Quasars in the MAMBO blank field survey

¹ Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: hvoss@mpifr-bonn.mpg.de
² Radioastronomisches Institut der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
³ National Radio Astronomy Observatory, PO Box, Socorro, NM 87801, USA
⁴ Max-Planck Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany
⁵ Gemini Observatory, Southern Operations Center, AURA, Casilla 603, La Serena, Chile

Received: 28 June 2005
Accepted: 24 October 2005

Abstract

Our MAMBO 1.2 mm blank field imaging survey of ~0.75 sqd has uncovered four unusually bright sources, with flux densities between 10 and 90 mJy, all located in the Abell 2125 field. The three brightest are flat spectrum radio sources with bright optical and X-ray counterparts. Their mm and radio flux densities are variable on timescales of months. Their X-ray luminosities classify them as quasars. The faintest of the four mm bright sources appears to be a bright, radio-quiet starburst at , similar to the sources seen at lower flux densities in the MAMBO and SCUBA surveys. It may also host a mildly obscured AGN of quasar-like X-ray luminosity. The three non-thermal mm sources imply an areal density of flat spectrum radio sources higher by at least 7 compared with that expected from an extrapolation of the lower frequency radio number counts.