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arXiv 1708.01698astro-ph.GA
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星系群和星系团中的积分HI辐射

Integrated HI emission in galaxy groups and clusters

Mei Ai, Ming Zhu, Jian Fu

摘要:

FAST可以在中等红移处探测到星系群和星系团等分级结构的综合HI辐射。在这里,我们建议使用FAST来研究全球HI含量的集群和团体在宇宙时间的演变,通过测量其综合HI排放。以室女星系团为例,估算了FAST的探测极限,并估算了在不同红移(z=0.1 ~ 1.5)下探测室女星系团所需的积分时间。我们还利用半解析模型(SAM)模拟了星系团中HI含量的演化。我们的模拟结果表明,当红移从z=0.3增加到z=1时,室女座星系团的HI质量可以增加2-3倍,物理尺寸可以减小50%以上.因此,积分时间可以显着减少,并在中间红移的富气集团可以检测到FAST在不到2小时的积分时间。对于本地宇宙,我们还使用SAM模拟来创建模拟星团目录,以预测FAST全天巡天的结果。通过与SDSS巡天和ALP-FA巡天星系表交叉匹配得到的光学选择星表的比较,发现积分时间为20秒的模拟星表的HI质量分布与观测值吻合较好。然而,模拟目录与120秒的整合时间预测更多的群体和集群,包含人口的低质量HI星系没有检测到的ALCARFA调查。未来使用FAST的深HI盲天调查将能够测试这种预测并对数值模拟模型设置约束。最后讨论了未来星系团高红移FAST观测的观测策略和样品选择。

英文摘要:

The integrated HI emission from hierarchical structures such as groups and clusters of galaxies can be detected by FAST at intermediate redshifts. Here we propose to use FAST to study the evolution of the global HI content of clusters and groups over cosmic time by measuring their integrated HI emissions. We use the Virgo cluster as an example to estimate the detection limit of FAST, and have estimated the integration time to detect a Virgo type cluster at different redshifts (from z=0.1 to z=1.5). We have also employed a semi-analytic model (SAM) to simulate the evolution of HI contents in galaxy clusters. Our simulations suggest that the HI mass of a Virgo-like cluster could be 2-3 times higher and the physical size could be more than 50\% smaller when redshift increases from z=0.3 to z=1. Thus the integration time could be reduced significantly and gas rich clusters at intermediate redshifts can be detected by FAST in less than 2 hour of integration time. For the local universe, we have also used SAM simulations to create mock catalogs of clusters to predict the outcomes from FAST all sky surveys. Comparing with the optically selected catalogs derived by cross matching the galaxy catalogs from the SDSS survey and the ALFALFA survey, we find that the HI mass distribution of the mock catalog with 20 second of integration time agrees well with that of observations. However, the mock catalog with 120 second integration time predicts much more groups and clusters that contains a population of low mass HI galaxies not detected by the ALFALFA survey. Future deep HI blind sky survey with FAST would be able to test such prediction and set constraints to the numerical simulation models. Observational strategy and sample selections for the future FAST observations of galaxy clusters at high redshifts are also discussed.

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