大椭圆星系的宜居性,Monthly Notices of the Royal Astronomical Society

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大椭圆星系的宜居性
Monthly Notices of the Royal Astronomical Society ( IF 4.7 ) Pub Date : 2020-04-13 , DOI: 10.1093/mnras/staa957
Daniel P Whitmire ₁

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根据恒星数量、超新星率和金属丰度，先前的一项研究（Dayal 等人，2015 年）得出结论，大型椭圆星系包含的宜居行星比银河系多 10,000 倍，因此是“生命的摇篮”。使用他们模型的结果并考虑到星系数量分布和超新星发生率，我在这里认为这个结果违反了适用于所有现存技术物种的参考类别的平庸原则。假设我们是居住在相对较大的以盘为主的星系属性上的典型技术物种，我概述了两个可能显着限制大型椭圆星系宜居性的假设：(1) 与类星体/AGN 活动和星暴超新星相关的大规模星系绝育事件，这些事件发生在当今大型椭圆星系的前身更加紧凑时；(2) 在大型椭圆星系中形成宜居行星的概率可能很小，因为由于大型椭圆星系中金属丰度普遍较高，预计会形成不成比例的大量气态行星。因此，如果气态行星向内迁移足够慢，那么宜居行星就会减少。假设 (1) 的绝育事件发生在更早的时期 (z $\geq$ 1)，因此它们必须有效地永久存在，这意味着关于生命起源和进化的两种可能情况。与这些场景之一有关，

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The habitability of large elliptical galaxies

Based on numbers of stars, supernova rates, and metallicity, a prior study (Dayal et al. 2015) concluded that large elliptical galaxies contain up to 10,000 times more habitable planets than the Milky Way and are thus the "cradles of life". Using the results of their model and taking into account galactic number distributions and supernova rates I argue here that this result constitutes a violation of the Principle of Mediocrity as applied to the reference class of all extant technological species. Assuming that we are a typical technological species in the attribute of inhabiting a relatively large disk-dominated galaxy, I outline two hypotheses that could significantly limit the habitability of large elliptical galaxies: (1) massive galactic sterilization events associated with quasar/AGN activity and starburst supernovae that occurred when the antecedents of today's large elliptical galaxies were much more compact; and (2) the probability of habitable planet formation in large elliptical galaxies may be small since a disproportionately larger number of gaseous planets are expected to form as a result of the generally higher metallicity in large elliptical galaxies. Consequently, fewer habitable planets will accrete if the gaseous planets inward migrations are sufficiently slow. The sterilization events of Hypothesis (1) occurred at earlier epochs (z $\geq$ 1) and so they must be effectively permanent, implying two possible scenarios regarding the origin and evolution of life. In connection with one of these scenarios, independent applications of the Principle of Mediocrity suggest that M-dwarf stars are not significant hosts of technological life.

更新日期：2020-04-13

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