ALMA observations of pre- JWSTz ∼ 10 galaxy candidates: A CO( J = 9–8) line from a ULIRG at z = 2.54 and revisit of the photometric redshifts with JWST photometry
Year: 2026
Type: article
Abstract: ABSTRACT We present Atacama Large Millimetre/submillimetre Array observations targeting the [O iii] $88\, \mu$m line for six $z\sim 10$ galaxy candidates selected with the Hubble Space Telescope and the Spitzer Space Telescope. We detect a line ($4.5\sigma$) and dust continuum emission ($30\sigma$) in UDS_18697, while detecting neither robust line nor continuum emission in the remaining five objects. The detected line in UDS_18697 is identified as CO($J=9\text{-}8$), because follow-up James Webb Space Telescope (JWST) NIRSpec observations have confirmed the redshift as $z=2.54$. UDS_18697 is classified as an ultra luminous infrared galaxy with far-infrared luminosity of $L_\mathrm{FIR}\approx 1.1\times 10^{12}\, \mathrm{L}_\odot$, assuming a dust temperature of $T_\mathrm{d}\approx 42\,$K, estimated using a physically-motivated method. We find that UDS_18697 follows the $L_\mathrm{FIR}-L^{\prime }_\mathrm{CO}$ relation for local and $z\gt 2$ galaxies, albeit being slightly brighter in CO($J=9\text{-}8$). Also, based on the follow-up NIRSpec observations and spectral energy distribution fitting using JWST/NIRCam photometry, we found that most of our targets are suggested to be low-z interlopers. Motivated by these redshift misclassifications, we investigate colour–colour selection criteria for high-z galaxies using JWST spectroscopic survey catalogues. We find that elevating a colour threshold tracing the Lyman break is crucial for constructing a robust high-z sample, particularly for wide field surveys such as Euclid Deep Fields and Roman High-Latitude Wide-Area Survey.
Institutions: Waseda University, University of Tsukuba, The University of Texas at Austin, Massachusetts Institute of Technology, Space Telescope Science Institute, University of Toronto, Institute for Cosmic Ray Research, The University of Tokyo, California Institute of Technology, Tohoku University, Infrared Processing and Analysis Center, Nagoya University, University of Missouri, University of Hawaiʻi at Mānoa
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,046
Funders: National Science Foundation, Brinson Foundation, National Radio Astronomy Observatory, Japan Society for the Promotion of Science London, Ministry of Education, Culture, Sports, Science and Technology, Korea Astronomy and Space Science Institute, Waseda University, National Astronomical Observatory of Japan, Japan Society for the Promotion of Science, National Institutes of Natural Sciences
OpenAlex ID: W7203831017
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