HST Imaging of the Ionizing Radiation from a Star-forming Galaxy at z=3.794

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  • Zhiyuan Ji
  • Mauro Giavalisco
  • Eros Vanzella
  • Brian Siana
  • Laura Pentericci
  • Anne Jaskot
  • Teng Liu
  • Mario Nonino
  • Henry C. Ferguson
  • Marco Castellano
  • Filippo Mannucci
  • Daniel Schaerer
  • Fynbo, Johan Peter Uldall
  • Casey Papovich
  • Adam C. Carnall
  • Ricardo Amorin
  • Raymond C. Simons
  • Nimish Hathi
  • Fergus Cullen
  • Derek McLeod

We report on the Hubble Space Telescope (HST) detection of the Lyman-continuum (LyC) radiation emitted by a galaxy at redshift z = 3.794 dubbed Ion1. The LyC from Ion1 is detected at 820-890 A with HST WFC3/UVIS in the F410M band (m(410) = 27.60 0.36 m(AB), peak signal-to-noise ratio (S/N) = 4.17 in an r = 012 aperture) and 700-830 A with the Very Large Telescope (VLT)/VIMOS in the U band (m(U) = 27.84 0.19 m(AB), peak S/N = 6.7 with an r = 06 aperture). A 20 hr VLT/VIMOS spectrum shows low- and high-ionization interstellar metal absorption lines and the P Cygni profile of C iv and Ly alpha in absorption. The latter spectral feature differs from what observed in known LyC emitters, which show strong Ly alpha emission. An HST far-UV color map reveals that the LyC emission escapes from a region of the galaxy that is bluer than the rest. The F410M image shows that the centroid of the LyC emission is offset from the centroid of the nonionizing UV emission by 012 003, corresponding to 0.85 0.21 kpc, and that its morphology is likely moderately resolved. These morphological characteristics favor a scenario where the LyC photons produced by massive stars escape from low H i column density "cavities" in the interstellar medium. We also collect the VIMOS U-band images of 107 Lyman-break galaxies at 3.40 z(spec) <3.95, i.e., sampling the LyC, and stack them with inverse-variance weights. No LyC emission is detected in the stacked image, resulting in a 32.5 m(AB) flux limit (1 sigma) and an upper limit of absolute LyC escape fraction f(esc)(abs)

Original languageEnglish
Article number109
JournalAstrophysical Journal
Volume888
Issue number2
Number of pages19
ISSN0004-637X
DOIs
Publication statusPublished - 10 Jan 2020

    Research areas

  • Reionization, High-redshift galaxies, Extragalactic astronomy, ORIGINS DEEP SURVEY, LYMAN-CONTINUUM EMISSION, SPACE-TELESCOPE SEARCH, GOODS-SOUTH FIELD, ESCAPE FRACTION, VLT/FORS2 SPECTROSCOPY, LY-ALPHA, FAR-ULTRAVIOLET, CENT LEAKAGE, PHOTONS

ID: 247444616