Asteroid families, traditionally defined as clusters of objects in orbital parameter space, often have distinctive optical colors. We show that the separation of family members from background interlopers can be improved with the aid of SDSS colors as a qualifier for family membership. Based on an ~88,000 object subset of the Sloan Digital Sky Survey Moving Object Catalog 4 with available proper orbital elements, we define 37 statistically robust asteroid families with at least 100 members using a simple Gaussian distribution model in both orbital and color space. The interloper rejection rate based on colors is typically ~10% for a given orbital family definition, with four families that can be reliably isolated only with the aid of colors. About 50% of all objects in this data set belong to families, and this fraction varies from about 35% for objects brighter than an H magnitude of 13 and rises to 60% for objects fainter than this. The fraction of C-type objects in families decreases with increasing H magnitude for H > 13, while the fraction of S-type objects above this limit remains effectively constant. This suggests that S-type objects require a shorter timescale for equilibrating the background and family size distributions via collisional processing. The size distributions for 15 families display a well-defined change of slope and can be modeled as a "broken" double power-law. Such "broken" size distributions are twice as likely for S-type familes than for C-type families, and are dominated by dynamically old families. The remaining families with size distributions that can be modeled as a single power law are dominated by young families. When size distribution requires a double power-law model, the two slopes are correlated and are steeper for S-type families.
A Catalog of Very Isolated Galaxies from the SDSS Data Release 1
我们提出了一个新的目录孤立星系通过自动化系统搜索。这2980个孤立星系是在斯隆数字巡天数据发布1（SDSS DR 1）测光中在大约2099平方度的天空中发现的。选择算法，实现了Karachentseva在1973年开发的标准的变化，被证明是非常有效和快速的。这个星表对研究星系的一般特性是有用的。在这里，我们报告我们的结果。
A Census of Object Types and Redshift Estimates in the SDSS Photometric Catalog from a Trained Decision-Tree Classifier
我们将ClassX（一种针对天文分析优化的倾斜决策树分类器）应用于斯隆数字巡天（SDSS）的同质多色成像数据库，在SDSS对象的子集上训练软件，这些对象的性质通过光谱学精确已知。我们发现，该软件，只使用光度数据，正确地分类了很大一部分的对象与现有的SDSS光谱，恒星和河外。ClassX还精确地预测了SDSS中正常星系和活动星系的红移。为了说明ClassX在SDSS研究中的应用，我们（a）推导出SDSS DR 2测光表的天体内容，（b）提供了一个包含大量候选AGN星系（27，000个）和63，000个候选正常星系的SDSS天体样本，这些星系的星等比SDSS光谱天体的典型星等要暗得多。ClassX选取的活动星系核的面密度为i~19，与SDSS给出的面密度一致。当ClassX应用于比SDSS光谱极限更暗的光度数据时，AGN的表面密度如预期的那样急剧上升。分类器能够准确地限制光度数据库中大量（最终约10^7）活动星系的红移，这为AGN研究的基本问题提供了新的见解，例如AGN光度函数随宇宙时间的演化，星暴-AGN的联系，以及AGN-星系形态关系。
SDSS AGNs with X-ray Emission from ROSAT PSPC Pointed Observations
本文给出了来自Sloan数字巡天（SDSS DR 4）光谱星表的1744个1型活动星系核（AGN）样本，以及ROSAT PSPC指向观测的White-Giommi-Angelini星表（WGACAT）中的X射线对应物。在1744个X射线源中，有1410个（80.9%）是新确认的活动星系核。我们在FIRST目录的射电源目录中找到了4574个SDSS DR 4活动星系核，其中224个出现在我们的SDSS X射线活动星系核样本中。样本天体在一个目录中给出，该目录包含光学和X射线参数以及可用的无线电发射参数。我们说明我们的目录的内容和活动星系核科学的潜力，通过提供目录数据的统计关系。通过对光学分辨和未分辨活动星系核的统计分析，强调了形态学信息的潜力。目录对象的直接属性包括X射线和光通量的显著相关性，这与预期一致。我们也预期X射线通量会向更高的红移方向减少。未分辨活动星系核的X射线与光通量之比随着红移的增加而减小，这与以前的结果一致。然而，分辨出的活动星系核却表现出相反的趋势。在给定的光学亮度下，射电宁静活动星系核的X射线通量增加了2倍。然而，我们要提醒的是，由于WGACAT和SDSS中都存在各种各样的选择效应，对基于我们的X射线活动星系核样本的任何关系的解释都需要仔细分析这些效应。
