Abstract
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 language | English |
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Pages (from-to) | 302-322 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 429 |
Publication status | Published - 1 Feb 2013 |
Keywords
- galaxies: evolution
- galaxies: formation
- galaxies: high-redshift