The MUSE Hubble Ultra Deep Field Survey

XI. Constraining the low-mass end of the stellar mass – star formation rate relation at z < 1^⋆

¹ Leiden Observatory, Leiden University, PO Box 9513 2300 RA, Leiden, The Netherlands
e-mail: boogaard@strw.leidenuniv.nl
² Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, PT4150-762 Porto, Portugal
³ IRAP (Institut de Recherche en Astrophysique et Planétologie), Université de Toulouse, CNRS, UPS, Toulouse, France
⁴ CRAL, Observatoire de Lyon, CNRS, Université Lyon 1, 9 Avenue Ch. André, 69561 Saint Genis Laval Cedex, France
⁵ Department of Physics, ETH Zürich, Wolfgang–Pauli–Strasse 27, 8093 Zürich, Switzerland
⁶ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
⁷ Harvard-Smithsonian Center for Astrophysics, 60 Garden St., 02138 Cambridge, MA, UK

Received: 30 March 2018
Accepted: 20 July 2018

Abstract

Star-forming galaxies have been found to follow a relatively tight relation between stellar mass (M_*) and star formation rate (SFR), dubbed the “star formation sequence”. A turnover in the sequence has been observed, where galaxies with M_* <  10¹⁰ M_⊙ follow a steeper relation than their higher mass counterparts, suggesting that the low-mass slope is (nearly) linear. In this paper, we characterise the properties of the low-mass end of the star formation sequence between 7 ≤ log M_*[M_⊙]  ≤  10.5 at redshift 0.11 <  z  <   0.91. We use the deepest MUSE observations of the Hubble Ultra Deep Field and the Hubble Deep Field South to construct a sample of 179 star-forming galaxies with high signal-to-noise emission lines. Dust-corrected SFRs are determined from Hβ λ4861 and Hα λ6563. We model the star formation sequence with a Gaussian distribution around a hyperplane between logM_*, logSFR, and log(1 + z), to simultaneously constrain the slope, redshift evolution, and intrinsic scatter. We find a sub-linear slope for the low-mass regime where log SFR [M_⊙yr⁻¹] = 0.83^+0.07_−0.06 log M_*[M_⊙]+1.74^+0.66_−0.68 log(1 + z), increasing with redshift. We recover an intrinsic scatter in the relation of σ_intr = 0.44^+0.05_−0.04, dex, larger than typically found at higher masses. As both hydrodynamical simulations and (semi-)analytical models typically favour a steeper slope in the low-mass regime, our results provide new constraints on the feedback processes which operate preferentially in low-mass halos.