VizieR Online Data Catalog: Radio-X-ray sources in the HDF(N) region. (Richards+, 2007)

A M S Richards, T W B Muxlow, R Beswick, M G Allen, K Benson, R C Dickson, M A Garrett, S T Garrington, E Gonzalez-Solarez, P A Harrison, A J Holloway, M M Kettenis, R A Laing, E A Richards, H Thrall, H J van Langevelde, N A Walton, P N Wilkinson, N Winstanley

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    This catalogue lists the properties of 62 radio sources in the Hubble Deep Field (North) and Flanking Fields (HDFN) which were also detected by the Chandra X-ray satellite (see Alexander et al., 2003, Cat. , file cdfn). This includes 55/92 sources brighter than 40uJy detected by MERLIN+VLA at 1.4GHz (see Muxlow et al., 2005, Cat. , Richards, 2000, Cat. ); some were also detected by the VLA at 8.4GHz (Richards et al., 1998AJ....116.1039R) including 7 selected at this frequency. The cross-matching, derivation of properties and analysis are described fully in the paper. The radio data have a positional accuracy of 15 mas with respect to the ICRS (Muxlow et al., 2005, Cat. ) but data using the GOODS HST ACS (Giavalisco et al., 2004, Cat. ) positions requires a shift of -342mas in Declination for alignment with the ICRS. We use measurements taken from the radio observations and from the literature to compile the flux densities, sizes and spectral/photon indices of the cross-matched radio+X-ray sources and their redshifts (where available), enabling us to derive the rest-frame luminosities. The 1.4-GHz detections are all resolved at 0.2-2arcsec resolution. The radio emission was classified using the source morphologies and radio spectral indices; optical and IR information was used as supporting evidence only. On this basis, starbursts outnumber radio AGN 3:1. The high-redshift starbursts have typical sizes of 5-10kpc and star formation rates of around 1000 Msun/yr, an order of magnitude more extended and intense than in the local universe. The X-ray sources are unresolved but their luminosity and spectral indices allows X-ray AGN and obscured (Type II) AGN to be identified (2004A&A...424..545P). In this way, we can distinguish between the origins of radio and X-ray emission from the same object. There is no obvious correlation between radio and X-ray luminosities nor spectral indices at z>1.3. About 70% of both the radio-selected AGN and the starburst samples were detected by Chandra. The X-ray luminosity indicates the presence of an AGN in at least half of the 45 cross-matched radio starbursts. Eleven of these are type-II AGN, of which 7 are at z>1.5. This distribution overlaps closely with the X-ray detected radio sources which were also detected by SCUBA. Almost all extended radio starbursts at z>1.3 host X-ray selected obscured AGN. The radio emission from most of these ultra-luminous objects is dominated by star formation although the highest redshift (z=4.424) source has a substantial AGN contribution. Star-formation appears to contribute less than 1/3 of their X-ray luminosity. Our results support the inferences from SCUBA and IR data, that at z>1.5, star formation is observably more extended and more copious, it is closely linked to AGN activity and it is triggered differently, compared with star formation at lower redshifts. (1 data file).
    Original languageEnglish
    JournalVizieR Online Data Catalog
    Publication statusPublished - 2007


    • Radio sources
    • X-ray sources
    • Active gal. nuclei


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