Detailed Study of Stars and Gas in a z = 8.3 Massive Merger with Extreme Dust Conditions

The Astrophysical Journal Letters Pub Date : 2024-12-12 DOI:10.3847/2041-8213/ad9741

Anishya Harshan, Roberta Tripodi, Nicholas S. Martis, Gregor Rihtaršič, Maruša Bradač, Yoshihisa Asada, Gabe Brammer, Guillaume Desprez, Vince Estrada-Carpenter, Jasleen Matharu, Vladan Markov, Adam Muzzin, Lamiya Mowla, Gaël Noirot, Ghassan T. E. Sarrouh, Marcin Sawicki, Victoria Strait and Chris Willott

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Abstract

We present galaxy MACS0416-Y1 at zspec = 8.312 as observed by the CAnadian NIRISS Unbiased Cluster Survey. MACS0416-Y1 has been shown to have extreme dust properties; thus, we study the physical properties and star formation histories of its resolved components. Overall, we find that MACS0416-Y1 is undergoing a star formation burst in three resolved clumps. The central clump is less massive compared to the other clumps and possibly formed in the merging process of the two larger clumps. Although the star formation history indicates an ongoing star formation burst, this gas-rich galaxy shows comparable star formation efficiency to cosmic noon galaxies. Using NIRSpec prism spectroscopy, we measure metallicity, , ionization parameter, , and electron temperature Te = 18000 ± 4000 K. The emission line ratios of the galaxy indicate an evolved interstellar medium similar to z ∼ 2 star-forming galaxies. Further, we find possible presence of ionization from an active galactic nucleus (AGN) using emission line diagnostics; however, we do not detect a broad-line component in the Hβ emission line. As this gas-rich galaxy is undergoing a major merger, we hypothesize that the high dust temperature in MACS0416-Y1 is caused by the star formation burst or a possible narrow-line AGN.

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极端尘埃条件下z = 8.3大质量合并中恒星和气体的详细研究

我们提出了由加拿大NIRISS无偏星团巡天观测到的位于zspec = 8.312的MACS0416-Y1星系。MACS0416-Y1已被证明具有极端的粉尘特性；因此，我们研究了其分解组分的物理性质和恒星形成历史。总的来说，我们发现MACS0416-Y1正在经历三个分解团块的恒星形成爆炸。与其他团块相比，中心团块的质量较小，可能是在两个较大团块的合并过程中形成的。虽然恒星形成的历史表明恒星形成正在爆发，但这个富含气体的星系显示出与宇宙正午星系相当的恒星形成效率。利用NIRSpec棱镜光谱测量了金属丰度、电离参数和电子温度Te = 18000±4000 K。该星系的发射谱线比值表明一种类似于z ~ 2恒星形成星系的演化星际介质。此外，我们使用发射线诊断发现可能存在来自活动星系核（AGN）的电离；然而，我们没有在Hβ发射线中检测到宽线成分。由于这个富含气体的星系正在经历一次大的合并，我们假设MACS0416-Y1中的高尘埃温度是由恒星形成爆发或可能的窄线AGN引起的。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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The Astrophysical Journal Letters

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