Chandra X-Rays from the Redshift 7.54 Quasar ULAS J1342+0928

Journal
Date Issued
2018
Author(s)
Bañados, Eduardo
•
Connor, Thomas
•
Stern, Daniel
•
Mulchaey, John
•
Fan, Xiaohui
•
•
Farina, Emanuele P.
•
Mazzucchelli, Chiara
•
Venemans, Bram P.
•
Walter, Fabian
•
Wang, Feige
•
Yang, Jinyi
DOI
Abstract
We present a 45 ks Chandra observation of the quasar ULAS J1342+0928 at z = 7.54. We detect {14.0}-3.7+4.8 counts from the quasar in the observed-frame energy range 0.5-7.0 keV (6σ detection), representing the most distant non-transient astronomical source identified in X-rays to date. The present data are sufficient only to infer rough constraints on the spectral parameters. We find an X-ray hardness ratio of { \mathcal H }{ \mathcal R }=-{0.51}-0.28+0.26 between the 0.5-2.0 keV and 2.0-7.0 keV ranges and derive a power-law photon index of {{Γ }}={1.95}-0.53+0.55. Assuming a typical value for high-redshift quasars of Γ = 1.9, ULAS J1342+0928 has a 2-10 keV rest-frame X-ray luminosity of {L}2-10={11.6}-3.5+4.3× {10}44 {erg} {{{s}}}-1. Its X-ray-to-optical power-law slope is {α }OX}=-{1.67}-0.10+0.16, consistent with the general trend indicating that the X-ray emission in the most bolometrically powerful quasars is weaker relative to their optical emission.
Volume
856
Issue
2
Start page
L25
Uri
Url
Issn Identifier
2041-8205
Ads BibCode
2018ApJ...856L..25B
Rights
open.access
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