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arXiv 1104.1174astro-ph.CO
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星系形成对物质功率谱的影响:对精确宇宙学的挑战

The effects of galaxy formation on the matter power spectrum: A challenge for precision cosmology

Marcel P. van Daalen, Joop Schaye, C. M. Booth, Claudio Dalla Vecchia

摘要:

即将到来的弱透镜调查,如LSST,EUCLID和WFIRST,旨在以前所未有的精度测量物质功率谱。为了充分利用这些观测结果,需要模型,给定一组宇宙学参数,可以预测1%或更好的水平的非线性物质功率谱对应于同向波数0.1<k<10 h/Mpc的尺度。我们采用了OWLS计划的大型模拟套件来研究各种重子过程对物质功率谱的影响。此外,我们还研究了不同质量分量上的功率分布,重子对CDM的反反应,以及对物质功率谱的主导效应的演化。我们发现,单个重子过程能够改变功率谱高达百分之几十。我们的模拟,包括活动星系核反馈,我们认为这是我们最现实的模拟,因为,与以前的研究中使用的,它已被证明可以解决过冷问题,并重现光学和X射线观测星系群,预测了相对于仅暗物质模拟的功率降低,在z=0时,从k~0.3 h/Mpc时的1%到k~1 h/Mpc时的10%以及k~10 h/Mpc时的30%。这与重子通过冷却提高功率的天真观点相矛盾,冷却仅在k>70 h/Mpc时才是主要效应。因此,当k> 0.3h/Mpc时,重子,特别是活动星系核的反馈在理论功率谱中是不可忽略的。因此,在我们能够实现即将到来的弱透镜巡天的目标之前,有必要提高我们对星系形成中反馈过程的理解,或者至少通过辅助观测来限制它们。

英文摘要:

Upcoming weak lensing surveys, such as LSST, EUCLID, and WFIRST, aim to measure the matter power spectrum with unprecedented accuracy. In order to fully exploit these observations, models are needed that, given a set of cosmological parameters, can predict the non-linear matter power spectrum at the level of 1% or better for scales corresponding to comoving wave numbers 0.1<k<10 h/Mpc. We have employed the large suite of simulations from the OWLS project to investigate the effects of various baryonic processes on the matter power spectrum. In addition, we have examined the distribution of power over different mass components, the back-reaction of the baryons on the CDM, and the evolution of the dominant effects on the matter power spectrum. We find that single baryonic processes are capable of changing the power spectrum by up to several tens of per cent. Our simulation that includes AGN feedback, which we consider to be our most realistic simulation as, unlike those used in previous studies, it has been shown to solve the overcooling problem and to reproduce optical and X-ray observations of groups of galaxies, predicts a decrease in power relative to a dark matter only simulation ranging, at z=0, from 1% at k~0.3 h/Mpc to 10% at k~1 h/Mpc and to 30% at k~10 h/Mpc. This contradicts the naive view that baryons raise the power through cooling, which is the dominant effect only for k>70 h/Mpc. Therefore, baryons, and particularly AGN feedback, cannot be ignored in theoretical power spectra for k>0.3 h/Mpc. It will thus be necessary to improve our understanding of feedback processes in galaxy formation, or at least to constrain them through auxiliary observations, before we can fulfil the goals of upcoming weak lensing surveys.

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