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

Дата и время публикации : 2012-07-11T18:06:01Z

Авторы публикации и институты :
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

Ссылка на журнал-издание: Ссылка на журнал-издание не найдена
Коментарии к cтатье: 23 pages, 12 figures, for submission to MNRAS
Первичная категория: astro-ph.CO

Все категории : astro-ph.CO

Краткий обзор статьи: 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<z<6.5, all with WFC3/IR and IRAC imaging from the HST/CANDELS and Spitzer/SEDS surveys. Based on fitting the observed photometry with SED templates covering a wide range of different star-formation histories, and a self consistent treatment of Lyman-alpha emission, we find that the derived stellar masses lie within the range 10^9 Msun < M*< 10^10 Msun and are robust to within a factor of two. In contrast, we confirm previous reports that the ages of the stellar populations are poorly constrained. Although the best-fitting models for three objects have ages >= 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).

Category: Physics