The impact of nebular emission on the ages of z~6 galaxies
The impact of nebular emission on the ages of z~6 galaxies
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星云发射对z~6星系年龄的影响
DOI：
10.1051/0004-6361/200911781
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
S. D. Barros
中科院分区：
文献类型：
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作者：
D. Schaerer;S. D. Barros
我们研究了高红移恒星形成星系中星云连续发射和线发射对SED拟合确定它们的年龄、形成红移和其他特性的影响。在我们的SED拟合工具中，我们将星云发射与恒星发射相一致，并对早期由Eyles等人（2007）研究的GOODS-S场中的10个z~6星系样本进行了差异分析。我们发现，在IRAC/Spitzer探测到的b> ~3.6微米的z~6星系中观测到的明显的Balmer/4000 Ang断裂可以通过强重构光学发射线的存在来模拟，这表明它们的年龄比以前认为的要年轻。将这些模型应用到z~6星系的小样本中，我们发现这种效应可能导致它们的恒星年龄被典型地向下修正了~3倍。因此，它们的平均形成红移可能会急剧减少，并且这些物体可能不会对zbbb60的宇宙再电离做出贡献。灭绝和恒星质量的估计也可能有所修改，但幅度较小。仔细的SED拟合包括星云发射和适当处理不确定性和简并对于更准确地确定高z星系的物理参数是必要的。
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. We include nebular emission consistently with the stellar emission in our SED fitting tool and analyse differentially a sample of 10 z~6 galaxies in the GOODS-S field studied earlier by Eyles et al. (2007). We find that the apparent Balmer/4000 Ang breaks observed in a number of z~6 galaxies detected at >~3.6 micron 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 z~6 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 drastically be reduced, and these objects may not have contributed to cosmic reionisation at z>6. Extinction and stellar mass estimates may also be somewhat modified, but to a lesser extent. 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.