原初星系的性质
Properties of Primitive Galaxies
AI总结：
研究9个邻近极低金属丰度星系，发现其星云光谱受X射线双星辐射，且金属丰度越低辐射越强，提出大质量恒星直接坍缩成黑洞解释硬辐射，为JWST观测高红移星系提供模板。
摘要：
我们报告了对9个邻近的恒星形成且极低金属丰度星系的研究，这些星系由哈勃的COS远紫外光谱仪观测，可作为JWST将要观测的高红移星系的模板。我们发现这些原初星系的星云光谱显示出X射线发射体辐射的证据。遵循Thuan et al. (2004)，我们将X射线发射的来源确定为包含大质量吸积恒星黑洞的大质量X射线双星。我们进一步发现，金属丰度越低，强X射线辐射的概率越高。遵循Heger et al. (2003)，我们提出这些吸积黑洞是由初始质量大于约50太阳质量的恒星直接坍缩产生的。我们建立的包含内嵌恒星黑洞的年轻星团模型对周围气体介质产生的影响与观测到的光谱一致。我们得出结论，原初星系在显示硬辐射证据方面与金属丰度更高的星系有定性差异，这最好通过存在一个或多个内嵌恒星黑洞来解释。
英文摘要：
We report on a study of 9 nearby star-forming, very low-metallicity galaxies observed by Hubble's COS far-UV spectrograph that can serve as templates of high-z galaxies to be observed by JWST. We find that the nebular spectra of these primitive galaxies show evidence of irradiation by X-ray emitters. Following Thuan et al. (2004), we identify the sources of X-ray emission as massive X-ray binaries containing a massive accreting stellar black hole. We further find that the lower the metallicity, the higher the probability of strong X-irradiation. Following Heger et al. (2003), we suggest that these accreting black holes are produced by direct collapse of stars having initial masses greater than $\sim50\, M_\odot$. Our models of young star clusters with an embedded stellar black hole produce effects on the surrounding gaseous medium that are consistent with the observed spectra. We conclude that primitive galaxies are qualitatively different from more metal-rich galaxies in showing evidence of hard radiation that can best be explained by the presence of one or more embedded stellar black holes.
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