标题： CORALS类星体的光学-红外颜色：寻找与高红移Damped Lyman Alpha系统相关的尘埃消光 显示英文标题

标题： The Optical - Infrared Colors of CORALS QSOs: Searching for Dust Reddening Associated With High Redshift Damped Lyman Alpha Systems

摘要： 类星体吸收系统（如强氢吸收线系统）中尘埃的存在可能会导致背景类星体看起来偏红。 我们通过比较有和没有中间吸收体的类星体的光学到红外颜色来研究这种潜在变红的程度。 我们的类星体样本基于 Ellison 等人（2001 年）的完整光学和射电吸收线系统（CORALS）调查。 我们获得了 CORALS 样本子集的近同时 B 和 K 波段星等，并补充了文献中发表的进一步测量结果。 为了考虑与红移相关的颜色变化，使用斯隆数字巡天（SDSS）类星体复合体对 B-K 颜色进行了归一化。 DLA 子样本的平均归一化 B-K 颜色为 +0.12，而无 DLA 样本的平均值为 -0.10；两个分布的均方根散度约为 0.5。 学生 t 检验和 KS 检验均未表明这两个颜色分布之间存在显著差异。 基于模拟重新变红具有中间 DLA 的类星体的颜色，我们在 99% 置信水平下（3 倍标准差）确定了一个消光限制，对应于 E(B-V) < 0.04（类似银河系消光），假设所有 DLA 的 E(B-V) 相同。 最后，我们没有发现吸收体属性（如 [Fe/Zn] 或中性氢柱密度）与 B-K 颜色之间存在普遍相关性。 其中一个类星体在 X 射线观测中显示出强烈相关吸收的证据，这是其非常红颜色的另一种可能解释。 我们得出结论，中间星系的存在使背景类星体产生最小程度的变红。 显示英文摘要

摘要： The presence of dust in quasar absorbers, such as damped Lyman alpha (DLA) systems, may cause the background QSO to appear reddened. We investigate the extent of this potential reddening by comparing the optical-to-infrared (IR) colors of QSOs with and without intervening absorbers. Our QSO sample is based on the Complete Optical and Radio Absorption Line System (CORALS) survey of Ellison et al (2001). We have obtained near-simultaneous B and K band magnitudes for subset of the CORALS sample and supplemented our observations with further measurements published in the literature. To account for redshift-related color changes, the B-K colors are normalized using the Sloan Digital Sky Survey (SDSS) QSO composite. The mean normalized B-K color of the DLA sub-sample is +0.12, whereas the mean for the no-DLA sample is -0.10; both distributions have RMS scatters ~0.5. Neither a student's T-test nor a KS test indicate that there is any significant difference between the two color distributions. Based on simulations which redden the colors of QSOs with intervening DLAs, we determine a reddening limit which corresponds to E(B-V) < 0.04 (SMC-like extinction) at 99% confidence (3 sigma), assuming that E(B-V) is the same for all DLAs. Finally, we do not find any general correlation between absorber properties (such as [Fe/Zn] or neutral hydrogen column density) and B-K color. One of these two QSOs shows evidence for strong associated absorption from X-ray observations, an alternative explanation for its very red color. We conclude that the presence of intervening galaxies causes a minimal reddening of the background QSO.