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arXiv 1412.7660astro-ph.GAastro-ph.CO
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作为SMBH馈送机制探针的AGN宿主星系的物理性质

Physical properties of AGN host galaxies as a probe of SMBH feeding mechanisms

M. Gatti, A. Lamastra, N. Menci, A. Bongiorno, F. Fiore

摘要:

利用一个先进的星系形成半解析模型(SAM),我们研究了两种不同的触发活动星系核活动的机制对活动星系核宿主星系性质的统计影响。我们已经考虑了第一个吸积模式,AGN活动是由孤立星系中的盘不稳定性(DI)触发的,第二个喂养模式,这样的活动是由星系合并和飞越事件(相互作用,IT)触发的。结果表明:(1)对于具有$M_* \lesssim 10^{11} M_{\bigodot}$的寄主,DI模和IT模都能解释观测到的活动星系核寄主恒星质量函数;对于更大规模的主机,DI方案预测的空间密度低于IT模型,ii)红移z <0.8的活动星系核主星系的色星等图(CMD)分析1.5可以提供一个很好的观测测试,以有效区分DI和IT模式,因为DI预计会产生AGN宿主星系的颜色偏向蓝色,而在IT方案中,大多数宿主预计居住在红色序列中。iii)虽然IT和DI方案都可以解释在主序星或星暴星系中触发的AGN,在被动星系中,DI不能触发活动星系核活动。iv)这两种模式的特征是活动星系核阶段的持续时间不同,DI甚至在时间尺度上持续$\sim $ Gyr,v)$SFR-L_{bol}$关系的离散度可以表示区分两种触发模式的另一个关键诊断,因为DI场景预测的关系的离散度比IT场景低得多。vi)盘不稳定性不能解释z <1时的AGN分组和z <0.7时的AGN集群,而IT情景提供了与观测数据的良好匹配。

英文摘要:

Using an advanced semi analytic model (SAM) for galaxy formation, we have investigated the statistical effects of assuming two different mechanisms for triggering AGN activity on the properties of AGN host galaxies. We have considered a first accretion mode where AGN activity is triggered by disk instabilities (DI) in isolated galaxies, and a second feeding mode where such an activity is triggered by galaxy mergers and fly-by events (interactions, IT). We obtained the following results:i) for hosts with $M_* \lesssim 10^{11} M_{\bigodot}$, both DI and IT modes are able to account for the observed AGN hosts stellar mass function; for more massive hosts, the DI scenario predicts a lower space density than the IT model, lying below the observational estimates for z>0.8.ii) The analysis of the color-magnitude diagram (CMD) of AGN hosts for redshift z < 1.5 can provide a good observational test to effectively discriminate between the DI and IT mode, since DIs are expected to yield AGN host galaxy colors skewed towards bluer colors, while in the IT scenario the majority of hosts are expected to reside in the red sequence.iii) While both IT and DI scenarios can account for AGN triggered in main sequence or starburst galaxies, DIs fail in triggering AGN activity in passive galaxies.iv) The two modes are characterized by a different duration of the AGN phase, with DIs lasting even on time scales $\sim $ Gyr, much longer with respect to the IT scenario.v) The scatter of the $SFR-L_{bol}$ relation could represent another crucial diagnostics to discriminate between the two triggering modes, since the DI scenario predicts an appreciably lower scatter of the relation than the IT scenario. vi) Disk instabilities are not able to account for the observed fraction of AGN in groups for z < 1 and clusters for z < 0.7, while the IT scenario provides a good match to observational data.

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