通过恒星形成星系和活动星系核的演化来阐明死亡类星体和星系规模减小现象
Clarifying Dead Quasars and Downsizing through the Evolution of Star-Forming Galaxies and Active Galactic Nuclei
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中文总结 AI 辅助
研究通过昴星团和凯克光谱仪及JWST对星系分类并分析其红移相关数密度，结合星系光度随宇宙年龄变化，解释了SFGs和AGNs演化现象，自然地阐明了‘死亡类星体’和‘星系规模减小’问题。
中文摘要 AI 辅助
利用昴星团光纤多目标光谱仪（Subaru - FMOS）和凯克红外探测多目标光谱仪（KECK - MOSFIRE）测量的星系可见发射线目录，基于鲍德温 - 菲利普斯 - 特里维奇（BPT）图将星系分为恒星形成星系（SFGs）和活动星系核（AGNs）。在红移（z）范围0.8 <= z <= 2.6内研究了它们的数密度与红移的关系，发现SFGs在较低红移占主导，AGNs分布在较高红移。利用詹姆斯·韦布空间望远镜（JWST）的近红外光谱仪（NIRSpec）和中红外成像仪（MIRI）对高达z ~ 6.6的星系进行红外分析也显示了类似趋势，且SFGs和AGNs的数密度在z ~ 1 - 3处交叉。结合星系光度随宇宙年龄单调下降这一事实，这些现象可通过一种演化情景来解释，即早期宇宙中SFGs合并形成类星体，其活动减弱后变为SFGs，在近邻宇宙中SFGs再次合并形成赛弗特星系。在此框架下，长期存在的‘死亡类星体’和‘星系规模减小’问题可得到自然解释。
英文摘要
From the catalogs of visible emission lines of galaxies measured by the Subaru Fiber Multi-Object Spectrograph (Subaru-FMOS) and the KECK Multi-Object Spectrograph For InfraRed Exploration (KECK-MOSFIRE), galaxies were classified into Star-Forming Galaxies (SFGs) and Active Galactic Nuclei (AGNs) based on the Baldwin-Phillips-Terlevich (BPT) diagram. In the redshift (z) range 0.8 <= z <= 2.6, z dependence of their number densities was examined, and it was found that SFGs dominate at lower redshifts, whereas AGNs are distributed at higher redshifts. Infrared analyses using the James Webb Space Telescope (JWST) NIRSpec and MIRI for galaxies up to z ~ 6.6 show similar trends, and the number densities of SFGs and AGNs were found to cross at z ~ 1-3. Combined with the fact that the luminosity of galaxies decreases monotonically with the age of the universe, these phenomena can be interpreted by an evolutionary scenario in which SFGs merged to form quasars in the early universe, whose activity weakened and they changed into SFGs later, and SFGs merged again to form Seyferts in the nearby universe. Within this framework, the longstanding issues of "dead quasars" and "downsizing" can be naturally explained.
