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arXiv 0911.2641astro-ph.COastro-ph.GAastro-ph.HE
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星系群中AGN反馈的情况

The case for AGN feedback in galaxy groups

Ian G. McCarthy, Joop Schaye, Trevor J. Ponman, Richard G. Bower, Craig M. Booth, Claudio Dalla Vecchia, Robert A. Crain, Volker Springel, Tom Theuns, Robert P. C. Wiersma

摘要:

[摘要]相对较新的见解是,来自超大质量黑洞(BH)的能量输入可以对星系的恒星形成率(SFR)产生重大影响,这促使我们研究其对星系群规模的影响。目前,星系群包含了大部分星系和宇宙中相当一部分的重子。为了探索BH反馈对群体的影响,我们分析了两个高分辨率的宇宙学水文模拟的OverWhelmomentally大型模拟项目。虽然两者都包括由超新星驱动的星系风,但只有一个包括来自BH的反馈。我们比较了模拟组的性质,以广泛的观测数据,包括热气体径向分布和气体质量分数(fgas),亮度质量温度(L-M-T)标度关系,K波段光度的组和它的中央最亮的星系(CBG),SFRs和年龄的CBG,和气体/恒星金属丰度。这两次运行产生的熵轮廓类似的数据,而没有活动星系核反馈的运行产生高度峰值的温度分布,与观测结果不一致。对于质量小于~10^14 Msun的基团,来自BH的能量输入显著减少了fgas,产生了与数据一致的fgas-T和L-T关系。在没有活动星系核反馈的情况下,会出现众所周知的过冷问题;由此产生的K波段光度比观测到的要大得多。相比之下,运行,包括BH反馈产生K波段光度和CBG SFR和年龄与目前的估计。这两次运行都产生了非常相似的气相金属丰度,与X射线数据相匹配,但它们预测的恒星金属丰度非常不同。基于以上所述,星系群提供了一个令人信服的案例,即BH反馈是大质量星系形成的关键因素。

英文摘要:

[Abridged] The relatively recent insight that energy input from supermassive black holes (BHs) can have a substantial effect on the star formation rates (SFRs) of galaxies motivates us to examine its effects on the scale of galaxy groups. At present, groups contain most of the galaxies and a significant fraction of the overall baryon content of the universe. To explore the effects of BH feedback on groups, we analyse two high resolution cosmological hydro simulations from the OverWhelmingly Large Simulations project. While both include galactic winds driven by supernovae, only one includes feedback from BHs. We compare the properties of the simulated groups to a wide range of observational data, including hot gas radial profiles and gas mass fractions (fgas), luminosity-mass-temperature (L-M-T) scaling relations, K-band luminosity of the group and its central brightest galaxy (CBG), SFRs and ages of the CBG, and gas/stellar metallicities. Both runs yield entropy profiles similar to the data, while the run without AGN feedback yields highly peaked temperature profiles, in discord with the observations. Energy input from BHs significantly reduces fgas for groups with masses less than ~10^14 Msun, yielding fgas-T and L-T relations that are in agreement with the data. The run without AGN feedback suffers from the well known overcooling problem; the resulting K-band luminosities are much larger than observed. By contrast, the run that includes BH feedback yields K-band luminosities and CBG SFRs and ages in agreement with current estimates. Both runs yield very similar gas-phase metallicities that match X-ray data, but they predict very different stellar metallicities. Based on the above, galaxy groups provide a compelling case that BH feedback is a crucial ingredient in the formation of massive galaxies.

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