Illuminating the Dark Side of Cosmic Star Formation III: Building the largest homogeneous sample of Radio-Selected Dusty Star-Forming Galaxies in COSMOS with PhoEBO

TL;DR

This paper presents the first large, homogeneous sample of radio-selected dusty star-forming galaxies in COSMOS, using a new photometric pipeline to analyze their properties and contribution to cosmic star formation at high redshift.

Contribution

It introduces a novel, comprehensive approach to identify and characterize NIR-dark DSFGs using radio data and a new deblending pipeline, expanding understanding of their role in galaxy evolution.

Findings

Sample of 263 radio-selected NIR-dark galaxies analyzed.

High median star formation rate (~500 Msun/yr) and extinction (Av ~ 4).

Significant number of high-redshift candidates (z > 4.5).

Abstract

In the last decades, an increasing scientific interest has been growing in the elusive population of "dark" (i.e. lacking an optical/NIR counterpart) Dusty Star-Forming Galaxies (DSFGs). Although extremely promising for their likely contribution to the cosmic Star Formation Rate Density and for their possible role in the evolution of the first massive and passive galaxies around $z\sim3$, the difficulty in selecting statistically significant samples of dark DSFGs is limiting their scientific potentialities. This work presents the first panchromatic study of a sample of 263 Radio-Selected NIRdark galaxies discovered in the COSMOS field following the procedure by Talia+21. These sources are selected as radio-bright galaxies (S(3GHz)>12.65 uJy) with no counterpart in the NIR-selected COSMOS2020 catalog (Ks > 25.5 mag). For these sources, we build a new photometric catalog including accurate photometry from the optical to the radio obtained with a new deblending pipeline (PhoEBO: Photometry Extractor for Blended Objects). We employ this catalog to estimate the photo-zs and the physical properties of the galaxies through an SED-fitting procedure performed with two different codes (Magphys and Cigale). Finally, we estimate the AGN contamination in our sample by performing a series of complementary tests. The high values of the median extinction (Av ~ 4) and star formation rate (SFR ~ 500 Msun/yr) confirm the likely DSFG nature of the RS-NIRdark galaxies. The median photo-z (z~3) and the presence of a significant tail of high-z candidates (z>4.5) suggest that these sources are important contributors to the cosmic SFRD and the evolutionary path of galaxies at high redshifts.