Radio-loud ROSAT sources near the North Ecliptic Pole

W. Brinkmann, M. Chester, R. Kollgaard, E. Feigelson, W. Voges, P. Hertz

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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 note-worthy: (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".

Original languageEnglish (US)
Pages (from-to)221-240
Number of pages20
JournalAstronomy and Astrophysics Supplement Series
Issue number2
StatePublished - Jan 2 1999

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)


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