从Grism到IFU：利用JWST和ALMA重新确定尘埃巨大星系S1的红移和性质
From Grism to IFU: Revising the Redshift and Nature of the Massive Dusty Galaxy S1 with JWST and ALMA
AI总结：
利用JWST和ALMA重新确定尘埃巨大星系S1的红移和性质，发现其红移修正后更接近主序大质量星系，揭示了slitless光谱学的局限性。
摘要：
我们报告了尘埃巨大星系S1的修订光谱红移，此前是通过极高的原子到恒星转换效率从NIRCam slitless grism数据中推断出的红移z_grism=5.58。我们的新JWST/NIRSpec IFU观测揭示了多个静止框架光学和近红外发射线，得出可靠的光谱红移z_spec=3.2439±0.0002。我们显示，先前的grism红移是由于附近星系的光谱痕迹重叠导致的，这揭示了slitless光谱学在仅有一个分散角度和一个发射特征时的已知挑战。此外，我们还提供了新的ALMA 1毫米观测，这稳健地检测到尘埃发射（S_1mm=0.99±0.03 mJy）并显示尘埃半光度半径（R_e,1mm=0.73±0.10 kpc）略小于恒星大小（R_e,F444W=0.97±0.01 kpc）。使用修订后的红移和综合多波段光度计，我们更新了紫外到远红外SED，并发现S1比之前推断的要不那么极端，但仍是一个非常巨大的（logM_★/M_⊙≈10.6）、高度遮蔽的恒星形成星系。更新的SED建模显示S1是一个非常尘埃和气体丰富的系统，具有中等的恒星形成率和较长的气体耗尽时间（τ_dep≈1.4 Gyr），偏离SMGs和OFGs，但更接近典型的主序大质量星系。我们注意到，尽管这次修订减少了Xiao等人2024年报告的超质量星系数量，但并未改变该工作的主要结论。总体而言，我们的研究澄清了S1的性质，并强调了多线光谱确认、多个位置角度的slitless观测和IFU数据对于早期宇宙中稀有大质量星系的红移和物理特征的稳健确定的重要性。
英文摘要：
We report a revised spectroscopic redshift for the dusty massive galaxy S1, previously inferred with an exceptionally high baryon-to-star conversion efficiency from NIRCam slitless grism data at $z_{\rm grism}=5.58$. Our new JWST/NIRSpec IFU observations reveal multiple rest-frame optical and NIR emission lines, yielding a secure spectroscopic redshift of $z_{\rm spec}=3.2439\pm0.0002$. We show that the earlier grism-based redshift resulted from contamination by a nearby galaxy whose dispersed spectral trace overlaps with S1, illustrating a known challenge of slitless spectroscopy when only a single dispersion angle and single emission feature are available. In addition, we present new ALMA 1 mm observations, which robustly detect dust emission ($S_{\rm 1mm}=0.99\pm0.03$ mJy) and show a dust half-light radius ($R_{\rm e,1mm}=0.73\pm0.10$ kpc) slightly smaller than the stellar size ($R_{\rm e, F444W} = 0.97\pm0.01$ kpc). Using the revised redshift and compiled multi-wavelength photometry, we update the UV-to-FIR SED and find that S1 is less extreme than previously inferred, yet remains a very massive (log$M_{\star}/M_{\odot}\sim10.6$), heavily obscured star-forming galaxy. The updated SED modeling reveals S1 to be a very dust- and gas-rich system with a moderate star formation rate and a long gas depletion time ($τ_{\rm dep} \sim 1.4$ Gyr), deviating from SMGs and OFGs, but more closely resembling typical massive main-sequence galaxies. We note that, although this revision reduces the number of ultra-massive galaxies reported in Xiao et al. 2024, it does not alter the main conclusions of that work. Overall, our study clarifies the nature of S1 and underscores the importance of multi-line spectroscopic confirmation, slitless observations at multiple position angles, and IFU data for robust redshift and physical characterization of rare massive galaxies in the early Universe.
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