标题： 银河系结束序列 显示英文标题

标题： The Galaxy End Sequence

摘要： 一个常见的假设是，在特定恒星形成率（SSFR）与星系恒星质量的图中，星系分为两个不同的区域：恒星形成星系主序（GMS）和一个单独的“被动”或“红色且死亡的星系”区域。 从一个体积有限的附近星系样本开始，该样本旨在包含该体积中的大部分恒星质量，因此是120亿年星系演化结束时宇宙的公平代表，我们研究了今天在这个图中的星系分布。 我们表明，星系遵循一个强烈弯曲的扩展GMS，在高星系恒星质量下具有陡峭的负斜率。 沿着这个分布，星系的形态有逐渐的变化，但早期类型和晚期类型星系之间没有明显的分界。 检查其他表明存在两个不同种群的证据，我们认为“红色序列”是由于在SSFR的一个临界值以下，星系的颜色变化很小，而不是意味着一个不同的星系种群，并且赫歇尔观测显示至少有一半的早期类型星系含有一个冷的星际介质，这也意味着早期类型和晚期类型星系之间存在连续性。 这种统一星系种群的图像需要比解释两个不同种群所需的快速熄灭过程更渐进的演化过程。 我们挑战理论家们重现这个“星系终末序列”的特性。 显示英文摘要

摘要： A common assumption is that galaxies fall in two distinct regions on a plot of specific star-formation rate (SSFR) versus galaxy stellar mass: a star-forming Galaxy Main Sequence (GMS) and a separate region of `passive' or `red and dead galaxies'. Starting from a volume-limited sample of nearby galaxies designed to contain most of the stellar mass in this volume, and thus being a fair representation of the Universe at the end of 12 billion years of galaxy evolution, we investigate the distribution of galaxies in this diagram today. We show that galaxies follow a strongly curved extended GMS with a steep negative slope at high galaxy stellar masses. There is a gradual change in the morphologies of the galaxies along this distribution, but there is no clear break between early-type and late-type galaxies. Examining the other evidence that there are two distinct populations, we argue that the `red sequence' is the result of the colours of galaxies changing very little below a critical value of the SSFR, rather than implying a distinct population of galaxies, and that Herschel observations, which show at least half of early-type galaxies contain a cool interstellar medium, also imply continuity between early-type and late-type galaxies. This picture of a unitary population of galaxies requires more gradual evolutionary processes than the rapid quenching processes needed to to explain two distinct populations. We challenge theorists to reproduce the properties of this `Galaxy End Sequence'.