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arXiv 2602.05808astro-ph.GA
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MIGHTEE/COSMOS-3D:发现三个光谱确认的射电选定恒星形成星系,红移z=4.9-5.6

MIGHTEE/COSMOS-3D: The discovery of three spectroscopically confirmed radio-selected star-forming galaxies at z=4.9-5.6

University of Oxford(牛津大学);University College London(伦敦大学学院);University of the Western Cape(西开普大学);University of Geneva(日内瓦大学);University of Edinburgh(爱丁堡大学)

R. G. Varadaraj, A. Saxena, S. Fakiolas, I. H. Whittam, M. J. Jarvis, R. A. Meyer, C. L. Hale, K. Kakiichi, M. Li, J. B. Champagne, B. Jin, Z. J. Li, M. Shuntov

AI总结:

研究发现三个z=4.9-5.6的射电选定恒星形成星系,通过光谱确认其恒星形成率,并揭示其在高红移下的恒星形成活动特征。

摘要:

射电观测提供了一种不依赖尘埃的恒星形成和活动星系核(AGN)活动的探测手段,但需要足够深的数据才能在高红移(z>4.5)时探测这两种过程的交叉光度。我们报道了三个高红移射电源(HzRSs),在1.3 GHz处检测到z=4.9-5.6,其射电光度覆盖L_{1.3 GHz}≈2-5×10^{24} W Hz^{-1}。这些源最初通过归档哈勃、JWST NIRCam+MIRI和地面光度数据的光谱能分布(SED)拟合被识别为高红移候选者,然后通过JWST COSMOS-3D的宽视场无狭缝光谱法利用Hα发射线进行光谱确认。通过SED拟合测量的恒星形成率(SFRs)、Hα流量和1.3 GHz光度覆盖约100-1800 M_⊙ yr^{-1},显示这些SFR探测器之间有广泛的共识。我们发现这三个源位于z=4-6的恒星形成主序列上或0.5-1.0个数量级以上,并且经历了最近的恒星形成爆发。这些源具有扩展的静止紫外/光学形态,没有主导点源成分的证据,表明AGN不太可能主导它们的静止紫外和光学发射。其中两个源具有复杂的、多成分的静止紫外/光学形态,表明它们的恒星爆发可能由合并活动触发。这些HzRSs为探测z>4.5由恒星形成驱动的射电发射打开了新的窗口,代表了一个开始追踪恒星形成、不依赖尘埃的早期宇宙的机会。

英文摘要:

Radio observations offer a dust-independent probe of star formation and active galactic nucleus (AGN) activity, but sufficiently deep data are required to access the crossover luminosity between these processes at high redshift ($z>4.5$). We present three spectroscopically confirmed high-redshift radio sources (HzRSs) detected at 1.3 GHz at $z=4.9$-$5.6$, with radio luminosities spanning $L_{\rm 1.3 \, GHz}\approx2$-$5\times10^{24} \, \rm W \, Hz^{-1}$. These sources were first identified as high-redshift candidates through spectral energy distribution (SED) fitting of archival Hubble, JWST NIRCam+MIRI, and ground-based photometry, and then spectroscopically confirmed via the $\rm H\,α$ emission line using wide-field slitless spectroscopy from JWST COSMOS-3D. The star formation rates (SFRs) measured from SED fitting, the $\rm H\,α$ flux, and the 1.3 GHz luminosity, span $\sim100$-$1800\, M_{\odot} \, \rm yr^{-1}$, demonstrating broad agreement between these SFR tracers. We find that these three sources lie either on or $0.5$-1.0 dex above the star-forming main sequence at $z=4$-6 and have undergone a recent burst of star formation. The sources have extended rest-UV/optical morphologies with no evidence for a dominant point source component, indicating that an AGN is unlikely to dominate their rest-UV and optical emission. Two of the sources have complex, multi-component rest-frame UV/optical morphologies, suggesting that their starbursts may be triggered by merging activity. These HzRSs open up a new window towards probing radio emission powered by star formation alone at $z> 4.5$, representing a remarkable opportunity to begin tracing star formation, independent of dust, in the early Universe.

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