OutThere 巡天：利用z~2处的普通星系样本解决ξ_ion与f_esc问题
OutThere Survey: Addressing $\mathrm{ξ_{ion}}$ and $\mathrm{f_{esc}}$ with a population of average galaxies at z$\sim$2
AI总结：
本研究基于OutThere巡天的230个z~2星系样本，测量ξ_ion与f_esc，发现ξ_ion与紫外斜率等无显著关联、与[OIII]5007埃EW等相关，f_esc处于理论范围且与红移等显著相关。
AI中文摘要：
限制早期宇宙电离的主要贡献者是高红移星系研究的持续目标。我们对OutThere巡天项目中观测到的230个中等红移（1.3<z<2.6）源样本，测量其电离光子产生效率和莱曼连续谱逃逸分数；OutThere巡天是一项纯平行、宽视场的JWST/NIRISS巡天，配套有JWST/NIRCam、NIRISS及HST测光数据。该样本的低阈值发射选择标准构建了一个庞大且稳健的控制样本，可与其他研究对比，尤其适用于z>5以上的低质量星系。该控制样本使我们能验证此前研究提出的电离与光谱/物理性质间的关联。我们发现电离光子产生效率（ξ_ion）与紫外斜率、M_UV、恒星质量（M_*）或比恒星形成率（sSFR）无显著关联；但ξ_ion与[OIII]5007埃等值宽度（EW）存在关联（斯皮尔曼系数ρ=0.24，p<4×10^-4），且与Hα EW的关联（ρ=0.63，p<<1×10^-6）即使在低EW下仍成立，只是离散度更大。我们还发现，本研究确定电离光子逃逸分数（f_esc）的新方法得到的数值处于理论范围（0-10%）内，但与经验结果差异显著：包含未检测源的f_esc中位数为0.9%^+1.1_(-0.5)，在0.01%阈值以上的f_esc中位数为1.9%^+8.9_(-1.8)。我们还发现，该逃逸分数方法与红移、恒星形成率（SFR）和M_UV始终存在显著关联，且与[OIII]5007埃EW、Hα EW及恒星质量存在样本依赖的关联。
英文摘要：
Constraining the major contributors to the ionisation of the early universe is an ongoing endeavour of high-redshift galaxy research. We measure the ionising photon production efficiency and Lyman Continuum escape fraction for a sample of 230 intermediate redshift ($1.3<z<2.6$) sources observed as a part of the \textit{OutThere survey}; a pure-parallel, wide-area JWST/NIRISS survey with accompanying JWST/NIRCam, NIRISS and HST photometry. The low threshold emission selection criteria for this sample makes for a large and robust control, against which other works may be contrasted, particularly for low-mass galaxies above z$>$5. This control sample allows us to verify the correlations between ionising and spectral/physical properties suggested by previous studies. We find no significant correlations between the ionising photon production efficiency ($\mathrm{ξ_{ion}}$) with the UV slope, $\mathrm{M_{UV}}$, M$_*$ or sSFR. We do find that $\mathrm{ξ_{ion}}$ correlates with [OIII]5007Å\, equivalent width (EW) (Spearman coefficient $ρ$ =0.24; p$< 4\times10^{-4}$) and H$α$ EW ($ρ$ =0.63; p$<< 1\times10^{-6}$) hold even at low EW albeit with more scatter. We also find that our novel approach to determining the ionising photon escape fraction $\mathrm{f_{esc}}$ results in values within theoretical ranges (0-10\%) though vary substantially in comparison to the empirical results (median $\mathrm{f_{esc}} = 0.9\%^{+1.1}_{-0.5}$ including non-detections, median $\mathrm{f_{esc}} = 1.9\%^{+8.9}_{-1.8}$ above a $0.01\%$ threshold). We find that this escape fraction method has consistently significant correlations with the redshift, SFR and M$_{UV}$ and sample-dependent correlations with [OIII]5007Å\,EW,H$α$ EW and stellar mass.
