{
  "id": "1403.3856",
  "version": "v1",
  "published": "2014-03-15T22:08:09.000Z",
  "updated": "2014-03-15T22:08:09.000Z",
  "title": "A $Chandra-Swift$ View of Point Sources in Hickson Compact Groups: High AGN fraction but a dearth of strong AGNs",
  "authors": [
    "P. Tzanavaris",
    "S. C. Gallagher",
    "A. E. Hornschemeier",
    "K. Fedotov",
    "M. Eracleous",
    "W. N. Brandt",
    "T. D. Desjardins",
    "J. C. Charlton",
    "C. Gronwall"
  ],
  "comment": "77 pages (emulateapj), 28 tables, 11 figures. Accepted by ApJS on March 5, 2014",
  "journal": "ApJS (2014) 212 9",
  "categories": [
    "astro-ph.GA",
    "astro-ph.CO"
  ],
  "abstract": "We present $Chandra$ X-ray point source catalogs for 9 Hickson Compact Groups (HCGs, 37 galaxies) at distances $34 - 89$ 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 ($L_X$) 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 ($\\Gamma$), hardness ratios, and $L_X$, 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 (LINERs). Two-thirds of our galaxies have nuclear X-ray sources with $Swift$/UVOT counterparts. Two nuclei have $L_{X,{\\rm 0.5-8.0 keV}}$~$ > 10^{42}$ erg s$^{-1}$, are strong multi-wavelength AGNs and follow the known $\\alpha_{\\rm OX}-\\nu L_{\\nu,\\rm near UV}$ 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 $\\alpha_{\\rm OX}-\\nu L_{\\nu,\\rm near UV}$ 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 $M_R \\le -20$ and $L_{X,{\\rm 0.5-8.0 keV}} \\ge 10^{41}$ erg s$^{-1}$ is $0.08^{+0.35}_{-0.01}$, somewhat higher than the $\\sim 5%$ fraction in galaxy clusters.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2014-03-15T22:08:09.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "specific star formation rate",
      "hickson compact groups",
      "high agn fraction",
      "strong agns",
      "formation rate spiral galaxies"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1088/0067-0049/212/1/9",
      "journal": "The Astrophysical Journal Supplement Series",
      "year": 2014,
      "month": "May",
      "volume": 212,
      "number": 1,
      "pages": 9
    },
    "note": {
      "typesetting": "TeX",
      "pages": 77,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1286105,
      "adsabs": "2014ApJS..212....9T"
    }
  }
}