标题： 伽马射线暴作为宇宙学探针 - 宇宙化学演化 显示英文标题

标题： GRBs as Cosmological Probes - Cosmic Chemical Evolution

摘要： 长时伽马射线暴（GRB）与金属贫乏的大质量恒星的死亡有关。 尽管它们是难以定位的高瞬态事件，但它们非常明亮，以至于可以在最困难的环境中被探测到。 GRB观测正在揭示遥远宇宙（红移z > 2）的化学状态的惊人景象。 与高红移金属贫乏恒星的预期相反，GRB周围的中性星际介质（ISM）并不贫金属（金属度从z = 6.3时的约1/10太阳金属度到z = 2时的约太阳金属度不等），并且富含尘埃（90-99%的铁以固态形式存在）。 如果将这些金属度与z < 1的GRB宿主星系的温暖ISM中测得的金属度结合起来，会观察到红移演化。 这种演化预测宿主星系的恒星质量在M* = 10^(8.6-9.8) Msun范围内。 这一预测利用了正常恒星形成星系中观测到的质量-金属度关系（以及其红移演化）。 来自GRB宿主星系光学-NIR光度测量的独立测量表明相同的恒星质量范围，典型值类似于大麦哲伦星云。 这种新发现的中等质量星系在高红移下使用传统天文学很难找到。 然而，它提供了一个有说服力且相对经济的机会，来探索已知边界之外的星系形成和宇宙化学演化，从原始宇宙到目前。 显示英文摘要

摘要： Long-duration gamma-ray bursts (GRBs) are associated with the death of metal-poor massive stars. Even though they are highly transient events very hard to localize, they are so bright that they can be detected in the most difficult environments. GRB observations are unveiling a surprising view of the chemical state of the distant universe (redshifts z > 2). Contrary to what is expected for a high-z metal-poor star, the neutral interstellar medium (ISM) around GRBs is not metal poor (metallicities vary from ~1/10 solar at z = 6.3 to about solar at z = 2) and is enriched with dust (90-99% of iron is in solid form). If these metallicities are combined with those measured in the warm ISM of GRB host galaxies at z < 1, a redshift evolution is observed. Such an evolution predicts that the stellar masses of the hosts are in the range M* = 10^(8.6-9.8) Msun. This prediction makes use of the mass-metallicity relation (and its redshift evolution) observed in normal star-forming galaxies. Independent measurements coming from the optical-NIR photometry of GRB hosts indicate the same range of stellar masses, with a typical value similar to that of the Large Magellanic Cloud. This newly detected population of intermediate-mass galaxies is very hard to find at high redshift using conventional astronomy. However, it offers a compelling and relatively inexpensive opportunity to explore galaxy formation and cosmic chemical evolution beyond known borders, from the primordial universe to the present.