XXL调查：XXXVII。0.1<z<0.5时环境在塑造星系恒星星族性质中的作用
The XXL Survey: XXXVII. The role of the environment in shaping the stellar population properties of galaxies at 0.1<z<0.5
摘要：
利用XXL-N多波长巡天中的星系样本，通过研究星系分数和恒星形成率（SFR）-恒星质量（M）关系，分析了0.1<z<0.5时星系的恒星星族性质。此外，我们利用和比较两个参数化的环境。当采用“全球”环境的定义时，我们分别考虑星系团维里/外部成员和场星系。在考虑“局部”环境时，我们考虑了天空中1 Mpc固定孔径中星系的投影数密度。我们发现，无论采用的环境定义，蓝色/恒星形成星系的比例是最高的领域/最不密集的区域和最低的维里区域的集群/最高密度。此外，无论环境如何，恒星形成星系的比例都高于蓝色星系的比例。这一结果在维里星系团区域尤为明显，很可能反映了不同环境中星系的不同恒星形成历史。此外，整体SFR-M关系似乎并不依赖于所采用的参数化。尽管如此，这两种定义的环境导致不同的结果，只要在恒星形成的主要序列和淬火制度之间的过渡的星系的分数而言。事实上，使用当地的环境下的主要序列的星系的分数是类似的低密度和高密度，而在集群（特别是维里半径内）的人口减少SFR相对于字段被观察到。我们的研究结果表明，这两个参数化所采用的环境有不同的物理意义，即有内在的联系，不同的物理过程作用于星系种群，并能够探测不同的物理尺度。
英文摘要：
Exploiting a sample of galaxies drawn from the XXL-N multiwavelength survey, we present an analysis of the stellar population properties of galaxies at 0.1<z<0.5, by studying galaxy fractions and the star formation rate (SFR)-stellar mass(M) relation. Furthermore, we exploit and compare two parametrisations of environment. When adopting a definition of "global" environment, we consider separately cluster virial/outer members and field galaxies. When considering the "local" environment, we take into account the projected number density of galaxies in a fixed aperture of 1Mpc in the sky. We find that regardless of the environmental definition adopted, the fraction of blue/star-forming galaxies is the highest in the field/least dense regions and the lowest in the virial regions of clusters/highest densities. Furthermore, the fraction of star-forming galaxies is higher than the fraction of blue galaxies, regardless of the environment. This result is particularly evident in the virial cluster regions, most likely reflecting the different star formation histories of galaxies in different environments. Also the overall SFR-M relation does not seem to depend on the parametrisation adopted. Nonetheless, the two definitions of environment lead to different results as far as the fraction of galaxies in transition between the star-forming main sequence and the quenched regime is concerned. In fact, using the local environment the fraction of galaxies below the main sequence is similar at low and high densities, whereas in clusters (and especially within the virial radii) a population with reduced SFR with respect to the field is observed. Our results show that the two parametrisations adopted to describe the environment have different physical meanings, i.e.are intrinsically related to different physical processes acting on galaxy populations and are able to probe different physical scales.
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