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Article
Constraining the Physical State of the Hot Gas Halos in NGC 4649 and NGC 5846
The Astrophysical Journal (2017)
  • Alessandro Paggi, Harvard-Smithsonian Center for Astrophysics
  • Dong-Woo Kim, Harvard-Smithsonian Center for Astrophysics
  • Craig Anderson, Harvard-Smithsonian Center for Astrophysics
  • Doug Burke, Harvard-Smithsonian Center for Astrophysics
  • Raffaele D'Abrusco, Harvard-Smithsonian Center for Astrophysics
  • Giuseppina Fabbiano, Harvard-Smithsonian Center for Astrophysics
  • Antonella Fruscione, Harvard-Smithsonian Center for Astrophysics
  • Tara Gokas, Harvard-Smithsonian Center for Astrophysics
  • Jen Lauer, Harvard-Smithsonian Center for Astrophysics
  • Michael McCollough, Harvard-Smithsonian Center for Astrophysics
  • Doug Morgan, Harvard-Smithsonian Center for Astrophysics
  • Amy Mossman, Harvard-Smithsonian Center for Astrophysics
  • Ewan O'Sullivan, Harvard-Smithsonian Center for Astrophysics
  • Ginevra Trinchieri, INAF-Osservatorio Astronomico di Brera
  • Saeqa Vrtilek, Harvard-Smithsonian Center for Astrophysics
  • Silvia Pellegrini, University of Bologna
  • Aaron J. Romanowsky, San Jose State University
  • Jean P. Brodie, University of California Observatories
Abstract
We present results of a joint Chandra/XMM-Newton analysis of the early-type galaxies NGC 4649 and NGC 5846 aimed at investigating differences between mass profiles derived from X-ray data and those from optical data, to probe the state of the hot interstellar medium (ISM) in these galaxies. If the hot ISM is at a given radius in hydrostatic equilibrium (HE), the X-ray data can be used to measure the total enclosed mass of the galaxy. Differences from optically derived mass distributions therefore yield information about departures from HE in the hot halos. The X-ray mass profiles in different angular sectors of NGC 4649 are generally smooth with no significant azimuthal asymmetries within 12 kpc. Extrapolation of these profiles beyond this scale yields results consistent with the optical estimate. However, in the central region ( kpc) the X-ray data underpredict the enclosed mass, when compared with the optical mass profiles. Consistent with previous results, we estimate a nonthermal pressure component accounting for 30% of the gas pressure, likely linked to nuclear activity. In NGC 5846 the X-ray mass profiles show significant azimuthal asymmetries, especially in the NE direction. Comparison with optical mass profiles in this direction suggests significant departures from HE, consistent with bulk gas compression and decompression due to sloshing on ~15 kpc scales; this effect disappears in the NW direction, where the emission is smooth and extended. In this sector we find consistent X-ray and optical mass profiles, suggesting that the hot halo is not responding to strong nongravitational forces.
Keywords
  • galaxies: ISM,
  • ISM: individual objects (NGC 4649,
  • NGC 5846),
  • X-rays: ISM
Publication Date
2017
DOI
10.3847/1538-4357/aa7897
Publisher Statement
This article was originally published in The Astrophysical Journal, volume 844, issue 1. © 2017. The American Astronomical Society. All rights reserved.

This article is also available online at the following link: https://doi.org/10.3847/1538-4357/aa7897
Citation Information
Alessandro Paggi, Dong-Woo Kim, Craig Anderson, Doug Burke, et al.. "Constraining the Physical State of the Hot Gas Halos in NGC 4649 and NGC 5846" The Astrophysical Journal Vol. 844 Iss. 1 (2017) ISSN: 0004-637X
Available at: http://works.bepress.com/aaron_romanowsky/128/