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22 October 2010

Lyman 'bump' galaxies - II. A possible signature of massive extremely metal-poor or metal-free stars in z = 3.1 Lya emitters

Authors: Inoue, et al.
Link to article: arXiv:1010.2582

Observations of both Lya emission and Lyman continuum emission (the Lyman 'bump') are presented for a sample of galaxies at z = 3.1.  Besides exhibiting the Lyman 'bump' (blueward of Lya), which could be a sign of a population of metal-poor stars which have hard spectra, some of the galaxies also show a spatial offset between the Lya emission and the Lyman continuum emission.  The authors argue that the observed properties of the galaxies may be best explained by the presence of massive, metal-free stars.  Interestingly, it is the same galaxies which show the spatial offset which also appear to require the largest fractions of Pop III stars.  Indeed, this would be consistent with a scenario in which Pop III star formation may take place at relatively low redshift, albeit only at the outskirts of metal-enriched regions.


  1. While there are still uncertainties that must be overcome, the observations and their interpretation are intriguing. It is especially interesting that there is a spatial offset, as this would be broadly consistent with recent theoretical predictions for where Pop III stars could be found at low redshift (e.g. Tornatore et al. 2007; Johnson 2010). Perhaps similar studies can be carried out on galaxies at higher redshift, the expectation being that stronger evidence for Pop III star formation could be uncovered.