, Demitri, Nidever, David L., Nguyen, Duy Cuong, O'Connell, Robert W., Pan, Kaike, Pinsonneault, Marc, Robin, Annie C., Schiavon, Ricardo P., Shane, Neville, Sobeck, Jennifer, Smith, Verne V., Troup, Nicholas, Weinberg, David H., Wilson, John C., Wood-Vasey, W. M., Zamora, Olga, and Zasowski, Gail
Abstract: The SDSS-III/APOGEE survey operated from 2011-2014 using the APOGEE spectrograph, which collects high-resolution (R~22,500), near-IR (1.51-1.70 microns) spectra with a multiplexing (300 fiber-fed objects) capability. We describe the survey data products that are publicly available, which include catalogs with radial velocity, stellar parameters, and 15 elemental abundances for over 150,000 stars, as well as the more than 500,000 spectra from which these quantities are derived. Calibration relations for the stellar parameters (Teff, log g, [M/H], [alpha/M]) and abundances (C, N, O, Na, Mg, Al, Si, S, K, Ca, Ti, V, Mn, Fe, Ni) are presented and discussed. The internal scatter of the abundances within clusters indicates that abundance precision is generally between 0.05 and 0.09 dex across a broad temperature range; within more limited ranges and at high S/N, it is smaller for some elemental abundances. We assess the accuracy of the abundances using comparison of mean cluster metallicities with literature values, APOGEE observations of the solar spectrum and of Arcturus, comparison of individual star abundances with other measurements, and consideration of the locus of derived parameters and abundances of the entire sample, and find that it is challenging to determine the absolute abundance scale; external accuracy may be good to 0.1-0.2 dex. Uncertainties may be larger at cooler temperatures (Teff<4000K). Access to the public data release and data products is described, and some guidance for using the data products is provided., Comment: 29 pages, 18 figures, submitted to Astronomical Journal
Published: 2015
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243. Hydra II: a faint and compact Milky Way dwarf galaxy found in the Survey of the Magellanic Stellar History

Author: Martin, Nicolas F., Nidever, David L., Besla, Gurtina, Olsen, Knut, Walker, Alistair R., Vivas, A. Katherina, Gruendl, Robert A., Kaleida, Catherine C., Muñoz, Ricardo R., Blum, Robert D., Saha, Abhijit, Conn, Blair C., Bell, Eric F., Chu, You-Hua, Cioni, Maria-Rosa L., de Boer, Thomas J. L., Gallart, Carme, Jin, Shoko, Kunder, Andrea, Majewski, Steven R., Martinez-Delgado, David, Monachesi, Antonela, Monelli, Matteo, Monteagudo, Lara, Noël, Noelia E. D., Olszewski, Edward W., Stringfellow, Guy S., van der Marel, Roeland P., Zaritsky, Denis, Martin, Nicolas F., Nidever, David L., Besla, Gurtina, Olsen, Knut, Walker, Alistair R., Vivas, A. Katherina, Gruendl, Robert A., Kaleida, Catherine C., Muñoz, Ricardo R., Blum, Robert D., Saha, Abhijit, Conn, Blair C., Bell, Eric F., Chu, You-Hua, Cioni, Maria-Rosa L., de Boer, Thomas J. L., Gallart, Carme, Jin, Shoko, Kunder, Andrea, Majewski, Steven R., Martinez-Delgado, David, Monachesi, Antonela, Monelli, Matteo, Monteagudo, Lara, Noël, Noelia E. D., Olszewski, Edward W., Stringfellow, Guy S., van der Marel, Roeland P., and Zaritsky, Denis
Abstract: We present the discovery of a new dwarf galaxy, Hydra II, found serendipitously within the data from the ongoing Survey of the MAgellanic Stellar History (SMASH) conducted with the Dark Energy Camera on the Blanco 4m Telescope. The new satellite is compact (r_h = 68 +/- 11 pc) and faint (M_V = -4.8 +/- 0.3), but well within the realm of dwarf galaxies. The stellar distribution of HydraII in the color-magnitude diagram is well-described by a metal-poor ([Fe/H] = -2.2) and old (13 Gyr) isochrone and shows a distinct blue horizontal branch, some possible red clump stars, and faint stars that are suggestive of blue stragglers. At a heliocentric distance of 134 +/- 10 kpc, Hydra II is located in a region of the Galactic halo that models have suggested may host material from the leading arm of the Magellanic Stream. A comparison with N-body simulations hints that the new dwarf galaxy could be or could have been a satellite of the Magellanic Clouds., Comment: 7 pages, 4 figures. Accepted for publication in ApJL. v2: minor corrections, conclusions unchanged
Published: 2015
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244. Chemical Cartography with APOGEE: Metallicity Distribution Functions and the Chemical Structure of the Milky Way Disk

Author: Hayden, Michael R., Bovy, Jo, Holtzman, Jon A., Nidever, David L., Bird, Jonathan C., Weinberg, David H., Andrews, Brett H., Prieto, Carlos Allende, Anders, Friedrich, Beers, Timothy C., Bizyaev, Dmitry, Chiappini, Cristina, Cunha, Katia, Frinchaboy, Peter, García-Herńandez, Domingo A., Pérez, Ana E. García, Girardi, Léo, Harding, Paul, Hearty, Fred R., Johnson, Jennifer A., Majewski, Steven R., Mészáros, Szabolcs, Minchev, Ivan, O'Connell, Robert, Pan, Kaike, Robin, Annie C., Schiavon, Ricardo P., Schneider, Donald P., Schultheis, Mathias, Shetrone, Matthew, Skrutskie, Michael, Steinmetz, Matthias, Smith, Verne, Zamora, Olga, Zasowski, Gail, Hayden, Michael R., Bovy, Jo, Holtzman, Jon A., Nidever, David L., Bird, Jonathan C., Weinberg, David H., Andrews, Brett H., Prieto, Carlos Allende, Anders, Friedrich, Beers, Timothy C., Bizyaev, Dmitry, Chiappini, Cristina, Cunha, Katia, Frinchaboy, Peter, García-Herńandez, Domingo A., Pérez, Ana E. García, Girardi, Léo, Harding, Paul, Hearty, Fred R., Johnson, Jennifer A., Majewski, Steven R., Mészáros, Szabolcs, Minchev, Ivan, O'Connell, Robert, Pan, Kaike, Robin, Annie C., Schiavon, Ricardo P., Schneider, Donald P., Schultheis, Mathias, Shetrone, Matthew, Skrutskie, Michael, Steinmetz, Matthias, Smith, Verne, Zamora, Olga, and Zasowski, Gail
Abstract: Using a sample of 69,919 red giants from the SDSS-III/APOGEE Data Release 12, we measure the distribution of stars in the [$\alpha$/Fe] vs. [Fe/H] plane and the metallicity distribution functions (MDF) across an unprecedented volume of the Milky Way disk, with radius $311$ kpc. The peak of the midplane MDF shifts to lower metallicity at larger $R$, reflecting the Galactic metallicity gradient. Most strikingly, the shape of the midplane MDF changes systematically with radius, with a negatively skewed distribution at $31$ kpc or [$\alpha$/Fe]$>0.18$, the MDF shows little dependence on $R$. The positive skewness of the outer disk MDF may be a signature of radial migration; we show that blurring of stellar populations by orbital eccentricities is not enough to explain the reversal of MDF shape but a simple model of radial migration can do so., Comment: Submitted, 18 pages, 16 figures
Published: 2015
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245. The APOGEE Spectroscopic Survey of Kepler Planet Hosts: Feasibility, Efficiency, and First Results

Author: Fleming, Scott W., Mahadevan, Suvrath, Deshpande, Rohit, Bender, Chad F., Terrien, Ryan C., Marchwinski, Robert C., Wang, Ji, Roy, Arpita, Stassun, Keivan G., Prieto, Carlos Allende, Cunha, Katia, Smith, Verne V., Agol, Eric, Ak, Hasan, Bastien, Fabienne A., Bizyaev, Dmitry, Crepp, Justin R., Ford, Eric B., Frinchaboy, Peter M., García-Hernández, Domingo Aníbal, Pérez, Ana Elia García, Gaudi, B. Scott, Ge, Jian, Hearty, Fred, Ma, Bo, Majewski, Steve R., Mészáros, Szabolcs, Nidever, David L., Pan, Kaike, Pepper, Joshua, Pinsonneault, Marc H., Schiavon, Ricardo P., Schneider, Donald P., Wilson, John C., Zamora, Olga, Zasowski, Gail, Fleming, Scott W., Mahadevan, Suvrath, Deshpande, Rohit, Bender, Chad F., Terrien, Ryan C., Marchwinski, Robert C., Wang, Ji, Roy, Arpita, Stassun, Keivan G., Prieto, Carlos Allende, Cunha, Katia, Smith, Verne V., Agol, Eric, Ak, Hasan, Bastien, Fabienne A., Bizyaev, Dmitry, Crepp, Justin R., Ford, Eric B., Frinchaboy, Peter M., García-Hernández, Domingo Aníbal, Pérez, Ana Elia García, Gaudi, B. Scott, Ge, Jian, Hearty, Fred, Ma, Bo, Majewski, Steve R., Mészáros, Szabolcs, Nidever, David L., Pan, Kaike, Pepper, Joshua, Pinsonneault, Marc H., Schiavon, Ricardo P., Schneider, Donald P., Wilson, John C., Zamora, Olga, and Zasowski, Gail
Abstract: The Kepler mission has yielded a large number of planet candidates from among the Kepler Objects of Interest (KOIs), but spectroscopic follow-up of these relatively faint stars is a serious bottleneck in confirming and characterizing these systems. We present motivation and survey design for an ongoing project with the SDSS-III multiplexed APOGEE near-infrared spectrograph to monitor hundreds of KOI host stars. We report some of our first results using representative targets from our sample, which include current planet candidates that we find to be false positives, as well as candidates listed as false positives that we do not find to be spectroscopic binaries. With this survey, KOI hosts are observed over ~20 epochs at a radial velocity precision of 100-200 m/s. These observations can easily identify a majority of false positives caused by physically-associated stellar or substellar binaries, and in many cases, fully characterize their orbits. We demonstrate that APOGEE is capable of achieving RV precision at the 100-200 m/s level over long time baselines, and that APOGEE's multiplexing capability makes it substantially more efficient at identifying false positives due to binaries than other single-object spectrographs working to confirm KOIs as planets. These APOGEE RVs enable ancillary science projects, such as studies of fundamental stellar astrophysics or intrinsically rare substellar companions. The coadded APOGEE spectra can be used to derive stellar properties (T_eff, log(g)) and chemical abundances of over a dozen elements to probe correlations of planet properties with individual elemental abundances., Comment: Accepted in AJ, 17 pages, 13 figures, 4 tables
Published: 2015
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246. The Puzzling Li-rich Red Giant Associated with NGC 6819

Author: Carlberg, Joleen K., Smith, Verne V., Cunha, Katia, Majewski, Steven R., Meszaros, Szabolcs, Shetrone, Matthew, Prieto, Carlos Allende, Bizyaev, Dmitry, Stassun, Keivan G., Fleming, Scott W., Zasowski, Gail, Hearty, Fred, Nidever, David L., Schneider, Donald P., Holtzman, Jon A., Frinchaboy, Peter M., Carlberg, Joleen K., Smith, Verne V., Cunha, Katia, Majewski, Steven R., Meszaros, Szabolcs, Shetrone, Matthew, Prieto, Carlos Allende, Bizyaev, Dmitry, Stassun, Keivan G., Fleming, Scott W., Zasowski, Gail, Hearty, Fred, Nidever, David L., Schneider, Donald P., Holtzman, Jon A., and Frinchaboy, Peter M.
Abstract: A Li-rich red giant star (2M19411367+4003382) recently discovered in the direction of NGC 6819 belongs to the rare subset of Li-rich stars that have not yet evolved to the luminosity bump, an evolutionary stage where models predict Li can be replenished. The currently favored model to explain Li enhancement in first-ascent red giants like 2M19411367+4003382 requires deep mixing into the stellar interior. Testing this model requires a measurement of 12C/13C, which is possible to obtain from APOGEE spectra. However, the Li-rich star also has abnormal asteroseismic properties that call into question its membership in the cluster, even though its radial velocity and location on color-magnitude diagrams are consistent with membership. To address these puzzles, we have measured a wide array of abundances in the Li-rich star and three comparison stars using spectra taken as part of the APOGEE survey to determine the degree of stellar mixing, address the question of membership, and measure the surface gravity. We confirm that the Li-rich star is a red giant with the same overall chemistry as the other cluster giants. However, its log g is significantly lower, consistent with the asteroseismology results and suggestive of a very low mass if the star is indeed a cluster member. Regardless of the cluster membership, the 12C/13C and C/N ratios of the Li-rich star are consistent with standard first dredge-up, indicating that Li dilution has already occurred, and inconsistent with internal Li enrichment scenarios that require deep mixing., Comment: 11 pages, 7 figures, 3 tables. Accepted for publication in The Astrophysical Journal
Published: 2015
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247. Exploring Anticorrelations and Light Element Variations in Northern Globular Clusters Observed by the APOGEE Survey

Author: Meszaros, Szabolcs, Martell, Sarah L., Shetrone, Matthew, Lucatello, Sara, Troup, Nicholas W., Bovy, Jo, Cunha, Katia, Garcia-Hernandez, Domingo A., Overbeek, Jamie C., Prieto, Carlos Allende, Beers, Timothy C., Frinchaboy, Peter M., Perez, Ana E. Garcia, Hearty, Fred R., Holtzman, Jon, Majewski, Steven R., Nidever, David L., Schiavon, Ricardo P., Schneider, Donald P., Sobeck, Jennifer S., Smith, Verne V., Zamora, Olga, Zasowski, Gail, Meszaros, Szabolcs, Martell, Sarah L., Shetrone, Matthew, Lucatello, Sara, Troup, Nicholas W., Bovy, Jo, Cunha, Katia, Garcia-Hernandez, Domingo A., Overbeek, Jamie C., Prieto, Carlos Allende, Beers, Timothy C., Frinchaboy, Peter M., Perez, Ana E. Garcia, Hearty, Fred R., Holtzman, Jon, Majewski, Steven R., Nidever, David L., Schiavon, Ricardo P., Schneider, Donald P., Sobeck, Jennifer S., Smith, Verne V., Zamora, Olga, and Zasowski, Gail
Abstract: We investigate the light-element behavior of red giant stars in Northern globular clusters (GCs) observed by the SDSS-III Apache Point Observatory Galactic Evolution Experiment (APOGEE). We derive abundances of nine elements (Fe, C, N, O, Mg, Al, Si, Ca, and Ti) for 428 red giant stars in 10 globular clusters. The intrinsic abundance range relative to measurement errors is examined, and the well-known C-N and Mg-Al anticorrelations are explored using an extreme-deconvolution code for the first time in a consistent way. We find that Mg and Al drive the population membership in most clusters, except in M107 and M71, the two most metal-rich clusters in our study, where the grouping is most sensitive to N. We also find a diversity in the abundance distributions, with some clusters exhibiting clear abundance bimodalities (for example M3 and M53) while others show extended distributions. The spread of Al abundances increases significantly as cluster average metallicity decreases as previously found by other works, which we take as evidence that low metallicity, intermediate mass AGB polluters were more common in the more metal poor clusters. The statistically significant correlation of [Al/Fe] with [Si/Fe] in M15 suggests that $^{28}$Si leakage has occurred in this cluster. We also present C, N and O abundances for stars cooler than 4500 K and examine the behavior of A(C+N+O) in each cluster as a function of temperature and [Al/Fe]. The scatter of A(C+N+O) is close to its estimated uncertainty in all clusters and independent on stellar temperature. A(C+N+O) exhibits small correlations and anticorrelations with [Al/Fe] in M3 and M13, but we cannot be certain about these relations given the size of our abundance uncertainties. Star-to-star variations of $\alpha-$elements (Si, Ca, Ti) abundances are comparable to our estimated errors in all clusters., Comment: 22 pages, 13 figures, 8 tables, accepted to AJ, fixed some typos in text
Published: 2015
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248. The Data Reduction Pipeline for the Apache Point Observatory Galactic Evolution Experiment

Author: Nidever, David L., Holtzman, Jon A., Prieto, Carlos Allende, Beland, Stephane, Bender, Chad, Bizyaev, Dmitry, Burton, Adam, Desphande, Rohit, Fleming, Scott W., Perez, Ana Elia Garcia, Hearty, Fred R., Majewski, Steven R., Meszaros, Szabolcs, Muna, Demitri, Nguyen, Duy, Schiavon, Ricardo P., Shetrone, Matthew, Skrutskie, Michael F., Sobeck, Jennifer S., Wilson, John C., Nidever, David L., Holtzman, Jon A., Prieto, Carlos Allende, Beland, Stephane, Bender, Chad, Bizyaev, Dmitry, Burton, Adam, Desphande, Rohit, Fleming, Scott W., Perez, Ana Elia Garcia, Hearty, Fred R., Majewski, Steven R., Meszaros, Szabolcs, Muna, Demitri, Nguyen, Duy, Schiavon, Ricardo P., Shetrone, Matthew, Skrutskie, Michael F., Sobeck, Jennifer S., and Wilson, John C.
Abstract: The Apache Point Observatory Galactic Evolution Experiment (APOGEE), part of the Sloan Digital Sky Survey III, explores the stellar populations of the Milky Way using the Sloan 2.5-m telescope linked to a high resolution (R~22,500), near-infrared (1.51-1.70 microns) spectrograph with 300 optical fibers. For over 150,000 predominantly red giant branch stars that APOGEE targeted across the Galactic bulge, disks and halo, the collected high S/N (>100 per half-resolution element) spectra provide accurate (~0.1 km/s) radial velocities, stellar atmospheric parameters, and precise (~0.1 dex) chemical abundances for about 15 chemical species. Here we describe the basic APOGEE data reduction software that reduces multiple 3D raw data cubes into calibrated, well-sampled, combined 1D spectra, as implemented for the SDSS-III/APOGEE data releases (DR10, DR11 and DR12). The processing of the near-IR spectral data of APOGEE presents some challenges for reduction, including automated sky subtraction and telluric correction over a 3 degree diameter field and the combination of spectrally dithered spectra. We also discuss areas for future improvement., Comment: 22 pages, 26 figures. Accepted for publication in AJ
Published: 2015
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249. HYDRA II: A FAINT AND COMPACT MILKY WAY DWARF GALAXY FOUND IN THE SURVEY OF THE MAGELLANIC STELLAR HISTORY

Author: Martin, Nicolas F, Nidever, David L., Besla, Gurtina, Olsen, Knut A. G., Walker, Alistair R, Vivas, Anna Katherina, Gruendl, R.A, Kaleida, Catherine C., Mũñoz, Ricardo R., Blum, Robert D., Conn, Blair, Martin, Nicolas F, Nidever, David L., Besla, Gurtina, Olsen, Knut A. G., Walker, Alistair R, Vivas, Anna Katherina, Gruendl, R.A, Kaleida, Catherine C., Mũñoz, Ricardo R., Blum, Robert D., and Conn, Blair
Abstract: We present the discovery of a new dwarf galaxy, Hydra II, found serendipitously within the data from the ongoing Survey of the Magellanic Stellar History conducted with the Dark Energy Camera on the Blanco 4 m Telescope. The new satellite is compact (rh = 68 ± 11 pc) and faint (MV = -4.8 ± 0.3), but well within the realm of dwarf galaxies. The stellar distribution of Hydra II in the color-magnitude diagram is well-described by a metal-poor ([Fe/H] = -2.2) and old (13 Gyr) isochrone and shows a distinct blue horizontal branch, some possible red clump stars, and faint stars that are suggestive of blue stragglers. At a heliocentric distance of 134 ± 10 kpc, Hydra II is located in a region of the Galactic halo that models have suggested may host material from the leading arm of the Magellanic Stream. A comparison with N-body simulations hints that the new dwarf galaxy could be or could have been a satellite of the Magellanic Clouds
Published: 2015

250. THE DATA REDUCTION PIPELINE FOR THE APACHE POINT OBSERVATORY GALACTIC EVOLUTION EXPERIMENT

Author: Nidever, David L., primary, Holtzman, Jon A., additional, Prieto, Carlos Allende, additional, Beland, Stephane, additional, Bender, Chad, additional, Bizyaev, Dmitry, additional, Burton, Adam, additional, Desphande, Rohit, additional, Fleming, Scott W., additional, García Pérez, Ana E., additional, Hearty, Fred R., additional, Majewski, Steven R., additional, Mészáros, Szabolcs, additional, Muna, Demitri, additional, Nguyen, Duy, additional, Schiavon, Ricardo P., additional, Shetrone, Matthew, additional, Skrutskie, Michael F., additional, Sobeck, Jennifer S., additional, and Wilson, John C., additional
Published: 2015
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