Cold dust and low [O iii ]/[C ii ] ratios: an evolved star-forming population at redshift 7
Cold dust and low [O iii ]/[C ii ] ratios: an evolved star-forming population at redshift 7
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冷尘埃和低 [O iii ]/[C ii ] 比率：红移 7 处演化的恒星形成族群
DOI：
10.1093/mnras/stad3111
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发表时间：
2024
影响因子：
4.8
通讯作者：
Algera H
中科院分区：
文献类型：
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作者：
Algera H
我们介绍了新的ALMA带8(静止框架)连续观测三个大质量()星系在≈7之前在[CII]m和潜在的尘埃连续发射在再电离时代的明亮发射线调查(反叛逆者)。我们探测到了我们在第8波段的两个目标(叛军-25和叛军-38)的粉尘排放，而叛军-12仍然没有被探测到。通过光学薄修正黑体拟合，我们确定了两个双波段探测目标的尘埃温度K，表明它们比大多数已知星系在∼7时更冷。此外，它们的尘埃质量很大()，尽管仍然符合高红移尘埃产生的模型。此外，我们还瞄准并检测到Refloment-12和Reverts-25中的[Oiii]m排放，并发现与迄今在已知≳6种群中观察到的$L_\mathm{[O\，\rm{\Small III}]}/L_\mathm{[C\，\rm{\Small II}]}\gtrsim 2-10$相比，[OIII]m的排放量较低。我们认为，较低的谱线比是由于我们的目标不那么星暴的性质导致的相对较弱的电离辐射场，尽管叛逆者-12可能是[Oiii]-亮和[Oiii]-弱分量的合并，这阻碍了对其[Oiii]/[CII]比的明确解释。然而，低突发性形成了一个自然的解释，可以解释寒冷的沙尘温度和低的反叛军-25和反叛军-38的相当宽度。总体而言，这些观测为≈7存在大量富含尘埃的星系群提供了证据，该星系以前经历了旺盛的恒星形成，但目前正在以稳定的方式形成恒星，而不是以爆发的方式形成恒星。
We present new ALMA Band 8 (rest-framem) continuum observations of three massive () galaxies atz≈ 7 previously detected in [Cii]m and underlying dust continuum emission in the Reionization Era Bright Emission Line Survey (REBELS). We detect dust emission from two of our targets in Band 8 (REBELS-25 and REBELS-38), while REBELS-12 remains undetected. Through optically thin modified blackbody fitting, we determine dust temperatures ofK in both of the dual-band detected targets, indicating they are colder than most known galaxies atz∼ 7. Moreover, their inferred dust masses are large (), albeit still consistent with models of high-redshift dust production. We furthermore target and detect [Oiii]m emission in both REBELS-12 and REBELS-25, and find– low compared to the $L_\mathrm{[O\, \rm{\small III}]}/L_\mathrm{[C\, \rm{\small II}]}\gtrsim 2-10$ observed in the knownz≳ 6 population thus far. We argue the lower line ratios are due to a comparatively weaker ionizing radiation field resulting from the less starbursty nature of our targets, although the possibility of REBELS-12 being a merger of an [Oiii]-bright and [Oiii]-faint component prevents the unambiguous interpretation of its [Oiii]/[Cii] ratio. Nevertheless, a low burstiness forms a natural explanation for the cold dust temperatures and low $\mathrm{[O\, \rm{\small III}]}\lambda \lambda 4959,5007+\mathrm{H} \, \beta$ equivalent widths of REBELS-25 and REBELS-38. Overall, these observations provide evidence for the existence of a massive, dust-rich galaxy population atz≈ 7 which has previously experienced vigorous star formation, but is currently forming stars in a steady, as opposed to bursty, manner.