4 results on '"Hunter, DA"'
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2. A Study of Two Dwarf Irregular Galaxies with Asymmetrical Star Formation Distributions
- Author
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Stacey N. Bright, Robert C. Kennicutt, Angela Adamo, David O. Cook, Deidre A. Hunter, Bruce G. Elmegreen, Michele Fumagalli, Elena Sabbi, Matteo Messa, Lauren Kahre, J. E. Ryon, Elena Sacchi, L. Ubeda, John S. Gallagher, Se-Heon Oh, Hong-Xin Zhang, Eva K. Grebel, Monica Tosi, Daniel A. Dale, Hwihyun Kim, Kathryn Grasha, Dimitrios A. Gouliermis, Samavarti Gallardo, Michele Cignoni, Daniela Calzetti, Janice C. Lee, Hunter, D, Gallardo, S, Zhang, H, Adamo, A, Cook, D, Oh, S, Elmegreen, B, Kim, H, Kahre, L, Ubeda, L, Bright, S, Ryon, J, Fumagalli, M, Sacchi, E, Kennicutt, R, Tosi, M, Dale, D, Cignoni, M, Messa, M, Grebel, E, Gouliermis, D, Sabbi, E, Grasha, K, Gallagher, J, Calzetti, D, Lee, J, Hunter, DA [0000-0002-3322-9798], Adamo, A [0000-0002-8192-8091], Cook, DO [0000-0002-6877-7655], Oh, SH [0000-0002-5648-9920], Elmegreen, BG [0000-0002-1723-6330], Kim, H [0000-0003-4770-688X], Kahre, L [0000-0002-2037-3096], Fumagalli, M [0000-0001-6676-3842], Sacchi, E [0000-0001-5618-0109], Tosi, M [0000-0002-0986-4759], Dale, DA [0000-0002-5782-9093], Cignoni, M [0000-0001-6291-6813], Grebel, EK [0000-0002-1891-3794], Gouliermis, DA [0000-0002-2763-0075], Sabbi, E [0000-0003-2954-7643], Grasha, K [0000-0002-3247-5321], Gallagher, JS [0000-0001-8608-0408], Calzetti, D [0000-0002-5189-8004], Lee, JC [0000-0002-2278-9407], and Apollo - University of Cambridge Repository
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010504 meteorology & atmospheric sciences ,FOS: Physical sciences ,galaxies: individual (DDO 187, NGC 3738) ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Rotation ,01 natural sciences ,0103 physical sciences ,Dispersion (optics) ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,0105 earth and related environmental sciences ,Physics ,NGC 3738) ,Star formation ,Astronomy and Astrophysics ,galaxies: dwarf ,galaxies: individual (DDO 187 ,Astrophysics - Astrophysics of Galaxies ,Galaxy ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,galaxies: star formation ,Irregular galaxy - Abstract
Two dwarf irregular galaxies DDO 187 and NGC 3738 exhibit a striking pattern of star formation: intense star formation is taking place in a large region occupying roughly half of the inner part of the optical galaxy. We use data on the HI distribution and kinematics and stellar images and colors to examine the properties of the environment in the high star formation rate (HSF) halves of the galaxies in comparison with the low star formation rate (LSF) halves. We find that the pressure and gas density are higher on the HSF sides by 30-70%. In addition we find in both galaxies that the HI velocity fields exhibit significant deviations from ordered rotation and there are large regions of high velocity dispersion and multiple velocity components in the gas beyond the inner regions of the galaxies. The conditions in the HSF regions are likely the result of large-scale external processes affecting the internal environment of the galaxies and enabling the current star formation there., Comment: In press in ApJ
- Published
- 2018
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3. The Resolved Stellar Populations in the LEGUS Galaxies1
- Author
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D. M. Elmegreen, Elena Sabbi, A. Dolphin, Geoffrey C. Clayton, Eva K. Grebel, Linda J. Smith, T. M. Brown, G. Ashworth, R. Walterbos, Matteo Messa, Lauren Kahre, J. Prieto, Alessandra Aloisi, Rupali Chandar, C. D. Martin, Mark R. Krumholz, M. W. Regan, Daniel A. Dale, Bruce G. Elmegreen, Hwihyun Kim, Kathryn Grasha, Elena Sacchi, F. Shabani, A. Herrero, R. C. Kennicutt, David O. Cook, J. E. Ryon, A. Nota, B. C. Whitmore, L. Ubeda, D. Schaerer, D. Schiminovich, Jennifer E. Andrews, J. C. Lee, Stacey N. Bright, Dimitrios A. Gouliermis, John S. Gallagher, D. J. Lennon, Michele Fumagalli, Daniela Calzetti, Kelsey E. Johnson, Michele Cignoni, S. D. Van Dyk, C. Christian, P. Nair, Clare Dobbs, Aaron S. Evans, Monica Tosi, G. Ostlin, Anne Pellerin, Deidre A. Hunter, David A. Thilker, Angela Adamo, S. E. de Mink, Aida Wofford, Sabbi, E, Calzetti, D, Ubeda, L, Adamo, A, Cignoni, M, Thilker, D, Aloisi, A, Elmegreen, B, Elmegreen, D, Gouliermis, D, Grebel, E, Messa, M, Smith, L, Tosi, M, Dolphin, A, Andrews, J, Ashworth, G, Bright, S, Brown, T, Chandar, R, Christian, C, Clayton, G, Cook, D, Dale, D, De Mink, S, Dobbs, C, Evans, A, Fumagalli, M, Gallagher, J, Grasha, K, Herrero, A, Hunter, D, Johnson, K, Kahre, L, Kennicutt, R, Kim, H, Krumholz, M, Lee, J, Lennon, D, Martin, C, Nair, P, Nota, A, Ostlin, G, Pellerin, A, Prieto, J, Regan, M, Ryon, J, Sacchi, E, Schaerer, D, Schiminovich, D, Shabani, F, Van Dyk, S, Walterbos, R, Whitmore, B, Wofford, A, Sabbi, E [0000-0003-2954-7643], Calzetti, D [0000-0002-5189-8004], Adamo, A [0000-0002-8192-8091], Cignoni, M [0000-0001-6291-6813], Thilker, D [0000-0002-8528-7340], Aloisi, A [0000-0003-4137-882X], Elmegreen, BG [0000-0002-1723-6330], Elmegreen, DM [0000-0002-1392-3520], Gouliermis, DA [0000-0002-2763-0075], Grebel, EK [0000-0002-1891-3794], Smith, LJ [0000-0002-0806-168X], Tosi, M [0000-0002-0986-4759], Dolphin, A [0000-0001-8416-4093], Chandar, R [0000-0003-0085-4623], Clayton, GC [0000-0002-0141-7436], Dale, DA [0000-0002-5782-9093], Grasha, K [0000-0002-3247-5321], Hunter, DA [0000-0002-3322-9798], Johnson, KE [0000-0001-8348-2671], Kahre, L [0000-0002-2037-3096], Pellerin, A [0000-0003-1887-1966], Prieto, J [0000-0003-0943-0026], Sacchi, E [0000-0001-5618-0109], Schaerer, D [0000-0001-7144-7182], Shabani, F [0000-0002-5266-1260], Walterbos, R [0000-0002-0782-3064], Apollo - University of Cambridge Repository, and Low Energy Astrophysics (API, FNWI)
- Subjects
Hertzsprung–Russell diagram ,Russell and C-M diagram ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Advanced Camera for Surveys ,symbols.namesake ,galaxies: star clusters: general ,galaxies: star formation ,galaxies: stellar content ,Hertzsprung ,Russell and C-M diagrams ,stars: formation ,Astronomy and Astrophysics ,Space and Planetary Science ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,Physics ,010308 nuclear & particles physics ,Star formation ,Galaxy ,Red-giant branch ,Stars ,Star cluster ,symbols ,Hertzsprung-Russell and C-M diagrams ,Astrophysics::Earth and Planetary Astrophysics ,Wide Field Camera 3 - Abstract
The Legacy ExtraGalactic UV Survey (LEGUS) is a multiwavelength Cycle 21 Treasury program on the Hubble Space Telescope. It studied 50 nearby star-forming galaxies in 5 bands from the near-UV to the I-band, combining new Wide Field Camera 3 observations with archival Advanced Camera for Surveys data. LEGUS was designed to investigate how star formation occurs and develops on both small and large scales, and how it relates to the galactic environments. In this paper we present the photometric catalogs for all the apparently single stars identified in the 50 LEGUS galaxies. Photometric catalogs and mosaicked images for all filters are available for download. We present optical and near-UV color-magnitude diagrams for all the galaxies. For each galaxy we derived the distance from the tip of the red giant branch. We then used the NUV color-magnitude diagrams to identify stars more massive than 14 M ☉, and compared their number with the number of massive stars expected from the GALEX FUV luminosity. Our analysis shows that the fraction of massive stars forming in star clusters and stellar associations is about constant with the star formation rate. This lack of a relation suggests that the timescale for evaporation of unbound structures is comparable or longer than 10 Myr. At low star formation rates this translates to an excess of mass in clustered environments as compared to model predictions of cluster evolution, suggesting that a significant fraction of stars form in unbound systems. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555.
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- 2018
4. Extinction Maps and Dust-to-gas Ratios in Nearby Galaxies with LEGUS
- Author
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Leonardo Ubeda, Aaron S. Evans, Debra Meloy Elmegreen, Brad Whitmore, Daniel A. Dale, Janice C. Lee, Rene A. M. Walterbos, Carol Christian, Linda J. Smith, Rupali Chandar, Hwihyun Kim, R. C. Kennicutt, F. Shabani, Kathryn Grasha, Clare Dobbs, Dimitrios A. Gouliermis, Jennifer E. Andrews, Bruce G. Elmegreen, Alessandra Aloisi, Daniela Calzetti, J. E. Ryon, Michele Cignoni, Aida Wofford, Deidre A. Hunter, Michele Fumagalli, S. E. de Mink, John S. Gallagher, Elena Sabbi, David A. Thilker, Stacey N. Bright, Daniel Schaerer, S. D. Van Dyk, Preethi Nair, Kelsey E. Johnson, Matteo Messa, Antonella Nota, A. Herrero, Mark R. Krumholz, Elena Sacchi, Thomas M. Brown, Angela Adamo, L. Kahre, G. Ashworth, Eva K. Grebel, Monica Tosi, David O. Cook, Anne Pellerin, Low Energy Astrophysics (API, FNWI), Kahre, L [0000-0002-2037-3096], Walterbos, RA [0000-0002-0782-3064], Kim, H [0000-0003-4770-688X], Thilker, D [0000-0002-8528-7340], Calzetti, D [0000-0002-5189-8004], Lee, JC [0000-0002-2278-9407], Sabbi, E [0000-0003-2954-7643], Aloisi, A [0000-0003-4137-882X], Cignoni, M [0000-0001-6291-6813], Cook, DO [0000-0002-6877-7655], Dale, DA [0000-0002-5782-9093], Elmegreen, BG [0000-0002-1723-6330], Elmegreen, DM [0000-0002-1392-3520], Fumagalli, M [0000-0001-6676-3842], Gallagher, JS [0000-0001-8608-0408], Gouliermis, DA [0000-0002-2763-0075], Grasha, K [0000-0002-3247-5321], Grebel, EK [0000-0002-1891-3794], Hunter, DA [0000-0002-3322-9798], Sacchi, E [0000-0001-5618-0109], Smith, LJ [0000-0002-0806-168X], Tosi, M [0000-0002-0986-4759], Adamo, A [0000-0002-8192-8091], Brown, TM [0000-0002-1793-9968], Chandar, R [0000-0003-0085-4623], Christian, C [0000-0002-2179-3308], De Mink, SE [0000-0001-9336-2825], Herrero, A [0000-0001-8768-2179], Johnson, KE [0000-0001-8348-2671], Krumholz, MR [0000-0003-3893-854X], Pellerin, A [0000-0003-1887-1966], Schaerer, D [0000-0001-7144-7182], Shabani, F [0000-0002-5266-1260], Van Dyk, SD [0000-0001-9038-9950], Apollo - University of Cambridge Repository, Kahre, L, Walterbos, R, Kim, H, Thilker, D, Calzetti, D, Lee, J, Sabbi, E, Ubeda, L, Aloisi, A, Cignoni, M, Cook, D, Dale, D, Elmegreen, B, Elmegreen, D, Fumagalli, M, Gallagher, J, Gouliermis, D, Grasha, K, Grebel, E, Hunter, D, Sacchi, E, Smith, L, Tosi, M, Adamo, A, Andrews, J, Ashworth, G, Bright, S, Brown, T, Chandar, R, Christian, C, De Mink, S, Dobbs, C, Evans, A, Herrero, A, Johnson, K, Kennicutt, R, Krumholz, M, Messa, M, Nair, P, Nota, A, Pellerin, A, Ryon, J, Schaerer, D, Shabani, F, Van Dyk, S, Whitmore, B, and Wofford, A
- Subjects
galaxies: spiral ,Metallicity ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Power law ,Hubble space telescope ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,ISM: general ,Physics ,Extinction ,010308 nuclear & particles physics ,extinction ,Astronomy and Astrophysics ,HERA ,galaxies: dwarf ,Astrophysics - Astrophysics of Galaxies ,Galaxy ,Stars ,dust ,galaxies: ISM ,galaxies: photometry ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,Spectral energy distribution ,dust, extinction ,Astrophysics::Earth and Planetary Astrophysics - Abstract
We present a study of the dust-to-gas ratios in five nearby galaxies NGC 628 (M74), NGC 6503, NGC 7793, UGC 5139 (Holmberg I), and UGC 4305 (Holmberg II). Using Hubble Space Telescope broad band WFC3/UVIS UV and optical images from the Treasury program LEGUS (Legacy ExtraGalactic UV Survey) combined with archival HST/ACS data, we correct thousands of individual stars for extinction across these five galaxies using an isochrone-matching (reddening-free Q) method. We generate extinction maps for each galaxy from the individual stellar extinctions using both adaptive and fixed resolution techniques, and correlate these maps with neutral HI and CO gas maps from literature, including The HI Nearby Galaxy Survey (THINGS) and the HERA CO-Line Extragalactic Survey (HERACLES). We calculate dust-to-gas ratios and investigate variations in the dust-to-gas ratio with galaxy metallicity. We find a power law relationship between dust-to-gas ratio and metallicity, consistent with other studies of dust-to-gas ratio compared to metallicity. We find a change in the relation when H$_2$ is not included. This implies that underestimation of $N_{H_2}$ in low-metallicity dwarfs from a too-low CO-to-H$_2$ conversion factor $X_{CO}$ could have produced too low a slope in the derived relationship between dust-to-gas ratio and metallicity. We also compare our extinctions to those derived from fitting the spectral energy distribution (SED) using the Bayesian Extinction and Stellar Tool (BEAST) for NGC 7793 and find systematically lower extinctions from SED-fitting as compared to isochrone matching., Comment: 22 pages, 14 figures, accepted by ApJ
- Published
- 2018
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