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Description
This table contains results of a complete radio follow-up obtained with the VLA and ATCA radio telescopes down to a 6-cm flux limit of about 0.3 mJy (3-sigma) of all the 147 X-ray sources detected in the BeppoSAX HELLAS survey (Fiore et al. 2001, MNRAS, 327, 771). The authors found 53 X-ray/radio likely associations, corresponding to about one-third of the X-ray sample. Using the two-point spectral index alpha<sub>ro</sub> = 0.35 they divided all the HELLAS X-ray sources into radio-quiet and radio-loud. They have 26 sources classified as radio-loud objects, corresponding to 18 per cent of the HELLAS sample. In agreement with previous results, the identified radio-loud sources are associated mainly with Type 1 active galactic nuclei (AGNs) with L<sub>5-10keV</sub> >~ 10<sup>44</sup> erg/s, while all the identified Type 2 AGNs and emission-line galaxies are radio-quiet objects with L<sub>5-10keV</sub> <~ 10<sup>44</sup> erg/s. The 20 HELLAS sources with Declinations south of -40<sup>o</sup> were observed with the ATCA, while the 127 sources with more northerly Declinations were observed with the VLA. For these latter sources a complete covering at 20 cm down to the 5-sigma flux limit of 2.5 mJy is already available with the NRAO/VLA Sky Survey (NVSS) while the FIRST survey (Faint Images of the Radio Sky at Twenty centimeters) is available only for 27 HELLAS sources (5-sigma limit of ~ 1 mJy).In order to obtain information also on the radio spectral properties of the HELLAS sources the authors adopted the following strategy. All the 147 HELLAS sources were observed at 6 cm down to a 1 -sigma flux limit of ~ 0.10 - 0.25 mJy. For the 20 HELLAS sources observed with the ATCA, they took advantage of the fact that the 6 and 3 cm receivers of the ATCA share a common feed-horn and they observed simultaneously also at 3 cm, obtaining a 3-cm flux limit of ~ 0.22 mJy (1-sigma level). Starting from the radio position of the 53 X-ray/radio associations, the authors searched for optical counterparts within 5 arcseconds from the radio position using the optical positions of the 61 HELLAS sources identified by La Franca et al. (2002, ApJ, 570, 100 = LF02), the USNO-A2.0 1 optical catalog, the APM 2 optical catalog and the NASA Extragalactic Database (NED). 24 X-ray/radio associations have been identified with sources in LF02 (10 Type 1 AGN, 4 Type 2 AGN, 2 BL Lacs, 3 Clusters, 4 ELGs and 1 Radio galaxy), 1 has been identified with a z = 0.708 Radio galaxy in the Lockman Hole using NED (see Table 2 source 116 in Lehmann et al. 2000, A&A, 354, 35 for a description of this source), 13 have an optical (R-band) identification in the USNO and/or APM catalogue while 15 X-ray/radio associations do not have an optical identification brighter than R=20. This table was created by the HEASARC in July 2014 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/342/575">CDS Catalog J/MNRAS/342/575</a> file table1.dat. There was a minor update to the HEASARC's implementation in June 2022 to make the two probability parameters into unitless quantities for improved clarity. This is a service provided by NASA HEASARC .
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