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51. Approaching hell’s kitchen: Molecular daredevil clouds in the vicinity of Sagittarius A*

Author

Moser, Lydia, primary, Sánchez-Monge, Álvaro, additional, Eckart, Andreas, additional, Requena-Torres, Miguel A., additional, García-Marin, Macarena, additional, Kunneriath, Devaky, additional, Zensus, Anton, additional, Britzen, Silke, additional, Sabha, Nadeen, additional, Shahzamanian, Banafsheh, additional, Borkar, Abhijeet, additional, and Fischer, Sebastian, additional

Published
2017
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52. Approaching hell's kitchen: Molecular daredevil clouds in the vicinity of Sagittarius A*

Author

Moser, Lydia, Sanchez-Monge, Alvaro, Eckart, Andreas, Requena-Torres, Miguel A., Garcia-Marin, Macarena, Kunneriath, Devaky, Zensus, Anton, Britzen, Silke, Sabha, Nadeen, Shahzamanian, Banafsheh, Borkar, Abhijeet, Fischer, Sebastian, Moser, Lydia, Sanchez-Monge, Alvaro, Eckart, Andreas, Requena-Torres, Miguel A., Garcia-Marin, Macarena, Kunneriath, Devaky, Zensus, Anton, Britzen, Silke, Sabha, Nadeen, Shahzamanian, Banafsheh, Borkar, Abhijeet, and Fischer, Sebastian

Abstract

We report serendipitous detections of line emission with the Atacama Large Millimeter/submillimeter Array (ALMA) in bands 3, 6, and 7 in the central parsec down to within 100 around Sgr A* at an up to now highest resolution (< 0.5) view of the Galactic center (GC) in the submillimeter (sub-mm) domain. From the 100 GHz continuum and the H39 alpha emission we obtain a uniform electron temperature around T-e similar to 6000 K for the minispiral. The spectral index (S alpha nu(alpha)) of Sagittarius A* (Sgr A*) is similar to 0.5 at 100-250 GHz and similar to 0.0 at 230-340 GHz. The bright sources in the center show spectral indices around -0.1 implying Bremsstrahlung emission, while dust emission is emerging in the minispiral exterior. Apart from CS, which is most widespread in the center, H13CO+, HC3N, SiO, SO, C2H, CH3OH, (CS)-C-13 and N2H+ are also detected. The bulk of the clumpy emission regions is at positive velocities and in a region confined by the minispiral northern arm (NA), bar, and the sources IRS 3 and 7. Although partly spatially overlapping with the radio recombination line (RRL) emission at same negative velocities, the relation to the minispiral remains unclear. A likely explanation is an infalling clump consisting of denser cloud cores embedded in diffuse gas. This central association (CA) of clouds shows three times higher CS/X (X: any other observed molecule) ratios than the circumnuclear disk (CND) suggesting a combination of higher excitation, by a temperature gradient and/or infrared (IR) pumping, and abundance enhancement due to UV and/or X-ray emission. Hence, we conclude that this CA is closer to the center than the CND is to the center. Moreover, we find molecular line emission at velocities up to 200 km s(-1). Apart from the CA, we identified two intriguing regions in the CND. One region shows emission in all molecular species and higher energy levels tested in this and previous observations and contains a methanol class I maser. The other

Published
2017

53. 230 GHz VLBI observations of M87: event-horizon-scale structure at the enhanced very-high-energy $\rm ��$-ray state in 2012

Author

Akiyama, Kazunori, Lu, Ru-Sen, Fish, Vincent L., Doeleman, Sheperd S., Broderick, Avery E., Dexter, Jason, Hada, Kazuhiro, Kino, Motoki, Nagai, Hiroshi, Honma, Mareki, Johnson, Michael D., Algaba, Juan C., Asada, Keiichi, Brinkerink, Christiaan, Blundell, Ray, Bower, Geoffrey C., Cappallo, Roger, Crew, Geoffrey B., Dexter, Matt, Dzib, Sergio A., Freund, Robert, Friberg, Per, Gurwell, Mark, Ho, Paul T. P., Inoue, Makoto, Krichbaum, Thomas P., Loinard, Laurent, MacMahon, David, Marrone, Daniel P., Moran, James M., Nakamura, Masanori, Nagar, Neil M., Ortiz-Leon, Gisela, Plambeck, Richard, Pradel, Nicolas, Primiani, Rurik A., Rogers, Alan E. E., Roy, Alan L., SooHoo, Jason, Tavares, Jonathan-Le��n, Tilanus, Remo P. J., Titus, Michael, Wagner, Jan, Weintroub, Jonathan, Yamaguchi, Paul, Young, Ken H., Zensus, Anton, and Ziurys, Lucy M.

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::High Energy Astrophysical Phenomena, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We report on 230 GHz (1.3 mm) VLBI observations of M87 with the Event Horizon Telescope using antennas on Mauna Kea in Hawaii, Mt. Graham in Arizona and Cedar Flat in California. For the first time, we have acquired 230 GHz VLBI interferometric phase information on M87 through measurement of closure phase on the triangle of long baselines. Most of the measured closure phases are consistent with 0$^{\circ}$ as expected by physically-motivated models for 230 GHz structure such as jet models and accretion disk models. The brightness temperature of the event-horizon-scale structure is $\sim 1 \times 10^{10}$ K derived from the compact flux density of $\sim 1$ Jy and the angular size of $\sim 40 $ $\rm ��$as $\sim$ 5.5 $R_{\rm s}$, which is broadly consistent with the peak brightness of the radio cores at 1-86 GHz located within $\sim 10^2$ $R_{\rm s}$. Our observations occurred in the middle of an enhancement in very-high-energy (VHE) $\rm ��$-ray flux, presumably originating in the vicinity of the central black hole. Our measurements, combined with results of multi-wavelength observations, favor a scenario in which the VHE region has an extended size of $\sim$20-60 $R_{\rm s}$., 11 pages, 4 figures, accepted to ApJ

Published
2015
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56. Molecular gas in the immediate vicinity of Sgr A* seen with ALMA

Author

Moser, Lydia, primary, Sánchez-Monge, Álvaro, additional, Eckart, Andreas, additional, Requena-Torres, Miguel A., additional, García-Marin, Macarena, additional, Kunneriath, Devaky, additional, Zensus, Anton, additional, Britzen, Silke, additional, Sabha, Nadeen, additional, Shahzamanian, Banafsheh, additional, Borkar, Abhijeet, additional, and Fischer, Sebastian, additional

Published
2016
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57. The Center of the Milky Way from Radio to X-rays

Author

Eckart, Andreas, primary, Valencia-S., Monica, additional, Shahzamanian, Banafsheh, additional, Garcia-Marin, M., additional, Peissker, Florian, additional, Zajacek, Michal, additional, Parsa, Marzieh, additional, Jalali, Behrang, additional, Saalfeld, Rebecca, additional, Sabha, Nadeen, additional, Yazici, Senol, additional, Karssen, Grischa, additional, Borkar, Abhijeet, additional, Markakis, Kostas, additional, Zensus, Anton, additional, and Straubmeier, Christian, additional

Published
2016
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58. The latest results from the Global mm-VLBI Array

Author

Hodgson, Jeffrey A., primary, Krichbaum, T. P., additional, Marscher, Alan, additional, Jorstad, Svetlana G., additional, Marti-Vidal, Ivan, additional, Bremer, Michael, additional, Lindqvist, Michael, additional, de Vicente, Pablo, additional, and Zensus, Anton, additional

Published
2016
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59. 230 GHz VLBI OBSERVATIONS OF M87: EVENT‐HORIZON‐SCALE STRUCTURE DURING AN ENHANCED VERY‐HIGH‐ENERGY $\gamma $‐RAY STATE IN 2012

Author

Akiyama, Kazunori, primary, Lu, Ru-Sen, additional, Fish, Vincent L., additional, Doeleman, Sheperd S., additional, Broderick, Avery E., additional, Dexter, Jason, additional, Hada, Kazuhiro, additional, Kino, Motoki, additional, Nagai, Hiroshi, additional, Honma, Mareki, additional, Johnson, Michael D., additional, Algaba, Juan C., additional, Asada, Keiichi, additional, Brinkerink, Christiaan, additional, Blundell, Ray, additional, Bower, Geoffrey C., additional, Cappallo, Roger, additional, Crew, Geoffrey B., additional, Dexter, Matt, additional, Dzib, Sergio A., additional, Freund, Robert, additional, Friberg, Per, additional, Gurwell, Mark, additional, Ho, Paul T. P., additional, Inoue, Makoto, additional, Krichbaum, Thomas P., additional, Loinard, Laurent, additional, MacMahon, David, additional, Marrone, Daniel P., additional, Moran, James M., additional, Nakamura, Masanori, additional, Nagar, Neil M., additional, Ortiz-Leon, Gisela, additional, Plambeck, Richard, additional, Pradel, Nicolas, additional, Primiani, Rurik A., additional, Rogers, Alan E. E., additional, Roy, Alan L., additional, SooHoo, Jason, additional, Tavares, Jonathan-León, additional, Tilanus, Remo P. J., additional, Titus, Michael, additional, Wagner, Jan, additional, Weintroub, Jonathan, additional, Yamaguchi, Paul, additional, Young, Ken H., additional, Zensus, Anton, additional, and Ziurys, Lucy M., additional

Published
2015
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60. Very Long Baseline Interferometry with the SKA

Author

Paragi, Zsolt, primary, Godfrey, Leith, additional, Reynolds, Cormac, additional, Rioja, Maria J., additional, Deller, Adam, additional, Zhang, Bo, additional, Gurvits, Leonid, additional, Bietenholz, Michael, additional, Szomoru, Arpad, additional, Bignall, Hayley E., additional, Boven, Paul, additional, Charlot, Patrick, additional, Dodson, Richard, additional, Frey, Sandor, additional, Garrett, Michael, additional, Imai, Hiroshi, additional, Lobanov, Andrei, additional, Reid, Mark J., additional, Ros, Eduardo, additional, van Langevelde, Huib Jan, additional, Zensus, Anton, additional, Zheng, Xing Wu, additional, Alberdi, Antxon, additional, Agudo, Ivan, additional, An, Tao, additional, Argo, Megan, additional, Beswick, Rob J., additional, Biggs, Andy, additional, Brunthaler, Andreas, additional, Campbell, Robert M., additional, Cimò, Giuseppe, additional, Colomer, Francisco, additional, Corbel, Stephane, additional, Conway, John E., additional, Cseh, David, additional, Deane, Roger, additional, Falcke, Heino, additional, Gawronski, Marcin, additional, Gaylard, Michael, additional, Giovannini, Gabriele, additional, Giroletti, Marcello, additional, Goddi, Ciriaco, additional, Goedhart, Sharmilla, additional, Gómez, José L., additional, Gunn, Alastair, additional, Kharb, Preeti, additional, Kloeckner, Hans Rainer, additional, Koerding, Elmar, additional, Kovalev, Yuri Y., additional, Kunert-Bajraszewska, Magdalena, additional, Lindqvist, Michael, additional, Lister, Matt L., additional, Mantovani, Franco, additional, Marti-Vidal, Ivan, additional, Mezcua, Mar, additional, McKean, John, additional, Middelberg, Enno, additional, Miller-Jones, James C.A., additional, Moldón, Javier, additional, Muxlow, Tom W.B., additional, O'Brien, Tim, additional, Perez-Torres, Miguel, additional, Pogrebenko, S. V., additional, Quick, Jonathan, additional, Rushton, Anthony, additional, Schilizzi, Richard, additional, Smirnov, Oleg, additional, Sohn, Bong Won, additional, Surcis, Gabriele, additional, Taylor, Greg B., additional, Tingay, Steven, additional, Tudose, Valeriu M., additional, van der Horst, Alexander, additional, van Leeuwen, Joeri, additional, Venturi, Tiziana, additional, Vermeulen, Rene C., additional, Vlemmings, Wouter H.T., additional, de Witt, Alet, additional, Wucknitz, Olaf, additional, Yang, Jun, additional, Gabányi, Krisztina E., additional, and Jung, Tae Hyun, additional

Published
2015
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61. Localizing the gamma rays from blazar PKS 1502+106

Author

Karamanavis, Vassilis, primary, Fuhrmann, L., additional, Krichbaum, T. P., additional, Angelakis, E., additional, Hodgson, Jeffrey A., additional, Myserlis, Ioannis, additional, Nestoras, Ioannis, additional, Zensus, Anton, additional, Ungerechts, Hans, additional, and Sievers, A., additional

Published
2015
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66. 5 year Global 3-mm VLBI survey of Gamma-ray active blazars

Author

Hodgson, Jeffrey A., primary, Krichbaum, T. P., additional, Marscher, Alan, additional, Jorstad, Svetlana G., additional, Marti-Vidal, I., additional, Lindqvist, Michael, additional, Bremer, Michael, additional, Sanchez, Savador, additional, de Vicente, Pablo, additional, and Zensus, Anton, additional

Published
2015
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68. pproaching hell’s kitchen: Molecular daredevil clouds in the vicinity of Sagittarius A.

Author

Moser, Lydia, Sánchez-Monge, Álvaro, Eckart, Andreas, Requena-Torres, Miguel A., García-Marin, Macarena, Kunneriath, Devaky, Zensus, Anton, Britzen, Silke, Sabha, Nadeen, Shahzamanian, Banafsheh, Borkar, Abhijeet, and Fischer, Sebastian

Abstract

We report serendipitous detections of line emission with the Atacama Large Millimeter/submillimeter Array (ALMA) in bands 3, 6, and 7 in the central parsec down to within 1′′ around Sgr A* at an up to now highest resolution (<0.5′′) view of the Galactic center (GC) in the submillimeter (sub-mm) domain. From the 100 GHz continuum and the H39α emission we obtain a uniform electron temperature around Te ~ 6000 K for the minispiral. The spectral index (S ∝ να) of Sagittarius A* (Sgr A*) is ~0.5 at 100–250 GHz and ~0.0 at 230–340 GHz. The bright sources in the center show spectral indices around –0.1 implying Bremsstrahlung emission, while dust emission is emerging in the minispiral exterior. Apart from CS, which is most widespread in the center, H13CO+, HC3N, SiO, SO, C2H, CH3OH, 13CS and N2H+ are also detected. The bulk of the clumpy emission regions is at positive velocities and in a region confined by the minispiral northern arm (NA), bar, and the sources IRS 3 and 7. Although partly spatially overlapping with the radio recombination line (RRL) emission at same negative velocities, the relation to the minispiral remains unclear. A likely explanation is an infalling clump consisting of denser cloud cores embedded in diffuse gas. This central association (CA) of clouds shows three times higher CS/X (X: any other observed molecule) ratios than the circumnuclear disk (CND) suggesting a combination of higher excitation, by a temperature gradient and/or infrared (IR) pumping, and abundance enhancement due to UV and/or X-ray emission. Hence, we conclude that this CA is closer to the center than the CND is to the center. Moreover, we find molecular line emission at velocities up to 200 km s-1. Apart from the CA, we identified two intriguing regions in the CND. One region shows emission in all molecular species and higher energy levels tested in this and previous observations and contains a methanol class I maser. The other region shows similar behavior of the line ratios such as the CA. Outside the CND, we find the traditionally quiescent gas tracer N2H+ coinciding with the largest IR dark clouds in the field. Methanol emission is found at and around previously detected methanol class I masers in the same region. We propose to make these particular regions subject to further studies in the scope of hot core, cold core, and extreme photon and/or X-ray dominated region (PDR/XDR) chemistry and consequent star formation in the central few parsecs. [ABSTRACT FROM AUTHOR]

Published
2017
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70. Properties of the radio jet emission of gamma-ray Narrow Line Seyfert 1s

Author

Angelakis, Emmanouil, primary, Fuhrmann, L., additional, Myserlis, Ioannis, additional, Nestoras, Ioannis, additional, Karamanavis, Vassilis, additional, Krichbaum, T. P., additional, Zensus, Anton, additional, Marchili, Nicola, additional, Foschini, Luigi, additional, Ungerechts, Hans, additional, and Sievers, A., additional

Published
2013
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72. The Galactic Center as a pradigm for low-luminosity nuclei? What can be learned from SgrA* for the central engine and conditions of star formation in nuclei of Seyfert galaxies and low luminosity nearby QSOs; The K-band identification of the DSO/G2 source from VLT and Keck data

Author

Eckart, Andreas, primary, Britzen, Silke, additional, Horrobin, Matthew, additional, ZAMANINASAB, Mohammad, additional, Muzic, Koraljka, additional, Sabha, Nadeen, additional, Shahzamanian, Banafsheh, additional, Yazici, Senol, additional, Moser, Lydia, additional, Zuther, Jens, additional, Garcia-Marin, M., additional, Valencia-S., Monica, additional, Bursa, Michal, additional, Karssen, Grischa, additional, Karas, Vladimir, additional, Jalali, Behrang, additional, Vitale, Mariangela, additional, Bremer, Marcus, additional, Fischer, Sebastian, additional, Smajic, Semir, additional, Rauch, Cristoph, additional, Kunneriath, Devaky, additional, Moultaka, Jihane, additional, Straubmeier, Christian, additional, Rashed, Yasir Ezzuldeen, additional, Iserlohe, Christof, additional, Busch, Gerold, additional, Markakis, Kostas, additional, Borkar, Abhijeet, additional, and Zensus, Anton, additional

Published
2013
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77. Towards mm-VLBI

Author

Krichbaum, T. P., primary, Bach, Uwe, additional, Graham, Dave A., additional, Alef, W., additional, Roy, Alan, additional, Witzel, A., additional, Zensus, Anton, additional, Bremer, Michael, additional, and Sanchez, Savador, additional

Published
2009
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79. A Newly Discovered Highly Variable IDV Source

Author

Gabányi, Kristina, primary, Marchili, Nicola, additional, Krichbaum, T. P., additional, Fuhrmann, L., additional, Britzen, S., additional, Witzel, A., additional, Zensus, Anton, additional, Liu, Xiang, additional, Huagang, Song, additional, and Han, JinLin, additional

Published
2008
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85. Rapid and correlated variability of blazar S5 0716+71 from radio- to sub-mm bands

Author

Fuhrmann, L., primary, Krichbaum, T. P., additional, Witzel, A., additional, Agudo, I., additional, Britzen, S., additional, Bernhart, S., additional, Impellizzeri, V., additional, Kraus, A., additional, Angelakis, E., additional, Bach, U., additional, Gabanyi, K., additional, Zensus, Anton, additional, Wagner, S. J., additional, and Ostorero, L., additional

Published
2007
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86. The kinematics of S5 1803+784

Author

Kudryavtseva, Nadezhda, primary, Britzen, S., additional, Witzel, A., additional, Ros, E., additional, Aller, M. F., additional, Aller, H. D., additional, Campbell, R. M., additional, Zensus, Anton, additional, Eckart, Andreas, additional, Roland, J., additional, and Mehta, A., additional

Published
2007
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87. Active Black Holes

Author

Falcke, Heino, primary, Zensus, Anton, additional, Komossa, Stefanie, additional, Wagner, Stefan, additional, Dietrich, Matthias, additional, and Mannheim, Karl, additional

Published
2003
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90. Spectral Evolution of the Parsec-Scale Jet in the Quasar 3C 345

Author

Lobanov, Andrew P. and Zensus, Anton

Abstract

The long-term evolution of the synchrotron emission from the parsec-scale jet in the quasar 3C 345 is analyzed on the basis of multifrequency monitoring with very long baseline interferometry (VLBI) and covering the period 1979-1994. We demonstrate that the compact radio structure of 3C 345 can be adequately represented by Gaussian model fits and that the model fits at different frequencies are sufficiently reliable for studying the spectral properties of the jet. We combine the model fits from 44 VLBI observations of 3C 345 made at eight different frequencies between 2.3 and 100 GHz. This combined database is used for deriving the basic properties of the synchrotron spectra of the VLBI core and the moving features observed in the jet. We calculate the turnover frequency, the turnover flux density, and the integrated 4-25 GHz flux and 4-25 GHz luminosity of the core and the moving features. The core has an estimated mean luminosity Lcore = (7.1 +- 3.5) x 1042 h-2 ergs s-1; the estimated total luminosity of 3C 345 on parsec scales is [?]3 x 1043 h-2 ergs s-1 (about 1% of the observed luminosity of the source between the radio to infrared regimes). The luminosities of the core and most of the moving features decrease at the average rate of 1.2 x 1035 h-2 (0.74 +- 0.06)t-1979.0 ergs s-2 (t measured in years). The derived luminosity variations require intrinsic acceleration of the moving features. The turnover frequency of one of the moving features reaches a peak during the above period. The combination of the overall spectral and kinematic changes in that feature cannot be reproduced satisfactorily by relativistic shocks, which may indicate rapid dissipation in shocks. The spectral changes in the core can be reconciled with a shock or dense plasma condensation traveling through the region where the jet becomes optically thin. We are able to describe the evolution of the core spectrum by a sequence of five flarelike events characterized by an exponential rise and decay of the particle number density of the material injected into the jet. The same model is also capable of predicting the changes in the flux density observed in the core. The flares occur approximately every 3.5-4 yr, roughly correlating with appearances of new moving features in the jet and indicating that a quasi-periodic process in the nucleus may be driving the observed emission and structural evolution of 3C 345.

Published
1999

92. A statistical study of SDSS radio-emitters

Author

Vitale, Mariangela, Jens Dierkes, García-Marín, Macarena, Eckart, Andreas, Bremer, Marcus, Valencia-S, Mónica, and Zensus, Anton

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

The cross-correlation of the Sloan Digital Sky Survey Data Release 7 with the Faint Images of the Radio Sky at Twenty-Centimeters survey allows for a multiwavelength statistical study of radio-optical galaxy properties on a very large number of sources. The correlation we find between $L_{[20 cm]}/L_{[H\alpha]}$ and optical emission line ratios suggests that the origin of the emission in powerful radio-galaxies is of nuclear rather than of stellar origin. In particular, the spectroscopic classification in Seyferts, Low Ionization Narrow Emission Regions (LINERs) and star-forming galaxies provided by emission-line diagnostic diagrams peaks on the AGN region for higher $L_{[20 cm]}/L_{[H\alpha]}$ values. The trend differs from Seyferts to LINERs. The [NII]/H$\alpha$ vs. equivalent width of the H$\alpha$ line diagram confirms the LINER classification for most of those that have been identified with the traditional diagnostic diagrams. A small fraction of sources seem to be powered by post-AGB stars instead., Comment: 8 pages, 4 figures, Proceedings of Nuclei of Seyfert galaxies and QSOs - Central engine \& conditions of star formation

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