Galaxy Number Counts in the Subaru Deep Field: Multiband Analysis in a Hierarchical Galaxy Formation Model
Galaxy Number Counts in the Subaru Deep Field: Multiband Analysis in a Hierarchical Galaxy Formation Model
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斯巴鲁深场中的星系数量：分层星系形成模型中的多波段分析
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
N. Gouda
中科院分区：
文献类型：
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作者：
M. Nagashima;Y. Yoshii;T. Totani;N. Gouda
星系的数量计数重新分析使用半解析模型（SAM）的星系形成的层次聚类方案的基础上。将斯巴鲁深场（SDF;近红外J和K′）和哈勃深场（HDF;紫外/光学U、B、V和I）中的暗星系与我们的模型星系进行了比较。我们已经确定了SAM中的天体物理参数，重现附近星系的观测，并用它们来预测三种宇宙学模型，标准冷暗物质（CDM）宇宙，低密度平坦宇宙与非零宇宙学常数，和低密度开放宇宙与零宇宙学常数的暗星系的计数和红移。我们的SAM分析的新奇在于，包含了高红移星系表面亮度的宇宙学变暗，以及内部尘埃和星系间H I云吸收可见光所产生的选择效应。在我们以前的工作中发现，其中的紫外/光学HDF星系与我们的模型星系进行了比较，我们发现，我们的SAM再现计数的近红外SDF星系在低密度宇宙中，无论有或没有宇宙学常数，和标准的CDM宇宙是不可取的，建议由其他最近的研究。此外，我们还发现：（1）星星形成的时间尺度与星系盘形成的动力学时间尺度成正比，（2）星系盘的大小与周围暗晕的比角动量相同，（3）尘埃光学厚度与冷气体的金属丰度成正比，不能完全解释所有的观测数据。从我们的SAM分析中，我们提出了改进的处方，其中包括轻度红移依赖。
Number counts of galaxies are reanalyzed using a semianalytic model (SAM) of galaxy formation based on the hierarchical clustering scenario. Faint galaxies in the Subaru Deep Field (SDF; near-infrared J and K′) and the Hubble Deep Field (HDF; ultraviolet/optical U, B, V, and I) are compared with our model galaxies. We have determined the astrophysical parameters in the SAM that reproduce observations of nearby galaxies and used them to predict the number counts and redshifts of faint galaxies for three cosmological models, the standard cold dark matter (CDM) universe, a low-density flat universe with nonzero cosmological constant, and a low-density open universe with zero cosmological constant. The novelty of our SAM analysis is the inclusion of selection effects arising from the cosmological dimming of surface brightness of high-redshift galaxies, and from the absorption of visible light by internal dust and intergalactic H I clouds. As was found in our previous work, in which the ultraviolet/optical HDF galaxies were compared with our model galaxies, we find that our SAM reproduces counts of near-infrared SDF galaxies in a low-density universe either with or without a cosmological constant, and that the standard CDM universe is not preferred, as suggested by other recent studies. Moreover, we find that simple prescriptions for (1) the timescale of star formation being proportional to the dynamical timescale of the formation of galactic disks, (2) the size of galactic disks being rotationally supported with the same specific angular momentum as that of surrounding dark halo, and (3) the dust optical depth being proportional to the metallicity of cold gas, cannot completely explain all of the observed data. Improved prescriptions incorporating mild redshift-dependence for those are suggested from our SAM analysis.