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arXiv 1305.0337astro-ph.CO
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邻近大质量早型星系的光度特性和光度函数

Photometric properties and luminosity function of nearby massive early-type galaxies

Y. Q. He, X. Y. Xia, C. N. Hao, Y. P. Jing, S. Mao, Cheng Li

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43 pages, 14 figures, version accepted for publication in the Astrophysical Journal
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摘要：

我们进行光度分析的一个明亮的早型星系（ETG）样本与2949星系（$M_{\rm r}<-22.5$等）的红移范围为0.05至0.15，从SDSS DR 7与星系动物园1的形态分类。我们测量了彼得罗斯和等照度线的星等，以及每个星系相应的半光半径。我们发现，对于最亮的星系（$M_{\rm r}<-23$等），我们给出的25 ${\rm mag/arcsec^2}$和1%天空亮度的彼得罗相星等和等光度值分别比SDSS的彼得罗相星等平均亮0.16等、0.20等和0.26等。在第一种情况下，低估是由SDSS PHOTO算法在天空背景中的高估引起的，而后两种情况也是由于更深的测光。类似地，由SDSS算法测量的典型半光半径（$r_{50}$）小于我们的测量。结果发现，$r$波段光度函数的亮端比以前的工作下降得更慢。我们测量的亮端光度密度比Blanton等人（2003）的高出一个数量级以上，而$M_{\ast}\sim 5\times10^{11} M_{\odot}$和$M_{\ast}\sim 10^{12} M_{\odot}$的恒星质量密度比Bernardi等人（2010）的高出十分之几和几倍。这些结果可能会显着缓解之间的紧张局势的观察和预测的分级结构形成模型的大质量星系的组装。

英文摘要：

We perform photometric analyses for a bright early-type galaxy (ETG) sample with 2949 galaxies ($M_{\rm r}<-22.5$ mag) in the redshift range of 0.05 to 0.15, drawn from the SDSS DR7 with morphological classification from Galaxy Zoo 1. We measure the Petrosian and isophotal magnitudes, as well as the corresponding half-light radius for each galaxy. We find that for brightest galaxies ($M_{\rm r}<-23$ mag), our Petrosian magnitudes, and isophotal magnitudes to 25 ${\rm mag/arcsec^2}$ and 1\% of the sky brightness are on average 0.16 mag, 0.20 mag, and 0.26 mag brighter than the SDSS Petrosian values, respectively. In the first case the underestimations are caused by overestimations in the sky background by the SDSS PHOTO algorithm, while the latter two are also due to deeper photometry. Similarly, the typical half-light radii ($r_{50}$) measured by the SDSS algorithm are smaller than our measurements. As a result, the bright-end of the $r$-band luminosity function is found to decline more slowly than previous works. Our measured luminosity densities at the bright end are more than one order of magnitude higher than those of Blanton et al. (2003), and the stellar mass densities at $M_{\ast}\sim 5\times10^{11} M_{\odot}$ and $M_{\ast}\sim 10^{12} M_{\odot}$ are a few tenths and a factor of few higher than those of Bernardi et al. (2010). These results may significantly alleviate the tension in the assembly of massive galaxies between observations and predictions of the hierarchical structure formation model.

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