Deep-Imaging Observations of a Candidate of an Absorbed QSO at z = 0.653, AX J131831+3341

The results of deep-imaging observations of a candidate of an absorbed QSO atz=0.653, AX J131831+3341, are presented. AX J131831+3341 was found during thecourse of optical follow-up observations of the ASCA Large Sky Survey, and hasan X-ray luminosity of 10^{45} erg s^{-1} (2-10keV), which corresponds to thoseof QSOs. Its optical spectrum shows no significant broad H_beta emission line,suggesting that the object is an absorbed QSO. Deep R and V band images revealthe presence of a point-like nucleus and an asymmetric extended component. Thenuclear component has a blue color, and the optical magnitude is much fainterthan that expected from the observed X-ray flux for typical type-1 AGNs. Thesephotometric properties and the presence of broad MgII 2800A emission can beexplained simultaneously if the observed nuclear light is dominated byscattered nuclear light, though there is a possibility that the nuclearcomponent is a slightly absorbed nucleus if its intrinsic X-ray to optical fluxratio is the largest among X-ray selected AGNs. The size of the extendedcomponent, which is thought to be the host galaxy of the QSO, is larger thanthose of normal disk galaxies at z=0-0.75, and the absolute magnitude issimilar to those of the brightest host galaxies of QSOs at redshifts smallerthan 0.5. The V-R and R-I colors of the component are consistent with a 1Gyr-old stellar population model without absorption.Comment: 19 pages with 5 figures, accepted for publication for PAS