A chandra snapshot survey of representative high-redshift radio-loud quasars from the parkes-MIT-NRAO sample

L. A. Lopez, W. N. Brandt, C. Vignali, D. P. Schneider, G. Chartas, G. P. Garmire

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

We present the results of Chandra ACIS-S snapshot observations of six radio-loud quasars (RLQs) at z ≈ 3.5-4.7. These observations sample luminous RLQs with moderate to high radio loudness (R ≈ 200-9600) and aim to connect the X-ray properties of radio-quiet quasars (R < 10) and highly radio-loud blazars (R > 1000) at high redshift. This work extends a study by Bassett and coworkers that used similar methods to examine z > 4 RLQs with moderate radio loudness (R ≈ 40-400). All of our targets are clearly detected. A search for extended X-ray emission associated with kiloparsec-scale radio jets revealed only limited evidence for X-ray extension in our sample: three sources showed no evidence of X-ray extension, and the other three had 3%-30% of their total X-ray fluxes extended >1″ away from their X-ray cores. In addition, we do not observe any systematic flattening of the optical-to-X-ray spectral index (α ox) compared to low-redshift quasars. These results suggest that kiloparsec-scale X-ray jet emission is not dominated by inverse Compton scattering of cosmic microwave background seed photons offjet electrons. We measured X-ray continuum shapes and performed individual and joint spectral fits of our data combined with eight archival RLQs. A single power-law model acceptably fitted the data, with best-fit photon indices of 1.72 -0.12 +0.11 for moderate-R sources and 1.47 -0.12 +0.13 for high-R sources. We added an intrinsic absorption component to our model, and neither the moderate-R nor the high-R fits set a lower bound on N H. The upper limits were N H < 3.0×10 22 cm -2 and N H < 2.8 × 10 22 cm -2, respectively. Our spectral results suggest that intrinsic absorption does not strongly depend on radio loudness, and high-R sources have flatter power laws than moderate-R sources. Overall, our high-redshift RLQs have basic X-ray properties consistent with similar RLQs in the local universe.

Original languageEnglish (US)
Pages (from-to)1914-1922
Number of pages9
JournalAstronomical Journal
Volume131
Issue number4
DOIs
StatePublished - Apr 1 2006

Fingerprint

quasars
radio
x rays
loudness
power law
photons
flattening
seeds
universe
continuums
scattering
microwaves
seed
electron

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

@article{25afe4142d0e4641a2143a6001ac2920,
title = "A chandra snapshot survey of representative high-redshift radio-loud quasars from the parkes-MIT-NRAO sample",
abstract = "We present the results of Chandra ACIS-S snapshot observations of six radio-loud quasars (RLQs) at z ≈ 3.5-4.7. These observations sample luminous RLQs with moderate to high radio loudness (R ≈ 200-9600) and aim to connect the X-ray properties of radio-quiet quasars (R < 10) and highly radio-loud blazars (R > 1000) at high redshift. This work extends a study by Bassett and coworkers that used similar methods to examine z > 4 RLQs with moderate radio loudness (R ≈ 40-400). All of our targets are clearly detected. A search for extended X-ray emission associated with kiloparsec-scale radio jets revealed only limited evidence for X-ray extension in our sample: three sources showed no evidence of X-ray extension, and the other three had 3{\%}-30{\%} of their total X-ray fluxes extended >1″ away from their X-ray cores. In addition, we do not observe any systematic flattening of the optical-to-X-ray spectral index (α ox) compared to low-redshift quasars. These results suggest that kiloparsec-scale X-ray jet emission is not dominated by inverse Compton scattering of cosmic microwave background seed photons offjet electrons. We measured X-ray continuum shapes and performed individual and joint spectral fits of our data combined with eight archival RLQs. A single power-law model acceptably fitted the data, with best-fit photon indices of 1.72 -0.12 +0.11 for moderate-R sources and 1.47 -0.12 +0.13 for high-R sources. We added an intrinsic absorption component to our model, and neither the moderate-R nor the high-R fits set a lower bound on N H. The upper limits were N H < 3.0×10 22 cm -2 and N H < 2.8 × 10 22 cm -2, respectively. Our spectral results suggest that intrinsic absorption does not strongly depend on radio loudness, and high-R sources have flatter power laws than moderate-R sources. Overall, our high-redshift RLQs have basic X-ray properties consistent with similar RLQs in the local universe.",
author = "Lopez, {L. A.} and Brandt, {W. N.} and C. Vignali and Schneider, {D. P.} and G. Chartas and Garmire, {G. P.}",
year = "2006",
month = "4",
day = "1",
doi = "10.1086/500827",
language = "English (US)",
volume = "131",
pages = "1914--1922",
journal = "Astronomical Journal",
issn = "0004-6256",
publisher = "IOP Publishing Ltd.",
number = "4",

}

A chandra snapshot survey of representative high-redshift radio-loud quasars from the parkes-MIT-NRAO sample. / Lopez, L. A.; Brandt, W. N.; Vignali, C.; Schneider, D. P.; Chartas, G.; Garmire, G. P.

In: Astronomical Journal, Vol. 131, No. 4, 01.04.2006, p. 1914-1922.

Research output: Contribution to journalArticle

TY - JOUR

T1 - A chandra snapshot survey of representative high-redshift radio-loud quasars from the parkes-MIT-NRAO sample

AU - Lopez, L. A.

AU - Brandt, W. N.

AU - Vignali, C.

AU - Schneider, D. P.

AU - Chartas, G.

AU - Garmire, G. P.

PY - 2006/4/1

Y1 - 2006/4/1

N2 - We present the results of Chandra ACIS-S snapshot observations of six radio-loud quasars (RLQs) at z ≈ 3.5-4.7. These observations sample luminous RLQs with moderate to high radio loudness (R ≈ 200-9600) and aim to connect the X-ray properties of radio-quiet quasars (R < 10) and highly radio-loud blazars (R > 1000) at high redshift. This work extends a study by Bassett and coworkers that used similar methods to examine z > 4 RLQs with moderate radio loudness (R ≈ 40-400). All of our targets are clearly detected. A search for extended X-ray emission associated with kiloparsec-scale radio jets revealed only limited evidence for X-ray extension in our sample: three sources showed no evidence of X-ray extension, and the other three had 3%-30% of their total X-ray fluxes extended >1″ away from their X-ray cores. In addition, we do not observe any systematic flattening of the optical-to-X-ray spectral index (α ox) compared to low-redshift quasars. These results suggest that kiloparsec-scale X-ray jet emission is not dominated by inverse Compton scattering of cosmic microwave background seed photons offjet electrons. We measured X-ray continuum shapes and performed individual and joint spectral fits of our data combined with eight archival RLQs. A single power-law model acceptably fitted the data, with best-fit photon indices of 1.72 -0.12 +0.11 for moderate-R sources and 1.47 -0.12 +0.13 for high-R sources. We added an intrinsic absorption component to our model, and neither the moderate-R nor the high-R fits set a lower bound on N H. The upper limits were N H < 3.0×10 22 cm -2 and N H < 2.8 × 10 22 cm -2, respectively. Our spectral results suggest that intrinsic absorption does not strongly depend on radio loudness, and high-R sources have flatter power laws than moderate-R sources. Overall, our high-redshift RLQs have basic X-ray properties consistent with similar RLQs in the local universe.

AB - We present the results of Chandra ACIS-S snapshot observations of six radio-loud quasars (RLQs) at z ≈ 3.5-4.7. These observations sample luminous RLQs with moderate to high radio loudness (R ≈ 200-9600) and aim to connect the X-ray properties of radio-quiet quasars (R < 10) and highly radio-loud blazars (R > 1000) at high redshift. This work extends a study by Bassett and coworkers that used similar methods to examine z > 4 RLQs with moderate radio loudness (R ≈ 40-400). All of our targets are clearly detected. A search for extended X-ray emission associated with kiloparsec-scale radio jets revealed only limited evidence for X-ray extension in our sample: three sources showed no evidence of X-ray extension, and the other three had 3%-30% of their total X-ray fluxes extended >1″ away from their X-ray cores. In addition, we do not observe any systematic flattening of the optical-to-X-ray spectral index (α ox) compared to low-redshift quasars. These results suggest that kiloparsec-scale X-ray jet emission is not dominated by inverse Compton scattering of cosmic microwave background seed photons offjet electrons. We measured X-ray continuum shapes and performed individual and joint spectral fits of our data combined with eight archival RLQs. A single power-law model acceptably fitted the data, with best-fit photon indices of 1.72 -0.12 +0.11 for moderate-R sources and 1.47 -0.12 +0.13 for high-R sources. We added an intrinsic absorption component to our model, and neither the moderate-R nor the high-R fits set a lower bound on N H. The upper limits were N H < 3.0×10 22 cm -2 and N H < 2.8 × 10 22 cm -2, respectively. Our spectral results suggest that intrinsic absorption does not strongly depend on radio loudness, and high-R sources have flatter power laws than moderate-R sources. Overall, our high-redshift RLQs have basic X-ray properties consistent with similar RLQs in the local universe.

UR - http://www.scopus.com/inward/record.url?scp=33744469834&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33744469834&partnerID=8YFLogxK

U2 - 10.1086/500827

DO - 10.1086/500827

M3 - Article

AN - SCOPUS:33744469834

VL - 131

SP - 1914

EP - 1922

JO - Astronomical Journal

JF - Astronomical Journal

SN - 0004-6256

IS - 4

ER -