Hot Dust in Panchromatic SED Fitting: Identification of Active Galactic Nuclei and Improved Galaxy Properties
Hot Dust in Panchromatic SED Fitting: Identification of Active Galactic Nuclei and Improved Galaxy Properties
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DOI：
10.3847/1538-4357/aaa8db
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发表时间：
2017-09
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影响因子：
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通讯作者：
J. Leja;Benjamin D. Johnson;C. Conroy;P. V. Dokkum
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作者：
J. Leja;Benjamin D. Johnson;C. Conroy;P. V. Dokkum
全星系 SED 的正向建模是一项强大的技术，可以对恒星年龄、尘埃特性和金属丰度提供自洽的约束。然而，这些结果的准确性取决于模型的准确性。不确定性的一个重要来源是模糊 AGN 的影响，因为它们相对常见，并且可以产生大量的中红外 (MIR) 发射。在这里，我们将尘埃 AGN 鸟居的发射纳入 Prospector SED 拟合框架中，并拟合 129 个附近星系的 UV-IR 宽带光度测量。我们发现 10% 的拟合星系拥有 AGN，贡献了超过 10% 的观测到的星系 MIR 光度。我们通过以下方式论证了该 AGN 组件的必要性。首先，我们将观察到的光谱特征与根据光度测量模型拟合预测的光谱特征进行比较。我们发现 AGN 分量极大地改善了对观测到的 Hα 和 Hβ 光度以及中红外 Akari 和 Spitzer/IRS 光谱的预测。其次，我们表明，包含 AGN 成分会使恒星年龄和恒星形成率最多改变 10 倍，尘埃衰减最多改变 2.5 倍。最后，我们表明我们的模型 AGN 分量的强度与独立的 AGN 指标相关，表明这些星系确实存在 AGN。值得注意的是，通过简单的 MIR 颜色选择，只有 46% 的 SED 检测到的 AGN 能够被检测到。基于这些结果，我们得出结论，在没有 AGN 组件的情况下拟合 MIR 数据的 SED 模型很容易受到其导出参数的重大偏差的影响。
Forward modeling of the full galaxy SED is a powerful technique, providing self-consistent constraints on stellar ages, dust properties, and metallicities. However, the accuracy of these results is contingent on the accuracy of the model. One significant source of uncertainty is the contribution of obscured AGN, as they are relatively common and can produce substantial mid-IR (MIR) emission. Here we include emission from dusty AGN torii in the Prospector SED-fitting framework, and fit the UV–IR broadband photometry of 129 nearby galaxies. We find that 10% of the fitted galaxies host an AGN contributing >10% of the observed galaxy MIR luminosity. We demonstrate the necessity of this AGN component in the following ways. First, we compare observed spectral features to spectral features predicted from our model fit to the photometry. We find that the AGN component greatly improves predictions for observed Hα and Hβ luminosities, as well as mid-infrared Akari and Spitzer/IRS spectra. Second, we show that inclusion of the AGN component changes stellar ages and SFRs by up to a factor of 10, and dust attenuations by up to a factor of 2.5. Finally, we show that the strength of our model AGN component correlates with independent AGN indicators, suggesting that these galaxies truly host AGN. Notably, only 46% of the SED-detected AGN would be detected with a simple MIR color selection. Based on these results, we conclude that SED models which fit MIR data without AGN components are vulnerable to substantial bias in their derived parameters.