Volume 371, Number 2, May IV 2001
|Page(s)||527 - 537|
|Section||Cosmology (including clusters of galaxies)|
|Published online||15 May 2001|
An X-ray selected sample of radio-loud quasars
Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy e-mail: firstname.lastname@example.org
2 S. I. S. S. A., via Beirut 2-4, 34014 Trieste, Italy e-mail: email@example.com
Corresponding author: A. Wolter, firstname.lastname@example.org
Accepted: 16 March 2001
We construct the first X-ray selected sample of broad line radio-loud AGN from the EMSS survey. In order to test unifying schemes for radio-loud objects, their spectral and statistical properties (both flat and steep spectrum objects) are examined and compared with those of other samples of blazars. The X-ray selection allows us to explore properties of radio-loud quasars 10-100 weaker in the radio band than classical samples. The most convincing interpretation of our results is that there are no radio-loud quasars whose synchrotron emission peak reaches the EUV-soft X-ray band at these (radio) flux levels. Moreover, due to the comparatively weak non-thermal emission, a quasi-thermal component appears to contribute at optical-UV energies. The detection of sources at low radio fluxes also reveals a large population of steep spectrum quasars and the lack of the predicted turnover in the quasar (radio) counts. The evolution of X-ray selected radio-loud quasars does not significantly differ from that of radio-selected ones, and flat spectrum and steep spectrum sources appear to behave quite similarly.
Key words: galaxies: active / galaxies: evolution / galaxies: luminosity function / quasars: general / radio continuum: galaxies / X-rays: galaxies
© ESO, 2001
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