Detecting relativistic X-ray jets in high-redshift quasars
File(s)
Accepted version
Author(s)
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.
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.
Date Issued
2016-12-12
Date Acceptance
2016-09-01
Citation
Astrophysical Journal, 2016, 833 (1)
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
The Royal Society
Commission of the European Communities
National Science Foundation (US)
Grant Number
WM110023
FP7-PEOPLE-2012-CIG-321865
DMS 15-13484
Subjects
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