{
  "id": "2207.00466",
  "version": "v1",
  "published": "2022-07-01T14:41:39.000Z",
  "updated": "2022-07-01T14:41:39.000Z",
  "title": "ALMA resolves the first strongly-lensed Optical/NIR-dark galaxy",
  "authors": [
    "M. Giulietti",
    "A. Lapi",
    "M. Massardi",
    "M. Behiri",
    "M. Torsello",
    "Q. D'Amato",
    "T. Ronconi",
    "F. Perrotta",
    "A. Bressan"
  ],
  "comment": "17 Pages, 12 Figures, 7 Tables. Submitted to ApJ",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We present high-resolution ($\\lesssim0.1$arcsec) ALMA observations of the strongly-lensed galaxy HATLASJ113526.2-01460 at redshift $z\\sim3.1$ discovered in the Gama 12$^{\\rm th}$ field of the Herschel-ATLAS survey. The gravitationally lensed system is remarkably peculiar in that neither the background source nor the foreground lens show a clearly detected optical/NIR emission. We perform accurate lens modeling and source morphology reconstruction in three different (sub-)mm continuum bands, and in the C[II] and CO(8-7) spectral lines. The modeling indicates a foreground lensing (likely elliptical) galaxy with mass $\\gtrsim10^{11}\\, M_\\odot$ at $z\\gtrsim1.5$, while the source (sub-)mm continuum and line emissions are amplified by factors $\\mu\\sim6-13$. We estimate extremely compact sizes $\\lesssim0.5$ kpc for the star-forming region and $\\lesssim 1$ kpc for the gas component, with no clear evidence of rotation or of ongoing merging events. We perform broadband SED-fitting and retrieve the intrinsic de-magnified physical properties of the source, which is found to feature a very high star-formation rate $\\gtrsim10^3\\, M_\\odot$ yr$^{-1}$, that given the compact sizes is on the verge of the Eddington limit for starbursts; the radio luminosity at 6 cm from available EVLA observations is consistent with the star-formation activity. The galaxy is found to be extremely rich in gas $\\sim10^{11}\\, M_\\odot$ and dust $\\gtrsim10^9\\, M_\\odot$. The stellar content $\\lesssim10^{11}\\, M_\\odot$ places the source well above the main sequence of starforming galaxies, indicating that the starburst is rather young with estimated age $\\sim10^8$ yr. Our results indicate that the overall properties of HATLASJ113526.2-01460 are consistently explained by in-situ galaxy formation and evolution scenarios.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2022-07-01T14:41:39.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "first strongly-lensed optical/nir-dark galaxy",
      "alma resolves",
      "foreground lens",
      "in-situ galaxy formation",
      "source morphology reconstruction"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 17,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}