光学和中红外光谱在星系和活动星系核演化研究中具有很强的优势互补性。大型光谱巡天为我们提供了大样本高质量光学光谱，但光学光谱一定程度上都受尘埃消光的影响。而中红外光谱则直接显示尘埃特征，并且有丰富的可以指示各种激发强度的分子原子谱线。本课题拟交叉匹配SDSS DR7星系数据库和Spitzer低色散光谱库，构建目前最大的具有统一光学和中红外光谱的样本（S3AGA：Spitzer-SDSS Spectral Atlas of Galaxies and AGNs）。本课题中，我们将利用S3AGA样本，不仅在技术上对很多常用的中红外光谱特征的测量方法进行评估，还将在科学上针对AGN尘埃特性和寄主星系开展一系列深入的研究，如利用II型AGN的硅吸收和光学Balmer比研究光学中红外消光及其反应的尘埃性质、利用部分I型AGN的硅发射特征研究尘埃的化学组成、利用光学中红外原子发射线研究AGN的寄主星系等。

Optical and infrared spectra are two most important tools in understanding the evolution of galaxies and Active Galactic Nuclei (AGNs). Large optical spectroscopic surveys (such as the Sloan Digital Sky Survey, SDSS) provide us millions of high-quality optical spectra of galaxies. However, optical spectra always suffer from extinction to some degree, and current extinction-correction method is quite uncertain in many ways. Meanwhile, infrared spectra directly show dust features, and there are abundant molecular and atomic spectral features in the infrared that can be used to indicate different excitation states of galaxies. In this project, we propose to cross-match all spectra observed by the Spitzer IRS low-resolution modules with the SDSS DR7 catalog, constructing the largest sample of galaxies with uniform optical (from SDSS) and infrared (from Spitzer IRS) spectra. We name this sample S3AGA：Spitzer-SDSS Spectral Atlas of Galaxies and AGNs. With this sample, we will not only calibrate different methods estimating the infrared features, but also carry out a series of studies on the dust properties and the host galaxies of AGNs.