X-Ray Observations of a z ∼ 6.2 Quasar/Galaxy Merger
Journal
Date Issued
2019
Author(s)
Connor, Thomas
•
Bañados, Eduardo
•
Stern, Daniel
•
•
Schindler, Jan-Torge
•
Fan, Xiaohui
•
Farina, Emanuele Paolo
•
Mazzucchelli, Chiara
•
Mulchaey, John S.
•
Walter, Fabian
Abstract
Quasars at early redshifts (z > 6) with companion galaxies offer unique insights into the growth and evolution of the first supermassive black holes. Here, we report on a 150 ks Chandra observation of PSO J308.0416-21.2339, a z = 6.23 quasar with a merging companion galaxy identified in [C II] and rest-frame UV emission. With {72.3}-8.6+9.6 net counts, we find that PSO J308.0416-21.2339 is powerful ({L}X={2.31}-0.76+1.14× {10}45 {erg} {{{s}}}-1 {cm}}-2 in rest-frame 2.0-10.0 keV) yet soft (spectral power-law index {{Γ }}={2.39}-0.36+0.37 and optical-to-X-ray slope α OX = -1.41 ± 0.11). In addition, we detect three hard-energy photons 2.″0 to the west of the main quasar, cospatial with the brightest UV emission of the merging companion. As no soft-energy photons are detected in the same area, this is potentially indicative of a highly obscured source. With conservative assumptions, and accounting for both background fluctuations and the extended wings of the quasar’s emission, these photons only have a probability P = 0.021 of happening by chance. If confirmed by deeper observations, this system is the first high-redshift quasar and companion individually detected in X-rays and is likely a dual active galactic nucleus.
Volume
887
Issue
2
Start page
171
Issn Identifier
0004-637X
Ads BibCode
2019ApJ...887..171C
Rights
open.access
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