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

Curtis-Lake, E. and McLure, R. J. and Dunlop, J. S. and Schenker, M. and Rogers, A. B. and Targett, T. and Cirasuolo, M. and Almaini, O. and Ashby, M. L. N. and Bradshaw, E. J. and Finkelstein, S. L. and Dickinson, M. and Ellis, R. S. and Faber, S. M. and Fazio, G. G. and Ferguson, H. C. and Fontana, A. and Grogin, N. A. and Hartley, W. G. and Kocevski, D. D. and Koekemoer, A. M. and Lai, A. and Robertson, B. E. and Vanzella, E. and Willner, S. P. (2013) The ages, masses and star formation rates of spectroscopically confirmed z ∼ 6 galaxies in CANDELS. Monthly Notices of the Royal Astronomical Society, 429 (1). pp. 302-322. ISSN 0035-8711.

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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 10^9< M_* < 10^(10) 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. <50 Myr). Finally, considering all of the different star formation histories explored, we find that the median best-fitting ages are of the order of ≃200–300 Myr and that the objects with the tightest constraints indicate ages in the range of 50–200 Myr.

Item Type:Article
Related URLs:
URLURL TypeDescription
Ashby, M. L. N.0000-0002-3993-0745
Finkelstein, S. L.0000-0001-8519-1130
Dickinson, M.0000-0001-5414-5131
Ellis, R. S.0000-0001-7782-7071
Faber, S. M.0000-0003-4996-214X
Fazio, G. G.0000-0002-0670-0708
Ferguson, H. C.0000-0001-7113-2738
Koekemoer, A. M.0000-0002-6610-2048
Robertson, B. E.0000-0002-4271-0364
Willner, S. P.0000-0002-9895-5758
Additional Information:© 2012 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2012 November 1. Received 2012 October 26; in original form 2012 July 17. First published online: December 10, 2012. First we would like to thank the anonymous referee who helped to improve this manuscript. EC-L would like to acknowledge financial support from the UK Science and Technology Facilities Council (STFC) and the Leverhulme Trust. RJM would like to acknowledge the funding of the Royal Society via the award of a University Research Fellowship and the Leverhulme Trust via the award of a Philip Leverhulme research prize. JSD acknowledges the support of the Royal Society via a Wolfson Research Merit award, and also the support of the European Research Council via the award of an Advanced Grant. MC acknowledges the award of an STFC Advanced Fellowship. ABR, and EJB acknowledge the award of STFC PhD studentships. WGH acknowledges the award of an STFC PD RA. This work is based on observations taken by the CANDELS Multi-Cycle Treasury Program with the NASA/ESA HST, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. This work is based (in part) on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.
Funding AgencyGrant Number
Leverhulme TrustUNSPECIFIED
European Research Council (ERC)UNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
NASANAS 5-26555
Subject Keywords: galaxies: evolution galaxies: formation galaxies: high-redshift
Issue or Number:1
Record Number:CaltechAUTHORS:20130625-081052724
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Official Citation: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, and S. P. Willner The ages, masses and star formation rates of spectroscopically confirmed z ∼ 6 galaxies in CANDELS MNRAS (February 11, 2013) Vol. 429 302-322 first published online December 10, 2012 doi:10.1093/mnras/sts338
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:39065
Deposited By: Ruth Sustaita
Deposited On:25 Jun 2013 16:17
Last Modified:09 Mar 2020 13:19

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