Hayes, Matthew and Schaerer, Daniel and Östlin, Göran and Mas-Hesse, J. Miguel and Atek, Hakim and Kunth, Daniel (2011) On the Redshift Evolution of the Lyα Escape Fraction and the Dust Content of Galaxies. Astrophysical Journal, 730 (1). Art. No. 8. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20110414-085412150
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The Lyα emission line has been proven to be a powerful tool for studying evolving galaxies at the highest redshift. However, in order to use Lyα as a physical probe of galaxies, it becomes vital to know the Lyα escape fraction (f^(Lyα)_(esc)). Unfortunately, due to the resonant nature of Lyα, f^(Lyα)_(esc) may vary unpredictably and requires empirical measurement. Here, we compile Lyα luminosity functions (LFs) between redshifts z = 0 and 8 and, combined with Hα and ultraviolet data, assess how f^(Lyα)_(esc) evolves with redshift. We find a strong upward evolution in f^(Lyα)_(esc) over the range z = 0.3-6, which is well fit by the power law f^(Lyα)_(esc)α(1 + z)^ξwith ξ = (2.57^(+0.19)_(–0.12)). This predicts that f^(Lyα)_(esc) should reach unity at z = 11.1. By comparing f^(Lyα)_(esc) and E_(B–V) in individual galaxies we derive an empirical relationship between f^(Lyα)_(esc) and E_(B–V) , which includes resonance scattering and can explain the redshift evolution of f^(Lyα)_(esc) between z = 0 and 6 purely as a function of the evolution in the dust content of galaxies. Beyond z ≈ 6.5, f^(Lyα)_(esc) drops more substantially, an effect attributed to either ionizing photon leakage, or an increase in the neutral gas fraction of the intergalactic medium. While distinguishing between these two scenarios may be extremely challenging, by framing the problem this way we remove the uncertainty of the halo mass from Lyα-based tests of reionization. We finally derive a new method by which to estimate the dust content of galaxies, based purely upon the observed Lyα and UV LFs. These data are characterized by an exponential with an e-folding scale of z_(EBV) ≈ 3.4.
|Additional Information:||© 2011 American Astronomical Society. Received 2010 August 17; accepted 2010 December 23; published 2011 February 24. M.H. and D.S. are supported by the Swiss National Science Foundation. G.Ö. is a Swedish Royal Academy of Sciences research fellow supported by the Knut and Alice Wallenberg foundation, and also acknowledges support from the Swedish research council (VR). J.M.M.-H. is funded by Spanish MICINN grants CSD2006-00070 (CONSOLIDER GTC) and AYA2007-67965. D.K. and H.A. are supported by the Centre National d’Etudes Spatiales (CNES). We thank Mark Dijkstra and Mauro Giavalisco for useful feedback on the manuscript.|
|Subject Keywords:||dark ages, reionization, first stars; galaxies: evolution; galaxies: high-redshift; galaxies: luminosity function, mass function; galaxies: star formation|
|Classification Code:||PACS: 98.62.Ai; 98.62.Py; 98.62.Ra|
|Official Citation:||On the Redshift Evolution of the Lyα Escape Fraction and the Dust Content of Galaxies Matthew Hayes, Daniel Schaerer, Göran Östlin, J. Miguel Mas-Hesse, Hakim Atek and Daniel Kunth doi: 10.1088/0004-637X/730/1/8|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||14 Apr 2011 23:03|
|Last Modified:||26 Dec 2012 13:09|
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