Reproducing the Stellar Mass/Halo Mass Relation in Simulated Λcdm Galaxies: Theory Versus Observational Estimates

Abstract

We examine the present-day total stellar-to-halo mass (SHM) ratio as a function of halo mass for a new sample of simulated field galaxies using fully cosmological, ΛCDM, high resolution SPH + N-Body simulations. These simulations include an explicit treatment of metal line cooling, dust and self-shielding, H 2 based star formation and supernova driven gas outflows. The 18 simulated halos have masses ranging from a few times 10 8 to nearly 10 12 M ⊙ . At z=0 our simulated galaxies have a baryon content and morphology typical of field galaxies. Over a stellar mass range of 2.2 × 10 3 -4.5 × 10 10 M ⊙ we find extremely good agreement between the SHM ratio in simulations and the presentday predictions from the statistical Abundance Matching Technique presented in Moster et al. (2012). This improvement over past simulations is due to a number systematic factors, each decreasing the SHM ratios: 1) gas outflows that reduce the overall SF efficiency but allow for the formation of a cold gas component 2) estimating the stellar masses of simulated galaxies using artificial observations and photometric techniques similar to those used in observations and 3) accounting for a systematic, up to 30% overestimate in total halo masses in DM-only simulations, due to the neglect of baryon loss over cosmic times. Our analysis suggests that stellar mass estimates based on photometric magnitudes can underestimate the contribution of old stellar populations to the total stellar mass, leading to stellar mass errors of up to 50% for individual galaxies. These results highlight the importance of using proper techniques to compare simulations with observations and reduce the perceived tension between the star formation efficiency in galaxy formation models and in real galaxies.

In-N-Out: The Gas Cycle From Dwarfs to Spiral Galaxies

“…a Appears in Governato et al (2012). b Appears in Munshi et al (2013). c Appears in Christensen et al (2014b).…”

“…Feedback primarily solves this problem by the strong suppression of star formation in dwarf galaxies (Munshi et al 2013). As a result of this suppression, there is less growth via merging that would otherwise generate an overly peaked central rotation curve (Governato et al 2009).…”

The distribution of mass components in simulated disc galaxies

“…As stated in Section 2, the MaGICC simulations were tuned to match the stellar mass-halo mass relation at one galaxy mass (in particular, to match the stellar to halo mass of galaxy g15784 Irr), and shown to then match the relation over a range of masses (Brook et al 2012b;Obreja et al 2014, see also the Nihao simulations, Wang et al 2015, which use very similar implementation of physics, and note that other models are also able to match the relation, e.g. Munshi et al 2013;Schaye et al 2015). The CLUES simulations were also calibrated to match the relation.…”

NIHAO – IV: core creation and destruction in dark matter density profiles across cosmic time

“…Governato et al 2010, Macciò et al 2012, Martizzi et al 2013, Munshi et al 2013, Di Cintio 2014a,b, Trujillo-Gomez et al 2015.…”