Publication Date:
2010-03-26
Description:
The Lyman-alpha (Lyalpha) emission line is the primary observational signature of star-forming galaxies at the highest redshifts, and has enabled the compilation of large samples of galaxies with which to study cosmic evolution. The resonant nature of the line, however, means that Lyalpha photons scatter in the neutral interstellar medium of their host galaxies, and their sensitivity to absorption by interstellar dust may therefore be greatly enhanced. This implies that the Lyalpha luminosity may be significantly reduced, or even completely suppressed. Hitherto, no unbiased empirical test of the escaping fraction (f(esc)) of Lyalpha photons has been performed at high redshifts. Here we report that the average f(esc) from star-forming galaxies at redshift z = 2.2 is just 5 per cent by performing a blind narrowband survey in Lyalpha and Halpha. This implies that numerous conclusions based on Lyalpha-selected samples will require upwards revision by an order of magnitude and we provide a benchmark for this revision. We demonstrate that almost 90 per cent of star-forming galaxies emit insufficient Lyalpha to be detected by standard selection criteria. Both samples show an anti-correlation of f(esc) with dust content, and we show that Lyalpha- and Halpha-selection recovers populations that differ substantially in dust content and f(esc).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hayes, Matthew -- Ostlin, Goran -- Schaerer, Daniel -- Mas-Hesse, J Miguel -- Leitherer, Claus -- Atek, Hakim -- Kunth, Daniel -- Verhamme, Anne -- de Barros, Stephane -- Melinder, Jens -- England -- Nature. 2010 Mar 25;464(7288):562-5. doi: 10.1038/nature08881.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Observatoire Astronomique de l'Universite de Geneve, 51 chemin des Maillettes, CH-1290 Sauverny, Switzerland. matthew.hayes@unige.ch〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20336139" target="_blank"〉PubMed〈/a〉
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
