Status Report

What Types of Jets does Nature Make: A New Population of Radio Quasars

By SpaceRef Editor
January 16, 2003
Filed under , ,

Astrophysics, abstract

From: Paolo Padovani <[email protected]>
Date: Mon, 13 Jan 2003 21:00:13 GMT (262kb)

What Types of Jets does Nature Make: A New Population of Radio Quasars

P. Padovani (1,2),
E. Perlman (1,3),
H. Landt (1,4),
P. Giommi (5),
M. Perri (5,6) ((1) STScI, (2) ESA, (3) JCA, UMBC, (4) Hamburg Observatory, Germany, (5) ASDC, ASI, Italy, (6) Phys. Dept., Univ. La Sapienza, Roma, Italy)

Comments: 15 pages, 12 figures. Accepted for publication in The Astrophysical
Journal (May 1 2003 issue). Postscript file also available at
this http URL

We use statistical results from a large sample of about 500 blazars, based on
two surveys, the Deep X-ray Radio Blazar Survey (DXRBS), nearly complete, and
the RASS-Green Bank survey (RGB), to provide new constraints on the spectral
energy distribution of blazars, particularly flat-spectrum radio quasars
(FSRQ). This reassessment is prompted by the discovery of a population of FSRQ
with spectral energy distribution similar to that of high-energy peaked BL
Lacs. The fraction of these sources is sample dependent, being ~ 10% in DXRBS
and ~ 30% in RGB (and reaching ~ 80% for the Einstein Medium Sensitivity
Survey). We show that these “X-ray strong” radio quasars, which had gone
undetected or unnoticed in previous surveys, indeed are the strong-lined
counterparts of high-energy peaked BL Lacs and have synchrotron peak
frequencies, nu_peak, much higher than “classical” FSRQ, typically in the UV
band for DXRBS. Some of these objects may be 100 GeV – TeV emitters, as are
several known BL Lacs with similar broadband spectra. Our large, deep, and
homogeneous DXRBS sample does not show anti-correlations between nu_peak and
radio, broad line region, or jet power, as expected in the so-called “blazar
sequence” scenario. However, the fact that FSRQ do not reach X-ray-to-radio
flux ratios and nu_peak values as extreme as BL Lacs and the elusiveness of
high nu_peak – high-power blazars suggest that there might be an intrinsic,
physical limit to the synchrotron peak frequency that can be reached by
strong-lined, powerful blazars. Our findings have important implications for
the study of jet formation and physics and its relationship to other properties
of active galactic nuclei.

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