Stellar discs in Aquarius dark matter haloes

Abstract

We investigate the gravitational interactions between live stellar discs and their dark matter haloes, using cold dark matter haloes similar in mass to that of the Milky Way taken from the Aquarius Project. We introduce the stellar discs by first allowing the haloes to respond to the influence of a growing rigid disc potential from z = 1.3 to 1.0. The rigid potential is then replaced with star particles which evolve self-consistently with the dark matter particles until z = 0.0. Regardless of the initial orientation of the disc, the inner parts of the haloes contract and change from prolate to oblate as the disc grows to its full size. When the disc's normal is initially aligned with the major axis of the halo at z = 1.3, the length of the major axis contracts and becomes the minor axis by z = 1.0. Six out of the eight discs in our main set of simulations form bars, and five of the six bars experience a buckling instability that results in a sudden jump in the vertical stellar velocity dispersion and an accompanying drop in the m = 2 Fourier amplitude of the disc surface density. The bars are not destroyed by the buckling but continue to grow until the present day. Bars are largely absent when the disc mass is reduced by a factor of 2 or more; the relative disc-to-halo mass is therefore a primary factor in bar formation and evolution. A subset of the discs is warped at the outskirts and contains prominent non-coplanar material with a ring-like structure. Many discs reorient by large angles between z = 1 and 0, following a coherent reorientation of their inner haloes. Larger reorientations produce more strongly warped discs, suggesting a tight link between the two phenomena. The origins of bars and warps appear independent: some discs with strong bars show little disturbances at the outskirts, while the discs with the weakest bars show severe warps.

Characterization of galactic bars from 3.6μm S4G imaging

“…However, this is not as clear from the visual classification. The fact that the bar fraction (estimated with criteria 2 and 3 above) decreases with M h /M * (<R opt ) could be interpreted as a result of dark matter halos stabilizing the stellar disk against bar formation (Hohl 1976;Mihos et al 1997;DeBuhr et al 2012) and might cause the dependence between bar fraction and stellar mass (or Hubble stage) given the coupling between luminous and dark matter. However, in contrast to Cervantes Sodi et al (2015), we did not find a statistically significant difference in M h /M * (<R opt ) between barred and and non-barred systems when limiting our search to individual mass bins ( Fig.…”

“…However, it becomes clearer when relying on the Fourier and ellipse fitting detection of bars. This could be interpreted as caused by the dark matter halos stabilizing the stellar disk against bar formation (Hohl 1976;Mihos et al 1997;DeBuhr et al 2012), which in turn would create the dependence between bar fraction and stellar mass (or Hubble stage) given the coupling between luminous and dark matter (Fig. 6).…”

Formation ofin situstellar haloes in Milky Way-mass galaxies

“…Kazantzidis et al 2008;Read et al 2008;Purcell et al 2010); in ab initio simulations there is an additional dependence on the subgrid physics governing the formation and structure of the disc (e.g. DeBuhr, Ma & White 2012;). This dependence is now being tackled directly, with some success, by recent generations of hydrodynamical simulations Schaye et al 2015;Snyder et al 2015).…”

Bringing the Galaxy's dark halo to life

“…Another study in which for a period the dark halo must have evolved adiabatically is that of DeBuhr et al (2012), for between redshift z = 1.3 and z = 1 they adiabatically grew a massive disc. At z = 1 the disc became a fully fledged Nbody disc capable of developing a bar and strict adiabaticity ended.…”