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The MUSE Hubble Ultra Deep Field Survey
XI. Constraining the low-mass end of the stellar mass - star formation rate relation at z < 1

L. A. Boogaard, J. Brinchmann, N. Bouchť, M. Paalvast, R. Bacon, R. J. Bouwens, T. Contini, M. Gunawardhana, H. Inami, R. A. Marino, M. Maseda, P. Mitchell, T. Nanayakkara, J. Richard, J. Schaye, C. Schreiber, S. Tacchella, L. Wisotzki, J. Zabl

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* < 1010M 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 [Myr−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 σintr = 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.

Keywords
galaxies: star formation; galaxies: formation; galaxies: evolution; galaxies: ISM; methods: statistical

Notes
Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programme IDs ID 060.A-9100(C), 094.A-2089(B), 095.A-0010(A), 096.A-0045(A), and 096.A-0045(B).

Astronomy and Astrophysics
Volume 619, Article Number A27, Number of pages 20
2018 November

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Instituto de Astrof√≠sica e Ci√™ncias do Espa√ßo Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia