用背景扣除技术研究MgII吸收系统及其邻近星系
MgII absorption systems and their neighbouring galaxies from a background subtraction technique
摘要：
我们估计的绝对星等分布的星系位于约百万分之一的Mg II吸收系统。吸收系统本身位于斯隆数字巡天数据第三版中类星体的1880条视线上，静止等效宽度大于0.88埃，红移在0.37 < z < 0.82之间。我们的测量是基于所有星系的投影距离约900 kpc/h的每个类星体证明吸收。这些投影近邻的红移是不可用的，所以我们使用背景扣除技术来估计真实近邻的绝对星等分布。(Our方法利用了这样一个事实，即虽然我们不知道邻居的红移，但我们知道吸收体的红移。我们发现绝对星等分布是一个钟形曲线，峰值在静止坐标系M_B =-20处，对应于L/L* = 1.4。这种观察到的分布在文献中的比较表明，它是不太可能从人口占主导地位的晚型星系。然而，强等效宽度系统可能与后来的星系类型有关。最后，我们使用绝对星等分布，以及观测到的约8%的覆盖率，来估计MgII吸收星系周围气体的程度。对于一个L* 星系，这个尺度大约是70 kpc/h。我们提供了一个分析描述我们的方法，这是一般适用于任何数据集，其中红移只适用于一个小的子样本。因此，我们希望它有助于分析星系的光度红移数据集的标度关系。
英文摘要：
We estimate the absolute magnitude distribution of galaxies which lie within about a Mpc of Mg II absorption systems. The absorption systems themselves lie along 1880 lines of sight to QSOs from the Sloan Digital Sky Survey Data Release 3, have rest equivalent widths greater than 0.88 Angstroms, and redshifts between 0.37 < z < 0.82. Our measurement is based on all galaxies which lie within a projected distance of about 900 kpc/h of each QSO demonstrating absorption. The redshifts of these projected neighbors are not available, so we use a background subtraction technique to estimate the absolute magnitude distribution of true neighbors. (Our method exploits the fact that, although we do not know the redshifts of the neighbors, we do know the redshift of the absorbers.) The absolute magnitude distribution we find is well described by a bell-shaped curve peaking at about rest-frame M_B = -20, corresponding to L/L* = 1.4. A comparison of this observed distribution to ones in the literature suggests that it is unlikely to be drawn from a population dominated by late-type galaxies. However, the strong equivalent width systems may be associated with later galaxy types. Finally we use the absolute magnitude distribution, along with the observed covering fraction of about 8 percent, to estimate the extent of the MgII absorbing gas around a galaxy. For an L* galaxy, this scale is about 70 kpc/h. We provide an analytic description of our method, which is generally applicable to any dataset in which redshifts are only available for a small sub-sample. Hence, we expect it to aid in the analysis of galaxy scaling relations from photometric redshift datasets.
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