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arXiv 2105.04557astro-ph.GA
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$z\sim4.5$的恒星形成率函数：从静止UV到光学的分析

Star Formation Rate Function at $z\sim4.5$: An Analysis from rest UV to Optical

Y. Asada, K. Ohta, F. Maeda

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16 pages, 16 figures, 2 tables, Accepted for publication in ApJ
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摘要：

本文根据CANDELS-GOODS-South场星系从静止紫外到光学的光度数据，利用光谱能量分布（SED）拟合，在$z\sim4.5$上提出了一个恒星形成率函数（SFRF）。我们评估我们的样本的不完整性，并纠正它，以正确地面对SFRF在这项研究中与其他探针的基础上估计。SFRF得到了下降到$\sim10\ M_\odot\ \mathrm{yr}^{-1}$，它显示出一个显着的过量，从紫外光度函数和尘埃校正的基础上紫外光谱斜率估计。与基于UV的SFRF相比，在固定的SFR下，$\sim1$ dex的数密度更大，或者$\mathrm{SFR}^*$的最佳拟合Schechter参数更大。我们广泛地研究了几个假设SED拟合看到我们的结果的鲁棒性，并发现过量仍然存在，即使假设的变化，如恒星形成的历史，尘埃消光定律，和一个或两个组件模型。通过对SFRF和$0.22\ M_\odot\ \mathrm{yr}^{-1}$的积分，计算出该时期的宇宙恒星形成率密度为$4.53^{+0.94}_{-0.87}\times10^{-2}\ M_\odot\ \mathrm{yr}^{-1}\ \mathrm{Mpc}^{-3}$，比以前基于紫外观测的测量值大$\sim0.25$ dex。我们还发现，具有密集恒星形成的星系（$>10\ M_\odot\ \mathrm{yr}^{-1}$）占据了宇宙恒星形成率密度（$\sim80\%$）的绝大部分，表明该时期的恒星形成活动主要是由密集恒星形成的星系所主导。

英文摘要：

We present a star formation rate function (SFRF) at $z\sim4.5$ based on photometric data from rest UV to optical of galaxies in the CANDELS GOODS-South field using spectral energy distribution (SED) fitting. We evaluate the incompleteness of our sample and correct for it to properly confront the SFRF in this study with those estimated based on other probes. The SFRF is obtained down to $\sim10\ M_\odot\ \mathrm{yr}^{-1}$ and it shows a significant excess to that estimated from UV luminosity function and dust correction based on UV spectral slope. As compared with the UV-based SFRF, the number density is larger by $\sim1$ dex at a fixed SFR, or the best-fit Schechter parameter of $\mathrm{SFR}^*$ is larger by $\sim1$ dex. We extensively examine several assumptions on SED fitting to see the robustness of our result, and find that the excess still exist even if the assumptions change such as star formation histories, dust extinction laws, and one- or two-component model. By integrating our SFRF to $0.22\ M_\odot\ \mathrm{yr}^{-1}$, the cosmic star formation rate density at this epoch is calculated to be $4.53^{+0.94}_{-0.87}\times10^{-2}\ M_\odot\ \mathrm{yr}^{-1}\ \mathrm{Mpc}^{-3}$, which is $\sim0.25$ dex larger than the previous measurement based on UV observations. We also find that galaxies with intensive star formation ($>10\ M_\odot\ \mathrm{yr}^{-1}$) occupies most of the cosmic star formation rate density ($\sim80\%$), suggesting that star formation activity at this epoch is dominant by intensively star-forming galaxies.

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