Serbian Astronomical Journal 2003 Issue 166, Pages: 13-30
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A multi-frequency study of the deep Pavo field

Filipović M.D., Anderson M., Ekers R.D., Danziger I.J., Zimmermann H.U., White G.L., Jones P.A., Borun B.C.P., Payne J.L., Dionne M., Ganis M., Ognjanović M.

We test the prediction of Hamilton and Helfand (1993) that faint radio selected galaxies are a new class contributing to the diffuse X-ray background (XRB) radiation. The test is based on the correlation of X-ray optical and radio positions for sources detected in ROSAT (S0.08−2.4 keV> 6 x 10−15 erg cm−2 s−1, 69 sources) and ATCA (S1.42GHz >250 µJy, 93 sources) observations of the Einstein Pavo field. A total of six ATCA radio sources inside the inner ring of the ROSAT image are located within 10" of the ROSAT X-ray positions, with one associated by random chance. Hence, five of the X-ray population are radio-emitters. Four of these sources in common to radio and X-ray surveys are identified in optical frequencies from which one is a well known (ATCAJ211544-675404) quasi stellar object (QSO). Another source (ATCAJ211139-674902) can be seen at optical frequencies and therefore is very likely to be a QSO. Two more of these sources are clear Active Galactic Nuclei (AGN) candidates (ATCAJ211217-674914 and ATCAJ211451-680038). Radio and X-ray source ATCAJ211420-680109= RXJ211420-680108 is a galaxy cluster candidate. The remaining source ATCAJ211414-675052, is a star-forming galaxy candidate assuming it is not associated by random chance. Even though the statistical sample is small this does not support the postulate that star-forming galaxies are significant contributors to the soft X-ray source population. This implies the contribution of radio emitting X-ray sources to the diffuse XRB at S0.08−2.4 keV > 6 x 10−15 erg cm−2 s−1 is at most a few per cent.

Keywords: cosmology: diffuse radiation, galaxies: active $ galaxies: Seyfert, radio continuum: galaxies, X-rays: galaxies

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