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arXiv 2102.08408astro-ph.GA
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银河系中再电离时期星族III和包络剥离星的光谱特征

Spectral Signatures of Population III and Envelope-stripped Stars in Galaxies at the Epoch of Reionization

Elizabeth Berzin, Amy Secunda, Renyue Cen, Alexander Menegas, Ylva Götberg

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16 pages, 9 figures. Accepted to ApJ
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摘要：

虽然大多数对再电离时代的模拟都集中在恒星形成矮星系中的单恒星星族，但预计双星演化的产物将对氢电离光子的排放做出重大贡献。在这些产物中，有剥离星（或氦星），它们的外壳从与双伴星的相互作用中剥离，留下暴露的氦核心。以前的工作表明，这些剥离的恒星可以主导高红移低光度星系的LyC光子输出。早期宇宙中的其他硬辐射源包括零金属丰度的第三族恒星，它们可能与辐射主要由剥离恒星辐射的星系具有类似的SED性质。在这里，我们使用两个指标（幂律指数在波长间隔240-500，600-900，和1200-2000，和FUV波长的总光度比LyC波长）比较模拟星系的SED只有单一的恒星演化，星系包含剥离的恒星，星系包含第III族恒星，四个不同的IMF。我们发现，剥离的恒星显着改变星系的LyC范围内的SEDs在再电离的时代。存在剥离恒星的星系中的SED在LyC范围内具有较低的幂律指数，并且FUV与LyC的光度比也较低。这些SED的差异存在于所有被考虑的光度（$M_{UV} > -15$，AB系统），并且在较低光度的星系中最为明显。我们还发现，与剥离的恒星和Pop III星的星系的SED是彼此不同的所有测试的IMF。

英文摘要：

While most simulations of the epoch of reionization have focused on single-stellar populations in star-forming dwarf galaxies, products of binary evolution are expected to significantly contribute to emissions of hydrogen-ionizing photons. Among these products are stripped stars (or helium stars), which have their envelopes stripped from interactions with binary companions, leaving an exposed helium core. Previous work has suggested these stripped stars can dominate the LyC photon output of high-redshift low luminosity galaxies. Other sources of hard radiation in the early universe include zero-metallicity Population III stars, which may have similar SED properties to galaxies with radiation dominated by stripped star emissions. Here, we use two metrics (the power-law exponent over wavelength intervals 240-500 Å, 600-900 Å, and 1200-2000 Å, and the ratio of total luminosity in FUV wavelengths to LyC wavelengths) to compare the SEDs of simulated galaxies with only single-stellar evolution, galaxies containing stripped stars, and galaxies containing Population III stars, with four different IMFs. We find that stripped stars significantly alter the SEDs in the LyC range of galaxies at the epoch of reionization. SEDs in galaxies with stripped stars present have lower power-law indices in the LyC range and lower FUV to LyC luminosity ratios. These differences in SEDs are present at all considered luminosities ($M_{UV} > -15$, AB system), and are most pronounced for lower luminosity galaxies. We also find that SEDs of galaxies with stripped stars and Pop III stars are distinct from each other for all tested IMFs.

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