第三類超新星殘骸對第一代星系的形成的影響 I. 氣體、 金屬及恆星

Abstract

近代宇宙學模擬成功地呈現了暗物質暈的階級制聚集過程，提供 了足夠的重力位能井，使原始氣體(未受金屬污染的氣體)生成恆星 及星系的形成。宇宙中最重要的天體之一——第一代星系，容納了第 一批恆星在其中，此類星系被視為早期宇宙的基石。為了了解第一代 星系的形成，我們先建立了較簡單的模型，根據不同的第一代恆星質 量分佈，設置了第一代超新星殘骸的初始溫度、密度、金屬比率，及 數量在模擬中。我們設法理解第三類超新星殘骸的聚集過程，以了解 下一代恆星生成的過程。我們根據不同的暗物質暈及不同第三類超新 星殘骸組成建立了十八組模型。從我們的結果發現，在第一代星系中 橫有可能有第三類恆星的生成，這些恆星會產生額外的金屬，並改 變下一代恆星的生成。下一代(第二類)恆星的質量分布可由指數函 數來描述，在十八組模型中，指數 α 的範圍大約落在 1.37-4.76 之間 (Salpeter IMF 的 α = 2.35)。因此，我們的結果提供了一條途徑，來了 解第一代恆星及第一代星系之間的關聯，而第一代星系未來將有可能 被詹姆士偉伯望遠鏡所觀測到。

Modern cosmological simulations successfully demonstrate that the hierarchical assembly of dark matter halos provided the gravitational wells that nurse the primordial gases to form the first stars and galaxies inside them. One of the most significant objects in the universe, the first galaxies, are naturally regarded as the foundation of the early Universe. To examine the effect of Pop III supernova remnants (SNRs) to the first galaxy formation, we perform high-resolution hydro simulations by considering initial Pop III SNRs from different Pop III initial mass functions (IMFs). We follow the mergers of Pop III SNRs with the primordial gas and study the consequent star formation in the first galaxies. We construct 18 models with different halo properties and Pop III SNR compositions. Our results suggest that it is still possible to form Pop III stars inside the first galaxies after the first supernovae, which inject extra metals and change the subsequent Pop II star formation history. We also find that Pop II stellar mass function in our simulated galaxies can be described by power-laws, dN/dM_star ∝ M_star^α, where the exponent α falls in a wide range of 1.37 – 4.76 (α = 2.35 for the Salpeter IMF). The mass distribution is highly sensitive to the previous Pop III supernovae and the properties of the host halos. Our study can provide a channel to correlate the populations of the first stars and supernovae to star formation inside these first galaxies which may be soon observed by the James Webb Space Telescope.