High-Ionization Fe K Emission From Luminous Infrared Galaxies
Abstract
The Chandra component of the Great Observatories All-Sky Luminous Infrared Galaxy Survey (GOALS) presently contains 44 luminous and ultraluminous infrared galaxies (ULIRGs) with log (L_(IR)/L_☉) = 11.73-12.57. Omitting 15 obvious active galactic nuclei (AGNs), the other galaxies are, on average, underluminous in the 2-10 keV band by 0.7 dex at a given far-infrared luminosity, compared with nearby star-forming galaxies with lower star formation rates. The integrated spectrum of these hard X-ray quiet galaxies shows strong high-ionization Fe K emission (Fe XXV at 6.7 keV), which is incompatible with X-ray binaries as its origin. The X-ray quietness and the Fe K feature could be explained by hot gas produced in a starburst, provided that the accompanying copious emission from high-mass X-ray binaries is somehow suppressed. Alternatively, these galaxies may contain deeply embedded supermassive black holes that power the bulk of their infrared luminosity and only faint photoionized gas is visible, as seen in some ULIRGs with a Compton-thick AGN.
Additional Information
© 2009. The American Astronomical Society. Received 2008 December 24; accepted 2009 March 4; published 2009 March 24. This research was supported in part by NASA through Chandra award Number GO7-8108A, issued by the Chandra X-Ray Observatory, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-39073.We acknowledge use of the NASA/IPAC Extragalactic Database (NED), and the software packages CIAO and HEASoft.Attached Files
Published - Iwasawa2009p1373Astrophys_J_Lett.pdf
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Additional details
- Eprint ID
- 15580
- Resolver ID
- CaltechAUTHORS:20090903-133006035
- NASA
- GO7-8108A
- NASA
- NAS8-39073
- Created
-
2009-09-14Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)