论文标题
星系中气体和恒星宇宙学演化的新经验约束
New empirical constraints on the cosmological evolution of gas and stars in galaxies
论文作者
论文摘要
我们结合了对暗物质光环中出色特性的最新观察动机约束，以及数据驱动的原子（HI）和星系中的分子（H $ _2 $）气体演变的预测，以得出银河系成分的经验关系与它们在宇宙时间上的进化之间的构建之间的经验关系。在高红移（$ z \ gtrsim 4 $）上，该框架暗示星系主要通过增生获得冷气（既有原子和分子），而冷气的一部分约为宇宙巴里昂分数的20％。我们推断出恒星形成速率对H $ _2 $质量的强烈依赖性，这表明在银河系尺寸的光环中，近乎宇宙的耗尽时间尺度为0.1-1 Gyr（$ 10^{12} \ m _ {\ odot} $ z = 0 $）。还有证据表明，如果假定恒定的转化因子（$α_ {\ rm co} $）将CO亮度的恒定转换因子（假定$α_ {\ rm co} $）与分子气体质量相关，那么对恒星质量的肯尼法特 - 施密特关系几乎是对恒星质量的依赖性的。将原子和分子气体观测与恒星堆积相结合，这表明，乳白色大小的光环中的银河质量组件从高红移处的平滑积聚到后期（$ z \ s \ lyssim 0.6 $）。我们的结果可用于限制宇宙历史上星系的主要生长和吸积过程的数值模拟。
We combine the latest observationally motivated constraints on stellar properties in dark matter haloes, along with data-driven predictions for the atomic (HI) and molecular (H$_2$) gas evolution in galaxies, to derive empirical relationships between the build-up of galactic components and their evolution over cosmic time. At high redshift ($z \gtrsim 4$), the frameworks imply that galaxies acquire their cold gas (both atomic and molecular) mostly by accretion, with the fraction of cold gas reaching about 20% of the cosmic baryon fraction. We infer a strong dependence of the star formation rate on the H$_2$ mass, suggesting a near-universal depletion timescale of 0.1-1 Gyr in Milky Way sized haloes (of masses $10^{12} \ M_{\odot}$ at $z = 0$). There is also evidence for a near-universality of the Kennicutt-Schmidt relation across redshifts, with very little dependence on stellar mass, if a constant conversion factor ($α_{\rm CO}$) of CO luminosity to molecular gas mass is assumed. Combining the atomic and molecular gas observations with the stellar build-up illustrates that galactic mass assembly in Milky-Way sized haloes proceeds from smooth accretion at high redshifts, towards becoming merger-dominated at late times ($z \lesssim 0.6$). Our results can be used to constrain numerical simulations of the dominant growth and accretion processes of galaxies over cosmic history.
