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arXiv 1708.07643astro-ph.GAastro-ph.CO
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利用Continuity Equation计算活动和静止星系的恒星质量函数

Stellar Mass Function of Active and Quiescent Galaxies via the Continuity Equation

A. Lapi, Claudia Mancuso, A. Bressan, L. Danese

摘要:

建立了星系质量含量的连续性方程,并利用该方程导出了红移范围$z\sim 0-8$内活动星系和静止星系的质量函数。连续性方程需要两个具体的观测数据:(一)根据最新的紫外线+远红外线/亚毫米/射电测量确定的恒星形成率函数;(二)单个星系的平均恒星形成历史,对盘状和球状体有不同的规定。连续性方程还包括一个源项,考虑到(干)合并,根据最近的数值模拟和观测一致。由连续性方程导出的恒星质量函数与晕质量函数和SFR函数耦合,通过丰度匹配技术得到恒星形成效率和恒星形成星系的主要序列。结果表明,所得到的活动星系和静止星系的恒星质量函数、星系主序和恒星形成效率与目前的观测结果非常一致;与数据的比较还允许强有力地约束大质量星系的恒星形成和静止的特征时间尺度,它们的祖先的恒星形成历史,以及由原位恒星形成所增加的恒星质量与外部合并事件所贡献的恒星质量。的连续性方程产生的定量结果,必须遵守详细的物理模型,可以提供一个基础,以改善(子网格)的物理配方实施的理论方法和数值模拟,并可以提供一个基准预测未来的观测与多波段覆盖,因为它将成为常规实现的时代JWST。

英文摘要:

The continuity equation is developed for the stellar mass content of galaxies, and exploited to derive the stellar mass function of active and quiescent galaxies over the redshift range $z\sim 0-8$. The continuity equation requires two specific inputs gauged on observations: (i) the star formation rate functions determined on the basis of the latest UV+far-IR/sub-mm/radio measurements; (ii) average star-formation histories for individual galaxies, with different prescriptions for discs and spheroids. The continuity equation also includes a source term taking into account (dry) mergers, based on recent numerical simulations and consistent with observations. The stellar mass function derived from the continuity equation is coupled with the halo mass function and with the SFR functions to derive the star formation efficiency and the main sequence of star-forming galaxies via the abundance matching technique. A remarkable agreement of the resulting stellar mass function for active and quiescent galaxies, of the galaxy main sequence and of the star-formation efficiency with current observations is found; the comparison with data also allows to robustly constrain the characteristic timescales for star formation and quiescence of massive galaxies, the star formation history of their progenitors, and the amount of stellar mass added by in-situ star formation vs. that contributed by external merger events. The continuity equation is shown to yield quantitative outcomes that must be complied by detailed physical models, that can provide a basis to improve the (sub-grid) physical recipes implemented in theoretical approaches and numerical simulations, and that can offer a benchmark for forecasts on future observations with multi-band coverage, as it will become routinely achievable in the era of JWST.

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