paper

NOEMA reveals the true nature of luminous red JWST z>10 galaxy candidates

arXiv:2310.20675 · doi:10.1051/0004-6361/202348306

Abstract

The first year of JWST has revealed a surprisingly large number of luminous galaxy candidates beyond . While some galaxies have already been spectroscopically confirmed, there is mounting evidence that a subsample of the candidates with particularly red inferred UV colours are, in fact, lower redshift contaminants. These interlopers are often found to be `HST-dark' or `optically faint' galaxies at , a population that is key to improving our understanding of dust-obscured star formation throughout cosmic time. This paper demonstrates the complementarity of ground-based mm-interferometry and JWST infrared imaging to unveil the true nature of red 1.5-2.0 dropouts that have been selected as ultra-high-redshift galaxy candidates. We present NOEMA Polyfix follow-up observations of four JWST red 1.5-2.0 dropouts selected by Yan et al., 2023 as ultra-high-redshift candidates in the PEARLS-IDF field. The new NOEMA observations constrain the rest-frame far-infrared continuum emission and efficiently discriminate between intermediate- and high-redshift solutions. We report NOEMA continuum detections of all our target galaxies at observed frequencies of and , with FIR slopes indicating a redshift of . We modelled their optical-to-FIR spectral energy distribution (SED) with multiple SED codes, finding that they are not galaxies but dust-obscured, massive star-forming galaxies at instead. The contribution to the cosmic star formation rate density (CSFRD) of such sources is not negligible at (; or of the total CSFRD), in line with previous studies of optically faint and sub-millimeter galaxies. This approach opens up a new window onto obscured star formation at intermediate redshifts [abridged].

arXiv comment6 pages. Accepted in A&A Letters. Updated to match accepted version

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