The star formation main sequence and stellar mass assembly of galaxies in the Illustris simulation
Abstract
Understanding the physical processes that drive star formation is a key challenge for galaxy formation models. In this paper, we study the tight correlation between the star formation rate (SFR) and stellar mass of galaxies at a given redshift, how halo growth influences star formation, and star formation histories of individual galaxies. We study these topics using Illustris, a state-of-the-art cosmological hydrodynamical simulation of galaxy formation. Illustris reproduces the observed relation (the star formation main sequence, SFMS) between SFR and stellar mass at redshifts z = 0 and 4, but at intermediate redshifts of z ≃ 1-2, the simulated SFMS has a significantly lower normalization than reported by observations. The scatter in the relation is consistent with the observed scatter. However, the fraction of outliers above the SFR-stellar mass relation in Illustris is less than that observed. Galaxies with halo masses of ∼1012 M⊙ dominate the SFR density of the Universe, in agreement with the results of abundance matching. Furthermore, more-massive galaxies tend to form the bulk of their stars at high redshift, which indicates that `downsizing' occurs in Illustris. We also studied the star formation histories of individual galaxies, including the use of a principal component analysis decomposition. We find that for fixed stellar mass, galaxies that form earlier have more-massive black holes at z = 0, indicating that star formation and black hole growth are tightly linked processes in Illustris. While many of the properties of normal star-forming galaxies are well reproduced in the Illustris simulation, forming a realistic population of starbursts will likely require higher resolution and probably a more sophisticated treatment of star formation and feedback from stars and black holes.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- March 2015
- DOI:
- 10.1093/mnras/stu2713
- arXiv:
- arXiv:1409.0009
- Bibcode:
- 2015MNRAS.447.3548S
- Keywords:
-
- methods: numerical;
- galaxies: evolution;
- galaxies: formation;
- galaxies: starburst;
- galaxies: star formation;
- cosmology: theory;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 16 pages, 16 figures, Accepted for MNRAS, Section 6 and Figure 16 are new. Data is available at http://martinsparre.com/dataproducts