Chandra X-ray observations of the hyper-luminous infrared galaxy IRAS F15307+3252

Hlavacek-Larrondo, J.; Gandhi, P.; Hogan, M.T.; Gendron-Marsolais, M.-L.; Edge, A.C.; Fabian, A.C.; Russell, H.R.; Iwasawa, K.; Mezcua, M.

Abstract

Hyper-luminous infrared galaxies (HyLIRGs) lie at the extreme luminosity end of the IR galaxy population with LIR > 1013 L⊙. They are thought to be closer counterparts of the more distant sub-millimeter galaxies, and should therefore be optimal targets to study the most massive systems in formation. We present deep Chandra observations of IRAS F15307+3252 (100 ks), a classical HyLIRG located at z = 0.93 and hosting a radio-loud AGN (L1.4 GHz ∼ 3.5 × 1025 W Hz−1). The Chandra images reveal the presence of extended (r = 160 kpc), asymmetric X-ray emission in the soft 0.3–2.0 keV band that has no radio counterpart. We therefore argue that the emission is of thermal origin originating from a hot intragroup or intracluster medium virializing in the potential. We find that the temperature (∼2 keV) and bolometric X-ray luminosity (∼3 × 1043 erg s−1) of the gas follow the expected LX-ray–T correlation for groups and clusters, and that the gas has a remarkably short cooling time of 1.2 Gyr. In addition, VLA radio observations reveal that the galaxy hosts an unresolved compact steep-spectrum (CSS) source, most likely indicating the presence of a young radio source similar to 3C186. We also confirm that the nucleus is dominated by a redshifted 6.4 keV Fe Kα line, strongly suggesting that the AGN is Compton-thick. Finally, Hubble images reveal an overdensity of galaxies and sub-structure in the galaxy that correlates with soft X-ray emission. This could be a snapshot view of on-going groupings expected in a growing cluster environment. IRAS F15307+3252 might therefore be a rare example of a group in the process of transforming into a cluster.

Citation

Hlavacek-Larrondo, J., Gandhi, P., Hogan, M., Gendron-Marsolais, M., Edge, A., Fabian, A., …Mezcua, M. (2017). Chandra X-ray observations of the hyper-luminous infrared galaxy IRAS F15307+3252. Monthly Notices of the Royal Astronomical Society, 464(2), 2223-2233. https://doi.org/10.1093/mnras/stw2468

• Journal Article Type: Article
• Acceptance Date: Sep 27, 2016
• Online Publication Date: Sep 28, 2016
• Publication Date: Jan 11, 2017
• Deposit Date: Apr 28, 2017
• Publicly Available Date: May 4, 2017
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 464
• Issue: 2
• Pages: 2223-2233
• DOI: https://doi.org/10.1093/mnras/stw2468
• Related Public URLs: arxiv.org/pdf/1606.07818.pdf