从低质量星系团的成簇性看高红移大质量星系团的同一性
Verifying the Identity of High-Redshift Massive Galaxies Through the Clustering of Lower Mass Galaxies Around Them
摘要：
大质量高红移星系形成于过密区域，在那里形成其他星系的可能性也大大增加。给定一个观测到的星系流量，其宿主晕的推断质量往往随着其推断红移的增加而变大。当星系晕的质量和红移增加时，它周围的其他星系的预期聚集会变得更强。因此，在光谱识别之前，我们可以通过周围星系的聚类来验证星系的高红移身份。我们以Mobasher et al.（2005）提出的红移z~6.5的大质量星系为例说明了这种方法。如果这个星系存在于z~6.5，那么平均应该有~10个星系大于其质量的百分之一，并且在HUDF中检测到z波段星等小于~25。我们计算了邻近星系的近似概率分布，并确定有不到0.3%的机会检测到没有大质量的邻近星系。在HUDF影像中没有其他z~6.5的大质量星系，因此Mobasher et al.（2005）星系是一个低红移的闯入者。我们将我们的结果推广到其他星系的质量和红移。
英文摘要：
Massive high-redshift galaxies form in over-dense regions where the probability of forming other galaxies is also strongly enhanced. Given an observed flux of a galaxy, the inferred mass of its host halo tends to be larger as its inferred redshift increases. As the mass and redshift of a galaxy halo increase, the expected clustering of other galaxies around it gets stronger. It is therefore possible to verify the high-redshift identity of a galaxy (prior to an unambiguous spectral identification) from the clustering of other galaxies around it. We illustrate this method for the massive galaxy suggested by Mobasher et al. (2005) to be at redshift z~6.5. If this galaxy were to exist at z~6.5, there should have been a mean of ~10 galaxies larger than a hundredth of its mass and having z-band magnitudes less than ~25 detected as i-dropouts in the HUDF. We calculate an approximate probability distribution for neighbor galaxies and determine that there is less than a ~0.3% chance of detecting no massive neighbor galaxies. The lack of other massive z~6.5 galaxies in the HUDF image argues that the Mobasher et al. (2005) galaxy is instead a low redshift interloper. We generalize our results to other galaxy masses and redshifts.
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