TY - JOUR
T1 - The Ages, Masses and Star Formation Rates of Spectroscopically Confirmed z Similar to 6 Galaxies in CANDELS
AU - Curtis-Lake, E.
AU - McLure, R. J.
AU - Dunlop, J. S.
AU - Targett, T.
AU - Cirasuolo, M.
AU - Almaini, O.
AU - Ellis, R. S.
PY - 2013/2/1
Y1 - 2013/2/1
N2 - 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 Ly alpha emission, we find that the derived stellar masses lie within the range of 10(9) <M-* <10(10) M-circle dot 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 greater than or similar to 300 Myr, the degeneracies introduced by dust extinction mean that only two of these objects actually require a greater than or similar to 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 similar or equal to 200-300 Myr and that the objects with the tightest constraints indicate ages in the range of 50-200 Myr.
AB - 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 Ly alpha emission, we find that the derived stellar masses lie within the range of 10(9) <M-* <10(10) M-circle dot 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 greater than or similar to 300 Myr, the degeneracies introduced by dust extinction mean that only two of these objects actually require a greater than or similar to 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 similar or equal to 200-300 Myr and that the objects with the tightest constraints indicate ages in the range of 50-200 Myr.
KW - galaxies: evolution
KW - galaxies: formation
KW - galaxies: high-redshift
U2 - 10.1093/mnras/sts338
DO - 10.1093/mnras/sts338
M3 - Article
VL - 429
SP - 302
EP - 322
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 1
ER -