X-Ray Observations of a [C II]-bright, z = 6.59 Quasar/Companion System
Journal
Date Issued
2020
Author(s)
Connor, Thomas
•
Bañados, Eduardo
•
Mazzucchelli, Chiara
•
Stern, Daniel
•
•
Fan, Xiaohui
•
Farina, Emanuele Paolo
•
•
Neeleman, Marcel
•
Walter, Fabian
Abstract
We present deep Chandra observations of PSO J231.6576-20.8335, a quasar at redshift z = 6.59 with a nearby (∼8 proper kpc) companion galaxy. The Atacama Large Millimeter/submillimeter Array observed both the quasar and companion to be bright in [C II], and the system has significant extended Lyα emission around the quasar, suggesting that a galaxy merger is ongoing. Unlike previous studies of two similar systems, and despite observing the system with Chandra for 140 ks, we do not detect the companion in X-rays. The quasar itself is detected, but only ${13.3}_{-3.7}^{+4.8}$ net counts are observed. From a basic spectral analysis, the X-ray spectrum of the quasar is soft (hardness ratio of ${ \mathcal H }{ \mathcal R }=-{0.60}_{-0.27}^{+0.17}$ , power-law index of ${\rm{\Gamma }}={2.6}_{-0.9}^{+1.0}$ ), which results in a rest-frame X-ray luminosity comparable to other bright quasars ( ${L}_{2\mbox{--}10}={1.09}_{-0.70}^{+2.20}\times {10}^{45}\ \mathrm{erg}\ {{\rm{s}}}^{-1}$ ) despite the faint observed X-ray flux. We highlight two possible interpretations of this result: the quasar has a steep value of Γ—potentially related to observed ongoing Eddington accretion—thereby pushing much of the emission out of our observed band, or the quasar has a more normal spectrum (Γ ∼ 2) but is therefore less X-ray luminous ( ${L}_{2\mbox{--}10}\sim 0.6\times {10}^{45}\ \mathrm{erg}\ {{\rm{s}}}^{-1}$ ).
Volume
900
Issue
2
Start page
189
Issn Identifier
0004-637X
Ads BibCode
2020ApJ...900..189C
Rights
open.access
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