ALMA Lensing Cluster Survey: A Near-infrared-dark Submillimeter Galaxy at z > 4.5

Abstract We present a study of a near-infrared-dark (NIR-dark) submillimeter galaxy R0600-C67, initially detected in the Atacama Large Millimeter/submillimeter Array (ALMA) Lensing Cluster Survey program. Due to the lack of robust emission lines from spectral line-scan observations at ALMA’s 3 mm and 2 mm bands, we utilize two spectral energy distribution (SED) fitting codes, EAZY and CIGALE , to derive a robust photometric redshift of z = 4.7 ± 0.9, based on the observations from ALMA and James Webb Space Telescope (JWST), making it as a rare NIR-dark object at high redshift. Based on the SED analysis, we derive the physical properties of R0600-C67. Joint spatial imaging analyses suggest that stellar body traced by JWST, significantly larger than the compact dust continuum from ALMA. While we test for an active galactic nucleus (AGN), the current SED fitting analysis provides no conclusive evidence for its presence. Future mid-infrared observations would be essential to clarify the presence of an AGN.