[论文解读] MIGHTEE: The evolving radio luminosity functions of star-forming galaxies to $z\sim 4.5$ and the cosmic history of star formation

Nijin Thykkathu, Matt J. Jarvis+10 more|arXiv (Cornell University)|Jan 21, 2026

Galaxies: Formation, Evolution, Phenomena被引用 0

一句话总结

论文使用 MIGHTEE 数据建模星形成星系（SFGs）与AGN 的 evolving 1.4 GHz 无线辉度函数（RLFs），推导到 z~4.5 的宇宙恒星形成率密度（SFRD），并讨论基于无线电的 SFRD 估计与 UV/FIR 追踪量的对比。

ABSTRACT

A key question in extragalactic astronomy is how the star-formation rate density (SFRD) evolves over cosmic time. A powerful way of addressing this question is using radio-continuum observations, where the radio waves are unaffected by dust and are able to reach sufficient resolution to resolve individual galaxies. We present an investigation of the 1.4 GHz radio luminosity functions (RLFs) of star-forming galaxies (SFGs) and Active Galactic Nuclei (AGN) using deep radio continuum observations in the COSMOS and XMM-LSS fields, covering a combined area of $\sim 4\,\mathrm{deg}^2$. These data enable the most accurate measurement of the evolution in the SFRD from mid-frequency radio continuum observations. We model the total RLF as the sum of evolving SFG and AGN components, negating the need for individual source classification. We find that the SFGs have systematically higher space densities at fixed luminosity than found in previous radio studies, but consistent with more recent studies with MeerKAT. We attribute this to the excellent low-surface brightness sensitivity of MeerKAT. We then determine the evolution of the SFRD. Adopting the far-infrared - radio correlation results in a significantly higher the SFRD at $z > 1$, compared to combined UV and far-infrared measurements. However, using more recent relations for the correlation between star-formation rate and radio luminosity, based on full spectral energy distribution modelling, can resolve this apparent discrepancy. Thus radio observations provide a powerful method of determining the total SFRD, in the absence of dust-sensitive far-infrared data.

研究动机与目标

• 使用深 MeerKAT MIGHTEE 数据在 COSMOS 和 XMM-LSS 场域，评估星形成星系和 AGN 的无线电辉度函数的演化。
• 通过拟合一个不依赖单个源分类的联合模型，量化 SFGs 与 AGN 对总 RLF 的贡献。
• 将演化的 RLF 转化为跨红移的宇宙恒星形成率密度，并将基于无线电的 SFRD 与 UV 与远红外追踪量进行比较。

提出的方法

• 使用固定光谱指数（alpha = -0.7）从观测的 1.4 GHz 磁通密度计算 rest-frame 1.4 GHz 光度。
• 在红shift 区间 (0.2 < z < 4.6) 以 0.25 dex 的光度分辨率（亮端 0.4 dex）构建 1/Vmax 无线电辉度函数。
• 将总RLF建模为演化的 SFG 与 AGN 两分量之和，SFG 通过纯光度进化演化，AGN 通过纯密度进化。
• 采用贝叶斯推断并使用 MultiNest 拟合 RLF 参数，先验由局部 RLF 指引，并对光度测红的概率分布函数进行采样以边缘化红移不确定性。
• 考虑不完整性（无线电和光学/NIR），并对非 XID 源以统计分配的红移进行处理。

Figure 1: Normalised Redshift distributions for radio sources in the COSMOS (left) and XMM-LSS (right) fields. Each panel shows the normalised redshift histograms for sources with spectroscopic redshifts (spec-z; blue), photometric redshifts where no spec-z is available (phot-z; orange), and radio s

实验结果

研究问题

• RQ1 SFGs 与 AGN 的局部和高红移无线电辉度函数的形状如何演化？
• RQ2 在联合从无线电数据建模时，SFGs 与 AGN 的演化（光度与密度）在 z~4.5 的情况下如何？
• RQ3 从 1.4 GHz 无线电辉度函数推导的宇宙恒星形成率密度历史是什么，与 UV 与 FIR 追踪量相比如何？
• RQ4 是否存在一个不逐源分类的联合 RLF 模型能稳健地恢复 SFG 与 AGN 的演化？

主要发现

• SFG 在固定光度下的空间密度高于一些早期的无线电研究，与最近的 MeerKAT 结果一致，这归因于改进的低表面亮度灵敏度。
• 若使用 FIR-无线电相关性结果，且采用全面的 SED 建模得到的新的 SFR–无线电光度关系，来自无线电连续观测的 SFRD 演化可能高于 UV+FIR 基于的估计，但可通过新近的 SFR–无线电光度关系进行调和。
• 在固定局部 AGN 形状与演化的 SFGs 参数下进行的联合 RLF 拟合给出 SFG-Schechter 式函数与 AGN PDE 演化的最佳拟合参数。
• 分析表明无线电观测提供了一种强大且不受尘埃偏差影响的手段来确定总 SFRD，直至 z~4.5，前提是采用的 SFR–无线电关系）。
• 非 XID 源通过红shift 指派策略和蒙特卡洛重采样来将红shift 不确定性传播到 RLF。]
• The study uses a combined area of ~4.06 deg^2 across COSMOS and XMM-LSS and a 40 μJy flux limit to minimize completeness concerns.

Figure 2: Completeness of the 1.4 GHz COSMOS catalogue as a function of input flux density. SKADS (green), modified SKADS (blue), SIMBA (maroon), the mean completeness is the back line. The vertical dashed line marks the uniform flux–density cut at 40 $\mu$ Jy; the horizontal dashed line marks 100%