THE SPECTRAL ENERGY DISTRIBUTION OF POST-STARBURST GALAXIES IN THE NEWFIRM MEDIUM-BAND SURVEY: A LOW CONTRIBUTION FROM TP-AGB STARS
THE SPECTRAL ENERGY DISTRIBUTION OF POST-STARBURST GALAXIES IN THE NEWFIRM MEDIUM-BAND SURVEY: A LOW CONTRIBUTION FROM TP-AGB STARS
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DOI：
10.1088/2041-8205/722/1/l64
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发表时间：
2010-08
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通讯作者：
M. Kriek;I. Labbé;C. Conroy;K. Whitaker;P. V. van Dokkum;G. Brammer;M. Franx;G. Illingworth;D. Marchesini;A. Muzzin;R. Quadri;G. Rudnick
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作者：
M. Kriek;I. Labbé;C. Conroy;K. Whitaker;P. V. van Dokkum;G. Brammer;M. Franx;G. Illingworth;D. Marchesini;A. Muzzin;R. Quadri;G. Rudnick
恒星族合成（SPS）模型是许多星系演化研究的关键组成部分。不幸的是，这些模型对于某些恒星演化阶段的校准仍然很差。特别值得关注的是热脉冲渐近巨分支（TP-AGB）相的处理，因为不同的实现会导致衍生星系特性的系统差异。星暴后星系是一个很有前途的校准样本，因为 TP-AGB 恒星被认为在此阶段最为明显。在这里，我们使用 NEWFIRM 中波段巡天中的星暴后星系来评估不同的 SPS 模型。可用的光度测量允许在 0.7 ≲ z ≲ 2.0 处选择 62 个星暴后星系的均匀且定义明确的样本，从中我们构建了 1200-40000 Å 范围内的良好采样的复合光谱能量分布 (SED)。 SED 非常适合 Bruzual 和 Charlot SPS 模型，而 Maraston 模型不能同时再现 SED 的静止框架光学和近红外部分。当拟合限制在 λ < 6000 Å 时，Maraston 模型会高估近红外光度，这意味着这些模型给予 TP-AGB 恒星过多的权重。使用 Conroy 等人提出的灵活的 SPS 模型。假设太阳金属丰度，我们发现 TP-AGB 恒星对集成 SED 的贡献比最新的 Padova TP-AGB 模型预测低约 3 倍。这是否是由于 TP-AGB 恒星的辐射光度较低、寿命较短和/或尘埃遮蔽严重所致，仍有待解决。总而言之，我们的数据要求 TP-AGB 恒星对星暴后星系 SED 的贡献较低。
Stellar population synthesis (SPS) models are a key ingredient of many galaxy evolution studies. Unfortunately, the models are still poorly calibrated for certain stellar evolution stages. Of particular concern is the treatment of the thermally pulsing asymptotic giant branch (TP-AGB) phase, as different implementations lead to systematic differences in derived galaxy properties. Post-starburst galaxies are a promising calibration sample, as TP-AGB stars are thought to be most prominently visible during this phase. Here, we use post-starburst galaxies in the NEWFIRM medium-band survey to assess different SPS models. The available photometry allows the selection of a homogeneous and well-defined sample of 62 post-starburst galaxies at 0.7 ≲ z ≲ 2.0, from which we construct a well-sampled composite spectral energy distribution (SED) over the range 1200–40000 Å. The SED is well fit by the Bruzual & Charlot SPS models, while the Maraston models do not reproduce the rest-frame optical and near-infrared parts of the SED simultaneously. When the fitting is restricted to λ < 6000 Å, the Maraston models overpredict the near-infrared luminosity, implying that these models give too much weight to TP-AGB stars. Using the flexible SPS models by Conroy et al. and assuming solar metallicity, we find that the contribution of TP-AGB stars to the integrated SED is a factor of ∼3 lower than predicted by the latest Padova TP-AGB models. Whether this is due to lower bolometric luminosities, shorter lifetimes, and/or heavy dust obscuration of TP-AGB stars remains to be addressed. Altogether, our data demand a low contribution from TP-AGB stars to the SED of post-starburst galaxies.