Tuesday, July 17, 2012

1207.3663 (S. de Barros et al.)

Properties of z ~ 3 to z ~ 6 Lyman Break Galaxies. I. Impact of nebular emission at high redshift    [PDF]

S. de Barros, D. Schaerer, D. P. Stark
We present a homogeneous, detailed analysis of the SED of \sim1700 LBGs from the GOODS-MUSIC catalog with deep multi-wavelength photometry from U band to 8 \mum, to determine stellar mass, age, dust attenuation and SFR. Using our SED fitting tool which takes into account nebular emission, we explore a wide parameter space. We also explore a set of different SFHs. Nebular emission is found to significantly affect the determination of the physical parameters for the majority of LBGs at z \sim 3-6. We identify two populations of galaxies by determining the importance of the contribution of emission lines. We find that \sim65% of LBGs show detectable signs of emission lines, whereas \sim35 % show weak or no emission lines. This distribution is found over the entire redshift range. We interpret these groups as actively star forming and more quiescent LBGs respectively. We find that models with constant star formation cannot reproduce the entire range of observed colors, whereas models with nebular emission and variable (declining or rising) star formation histories succeed. Other arguments favoring episodic star formation and relatively short star formation timescales are also discussed. Taking into account nebular emission generally leads, for a given SFH, to a younger age, lower stellar mass, higher dust attenuation, and higher star formation rate, although with increased uncertainties. We find a trend of increasing dust attenuation with galaxy mass, and a large scatter in the SFR- M\star relation. Our analysis yields a trend of increasing specific star formation rate with redshift, as predicted by recent galaxy evolution models. SED models including nebular emission shed new light on the properties of LBGs with numerous important implications.
View original: http://arxiv.org/abs/1207.3663

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