The Hubble Space Telescope colours of high-redshift Population III galaxies with strong Lyα emission

Erik Zackrisson*, Akio K. Inoue, Claes Erik Rydberg, Florent Duval

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


Population III (pop III) galaxies, made partly or exclusively of metal-free stars, are predicted to exist at high redshifts and may produce very strong Lyα emission. A substantial fraction of these Lyα photons are likely absorbed in the intergalactic medium at z > 6, but recent simulations suggest that significant Lyα emission may be detectable up to z≈ 8.5, i.e. well into the reionization epoch. Here, we argue that high-redshift pop III galaxies with strong Lyα emission can be identified in Hubble Space Telescope imaging data because of their unusual colours. We quantify this effect in some of the filters used in Y-band dropout searches for galaxies at z≈ 8 and find that pop III galaxies with high Lyα fluxes may exhibit much bluer J-H colours at z≈ 8-10 than any normal type of galaxy at these redshifts. This colour signature can arise even if pop III stars account for as little as ~10-3 to 10-2 of the stellar mass in these galaxies. Some of the anomalously blue objects reported in current Y-band dropout samples do in fact meet the colour criteria for Lyα-emitting pop III galaxies.

Original languageEnglish
Pages (from-to)L104-L108
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
Publication statusPublished - 2011 Nov
Externally publishedYes


  • Dark ages, reionization, first stars
  • Galaxies: high-redshift
  • Stars: Population III

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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