低红移帕洛玛-格林类星体与复合光谱的近红外光谱研究
Near-Infrared Spectroscopy of Low-Redshift Palomar-Green Quasars and Composite Spectra
AI总结：
本研究观测87个低红移PG类星体的近红外光谱，构建其复合光谱并分析特性，发现光度更高的近红外复合光谱长波长更红，为AGN尘埃发射研究提供了近红外基准。
AI中文摘要：
帕洛玛-格林（PG）类星体已被广泛用于在多个波段确立低红移明亮活动星系核（AGN）的光谱特性，但近红外（NIR）波段的相关研究尚未充分开展。我们使用阿帕奇角天文台3.5米望远镜及TripleSpec摄谱仪，以标准交叉色散模式观测了所有87个红移z<0.5的PG类星体，获得了它们的近红外光谱。利用该数据集，我们构建了覆盖静止波长约8800至22000埃的近红外复合类星体光谱，其H波段每4埃像素的信噪比达到数百。我们表征了该复合光谱的连续谱与发射线特性，还按光度和爱丁顿比率构建了复合光谱，发现了一些并不完全意外的差异；特别是，更亮的近红外复合光谱在长波长处变得更红，这与更高温度下相对更强的尘埃发射相符。
英文摘要：
The Palomar-Green (PG) Quasars have been used extensively to establish the spectral properties of luminous active galactic nuclei (AGNs) at low redshifts in many wavebands, but not the near-infrared (NIR). We present NIR spectra of all 87 PG quasars with z < 0.5 observed with the Apache Point Observatory 3.5-m telescope and the TripleSpec spectrograph in standard cross-dispersed mode. Here we employ our data set to construct a NIR composite quasar spectrum spanning rest-frame wavelengths from approximately 8800-22000 angstroms reaching a signal-to-noise ratio of several hundred in the H-band for 4 angstrom pixels. We characterize the continuum and emission-line properties of this composite. Additionally, we construct composite spectra as a function of luminosity and Eddington ratio, finding some differences, not entirely unexpected. In particular, more luminous composite NIR spectra grow increasingly red at long wavelengths, consistent with relatively stronger dust emission at higher temperatures.
