New constraints on the Lyman continuum escape fraction at z ∼ 1.3

Brian Siana, Harry I. Teplitz, James Colbert, Henry C. Ferguson, Mark Dickinson, Thomas M. Brown, Christopher J. Conselice, Duilia F. De Mello, Jonathan P. Gardner, Mauro Giavalisco, Felipe Menanteau

Research output: Contribution to journalArticlepeer-review


We examine deep far-UV (1600 Å) imaging of the HDF-N and the HUDF to search for leaking Lyman continuum radiation from starburst galaxies at z ∼ 1.3. There are 21 (primarily sub-L*) galaxies with spectroscopic redshifts between 1.1 < z < 1.5, and none are detected in the far-UV. We fit stellar population templates to the galaxies' optical/near-infrared SEDs to determine the starburst age and level of dust attenuation for each individual galaxy, giving a more accurate estimate of the intrinsic Lyman continuum ratio, f1500/f700, allowing a conversion from f700 to relative escape fraction (fesc,rel). We show that previous high-redshift studies may have underestimated the amplitude of the Lyman break, and thus the relative escape fraction, by a factor ∼2. Once the starburst age and intergalactic H I absorption are accounted for, 18 galaxies in our sample have limits to the relative escape fraction, fesc,rel < 1.0 with some limits as low as fesc,rel < 0.10 and a stacked limit of fesc,rel < 0.08. This demonstrates, for the first time, that most sub-L* galaxies at this redshift do not have large escape fractions. When combined with a similar study of more luminous galaxies at the same redshift, we show that, if all star-forming galaxies at z ∼ 1 have similar relative escape fractions, the value must be less than 0.14 (3 σ). We also show that less than 20% (3 σ) of star-forming galaxies at z ∼ 1 have relative escape fractions near unity. These limits contrast with the large escape fractions found at z ∼ 3 and suggest that the average escape fraction has decreased between z ∼ 3 and z ∼ 1.

Original languageEnglish (US)
Pages (from-to)62-73
Number of pages12
JournalAstrophysical Journal
Issue number1 I
StatePublished - 2007
Externally publishedYes


  • Cosmology: observations
  • Galaxies: evolution
  • Ultraviolet: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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