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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.

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


J. Hlavacek-Larrondo

P. Gandhi

M.T. Hogan

M.-L. Gendron-Marsolais

A.C. Fabian

H.R. Russell

K. Iwasawa

M. Mezcua


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.


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.

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
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Published Journal Article (1.4 Mb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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