AI 中文总结
本研究在COSMOS-Web中确定红移z≈8处质量完整的恒星形成主序，结合连续性方程框架演化GSMF，发现其低质量端演化更匹配观测，强调需精确测量MS的斜率与归一化。
AI 中文摘要
恒星形成主序（MS）将星系的瞬时恒星形成率与其恒星质量增长关联起来，进而关联到星系恒星质量函数（GSMF）的演化。我们在COSMOS-Web中确定了红移z≈8处质量完整的MS，并检验其质量和红移依赖性是否与观测到的GSMF演化一致。我们在Herschel和JCMT图像中堆叠了251462个恒星形成星系，并使用前向建模图像校正了远红外通量的混合效应。我们将得到的红外光度与未被消光的紫外发射结合，推导总恒星形成率，并拟合出红移依赖性的MS。我们独立测量了宁静星系占比，并在包含恒星质量返回、宁静星系占比对原位增长的抑制以及并合的连续性方程框架内，将观测到的z≈8处COSMOS-Web GSMF向前演化。该MS在低质量端可由幂律很好描述，在高质量端呈现红移依赖性的转折。我们测得低质量斜率为γ=1.215±0.028，这意味着比恒星质量随质量呈轻微上升的恒星形成率密度。利用该关系演化得到的GSMF，与本文所考虑的文献中MS预设相比，能更好地匹配观测到的低质量端逐渐变平的趋势。并合在z≈0.65时对低质量数密度的改变≤0.2 dex，且对斜率几乎无影响。MS归一化的微小差异会强烈累积，在数十亿年后产生演化后GSMF的巨大差异。观测到的GSMF演化为MS提供了独立的积分检验。我们的结果支持轻微超线性的低质量MS，表明必须精确测量其斜率和归一化，才能重现星系恒星质量分布的形成过程。
英文摘要
The star-forming main sequence (MS) links the instantaneous star-formation rate of galaxies to their stellar-mass growth and therefore to the evolution of the galaxy stellar mass function (GSMF). We determine a mass-complete MS in COSMOS-Web out to z=8 and test whether its mass and redshift dependence is consistent with the observed evolution of the GSMF. We stacked 251,462 star-forming galaxies in Herschel and JCMT maps and corrected the far-infrared fluxes for blending using forward-modeled maps. We combined the resulting infrared luminosities with the unobscured ultraviolet emission to derive total star-formation rates and fitted a redshift-dependent MS. We independently measured the quiescent fraction and evolved the observed z=8 COSMOS-Web GSMF forward within a continuity-equation framework including stellar-mass return, suppression of in-situ growth by the quiescent fraction, and mergers. The MS is well described by a power law at low masses with a redshift-dependent turnover toward high masses. We measure a low-mass slope of gamma=1.215+/-0.028, implying a mildly increasing specific star-formation rate with stellar mass. The GSMF evolved using this relation follows the observed progressive flattening of the low-mass end substantially better than the literature MS prescriptions considered here. Mergers change the low-mass number densities by <=0.2 dex by z~0.65 and have little effect on the slope. Small differences in MS normalization also accumulate strongly, producing large differences in the evolved GSMF after several Gyr. The observed GSMF evolution provides an independent integral test of the MS. Our results favor a mildly super-linear low-mass MS and show that both its slope and normalization must be measured accurately to reproduce the buildup of the galaxy stellar-mass distribution.
Comments14 pages, 5 figures, submitted to Astronomy & Astrophysics (A&A)
