Dark progenitors and massive descendants: A first ALMA perspective of radio-selected near-IR-dark galaxies in the COSMOS field

¹ University of Bologna, Department of Physics and Astronomy (DIFA), Via Gobetti 93/2, 40129 Bologna, Italy
e-mail: fabrizio.gentile3@unibo.it
² INAF – Osservatorio di Astrofisica e Scienza dello Spazio, Via Gobetti 93/3, 40129 Bologna, Italy
³ CEA, IRFU, DAp, AIM, Université Paris-Saclay, Université Paris Cité, Sorbonne Paris Cité, CNRS, 91191 Gif-sur-Yvette, France
⁴ SISSA, Via Bonomea 265, 34136 Trieste, Italy
⁵ IFPU – Institute for fundamental physics of the Universe, Via Beirut 2, 34014 Trieste, Italy
⁶ INFN-Sezione di Trieste, Via Valerio 2, 34127 Trieste, Italy
⁷ INAF/IRA, Istituto di Radioastronomia, Via Piero Gobetti 101, 40129 Bologna, Italy
⁸ INAF, Istituto di Radioastronomia – Italian ARC, Via Piero Gobetti 101, 40129 Bologna, Italy
⁹ Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, 67000 Strasbourg, France
¹⁰ Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
¹¹ INAF – Osservatorio Astronomico di Brera, Via Brera 28, 20121, Milano, Italy & Via Bianchi 46, 23807 Merate, Italy
¹² Caltech/IPAC, MS314-6, 1200 E. California Blvd, Pasadena, CA 91125, USA
¹³ Inter-University Institute for Data Intensive Astronomy, Department of Astronomy, University of Cape Town, 7701 Rondebosch, Cape Town, South Africa
¹⁴ Inter-University Institute for Data Intensive Astronomy, Department of Physics and Astronomy, University of the Western Cape, 7535 Bellville, Cape Town, South Africa
¹⁵ Department of Physics, University of Zagreb, Bijenicka cesta 32, 10002 Zagreb, Croatia

Received: 15 November 2023
Accepted: 10 May 2024

Abstract

We present the first spectroscopic ALMA follow-up for a pilot sample of nine radio-selected near-IR-dark galaxies in the COSMOS field. These sources were initially selected as radio-detected sources (S_3 GHz > 12.65 μJy) without an optical or near-IR (NIR) counterpart in the COSMOS2015 catalog (Ks ≳ 24.7 mag), and just three of them were subsequently detected in the deeper COSMOS2020. Several studies highlighted that this selection could provide a population of highly dust-obscured, massive, and star-bursting galaxies. With these new ALMA observations, we assess the spectroscopic redshifts of this pilot sample of sources and improve the quality of the physical properties estimated through SED-fitting. Moreover, we measure the quantity of molecular gas inside these galaxies and forecast their potential evolutionary path, finding that the radio-selected NIR-dark galaxies might likely represent a population of high-z progenitors of the massive and passive galaxies that were discovered at z ∼ 3. Finally, we present some initial constraints on the kinematics of the interstellar medium within the analyzed galaxies, reporting a high fraction (∼55%) of double-peaked lines that can be interpreted as the signature of a rotating structure in our targets or as the presence of major mergers in our sample. The results we present here show the scientific potential of (sub)mm observations for this elusive population of galaxies and highlight the potential contribution of these sources to the evolution of the massive and passive galaxies at high z.