Title: Detection of isolated population III stars with the James Webb Space Telescope Show Chinese title

Title: 使用詹姆斯韦伯太空望远镜探测孤立的第三星族恒星

Abstract: The first population III stars are predicted to form in minihalos at a redshift of approximately 10-30. The James Webb Space Telescope (JWST), tentatively scheduled for launch in 2018, will probably be able to detect some of the first galaxies, but whether it will also be able to detect the first stars remains more doubtful. Here, we explore the prospects of detecting an isolated population III star or a small cluster of population III stars down to redshift 2 in either lensed or unlensed fields. Our calculations are based on realistic stellar atmospheres and take into account the potential flux contribution from the surrounding HII region. We find that unlensed population III stars are beyond the reach of JWST, and that even lensed population III stars will be extremely difficult to detect. However, the main problem with the latter approach is not necessarily that the lensed stars are too faint, but that their surface number densities are too low. To detect even one population III star of 60 solar masses when pointing JWST through the galaxy cluster MACS J0717.5+3745, the lensing cluster with the largest Einstein radius detected so far, the cosmic star formation rate of population III stars would need to be approximately an order of magnitude higher than predicted by the most optimistic current models. Show Chinese abstract

Abstract: 预计第一批第三族恒星会在约10到30的红移值时形成于小晕中。 计划于2018年发射的詹姆斯韦伯太空望远镜（JWST）可能会探测到一些最早的星系，但是否也能探测到第一批恒星则更加令人怀疑。 在这里，我们探讨了探测孤立的第三族恒星或小簇第三族恒星的可能性，这些恒星的红移值可以低至2，并且可以在透镜效应场或未受透镜效应影响的场中进行探测。 我们的计算基于现实的恒星大气层，并考虑了周围HII区域可能的辐射贡献。 我们发现，未受透镜效应影响的第三族恒星超出了JWST的能力范围，即使受到透镜效应影响的第三族恒星也极其难以被探测到。 然而，后一种方法的主要问题并不一定是透镜效应导致恒星太暗，而是它们的表面数密度太低。 当使用JWST指向星团MACS J0717.5+3745（迄今为止检测到具有最大爱因斯坦半径的透镜效应星团）时，为了探测一个质量为60个太阳质量的第三族恒星，第三族恒星的宇宙恒星形成率需要比目前最乐观模型预测的高出大约一个数量级。