Radio-loud ROSAT sources near the North Ecliptic Pole
Abstract
A deep and large-area survey of the North Ecliptic Pole region was made with the ROSAT All-Sky Survey and the VLA to elucidate the population of radio-loud extragalactic objects. A region of 29.3 square degrees was surveyed with sensitivities around 5 \ 10(-14) erg s(-1) cm(-2) in the soft X-ray band and 1 mJy at 1.5 GHz. Optical counterparts were sought on digitized Schmidt plates from POSS-I and II. Seventy-four reliable RASS-VLA sources were found. The sample is a heterogeneous mixture of Seyfert galaxies, quasars, BL Lac objects, galaxy clusters and groups containing a radio galaxy. Optical magnitudes range from B =~ 14 to B > 22. Three results are noteworthy: (1) the bimodality in the ratio of radio to optical emission seen in optically- and X-ray-selected AGN samples is also evident in the ROSAT-VLA objects; (2) X-ray and radio selection is an effective method for locating poor galaxy clusters and groups; and (3) a considerable population of optically faint but X-ray/radio-bright objects is present. This last group may be either distant clusters with radio galaxies or ``red quasars".
- Publication:
-
Astronomy and Astrophysics Supplement Series
- Pub Date:
- January 1999
- DOI:
- 10.1051/aas:1999136
- Bibcode:
- 1999A&AS..134..221B
- Keywords:
-
- GALAXIES: ACTIVE;
- CLUSTERS: GENERAL;
- QUASARS: GENERAL;
- X-RAYS: GENERAL;
- RADIO CONTINUUM: GALAXIES