{
  "id": "0906.3648",
  "version": "v2",
  "published": "2009-06-19T12:30:25.000Z",
  "updated": "2009-09-04T19:17:55.000Z",
  "title": "Dynamical masses of early-type galaxies at z~2: Are they truly superdense?",
  "authors": [
    "Michele Cappellari",
    "S. di Serego Alighieri",
    "A. Cimatti",
    "E. Daddi",
    "A. Renzini",
    "J. D. Kurk",
    "P. Cassata",
    "M. Dickinson",
    "A. Franceschini",
    "M. Mignoli",
    "L. Pozzetti",
    "G. Rodighiero",
    "P. Rosati",
    "G. Zamorani"
  ],
  "comment": "6 pages, 4 figures, LaTeX with emulateapj. Accepted for publication in ApJ Letters",
  "journal": "Astrophys.J.704:L34-L39,2009",
  "doi": "10.1088/0004-637X/704/1/L34",
  "categories": [
    "astro-ph.GA",
    "astro-ph.CO"
  ],
  "abstract": "We measured stellar velocity dispersions sigma and dynamical masses of 9 massive (M~10^11 Msun) early-type galaxies (ETG) from the GMASS sample at redshift 1.4<z<2.0. The sigma are based on individual spectra for two galaxies at z~1.4 and on a stacked spectrum for 7 galaxies with 1.6<z<2.0, with 202-h of exposure at the ESO Very Large Telescope. We constructed detailed axisymmetric dynamical models for the objects, based on the Jeans equations, taking the observed surface brightness (from deep HST/ACS observations), PSF and slit effects into account. Our dynamical masses M_Jeans agree within ~30% with virial estimates M_vir=5*Re*sigma^2/G, although the latter tend to be smaller. This suggests that sizes are not underestimated by more than a similar fraction. Our M_Jeans also agrees within a factor <2 with the M_pop previously derived using stellar population models and 11 bands photometry. This confirms that the galaxies are intrinsically massive. The inferred mass-to-light ratios M/L_U in the very age-sensitive rest frame U-band are consistent with passive evolution in the past ~1 Gyr (formation redshift z_f~3). A 'bottom-light' stellar Initial Mass Function (IMF) appears to be required to ensure close agreement between M_Jeans and M_pop at z~2, as it does at z~0. The GMASS ETGs are on average more dense than their local counterpart. However a few percent of local ETGs of similar dynamical masses also have comparable sigma and mass surface density Sigma_50 inside Re.",
  "revisions": [
    {
      "version": "v2",
      "updated": "2009-09-04T19:17:55.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "dynamical masses",
      "early-type galaxies",
      "truly superdense",
      "detailed axisymmetric dynamical models",
      "stellar initial mass function"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "journal": "The Astrophysical Journal",
      "year": 2009,
      "month": "Oct",
      "volume": 704,
      "number": 1
    },
    "note": {
      "typesetting": "LaTeX",
      "pages": 6,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 823635,
      "adsabs": "2009ApJ...704L..34C"
    }
  }
}