COSMOS Morphological Classification with the Zurich Estimator of Structural Types (ZEST) and the Evolution Since z = 1 of the Luminosity Function of Early, Disk, and Irregular Galaxies-猫眼课题宝

DOI：

10.1086/516582

发表时间：

2006-11

期刊：

The Astrophysical Journal Supplement Series

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

C. Scarlata;C. Carollo;S. Lilly;M. Sargent;R. Feldmann;P. Kampczyk;C. Porciani;A. Koekemoer;N. Scoville;J. Kneib;A. Leauthaud;R. Massey;J. Rhodes;J. Rhodes;L. Tasca;P. Capak;C. Maier;H. McCracken;B. Mobasher;A. Renzini;Y. Taniguchi;D. Thompson;D. Thompson;K. Sheth;M. Ajiki;H. Aussel;T. Murayama;D. Sanders;S. Sasaki;S. Sasaki;Y. Shioya;M. Takahashi;M. Takahashi

出于对数以千计的宇宙星系结构进行可靠和自动分类的愿望，我们提出了结构类型的苏黎世估计器ZEST。为了对星系结构进行分类，ZEST使用了(1)五种非参数诊断方法：不对称性、浓度、基尼系数、最亮的20%的星系像素的二阶矩和椭圆度；(2)单S的指数n符合二维表面亮度分布。为了充分利用丰富的信息，同时减少这些诊断中存在的冗余，ZEST执行主成分(PC)分析。我们使用一个约56,000个IAB≤24宇宙星系的样本来表明，前三个PC完全描述了星系结构的关键方面，即校准由PC1、PC2和PC3轴组成的三维分类网格。我们在Frei等人的z=0样本上证明了ZEST网格的稳健性。ZEST分类打破了不同星系群体之间的大部分退化，这种退化只基于ZEST中包含的一些诊断来影响形态分类。作为第一个应用，我们给出了早期星系、盘状星系和不规则星系的宇宙星系光度函数(LF)自z~1以来的演化，以及盘状星系不同凸盘比的演化。总体而言，我们发现红移z=1的Lf与纯光度演化是一致的(在z~0.7处约为0.95mag)。然而，我们强调了两个趋势，这两个趋势与星系形成的缩小情景基本一致，即(1)在结构分类的早期类型星系MB&gt；-20.5的z~0.7处，亏损约2倍；(2)在类似红移的不规则星系中，过剩约3倍。

Motivated by the desire to reliably and automatically classify structure of thousands of COSMOS galaxies, we present ZEST, the Zurich Estimator of Structural Types. To classify galaxy structure, ZEST uses (1) five nonparametric diagnostics: asymmetry, concentration, Gini coefficient, second-order moment of the brightest 20% of galaxy pixels, and ellipticity; and (2) the exponent n of single-Sérsic fits to the two-dimensional surface brightness distributions. To fully exploit the wealth of information while reducing the redundancy present in these diagnostics, ZEST performs a principal component (PC) analysis. We use a sample of ~56,000 IAB ≤ 24 COSMOS galaxies to show that the first three PCs fully describe the key aspects of the galaxy structure, i.e., to calibrate a three-dimensional classification grid of axes PC1, PC2, and PC3. We demonstrate the robustness of the ZEST grid on the z = 0 sample of Frei et al. The ZEST classification breaks most of the degeneracy between different galaxy populations that affects morphological classifications based on only some of the diagnostics included in ZEST. As a first application, we present the evolution since z ~ 1 of the luminosity functions (LFs) of COSMOS galaxies of early, disk, and irregular galaxies and, for disk galaxies, of different bulge-to-disk ratios. Overall, we find that the LF up to a redshift z = 1 is consistent with a pure luminosity evolution (of about 0.95 mag at z ~ 0.7). We highlight, however, two trends that are in general agreement with a downsizing scenario for galaxy formation, i.e., (1) a deficit of a factor of about 2 at z ~ 0.7 of MB > -20.5 structurally classified early-type galaxies and (2) an excess of a factor of about 3, at a similar redshift, of irregular galaxies.

COSMOS Morphological Classification with the Zurich Estimator of Structural Types (ZEST) and the Evolution Since z = 1 of the Luminosity Function of Early, Disk, and Irregular Galaxies

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