Astrophys. J., Suppl. Ser., 212, 9 (2014/May-0)
A Chandra-Swift view of point sources in Hickson compact groups: high AGN fraction but a dearth of strong AGNs.
TZANAVARIS P., GALLAGHER S.C., HORNSCHEMEIER A.E., FEDOTOV K., ERACLEOUS M., BRANDT W.N., DESJARDINS T.D., CHARLTON J.C. and GRONWALL C.
Abstract (from CDS):
We present Chandra X-ray point source catalogs for 9 Hickson Compact Groups (HCGs, 37 galaxies) at distances of 34-89 Mpc. We perform detailed X-ray point source detection and photometry and interpret the point source population by means of simulated hardness ratios. We thus estimate X-ray luminosities (LX) for all sources, most of which are too weak for reliable spectral fitting. For all sources, we provide catalogs with counts, count rates, power-law indices (Γ), hardness ratios, and LX, in the full (0.5-8.0 keV), soft (0.5-2.0 keV), and hard (2.0-8.0 keV) bands. We use optical emission-line ratios from the literature to re-classify 24 galaxies as star-forming, accreting onto a supermassive black hole (AGNs), transition objects, or low-ionization nuclear emission regions. Two-thirds of our galaxies have nuclear X-ray sources with Swift/UVOT counterparts. Two nuclei have L_X, 0.5-8.0 keV_>1042 erg/s, are strong multi-wavelength active galactic nuclei (AGNs), and follow the known αOX-νL ν(nearUV) correlation for strong AGNs. Otherwise, most nuclei are X-ray faint, consistent with either a low-luminosity AGN or a nuclear X-ray binary population, and fall in the "non-AGN locus" in αOX-νLν(nearUV)space, which also hosts other normal galaxies. Our results suggest that HCG X-ray nuclei in high specific star formation rate spiral galaxies are likely dominated by star formation, while those with low specific star formation rates in earlier types likely harbor a weak AGN. The AGN fraction in HCG galaxies with MR ≤ -20 and L_X, 0.5-8.0 keV_ ≥ 1041 erg/s is 0.08–0.010+0.35, somewhat higher than the ∼5% fraction in galaxy clusters.
catalogs - galaxies: active - galaxies: nuclei - ultraviolet: galaxies - X-rays: galaxies
VizieR on-line data:
<Available at CDS (J/ApJS/212/9): table1.dat table2.dat table3.dat>
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