分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shuowen Jin
Nikolaj B. Sillassen
Georgios E. Magdis
Aswin P. Vijayan
Gabriel B. Brammer
Vasily Kokorev
John R. Weaver
Raphael Gobat
Clara Giménez-Arteaga
Francesco Valentino
Malte Brinch
Carlos Gómez-Guijarro
Marko Shuntov
Sune Toft
Thomas R. Greve
David Blanquez Sese
摘要： We report the discovery of a compact group of galaxies, CGG-z5, at z~5.2 in the EGS field covered by the JWST/CEERS survey. CGG-z5 was selected as the highest overdensity of galaxies at z>2 in recent JWST public surveys and it consists of six candidate members lying within a projected area of $1.5''\times3''$ (10$\times$20~kpc$^2$). All group members are HST/F435W and HST/F606W dropouts while securely detected in the JWST/NIRCam bands, yielding a narrow range of robust photometric redshifts $5.011$) at z~1. This implies that CGG-z5 could be a "proto-massive galaxy" captured during a short-lived phase of massive galaxy formation.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Vasily Kokorev
Shuowen Jin
Georgios E. Magdis
Karina I. Caputi
Francesco Valentino
Pratika Dayal
Maxime Trebitsch
Gabriel Brammer
Seiji Fujimoto
Franz Bauer
Edoardo Iani
Kotaro Kohno
David Blanquez Sese
Carlos Gómez-Guijarro
Pierluigi Rinaldi
Rafael Navarro-Carrera
摘要： Using the novel $JWST$/NIRCam observations in the Abell 2744 field, we present a first spatially resolved overview of an $HST$-dark galaxy, spectroscopically confirmed at $z=2.58$ with magnification $\mu\approx1.9$. While being largely invisible at $\sim$1 $\mu$m with NIRCam, except for sparse clumpy sub-structures, the object is well-detected and resolved in the long-wavelength bands with a spiral shape clearly visible in F277W. By combining ancillary ALMA and $Herschel$ data, we infer that this object is an edge-on dusty spiral with an intrinsic stellar mass log$(M_*/M_\odot)\sim11.3$ and a dust-obscured SFR$\sim 300~M_\odot$~yr$^{-1}$. A massive quiescent galaxy (log$(M_*/M_\odot)\sim10.8$) with tidal features lies 2\farcs{0} away ($r$$\sim$9 kpc), at a consistent redshift as inferred by $JWST$ photometry, indicating a potential major merger. The dusty spiral lies on the main-sequence of star formation, and shows high dust attenuation in the optical ($34$ would be only detectable in F356W and F444W in UNCOVER-like survey, and become totally $JWST$-dark at $z\sim6$. This suggests that detecting highly attenuated galaxies in the Epoch of Reionization might be a challenging task for $JWST$.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shuowen Jin
Emanuele Daddi
Georgios E. Magdis
Daizhong Liu
John R. Weaver
Qinghua Tan
Francesco Valentino
Yu Gao
Eva Schinnerer
Antonello Calabro
Qiusheng Gu
David Blanquez Sese
摘要： Using NOEMA and ALMA 3mm line scans, we measure spectroscopic redshifts of six new dusty galaxies at 3.56, based on template IR spectrum energy distribution (SED) from known submillimeter galaxies at z=4--6. Dust SED analyses explain the photo-z overestimate from seemingly cold dust temperatures (Td) and steep Rayleigh-Jeans (RJ) slopes, providing additional examples of cold dusty galaxies impacted by the Cosmic Microwave Background (CMB) as found in Jin et al. (2019). We thus study the general properties of the enlarged sample of 10 ``cold" dusty galaxies over 3.5~4, together with the severe impact of the CMB on their RJ observables, paving the way for the diagnostics of optically thick dust in the early universe. Conventional gas mass estimates based on RJ dust continuum luminosities implicitly assume an optically thin case, overestimating gas masses by a factor of 2--3 on average in compact dusty star-forming galaxies.
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