Manners, J.C.; Serjeant, S.; Bottinelli, S.; Vaccari, M.; Franceschini, A.; Perez-Fournon, I.; Gonzalez-Solares, E.; Willott, C.J.; Johnson, O.; Almaini, O.; Rowan-Robinson, M. and Oliver, S.
Mid-infrared sources in the ELAIS Deep X-ray Survey.
Monthly Notices of the Royal Astronomical Society, 355(1) pp. 97–105.
We present a cross-correlation of the European Large Area Infrared Space Observatory (ISO) survey (ELAIS) with the ELAIS Deep X-ray Survey of the N1 and N2 fields. There are seven Chandra point sources with matches in the ELAIS Final Analysis 15-μm catalogue, out of a total of 28 extragalactic ISO sources present in the Chandra fields. Five of these are consistent with active galactic nuclei (AGN) giving an AGN fraction of ~19 per cent in the 15-μm flux range 0.8-6mJy. We have co-added the hard X-ray fluxes of the individually undetected ISO sources and find a low significance detection consistent with star formation in the remaining population. We combine our point source cross-correlation fraction with the XMM-Newton observations of the Lockman Hole and Chandra observations of the Hubble Deep Field North to constrain source count models of the mid-infrared galaxy population. The low dust-enshrouded AGN fraction in ELAIS implied by the number of cross-identifications between the ELAIS mid-infrared sample and the Chandra point sources is encouraging for the use of mid-infrared surveys to constrain the cosmic star formation history, provided there are not further large undetected populations of Compton-thick AGN.
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