标题： 活动星系核和极端亮红外星系的斯皮策光谱中的硅酸盐强度分布 显示英文标题

标题： The distribution of silicate strength in Spitzer spectra of AGNs and ULIRGs

摘要： 利用斯皮策望远镜上的红外光谱仪（IRS）观测的196个AGN（活动星系核）和ULIRG（极端亮红外星系）样本被用于研究9.7微米硅特征强度的分布。我们为类星体、Seyfert 1型和Seyfert 2型AGN以及ULIRG平均光谱进行了推导。我们发现类星体以发射型硅特征为特征，而Seyfert 1型同样表现为发射或弱吸收。Seyfert 2型则主要表现为弱硅吸收，ULIRG以强硅吸收为特征（平均表观光学深度约为1.5）。光度分布表明，最亮的类星体和ULIRG在静止框架5.5微米处的光度相似，并且比样本中最暗的AGN亮约10⁵倍。光谱特征和光度的分布与通过IRS发现的z~2处光学较暗的红外源相比，这些源也以强硅吸收为特征。研究发现，本地ULIRG是一种类似的群体，尽管它们的光度较低且吸收稍强于高红移源。 显示英文摘要

摘要： A sample of 196 AGNs and ULIRGs observed by the Infrared Spectrograph (IRS) on Spitzer is analyzed to study the distribution of the strength of the 9.7 micron silicate feature. Average spectra are derived for quasars, Seyfert 1 and Seyfert 2 AGNs, and ULIRGs. We find that quasars are characterized by silicate features in emission and Seyfert 1s equally by emission or weak absorption. Seyfert 2s are dominated by weak silicate absorption, and ULIRGs are characterized by strong silicate absorption (mean apparent optical depth about 1.5). Luminosity distributions show that luminosities at rest frame 5.5 micron are similar for the most luminous quasars and ULIRGs and are almost 10^5 times more luminous than the least luminous AGN in the sample. The distributions of spectral characteristics and luminosities are compared to those of optically faint infrared sources at z~2 being discovered by the IRS, which are also characterized by strong silicate absorption. It is found that local ULIRGs are a similar population, although they have lower luminosities and somewhat stronger absorption compared to the high redshift sources.