Siana, Brian and Teplitz, Harry I. and Colbert, James and Ferguson, Henry C. and Dickinson, Mark and Brown, Thomas M. and Conselice, Christopher J. and de Mello, Duilia F. and Gardner, Jonathan P. and Giavalisco, Mauro and Menanteau, Felipe (2007) New Constraints on the Lyman Continuum Escape Fraction at z ~ 1.3. Astrophysical Journal, 668 (1). pp. 62-73. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20100205-102215449
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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, f_(1500)/f_(700), and allowing a conversion from f_(700) to relative escape fraction (f_(esc,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, f_(esc,rel) < 1.0 with some limits as low as f_(esc,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.
|Additional Information:||© 2007 The American Astronomical Society. Received 2007 March 13; accepted 2007 June 23. The authors would like to thank M. Malkan for reanalyzing the results of M03 to facilitate direct comparison with our data. The research described in this paper was carried out, in part, by the Jet Propulsion Laboratory, California Institute of Technology, and was sponsored by the National Aeronautics and Space Administration (NASA). Support for programs 9478 and 10403 was provided by NASA through grants from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Facilities: HST(ACS).|
|Subject Keywords:||cosmology : observations; galaxies : evolution; ultraviolet : galaxies|
|Official Citation:||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, and Felipe Menanteau 2007 ApJ 668 62-73 doi: 10.1086/521185|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||09 Feb 2010 03:26|
|Last Modified:||26 Dec 2012 11:45|
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