Alice E. Shapley, Charles C. Steidel, Allison L. Strom, Milan Bogosavljević, Naveen A. Reddy, Brian Siana, Robin E. Mostardi, Gwen C. Rudie

Research output: Contribution to journalArticlepeer-review


We present observations of Q1549-C25, an L∗star-forming galaxy at z<3.15 for which Lyman-continuum (LyC) radiation is significantly detected in deep Keck/LRIS spectroscopy. We find no evidence of contamination from a lower-redshift interloper close to the line of sight in the high signal-to-noise spectrum of Q1549-C25. Furthermore, the morphology of Q1549-C25 in V606, J125, and H160 Hubble Space TelESCope (HST) imaging reveals that the object consists of a single, isolated component within 1?. In combination, these data indicate Q1549-C25 as a clean spectroscopic detection of LyC radiation, only the second such object discovered to date at Z3. We model the spectral energy distribution of Q1549-C25, finding evidence of negligible dust extinction, an age (assuming continuous star formation) of1 Gyr, and a stellar mass of M∗< 7.9 109 M⊙. Although it is not possible to derive strong constraints on the absolute ESCape fraction of LyC emission, fESC(LyC), from a single object, we use simulations of intergalactic and circumgalactic absorption to infer fESC (LyC) ≥ 0.51 at 95% confidence. The combination of deep Keck/LRIS spectroscopy and Hubble Space TelESCope imaging is required to assemble a larger sample of objects like Q1549-C25, and obtain robust constraints on the average fESC(LyC) at z 3 and beyond.

Original languageEnglish (US)
Article numberL24
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Aug 1 2016


  • Cosmology: Observations
  • Diffuse radiation
  • Galaxies: High-redshift
  • Intergalactic Medium

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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