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Detecting relativistic X-ray jets in high-redshift quasars

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Title: Detecting relativistic X-ray jets in high-redshift quasars
Authors: McKeough, K
Siemiginowska, A
Cheung, CC
Stawarz, L
Kashyap, V
Stein, N
Stampoulis, V
Van Dyk, DA
Wardle, JFC
Lee, NP
Harris, DE
Schwartz, DA
Donato, D
Maraschi, L
Tavecchio, F
Item Type: Journal Article
Abstract: We analyze Chandra X-ray images of a sample of 11 quasars that are known to contain kiloparsec scale radio jets. The sample consists of five high-redshift (z ≥ 3.6) flat-spectrum radio quasars, and six intermediate redshift (2.1 < z < 2.9) quasars. The dataset includes four sources with integrated steep radio spectra and three with flat radio spectra. A total of 25 radio jet features are present in this sample. We apply a Bayesian multi-scale image reconstruction method to detect and measure the X-ray emission from the jets. We compute deviations from a baseline model that does not include the jet, and compare observed X-ray images with those computed with simulated images where no jet features exist. This allows us to compute p-value upper bounds on the significance that an Xray jet is detected in a pre-determined region of interest. We detected 12 of the features unambiguously, and an additional 6 marginally. We also find residual emission in the cores of 3 quasars and in the background of 1 quasar that suggest the existence of unresolved X-ray jets. The dependence of the X-ray to radio luminosity ratio on redshift is a potential diagnostic of the emission mechanism, since the inverse Compton scattering of cosmic microwave background photons (IC/CMB) is thought to be redshift dependent, whereas in synchrotron models no clear redshift dependence is expected. We find that the high-redshift jets have X-ray to radio flux ratios that are marginally inconsistent with those from lower redshifts, suggesting that either the X-ray emissions is due to the IC/CMB rather than the synchrotron process, or that high redshift jets are qualitatively different.
Issue Date: 12-Dec-2016
Date of Acceptance: 1-Sep-2016
URI: http://hdl.handle.net/10044/1/39890
DOI: https://dx.doi.org/10.3847/1538-4357/833/1/123
ISSN: 0004-637X
Publisher: American Astronomical Society
Journal / Book Title: Astrophysical Journal
Volume: 833
Issue: 1
Copyright Statement: © 2016. The American Astronomical Society. All rights reserved.
Sponsor/Funder: The Royal Society
Commission of the European Communities
National Science Foundation (US)
Funder's Grant Number: WM110023
FP7-PEOPLE-2012-CIG-321865
DMS 15-13484
Keywords: Science & Technology
Physical Sciences
Astronomy & Astrophysics
galaxies: active
galaxies: jets
quasars: general
radiation mechanisms: non-thermal
radio continuum: galaxies
X-rays: galaxies
RADIO-LOUD QUASARS
CELESTIAL REFERENCE FRAME
ACTIVE GALACTIC NUCLEI
EMISSION MODELS
COMPLETE SAMPLE
DATA RELEASE
SCALE JETS
CHANDRA
EVOLUTION
DISCOVERY
astro-ph.HE
0201 Astronomical And Space Sciences
0305 Organic Chemistry
0306 Physical Chemistry (Incl. Structural)
Publication Status: Published
Article Number: 123
Appears in Collections:Mathematics
Statistics
Faculty of Natural Sciences



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