Milky Way卫星的光度函数
The Luminosity Function of the Milky Way Satellites
摘要：
我们量化了斯隆数字巡天（SDSS）数据发布5中恒星银河系卫星的可探测性。我们发现，最近发现的SDSS-卫星的有效搜索量强烈依赖于它们的光度，其最大距离，$D_{max}$，大大小于银河系晕的维里半径。计算最大可达体积，$V_{max}$，为所有微弱的检测到的卫星，允许计算银河系卫星星系的光度函数，定量说明其可探测性。我们发现，卫星星系的数量密度继续上升，对低光度，但可能会平坦的$M_V \sim -5$内的不确定性，光度函数可以描述为一个单一的幂律$dN/dM_{V}= 10 \times 10^{0.1 (M_V+5)}$，跨越光度从$M_V=-2$所有的方式光度的大麦云。将这些结果与几个半解析星系形成模型进行比较，我们发现它们的预测与数据有很大的不同：无论是光度函数的形状，还是模型的表面亮度分布，都不匹配。
英文摘要：
We quantify the detectability of stellar Milky Way satellites in the Sloan Digital Sky Survey (SDSS) Data Release 5. We show that the effective search volumes for the recently discovered SDSS--satellites depend strongly on their luminosity, with their maximum distance, $D_{max}$, substantially smaller than the Milky Way halo's virial radius. Calculating the maximum accessible volume, $V_{max}$, for all faint detected satellites, allows the calculation of the luminosity function for Milky Way satellite galaxies, accounting quantitatively for their detectability. We find that the number density of satellite galaxies continues to rise towards low luminosities, but may flatten at $M_V \sim -5$; within the uncertainties, the luminosity function can be described by a single power law $dN/dM_{V}= 10 \times 10^{0.1 (M_V+5)}$, spanning luminosities from $M_V=-2$ all the way to the luminosity of the Large Magellanic Cloud. Comparing these results to several semi-analytic galaxy formation models, we find that their predictions differ significantly from the data: either the shape of the luminosity function, or the surface brightness distributions of the models, do not match.
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