伽马射线暴和恒星形成率：它们比值红移演化的物理起源
Gamma Ray Burst and star formation rates: The physical origin for the redshift evolution of their ratio
摘要：
伽马射线暴（GRB）和高红移星系是宇宙恒星形成历史的互补探测器。事实上，GRB速率和星系光度密度都与潜在的恒星形成有关。在这里，我们结合了恒星形成模型的星系光度函数的演变，从z=0到z=10与金属依赖的效率GRB形成，同时预测共动GRB率。我们的模型揭示了伽玛暴速率和由光度密度导出的恒星形成速率之间的经验关系的物理起源：Rgrb（z）= ε（z）* SFR_{obs}（z），其中ε（z）（1+z）^{1.2}。当z<4时，金属丰度演化对γ暴效率的影响占主导地位。我们的最佳拟合模型只需要对低金属丰度有适度的偏好，即log（Z/Zsun）<-3时每单位恒星质量的GRB率比log（Z/Zsun）>0时高出约4倍。在log（Z/Zsun）>0时完全抑制GRB形成的模型是不受欢迎的。在z>4时，大部分恒星形成发生在低金属含量的宿主中，每单位恒星质量的GRB产生效率接近饱和。然而，在同一时期，由于通量限制，星系巡天错过了预测光度密度的越来越多的部分，与从较低z的经验幂律拟合相比，推动了ε（z）的加速演化。我们的发现与在z>5的超深成像中未检测到GRB宿主一致，并且指向当前在z>8的星系调查仅观察到总光度密度的顶部15- 20%。
英文摘要：
Gamma Ray Bursts (GRBs) and galaxies at high redshift represent complementary probes of the star formation history of the Universe. In fact, both the GRB rate and the galaxy luminosity density are connected to the underlying star formation. Here, we combine a star formation model for the evolution of the galaxy luminosity function from z=0 to z=10 with a metallicity-dependent efficiency for GRB formation to simultaneously predict the comoving GRB rate. Our model sheds light on the physical origin of the empirical relation often assumed between GRB rate and luminosity density-derived star formation rate: Rgrb(z) = ε(z)*SFR_{obs}(z), with ε(z) (1+z)^{1.2}. At z<4, ε(z) is dominated by the effects of metallicity evolution in the GRB efficiency. Our best-fitting model only requires a moderate preference for low-metallicity, that is a GRB rate per unit stellar mass about four times higher for log(Z/Zsun)<-3 compared to log(Z/Zsun)>0. Models with total suppression of GRB formation at log(Z/Zsun)>0 are disfavored. At z>4, most of the star formation happens in low-metallicity hosts with nearly saturated efficiency of GRB production per unit stellar mass. However at the same epoch, galaxy surveys miss an increasing fraction of the predicted luminosity density because of flux limits, driving an accelerated evolution of ε(z) compared to the empirical power-law fit from lower z. Our findings are consistent with the non-detections of GRB hosts in ultradeep imaging at z>5, and point toward current galaxy surveys at z>8 only observing the top 15-20 % of the total luminosity density.
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