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arXiv · 1207.2727

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. Kocevski·A. M. Koekemoer·K. Lai·B. E. Robertson·E. Vanzella·S. P. Willner
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Abstract

We report the results of a study exploring the stellar populations of 13 luminous (L>L*), spectroscopically confirmed, galaxies in the redshift interval 5.5 = 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. Moreover, when considering only smoothly-varying star-formation histories, we observe a clear tension between the data and models such that a galaxy SED template with an old age is often chosen in order to try and fit objects with blue UV-slopes but red UV-to-optical colours. To break this tension we explore SED fitting with two-component models (burst plus on-going star-formation) and allow for nebular 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 (<50 Myr). Finally, considering all of the different star-formation histories explored, we find that the median best-fitting ages are of the order 200-300 Myr and that the objects with the tightest constraints indicate ages in the range 50-200 Myr (Abridged).

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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. Kocevski, A. M. Koekemoer, K. Lai, B. E. Robertson, E. Vanzella, S. P. Willner. 2012-07-23. The ages, masses and star-formation rates of spectroscopically confirmed z~6 galaxies in CANDELS. https://doi.org/10.1093/mnras%2Fsts338

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