The ages, masses and star formation rates of spectroscopically confirmed z ˜ 6 galaxies in CANDELS

E. Curtis-Lake, R. J. McLure, J. S. Dunlop, M. Schenker, A. B. Rogers, T. Targett, M. Cirasuolo, O. Almaini, M. L. N. Ashby, E. J. Bradshaw, S. L. Finkelstein, M. Dickinson, R. S. Ellis, S. M. Faber, G. G. Fazio, H. C. Ferguson, A. Fontana, N. A. Grogin, W. G. Hartley, D. D. KocevskiA. M. Koekemoer, K. Lai, B. E. Robertson, E. Vanzella, S. P. Willner

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

We report the results of a study exploring the stellar populations of 13 luminous (L > 1.2L*), spectroscopically confirmed, galaxies in the redshift interval 5.5 <z <6.5, all with Hubble Space Telescope (HST) Wide Field Camera 3/infrared and Spitzer Infrared Array Camera imaging from the HST/Cosmic Assembly Near-infrared Deep Survey and Spitzer Extended Deep Survey. Based on fitting the observed photometry with galaxy spectral energy distribution (SED) templates covering a wide range of different star formation histories, including exponentially increasing star formation rates and a self-consistent treatment of Lyα emission, we find that the derived stellar masses lie within the range of 109<M* <1010 M⊙ and are robust to within a factor of 2. In contrast, we confirm previous reports that the ages of the stellar populations are poorly constrained. Although the best-fitting models for 3/13 of the sample have ages of ≳300 Myr, the degeneracies introduced by dust extinction mean that only two of these objects actually require a ≳300 Myr old stellar population to reproduce the observed photometry. We also explore SED fitting with more general, two-component models (burst plus ongoing star formation), thereby relaxing the requirement that the current star formation rate and assembled stellar mass must be coupled, and allow for nebular line+continuum emission. On average, the inclusion of nebular emission leads to lower stellar mass estimates (median offset 0.18 dex), moderately higher specific star formation rates, and allows for a wider range of plausible stellar ages. However, based on our SED modelling, we find no strong evidence for extremely young ages in our sample (i.e.
Original languageEnglish
Pages (from-to)302-322
JournalMonthly Notices of the Royal Astronomical Society
Publication statusPublished - 1 Feb 2013

Keywords / Materials (for Non-textual outputs)

  • galaxies: evolution
  • galaxies: formation
  • galaxies: high-redshift


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