EDP Sciences
Free access
Volume 371, Number 2, May IV 2001
Page(s) 527 - 537
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20010415

A&A 371, 527-537 (2001)
DOI: 10.1051/0004-6361:20010415

An X-ray selected sample of radio-loud quasars

A. Wolter1 and A. Celotti2

1  Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
    e-mail: anna@brera.mi.astro.it
2  S. I. S. S. A., via Beirut 2-4, 34014 Trieste, Italy
    e-mail: celotti@sissa.it

(Received 29 August 2001 / 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

Offprint request: A. Wolter, anna@brera.mi.astro.it

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© ESO 2001