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arXiv 2202.02099astro-ph.COastro-ph.GAastro-ph.SR
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原始恒星初始质量函数对21厘米信号的影响

Impact of the Primordial Stellar Initial Mass Function on the 21-cm Signal

T. Gessey-Jones, N. S. Sartorio, A. Fialkov, G. M. Mirouh, M. Magg, R. G. Izzard, E. de Lera Acedo, W. J. Handley, R. Barkana

摘要:

第一代恒星(Pop III)的性质,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星族。在本文中,我们调查的影响,Pop III IMF的宇宙黎明21厘米信号通过Wouthuysen场效应,莱曼-沃纳反馈,Ly-alpha加热,和CMB加热。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,计算从一组恒星演化的历史和恒星大气,并考虑到光谱的变化与恒星年龄。因此,通过这项研究,我们放宽了两个常见的假设:零年龄的主序发射率的Pop III星是其一生的平均发射率的代表,和Pop III排放可以被视为瞬时。探索底部重,顶部重,和中间IMF,我们表明,在21厘米的信号的变化是由轻于20个太阳质量的恒星驱动。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。

英文摘要:

Properties of the first generation of stars (Pop III), 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-alpha heating, and CMB heating. We calculate the emission spectra of star-forming halos 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 a bottom-heavy, a top-heavy, and intermediate IMFs, we show that variations in the 21-cm signal are driven by stars lighter than 20 solar masses. For the explored models we find maximum relative differences of 59% in the cosmic dawn global 21-cm signal, and 131% 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.

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