ALMA对JWST之前红移z~10的星系候选体的观测：来自红移z=2.54的极亮红外星系（ULIRG）的CO(J=9-8)谱线及利用JWST测光数据重新审视测光红移
ALMA observations of pre-JWST z ~ 10 galaxy candidates: A CO(J = 9-8) line from a ULIRG at z = 2.54 and revisit of the photometric redshifts with JWST photometry
浏览论文内容
中文总结 AI 辅助
本研究利用ALMA观测6个z~10星系候选体，发现UDS_18697实为z=2.54的ULIRG，多数候选体为低红移闯入者，据此提出提高莱曼断裂颜色阈值以优化高红移星系筛选。
中文摘要 AI 辅助
我们利用阿塔卡马大型毫米/亚毫米波阵列（ALMA），对6个由哈勃空间望远镜和斯皮策空间望远镜筛选出的红移z~10的星系候选体开展[OIII]88μm谱线的靶向观测。我们在UDS_18697中探测到一条置信度4.5σ的谱线，以及置信度30σ的尘埃连续谱辐射；其余5个目标中既未探测到可靠的谱线，也未探测到连续谱辐射。后续詹姆斯·韦布空间望远镜（JWST）的NIRSpec观测已确认该源红移为z=2.54，据此UDS_18697中探测到的谱线被识别为CO(J=9-8)。基于物理驱动的方法估算出尘埃温度约为42K，在此假设下，UDS_18697被归类为极亮红外星系（ULIRG），其远红外（FIR）光度约为1.1×10^12倍太阳光度（L☉）。我们发现，UDS_18697符合局域星系及红移z>2星系的远红外光度-CO光度（L_FIR-L'_CO）关系，尽管其CO(J=9-8)辐射稍亮。此外，结合后续NIRSpec观测以及利用JWST/NIRCam测光数据开展的光谱能量分布拟合结果，我们发现本次研究的多数目标大概率是低红移的闯入天体。受这些红移误分类结果的启发，我们利用JWST光谱巡天目录，研究了高红移星系的色-色筛选准则。我们发现，提高用于追踪莱曼断裂的颜色阈值，对于构建可靠的高红移星系样本至关重要，这对于欧几里得深场（Euclid Deep Fields）、罗曼高纬度大天区巡天（Roman High-Latitude Wide-Area Survey）这类大天区巡天项目尤其重要。
英文摘要
We present Atacama Large Millimetre/submillimetre Array (ALMA) observations targeting the [OIII]$88\,μ$m line for six $z\sim10$ galaxy candidates selected with the Hubble Space Telescope and the Spitzer Space Telescope. We detect a line ($4.5σ$) and dust continuum emission ($30σ$) in UDS_18697, while detecting neither robust line nor continuum emission in the remaining five objects. The detected line in UDS_18697 is identified as CO($J=9-8$), because follow-up James Webb Space Telescope (JWST) NIRSpec observations have confirmed the redshift as $z=2.54$. UDS_18697 is classified as an ultra luminous infrared galaxy (ULIRG) with far-infrared (FIR) luminosity of $L_\mathrm{FIR}\approx1.1\times10^{12}\,L_\odot$, assuming a dust temperature of $T_\mathrm{d}\approx42\,$K, estimated using a physically-motivated method. We find that UDS_18697 follows the $L_\mathrm{FIR}-L'_\mathrm{CO}$ relation for local and $z>2$ galaxies, albeit being slightly brighter in CO($J=9-8$). Also, based on the follow-up NIRSpec observations and spectral energy distribution fitting using JWST/NIRCam photometry, we found that most of our targets are suggested to be low-$z$ interlopers. Motivated by these redshift misclassifications, we investigate colour--colour selection criteria for high-$z$ galaxies using JWST spectroscopic survey catalogues. We find that elevating a colour threshold tracing the Lyman break is crucial for constructing a robust high-$z$ sample, particularly for wide field surveys such as Euclid Deep Fields and Roman High-Latitude Wide-Area Survey.
