Issue |
A&A
Volume 502, Number 2, August I 2009
|
|
---|---|---|
Page(s) | 423 - 426 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361/200911781 | |
Published online | 04 June 2009 |
The impact of nebular emission on the ages of z
6 galaxies
1
Geneva Observatory, University of Geneva, 51 Ch. des Maillettes, 1290 Versoix, Switzerland e-mail: daniel.schaerer@unige.ch
2
Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 Avenue E. Belin, 31400 Toulouse, France
Received:
3
February
2009
Accepted:
27
April
2009
Aims. We examine the influence of nebular continuous and line emission in high-redshift star forming galaxies on determinations of their age, formation redshift, and other properties from SED fits.
Methods.
We include nebular emission consistently with the stellar emission in our SED fitting tool
and analyse differentially a sample of 10 galaxies in the GOODS-S field studied
earlier elsewhere.
Results.
We find that the apparent Balmer/4000 Å breaks observed in a number of galaxies
detected at
3.6 μm with IRAC/Spitzer can be mimicked by the presence of
strong restframe optical emission lines, implying in particular younger ages than previously thought.
Applying these models to the small sample of
galaxies, we find that this effect
may lead to a typical downward revision of their stellar ages by a factor ∼3.
In consequence their average formation redshift
may be reduced drastically, and these objects may not have contributed to cosmic
reionisation at
. Extinction and stellar mass estimates may also be
somewhat modified, but to a lesser extent.
Conclusions. Careful SED fits including nebular emission and treating properly uncertainties and degeneracies are necessary for more accurate determinations of the physical parameters of high-z galaxies.
Key words: galaxies: starburst / galaxies: high-redshift
© ESO, 2009
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