Galaxy clustering in the CFHTLS-Wide: the changing relationship between galaxies and haloes since z ~ 1.2
J. Coupon, M. Kilbinger, H. J. McCracken, O. Ilbert, S. Arnouts, Y. Mellier, U. Abbas, S. de la Torre, Y. Goranova, P. Hudelot, J. -P. Kneib, O. Le fèvre
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35 pages, 20 figures, accepted for publication in Astronomy & Astrophysics
We present a detailed investigation of the changing relationship between galaxies and the dark matter haloes they inhabit from z~1.2 to the present day. We do this by comparing precise galaxy clustering measurements over 133 deg2 of the "Wide" component of the CFHT Legacy Survey (CFHTLS) with predictions of an analytic HOD model where the number of galaxies in each halo depends only on the halo mass. Starting from a parent catalogue of ~ 3x10^6 galaxies at i'_AB < 22.5 we use accurate photometric redshifts calibrated using ~ 10^4 spectroscopic redshifts to create a series of type-selected volume-limited samples covering 0.2 < z < 1.2. Our principal result, based on clustering measurements in these samples, is a robust determination of the luminosity-to-halo mass ratio and its dependence on redshift and galaxy type. For the full sample, this reaches a peak at low redshifts of Mh,peak = 4.5x10^11 h^-1 M_sun and moves towards higher halo masses at higher redshifts. For redder galaxies the peak is at higher halo masses and does not evolve significantly over the entire redshift range of our survey. We also consider the evolution of bias, average halo mass and the fraction of satellites as a function of redshift and luminosity. Our observed growth of a factor of ~ 2 in satellite fraction between z~1 and z~0 is testament to the limited role that galaxy merging plays in galaxy evolution for ~ 10^12 h^-1 M_sun mass haloes at z<1. Qualitatively, our observations are consistent with a picture in which red galaxies in massive haloes have already accumulated most of their stellar mass by z~1 and subsequently undergo little evolution until the present day. The observed movement of the peak location for the full galaxy population is consistent with the bulk of star-formation activity migrating from higher mass haloes at high redshifts to lower mass haloes at lower redshifts.
The Galaxy--Halo Connection in High-Redshift Universe: Details and Evolution of Stellar-to-Halo Mass Ratios of Lyman Break Galaxies on CFHTLS Deep Fields
Resolving the problem of galaxy clustering on small scales: any new physics needed?
星系团对控制星系形成和演化的物理学有很强的限制。然而，目前大多数的模型不能再现小尺度上的低质量星系团（$r<1Mpc/h$）。本文研究了几种半解析模型预测的星系团。我们首先比较了两个慕尼黑版本，Guo et al.（2011，Guo11）和De Lucia \& Blazoit（2007，DLB07）。Guo 11模型很好地再现了星系的恒星质量函数，但在小尺度上高估了低质量星系的成团。DLB07模型在小尺度上提供了更好的聚类拟合，但过度预测了恒星质量函数。这些似乎令人费解。我们发现Guo 11模型中有更多的卫星星系分布在大质量星系晕中，这是导致两个模型之间星系团簇差异的主要原因。然而，这两个模型仍然过度预测的集群在$0.1Mpc/h<r<10Mpc/h$的低质量星系。这是因为两个模型都过度预测了$30\%$在大规模晕中的卫星数量，而不是数据。实际上，DLB07模型与小尺度数据的更好的一致性是一个巧合，因为它预测了太多的低质量中心星系，这些星系不太聚集，从而降低了总的聚集。最后，我们展示了Kang et al.（2012）的半分析预测。我们发现，如果卫星星系中的超新星反馈较强，该模型可以同时拟合恒星质量函数和星系成团。我们的结论是，半解析模型现在能够解决小尺度的集群问题，而不调用任何其他新的物理或改变暗物质的属性，如最近青睐的温暖暗物质。
