Impact of the primordial stellar initial mass function on the 21-cm signal
Impact of the primordial stellar initial mass function on the 21-cm signal
复制标题
原初恒星初始质量函数对 21 厘米信号的影响
DOI：
10.1093/mnras/stac2049
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发表时间：
2022
影响因子：
4.8
通讯作者：
Gessey-Jones T
中科院分区：
文献类型：
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作者：
Gessey-Jones T
第一代恒星[称为第三星族（PopIII）恒星]的性质，例如它们的初始质量函数（IMF），受到观测的约束很差，并且在模拟之间尚未收敛。中性氢的宇宙学21厘米信号被预测对这些恒星产生的莱曼带光子敏感，从而提供了一种独特的方式来探测第一个恒星种群。本文通过Wouthuysen-Field效应、Lyman-Werner反馈、Ly α加热和宇宙微波背景加热研究了Pop III IMF对宇宙黎明21 cm信号的影响。我们计算不同IMF的恒星形成晕的发射光谱，通过整合个人的无金属恒星光谱，计算从一组恒星的演化历史和恒星大气，并考虑到光谱与恒星年龄的变化。因此，通过这项研究，我们放宽了两个常见的假设：零年龄的主序的波普III星星的发射率是其一生的平均发射率的代表，波普III排放可以被视为瞬时。探索底重，头重脚轻，和中间IMF，我们表明，在21厘米的信号的变化是由轻于20 M的恒星。对于探索的模型，我们发现在宇宙黎明全球21厘米信号的最大相对差异为59%，功率谱之间的最大相对差异为131%。虽然这种影响是适度的，但对第一批恒星及其演变的精确建模对于准确预测和解释21厘米信号是必要的。
Properties of the first generation of stars [referred to as the Population III (Pop III) stars], such as their initial mass function (IMF), are poorly constrained by observations and have yet to converge between simulations. The cosmological 21-cm signal of neutral hydrogen is predicted to be sensitive to Lyman-band photons produced by these stars, thus providing a unique way to probe the first stellar population. In this paper, we investigate the impacts of the Pop III IMF on the cosmic-dawn 21-cm signal via the Wouthuysen–Field effect, Lyman–Werner feedback, Ly α heating, and cosmic microwave background heating. We calculate the emission spectra of star-forming haloes for different IMFs by integrating over individual metal-free stellar spectra, computed from a set of stellar evolution histories and stellar atmospheres, and taking into account variability of the spectra with stellar age. Through this study, we therefore relax two common assumptions: that the zero-age main-sequence emission rate of a Pop III star is representative of its lifetime mean emission rate, and that Pop III emission can be treated as instantaneous. Exploring bottom-heavy, top-heavy, and intermediate IMFs, we show that variations in the 21-cm signal are driven by stars lighter than 20 M⊙. For the explored models, we find maximum relative differences of 59 per cent in the cosmic-dawn global 21-cm signal, and 131 per cent between power spectra. Although this impact is modest, precise modelling of the first stars and their evolution is necessary for accurate prediction and interpretation of the 21-cm signal.