Exploring the nature of the Lyman-α emitter CR7

Tilman Hartwig, Muhammad A. Latif, Mattis Magg, Volker Bromm, Ralf S. Klessen, Simon C. O. Glover, Daniel J. Whalen, Eric W. Pellegrini, Marta Volonteri

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Abstract

CR7 is the brightest Lyman-α emitter observed at z > 6, which shows very strong Lyman-α and HeII 1640\AA\ line luminosities, but no metal line emission. Previous studies suggest that CR7 hosts either young primordial stars with a total stellar mass of ∼107M or a black hole of ≳106M⊙. Here, we explore different formation scenarios for CR7 with a semianalytical model, based on the random sampling of dark matter merger trees. We are unable to reproduce the observational constraints with a primordial stellar source, given our model assumptions, due to the short stellar lifetimes and the early metal enrichment. Black holes that are the remnants of the first stars are either not massive enough, or reside in metal-polluted haloes, ruling out this possible explanation of CR7. Our models instead suggest that direct collapse black holes, which form in metal-free haloes exposed to large Lyman-Werner fluxes, are more likely the origin of CR7. However, this result is derived under optimistic assumptions and future observations are necessary to further constrain the nature of CR7.
Original languageEnglish
Pages (from-to)2184-2202
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Volume462
Issue number2
Early online date28 Jul 2016
DOIs
Publication statusPublished - 21 Oct 2016

Keywords

  • astro-ph.GA
  • astro-ph.CO
  • black hole physics
  • stars: Population III
  • galaxies: high-redshift
  • early Universe

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