The OTELO survey

New evidence of downsizing from the specific star formation rates, stellar mass functions, and star formation histories of a sample of low-mass galaxies at 0.38 < z < 1.43

¹ Instituto de Astrofísica de Canarias (IAC), 38200 La Laguna, Tenerife, Spain
² Departamento de Astrofísica, Universidad de La Laguna (ULL), 38205 La Laguna, Tenerife, Spain
³ Asociación Astrofísica para la Promoción de la Investigación, Instrumentación y su Desarrollo, ASPID, 38205 La Laguna, Tenerife, Spain
⁴ Institut de Radioastronomie Millimétrique (IRAM), Av. Divina Pastora 7, Núcleo Central, 18012 Granada, Spain
⁵ Fundación Galileo Galilei–INAF, Rambla José Ana Fernández Pérez, 7, 38712 Breña Baja, Tenerife, Spain
⁶ Astronomical Observatory Institute, Faculty of Physics and Astronomy, Adam Mickiewicz University, ul. Słoneczna 36, 60-286 Poznań, Poland
⁷ Departamento de Física de la Tierra y Astrofísica, Instituto de Física de Partículas y del Cosmos, IPARCOS, Universidad Complutense de Madrid (UCM), 28040 Madrid, Spain
⁸ Instituto de Física de Cantabria (CSIC-Universidad de Cantabria), 39005 Santander, Spain
⁹ Instituto de Astrofísica de Andalucía (CSIC), 18080 Granada, Spain
¹⁰ Centro de Astrobiología (CSIC/INTA), ESAC Campus, 28692 Villanueva de la Cañada, Madrid, Spain
¹¹ Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70-264, 04510 Ciudad de México, Mexico
¹² ISDEFE for European Space Astronomy Centre (ESAC)/ESA, PO Box 78 28690 Villanueva de la Cañada, Madrid, Spain
¹³ Space Science and Geospatial Institute (SSGI), Entoto Observatory and Research Center (EORC), Astronomy and Astrophysics Research Division, PO Box 33679 Addis Abbaba, Ethiopia
¹⁴ Physics Department, Mbarara University of Science and Technology (MUST), Mbarara, Uganda

^⋆ Corresponding author; bcedres@iac.es

Received: 6 November 2024
Accepted: 28 February 2025

Abstract

Aims. We present an analysis of the emitters (Hα, Hβ, and [O II]) from the OTELO survey, in order to characterize the star formation properties of low-mass galaxies (< 10⁹ M_⊙ stellar masses).

Methods. We calculated the specific star formation rate function, the stellar mass function, and, by integrating them, the associated densities for both quantities: the specific star formation rate density and the stellar mass density. We obtained the star formation history of our low-mass sample galaxies by fitting the spectral energy distribution of the galaxies. We also compared our results with those from the literature at different mass regimes and redshifts.

Results. The specific star formation rate density and the stellar mass density for low-mass galaxies do not depend on the redshift, contrary to the behaviour presented by the high-mass galaxies. We found that the star formation histories of low-mass galaxies are characterized by a constant star formation rate, in contrast to high-mass galaxies. We interpret these results, in the context of the downsizing effect, as representative of the faster evolution of massive galaxies compared with low-mass ones.