Cosmological galaxy formation simulations using smoothed particle hydrodynamics

Abstract

We present the McMaster Unbiased Galaxy Simulations (MUGS), the first nine galaxies of an unbiased selection ranging in total mass from 5 × 10 11 M to 2 × 10 12 M simulated using N-body smoothed particle hydrodynamics at high resolution. The simulations include a treatment of low-temperature metal cooling, UV background radiation, star formation and physically motivated stellar feedback. Mock images of the simulations show that the simulations lie within the observed range of relations such as that between colour and magnitude and that between brightness and circular velocity (Tully-Fisher). The greatest discrepancy between the simulated galaxies and observed galaxies is the high concentration of material at the centre of the galaxies as represented by the centrally peaked rotation curves and the high bulge-tototal ratios of the simulations determined both kinematically and photometrically. This central concentration represents the excess of low angular momentum material that long has plagued morphological studies of simulated galaxies and suggests that higher resolutions and a more accurate description of feedback will be required to simulate more realistic galaxies. Even with the excess central mass concentrations, the simulations suggest the important role merger history and halo spin play in the formation of discs.

Simulations of galaxy formation and evolution

“…Although it is usually assumed that the galaxies with higher spin parameters have larger D/T ratios, we find no clear correlation between them. A similar result is found by Stinson et al (2010) in their simulations.…”

“…For example, we have shown that, in our simulations, the D/T ratios obtained using kinematic methods are very small in comparison with those of spirals (see also Stinson et al 2010). Scannapieco et al (2010) investigated whether the kinematic disk-spheroid decompositions usually used in simulation studies can be directly compared to the results of photometric decompositions, as done in real observations.…”

“…A few recent studies have been able to simulate 8-10 galaxies in its full cosmological context (Brooks et al 2009;Scannapieco et al 2009;Stinson et al 2010); opening up the possibility to investigate the variety of galaxy properties. Moreover, they allowed to study important relations such as the one between the morphology of a galaxy (usually quantified by the D/T ratio) and the spin parameter of its host halo (λ ).…”

“…Navarro et al 1995;Navarro & Steinmetz 1997). More recent simulation codes including feedback processes, in particular from SN explosions, have shown to be successful in reproducing disk-like systems, suggesting that feedback processes are indeed a crucial ingredient in galaxy formation (e.g., Governato et al 2004Governato et al , 2007Okamoto et al 2005;Scannapieco et al 2008Scannapieco et al , 2009Ceverino & Klypin 2009;Stinson et al 2010). SN feedback, through the return of energy and mass to the interstellar medium, is efficient in regulating star formation, preventing overcooling and helping baryons to retain their angular momentum (e.g.…”

Star formation in mergers with cosmologically motivated initial conditions

“…Full cosmological hydrodynamical simulations and semi-analytic models (SAMs) of galaxy formation predict a large amount of hot gas around the galaxy, in quasi static equilibrium with the gravitational potential (e.g. Kauffmann et al 1993;Bower et al 2006;Stinson et al 2010Stinson et al , 2012Brook et al 2014, but see also Cox et al 2004 for the generation of a hot halo during mergers). Recently, several X-ray studies found evidence for a hot gas component around the Milky Way (Gupta et al 2012;Hodges-Kluck & Bregman 2013) and normal massive disc galaxies (e.g.…”