SQuIGG$\vec{L}$E：JWST/NIRSpec Pa$\alpha$空间分辨观测揭示，$z\sim0.7$最亮CO后星暴星系在光学厚尘埃遮蔽下呈现下降但仍活跃的恒星形成
SQuIGG$\vec{L}$E: Spatially resolved NIRSpec Pa$α$ reveals that the most CO-luminous, $z\sim0.7$ post-starburst galaxies exhibit falling---but still active---star formation behind optically thick dust
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中文总结 AI 辅助
利用JWST/NIRSpec对三个CO最亮后星暴星系进行空间分辨光谱观测，发现其恒星形成率虽低于峰值但仍活跃，表明该阶段是快速熄灭路径上恒星形成的最后阶段。
中文摘要 AI 辅助
在恒星形成与静止星系交界处的后星暴星系研究中，一个基本的不确定性问题在于其瞬时恒星形成率。尽管这些星系在静止系紫外-光学波段看似宁静，但许多最年轻的系统具有极高的CO光度，暗示存在稠密分子气体以及潜在的恒星形成。然而，由于静止系光学发射线测量或紫外到红外的SED拟合给出的结果存在数量级的不确定性，它们的瞬时恒星形成率一直难以确定。本文我们展示了SQuIGG$\vec{L}$E巡天中三个CO光度最高的大质量星系的JWST/NIRSpec G395M/170LP积分场光谱，空间分辨了Pa$\alpha$/Br$\gamma$/Br$\beta$以绘制尘埃校正后的恒星形成率图。我们发现这些星系的恒星形成率为$27-80\\ M_\odot \\ \mathrm{yr^{-1}}$，尽管其中约$\sim30-40\\%$的发射可能来自非恒星形成电离（AGN或激波），这由中心空间像素中高的[FeII]/Pa$\alpha$比值所暗示。我们还发现有效的$A_{\mathrm{Pa}\alpha}\sim1$以及单个约$\sim700$ pc空间像素的$A_{\mathrm{Pa\alpha}}\sim2$，这意味着对静止系光学谱线贡献很小的星云区域存在显著的尘埃消光。这些星系并非完全静止；测得的恒星形成率使这些星系位于主序带上或之上。然而，它们的恒星形成率确实显著低于（约$\sim0.5-1$ dex）由分光光度拟合推断的峰值恒星形成率。我们提出，CO发光的后星暴阶段代表了快速熄灭路径上星系恒星形成的最后喘息，并且尘埃遮蔽的恒星形成、外流以及（推测性地）不确定的CO-to-H2转换因子协调了其气体耗尽与观测到的衰减时标。
英文摘要
One of the fundamental uncertainties in the study of galaxies at the interface between star formation and quiescence--post-starburst galaxies--is their instantaneous star formation rate. While these galaxies appear quiescent in the rest UV-optical, many of the youngest systems are highly CO luminous, implying dense molecular gas, and potentially star formation. However, their instantaneous star formation rates have proved elusive, as measurements with rest-optical emission lines or UV-to-IR SED fitting yield order-of-magnitude uncertainty. Here, we present JWST/NIRSpec G395M/170LP integral field spectroscopy of the three most CO-luminous massive galaxies in the SQuIGG$\vec{L}$E survey, spatially resolving Pa$α$/Br$γ$/Br$β$ to map the dust-corrected star formation rate. We find that these galaxies host star formation rates of $27-80$ $M_\odot \ \mathrm{yr^{-1}}$, though $\sim30-40\%$ of the emission may arise from non-star-forming ionization (AGN or shocks), implied by high [FeII]/Pa$α$ in central spaxels. We also find effective $A_{\mathrm{Pa}α}\sim1$ and individual $\sim700$ pc spaxels with $A_{\mathrm{Paα}}\sim2$, implying significant dust obscuration of nebular regions that contribute little to the rest-optical lines. These galaxies are not consistent with total quiescence; the measured star formation rates place these galaxies on or above the main sequence. However, their star formation rates \textit{are} significantly lower ($\sim0.5-1$ dex) than the peak star formation rates inferred from spectrophotometric fitting. We propose that the CO luminous post-starburst phase represents the last gasp of star formation in galaxies on the rapid quenching pathway, and that dust-obscured star formation, outflows, and (speculatively) an uncertain CO-to-H2 conversion reconcile their gas exhaustion with observed timescales of fading.
发表机构
- The Johns Hopkins University（约翰斯·霍普金斯大学）
- Princeton University（普林斯顿大学）
- University of Pittsburgh（匹兹堡大学）
- University of Colorado, Boulder（科罗拉多大学博尔德分校）
- Texas A&M University（德克萨斯农工大学）
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