Probing the Star Formation Main Sequence Down to 108M⊙ at 1.0 < z < 3.0

• Published in: The Astrophysical journal 2023-06, Vol.950 (2), p.125
• Main Authors: Mérida, Rosa M, Pérez-González, Pablo G, Sánchez-Blázquez, Patricia, García-Argumánez, Ángela, Annunziatella, Marianna, Costantin, Luca, Lumbreras-Calle, Alejandro, Alcalde-Pampliega, Belén, Barro, Guillermo, Espino-Briones, Néstor, Koekemoer, Anton M
• Format: Article
• Language: English
• Subjects: Astrophysics; Broadband; Galaxies; Slopes; Star & galaxy formation; Star formation; Starburst galaxies; Stars; Stars & galaxies; Stellar populations
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/acc7a3

We investigate the star formation main sequence (MS; SFR–M⋆) down to 108−9M⊙ using a sample of 34,061 newly discovered ultrafaint (27 mag ≲ i ≲ 30 mag) galaxies at 1 < z < 3 detected in the GOODS-N field. Virtually none of these galaxies are contained in previous public catalogs, effectively doubling the number of known sources in the field. The sample was constructed by stacking the optical broadband observations taken by the HST/GOODS-CANDELS surveys, as well as the 25 ultradeep medium-band images gathered by the GTC/SHARDS project. Our sources are faint (average observed magnitudes 〈i〉 ∼ 28.2 and 〈H〉 ∼ 27.9 mag), blue (UV slope 〈β〉 ∼ −1.9), star-forming (rest-frame colors 〈U − V〉 ∼ 0.10 and 〈V − J〉 ∼ 0.17 mag) galaxies. These observational characteristics are identified with young (mass-weighted age 〈tM−w〉 ∼ 0.014 Gyr) stellar populations subject to low attenuations (〈A(V)〉 ∼ 0.30 mag). Our sample allows us to probe the MS down to 108.0M⊙ at z = 1 and 108.5M⊙ at z = 3, around 0.6 dex deeper than previous analyses. In the low-mass galaxy regime, we find an average value for the slope of 0.97 at 1 < z < 2 and 1.12 at 2 < z < 3. Nearly 60% of our sample presents stellar masses in the range 106-8M⊙ at 1 < z