Equilibrium model prediction for the scatter in the star-forming main sequence

Sourav Mitra, Romeel Davé, Vimal Simha, Kristian Finlator

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

The analytic 'equilibrium model' for galaxy evolution using a mass balance equation is able to reproduce mean observed galaxy scaling relations between stellar mass, halo mass, star formation rate (SFR), and metallicity across the majority of cosmic time with a small number of parameters related to feedback. Here, we aim to test this data-constrained model to quantify deviations from the mean relation between stellar mass and SFR, i.e. the star-forming galaxy main sequence (MS). We implement fluctuation in halo accretion rates parametrized from merger-based simulations, and quantify the intrinsic scatter introduced into the MS under the assumption that fluctuations in star formation follow baryonic inflow fluctuations. We predict the 1σ MS scatter to be ∼0.2-0.25 dex over the stellar mass range 108-1011 M☉ and a redshift range 0.5 ≾ z ≾ 3 for SFRs averaged over 100 Myr. The scatter increases modestly at z ≿ 3, as well as by averaging over shorter time-scales. The contribution from merger-induced star formation is generally small, around 5 per cent today and 10-15 per cent during the peak epoch of cosmic star formation. These results are generally consistent with available observations, suggesting that deviations from the MS primarily reflect stochasticity in the inflow rate owing to halo mergers.

Original languageEnglish (US)
Pages (from-to)2766-2776
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume464
Issue number3
DOIs
StatePublished - Jan 1 2017

Keywords

  • Galaxies: abundances
  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: luminosity function
  • Mass function

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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