Curtis-Lake, E., McLure, R. J., Dunlop, J. S., Schenker, M., Rogers, A. B., Targett, T., Cirasuolo, M., Almaini, O., Ashby, Matthew L. N., Bradshaw, E. J., Finkelstein, S. L., Dickinson, M., Ellis, R. S., Faber, S. M., Fazio, Giovanni G., Ferguson, H. C., Fontana, A., Grogin, N. A., Hartley, W. G., Kocevski, D. D., Koekemoer, A. M., Lai, K., Robertson, B. E., Vanzella, E., and Willner, Steven P. 2013. "The ages, masses and star formation rates of spectroscopically confirmed z ˜ 6 galaxies in CANDELS." Monthly Notices of the Royal Astronomical Society, 429 302–322. https://doi.org/10.1093/mnras/sts338.
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 9*10 M&sun; 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.
