发表机构
University of California, Berkeley（加州大学伯克利分校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究提出膨胀的超大质量恒星可解释JWST发现的小红点现象，并作为超大质量黑洞的前身，其模型预测与观测相符。
AI 中文摘要
JWST发现了高红移处大量致密、红色的源，称为小红点（LRDs）。我们研究它们是否可以用热弛豫的、氢燃烧的、金属增丰的超大质量恒星（SMSs）来解释。我们构建了流体静力学和热平衡下的一维模型，包括辐射压主导的CNO燃烧核心和具有金属依赖性不透明度、非绝热对流以及超爱丁顿表面层有效处理的外层包层。光度接近汤姆逊散射爱丁顿极限。铁元素不透明度凸起驱动了强烈膨胀的低质量包层的形成，而氢复合在束缚光球处终止包层。对于质量M=$10^4$到$10^6$太阳质量，金属质量分数Z=$10^{-4}$到$10^{-2}$，我们发现金属含量最高的模型（Z~$10^{-2}$）发展出高度膨胀的包层，并达到有效温度约7000 K。我们提出，这种增丰的SMSs可能通过致密星团中的失控恒星碰撞而聚集形成。广义相对论不稳定性设定了依赖于核心旋转速率的最大质量。非旋转和旋转模型的最大质量为$3\ imes10^5$到$3\ imes10^6$太阳质量，最大光度约为$10^{44}$尔格/秒，与观测到的LRD光度函数的亮端截止相当。核心氢耗尽可以在约1百万年的寿命后将初始稳定的SMSs驱动跨越不稳定性阈值。如果每个LRD留下一个保留其大部分质量的黑洞，观测到的LRD丰度意味着当今的遗迹密度约为$10^{-2}$ cMpc$^{-3}$，与当地超大质量黑洞的丰度一致。冷的SMSs自然产生弱的X射线和弱的高电离谱线。非局部热动平衡效应可能显著改变巴尔默特征和连续谱不透明度，并可能使有效温度低于我们的局部热动平衡值。
英文摘要
JWST has uncovered an abundant population of compact, red sources at high redshifts, termed little red dots (LRDs). We study whether they could be explained by thermally relaxed, hydrogen-burning, metal-enriched supermassive stars (SMSs). We construct 1D models in hydrostatic and thermal equilibrium, including a radiation-pressure-dominated, CNO-burning core and an outer envelope with metallicity-dependent opacity, non-adiabatic convection, and an effective treatment of super-Eddington surface layers. The luminosity is close to the Thomson-scattering Eddington limit. The Fe-opacity bump drives the formation of a strongly inflated, low-mass envelope, while hydrogen recombination terminates the envelope at a bound photosphere. For M=$10^4$ to $10^6$ Msun and metal mass fractions $Z=10^{-4}$ to $10^{-2}$, we find that the most metal-rich models (Z ~ $10^{-2}$) develop highly inflated envelopes and reach Teff ~ 7000 K. We suggest that such enriched SMSs could instead be assembled through runaway stellar collisions in compact star clusters. The GR instability sets a maximum mass that depends on the core rotation rate. The nonrotating and rotating models have maximum masses $3\times10^5$ to $3\times 10^6$ Msun, and maximum luminosity of the order $10^{44}$ erg/s, comparable to the observed bright-end cutoff of the LRD luminosity function. Core hydrogen depletion can drive initially stable SMSs across the instability threshold after a lifetime of order 1 Myr. If each LRD leaves a black hole retaining most of its mass, the observed LRD abundance implies a present-day remnant density of order $10^{-2}\rm cMpc^{-3}$, consistent with the local abundance of supermassive black holes. Cool SMSs naturally produce weak X-ray and weak high-ionization lines. Non-LTE effects may significantly modify the Balmer features and the continuum opacity, and may lower Teff below our LTE value.
Comments29 pages, 17 figures, plus appendix
