Is main-sequence galaxy star formation controlled by halo mass accretion?

Abstract

The galaxy stellar-to-halo mass relation (SHMR) is nearly time-independent for z < 4. We therefore construct a time-independent SHMR model for central galaxies, wherein the in-situ star formation rate (SFR) is determined by the halo mass accretion rate (MAR), which we call Stellar-Halo Accretion Rate Coevolution (SHARC). We show that the ∼ 0.3 dex dispersion of the halo MAR matches the observed dispersion of the SFR on the star-formation main sequence (MS). In the context of "bathtub"-type models of galaxy formation, SHARC leads to mass-dependent constraints on the relation between SFR and MAR. Despite its simplicity and the simplified treatment of mass growth from mergers, the SHARC model is likely to be a good approximation for central galaxies with M * = 10 9 − 10 10.5 M ⊙ that are on the MS, representing most of the star formation in the Universe. SHARC predictions agree with observed SFRs for galaxies on the MS at low redshifts, agree fairly well at z ∼ 4, but exceed observations at z > ∼ 4. Assuming that the interstellar gas mass is constant for each galaxy (the "equilibrium condition" in bathtub models), the SHARC model allows calculation of net mass loading factors for inflowing and outflowing gas. With assumptions about preventive feedback based on simulations, SHARC allows calculation of galaxy metallicity evolution. If galaxy SFRs indeed track halo MARs, especially at low redshifts, that may help explain the success of models linking galaxy properties to halos (including age-matching) and the similarities between two-halo galaxy conformity and halo mass accretion conformity.

The relationship between galaxy and dark matter halo size from z ∼ 3 to the present

“…1. This figure illustrates the differences in the SMHM derived by two different sets of authors (Rodriguez-Puebla et al (2017) and Behroozi et al in prep,hereafter RP17 and B17 respectively) based on the same underlying (sub)-halo distributions. Differences can arise from the choice of observations used to constrain the SHAM, as well as details of the methodology.…”

“…However, we do not support "pseudoevolution" as a complete explanation for two reasons. First, the concept of pseudoevolution does not appear to apply to gas within forming halos, as discussed above (see also arguments presented in Rodríguez-Puebla et al 2016b). Second, the "stagnation" of disks since z ∼ 2 does not appear to be consistent with the star formation histories of galaxies derived from multi-epoch abundance matching.…”

UVI colour gradients of 0.4 < z < 1.4 star-forming main-sequence galaxies in CANDELS: dust extinction and star formation profiles

“…This correction more than removes the steep central drops in raw A H α seen in Nelson et al (2016b), showing that they are plausibly due to dust and not to drops in central sSFR. The orange dotted curve are the sSFR values measured by Tacchella et al (2017) using the UV-β method, which have been scaled down by a factor of 3 to correct for the general decline of sSFR with redshift (see Rodríguez-Puebla et al 2016). Considering the vastly different radial dust corrections in Nelson et al (2016a) versus the two continuum methods, it is remarkable that all three methods wind up giving sSFR profiles that broadly agree in shape and overall magnitude.…”

The Star Formation Histories of Disk Galaxies: The Live, the Dead, and the Undead

“…Such a tight correlation between star formation and mass has suggested to some authors (e.g. Peng et al 2010, Dutton et al 2010, Sparre et al 2015, Rodríguez-Puebla et al 2016, Tacchella et al 2016) that the myriad physical processes mentioned above somehow conspire to produce one evolutionary track for all galaxies, that track being the main sequence. The majority of galaxies remain on that track even today, but a significant number have been "quenched"; driven off the main sequence by one or more processes, including perhaps such classic mechanisms as stripping, starvation, etc.…”