矮星系成簇与超新星失踪
Dwarf Galaxy Clustering and Missing Satellites
摘要：
在红移约为0.1时，CFHT遗产巡天深场包含一些6 × 10^4星系，质量范围从10^5到10^12 Msun。我们测量恒星质量的依赖性的两点相关性，使用角度测量，在很大程度上绕过的错误，约0.02的中位数，光度红移。将幂律与林伯方程进行反演，我们发现自相关长度从10^5.5 Msun时非常低的0.4hMpc增加到10^10.5 Msun时的常规4.5hMpc。拟合到关联函数的幂律具有从高质量处的伽马约1.6增加到低质量处的伽马约2.3的斜率。矮星系与更大质量星系的空间互相关性显示出相当相似的趋势，在低质量下的径向依赖性比在星系晕内的子晕的数值模拟中预测的更陡。为了研究失踪卫星的问题，我们结合了互相关测量与我们的估计低质量星系数密度。我们发现，对于一个典型的本星系群M（总）/M（恒星）=30，平均有60+/-20个矮星处于M（总）> 10^7 Msun的次晕中，对应于一个没有最近恒星形成的星系的M/L_V约为100。每个星系的矮星数量大约是目前银河系的两倍。尽管如此，平均矮星数量大约是LCDM模拟结果的30倍。与LCDM预测的偏差是关系的斜率之一，约为dN/dlnM约为-0.5而不是预测的-0.9，在某些特征尺度上不是突然开始的。矮星系的恒星形成率从被动到爆发，这表明几乎没有完全黑暗的晕。
英文摘要：
At redshifts around 0.1 the CFHT Legacy Survey Deep fields contain some 6x10^4 galaxies spanning the mass range from 10^5 to 10^12 Msun. We measure the stellar mass dependence of the two point correlation using angular measurements to largely bypass the errors, approximately 0.02 in the median, of the photometric redshifts. Inverting the power-law fits with Limber's equation we find that the auto-correlation length increases from a very low 0.4hMpc at 10^5.5 Msun to the conventional 4.5hMpc at 10^10.5 Msun. The power law fit to the correlation function has a slope which increases from gamma approximately 1.6 at high mass to gamma approximately 2.3 at low mass. The spatial cross-correlation of dwarf galaxies with more massive galaxies shows fairly similar trends, with a steeper radial dependence at low mass than predicted in numerical simulations of sub-halos within galaxy halos. To examine the issue of missing satellites we combine the cross-correlation measurements with our estimates of the low mass galaxy number density. We find on the average there are 60+/-20 dwarfs in sub-halos with M(total) > 10^7 Msun for a typical Local Group M(total)/M(stars)=30, corresponding to M/L_V approximately 100 for a galaxy with no recent star formation. The number of dwarfs per galaxy is about a factor of two larger than currently found for the Milky Way. Nevertheless, the average dwarf counts are about a factor of 30 below LCDM simulation results. The divergence from LCDM predictions is one of slope of the relation, approximately dN/dlnM approximately -0.5 rather than the predicted -0.9, not sudden onset at some characteristic scale. The dwarf galaxy star formation rates span the range from passive to bursting, which suggests that there are few completely dark halos.
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