有哪些信誉好的足球投注网站A Chandra Snapshot Survey of Representative High-Redshift Radio-Loud Quasars from the Parke.pdf
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A Chandra Snapshot Survey of Representative High-Redshift Radio-Loud Quasars from the Parke
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A Chandra Snapshot Survey of Representative High-Redshift
Radio-Loud Quasars from the Parkes-MIT-NRAO Sample
L. A. Lopez,1,2,3 W. N. Brandt,1 C. Vignali,4,5 D. P. Schneider,1 G. Chartas,1 and G. P.
Garmire1
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 et al.
(2004) which 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 kpc-scale radio jets revealed only lim-
ited 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 ex-
tended 1′′ away from their X-ray cores. Additionally, we do not observe any
systematic flattening of the optical-to-X-ray spectral index (αox) compared to
low-redshift quasars. These results suggest that kpc-scale X-ray jet emission is
not dominated by inverse-Compton scattering of CMB-seed photons off jet elec-
trons. 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 fit the data, with best-fit photon indices of 1.72+0.11
?0.12 for
moderate-R sources and 1.47+0.13
?0.12 for high-R sources. We added an intrinsic ab-
sorption component to our model, and neither the moderate-R nor the high-R
fits set a lower bound on NH . The upper limits were NH 3.0 × 10
22 cm?2 and
1Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Labora-
tory, University Park, PA 16802, USA; lalopez@, nie
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