ALMA Lensing Cluster Survey: Physical Characterization of Near-infrared-dark Intrinsically Faint ALMA Sources at z = 2–4

Tsujita, Akiyoshi; Kohno, Kotaro; Huang, Shuo; Oguri, Masamune; Tadaki, Ken-ichi; Smail, Ian; Umehata, Hideki; Gao, Zhen-Kai; Wang, Wei-Hao; Sun, Fengwu; Fujimoto, Seiji; Wang, Tao; Uematsu, Ryosuke; Espada, Daniel; Valentino, Francesco; Ao, Yiping; Bauer, Franz E.; Hatsukade, Bunyo; Egusa, Fumi; Nishimura, Yuri; Koekemoer, Anton M.; Schaerer, Daniel; Lagos, Claudia; Dessauges-Zavadsky, Miroslava; Brammer, Gabriel; Caputi, Karina; Egami, Eiichi; González-López, Jorge; Jolly, Jean-Baptiste; Knudsen, Kirsten K.; Kokorev, Vasily; Magdis, Georgios E.; Ouchi, Masami; Toft, Sune; Wu, John F.; Zitrin, Adi

Abstract

We present results from Atacama Large Millimeter/submillimeter Array (ALMA) spectral line-scan observations at 3 mm and 2 mm bands of three near-infrared-dark (NIR-dark) galaxies behind two massive lensing clusters MACS J0417.5-1154 and RXC J0032.1+1808. Each of these three sources is a (sub)millimeter faint (delensed S1.2 mm < 1 mJy) triply lensed system originally discovered in the ALMA Lensing Cluster Survey. We have successfully detected CO and [C i] emission lines and confirmed that their spectroscopic redshifts are z = 3.652, 2.391, and 2.985. By utilizing a rich multiwavelength data set, we find that the NIR-dark galaxies are located on the star formation main sequence in the intrinsic stellar mass range of log (M*/M⊙) = 9.8–10.4, which is about 1 order of magnitude lower than that of typical submillimeter galaxies (SMGs). These NIR-dark galaxies show a variety in gas depletion times and spatial extent of dust emission. One of the three is a normal star-forming galaxy with gas depletion time consistent with a scaling relation, and its infrared surface brightness is an order of magnitude smaller than that of typical SMGs. Since this galaxy has an elongated axis ratio of ∼0.17, we argue that normal star-forming galaxies in an edge-on configuration can be heavily dust-obscured. This implies that existing deep WFC3/F160W surveys may miss a fraction of typical star-forming main-sequence galaxies due to their edge-on orientation.

Citation

Tsujita, A., Kohno, K., Huang, S., Oguri, M., Tadaki, K., Smail, I., Umehata, H., Gao, Z.-K., Wang, W.-H., Sun, F., Fujimoto, S., Wang, T., Uematsu, R., Espada, D., Valentino, F., Ao, Y., Bauer, F. E., Hatsukade, B., Egusa, F., …Zitrin, A. (2025). ALMA Lensing Cluster Survey: Physical Characterization of Near-infrared-dark Intrinsically Faint ALMA Sources at z = 2–4. The Astrophysical Journal, 989, 115. https://doi.org/10.3847/1538-4357/adb41d

• Journal Article Type: Article
• Acceptance Date: Feb 7, 2025
• Online Publication Date: Aug 7, 2025
• Publication Date: Aug 10, 2025
• Deposit Date: Aug 21, 2025
• Publicly Available Date: Aug 21, 2025
• Journal: The Astrophysical Journal
• Electronic ISSN: 1538-4357
• Peer Reviewed: Peer Reviewed
• Volume: 989
• Article Number: 115
• DOI: https://doi.org/10.3847/1538-4357/adb41d
• Keywords: High-redshift galaxies, Starburst galaxies, Millimeter-wave spectroscopy, Strong gravitational lensing
• Public URL: https://durham-repository.worktribe.com/output/4422848