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

Abstract

Hyper-luminous infrared galaxies (HyLIRGs) lie at the extreme luminosity end of the IR galaxy population with L IR > 10 13 L ⊙ . They are thought to be closer counterparts of the more distant sub-mm galaxies, and should therefore be optimal targets to study the most massive systems in formation. We present deep Chandra observations of IRAS F15307+3252 (100ks), a classical HyLIRG located at z =0.93 and hosting a radio-loud AGN (L 1.4 GHz ∼ 3.5 × 10 25 W/Hz). 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 × 10 43 erg s −1 ) of the gas follow the expected L X−ray − T correlation for groups and clusters, and that the gas has a remarkably short cooling time of 1.2 Gyrs. 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 Comptonthick. Finally, Hubble images reveal an over-density 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.

The Fundamental Signature of Star Formation Quenching from AGN Feedback: A Critical Dependence of Quiescence on Supermassive Black Hole Mass, Not Accretion Rate

“…There is abundant evidence that AGN produce more than enough energy to quench star formation (e.g., Silk & Rees 1998;Bluck et al 2011;Fabian 2012;Maiolino et al 2012). Yet, direct observational evidence for AGN feedback causing quenching within galaxies remains sparse and hotly debatedalthough see Hlavacek-Larrondo et al (2012), Hlavacek-Larrondo et al (2017), andHlavacek-Larrondo et al (2018), for perhaps the strongest direct evidence to date, primarily within galaxy clusters and very massive groups. Thus, it remains unclear whether or not the crucial ingredient in cosmological models to quench galaxies is viable for the vast majority of systems.…”

Unveiling the 100 pc scale nuclear radio structure of NGC 6217 with e-MERLIN and the VLA

“…This is a restrictive prerogative of powerful radio-loud AGN, which show large kpc-scale collimated jets and massive BH (>10 8 M ). There are some rare cases of X-ray jets observed without any associated radio jet (see for example Simionescu et al 2016;Meyer et al 2017;Hlavacek-Larrondo et al 2017), but we note that these jets are found in very luminous galaxies with powerful AGN also, unlike NGC 6217.…”

1321+045: a Compact Steep Spectrum radio source in a cool-core galaxy cluster

“…Confirmation of a new phase of jet activity can be provided by imaging studies, as in the nearby group-dominant galaxy NGC 5044, where X-ray and radio observations have shown three epochs of old jet activity, but recent VLBA data show that a new jet has been launched on a different axis (Schellenberger et al, 2021). Examples of cluster-central CSS sources include the quasars 3C 186 (Migliori, Siemiginowska, & Celotti, 2012;Siemiginowska et al, 2010Siemiginowska et al, , 2005 and IRAS F15307+3252 (Hlavacek-Larrondo et al, 2017). The former is located in an 8 keV cluster at =1.06, but the AGN is so bright in X-rays that detailed analysis of the cooling region is impossible, while the latter occupies a 2 keV group at =0.93 and is faint enough that only global properties can be determined using current X-ray observatories.…”