Search

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) log SFR [ M ⊙ yr − 1 ] = 0. 83 − 0.06 + 0.07 log M ∗ [ M ⊙ ] + 1. 74 − 0.68 + 0.66 log (1 + z) $ \log \text{ SFR}[M_{\odot}\,{\mathrm{yr}}^{-1}] = 0.83^{+0.07}_{-0.06}\log{M_{*}}[M_{\odot}] + {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 σ intr = 0. 44 − 0.04 + 0.05 $ \sigma_{\text{ 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. [ABSTRACT FROM AUTHOR]

We aim to measure the average dust and molecular gas content of massive star-forming galaxies (>3 × 1010 M⊙) up to z = 4 in the COSMOS field to determine if the intense star formation observed at high redshift is induced by major mergers or is caused by large gas reservoirs. Firstly, we measured the evolution of the average spectral energy distributions as a function of redshift using a stacking analysis of Spitzer, Herschel, LABOCA, and AzTEC data for two samples of galaxies: normal star-forming objects and strong starbursts, as defined by their distance to the main sequence. We found that the mean intensity of the radiation field heating the dust (strongly correlated with dust temperature) increases with increasing redshift up to z = 4 in main-sequence galaxies. We can reproduce this evolution with simple models that account for the decrease in the gas metallicity with redshift. No evolution of with redshift is found in strong starbursts. We then deduced the evolution of the molecular gas fraction (defined here as Mmol/(Mmol +M*)) with redshift and found a similar, steeply increasing trend for both samples. At z ~ 4, this fraction reaches ~60%. The average position of the main-sequence galaxies is on the locus of the local, normal star-forming disks in the integrated Schmidt-Kennicutt diagram (star formation rate versus mass of molecular gas), suggesting that the bulk of the star formation up to z = 4 is dominated by secular processes. [ABSTRACT FROM AUTHOR]