The Impact of Galactic Winds on the Angular Momentum of Disk Galaxies in the Illustris Simulation

Abstract

Observed galactic disks have specific angular momenta similar to expectations for typical dark matter halos in ΛCDM. Cosmological hydrodynamical simulations have recently reproduced this similarity in large galaxy samples by including strong galactic winds, but the exact mechanism that achieves this is not yet clear. Here we present an analysis of key aspects contributing to this relation: angular momentum selection and evolution of Lagrangian mass elements as they accrete onto dark matter halos, condense into Milky Way-scale galaxies, and join the z = 0 stellar phase. We contrast this evolution in the Illustris simulation with that in a simulation without galactic winds, where the z = 0 angular momentum is ≈ 0.6 dex lower. We find that winds induce differences between these simulations in several ways: increasing angular momentum, preventing angular momentum loss, and causing z = 0 stars to sample the accretion-time angular momentum distribution of baryons in a biased way. In both simulations, gas loses on average ≈ 0.4 dex between accreting onto halos and first accreting onto central galaxies. In Illustris, this is followed by ≈ 0.2 dex gains in the 'galactic wind fountain' and no further net evolution past the final accretion onto the galaxy. Without feedback, further losses of ≈ 0.2 dex occur in the gas phase inside the galaxies. An additional ≈ 0.15 dex difference arises from feedback preferentially selecting higher angular momentum gas at accretion by expelling gas that is poorly aligned. These and additional effects of similar magnitude are discussed, suggesting a complex origin of the similarity between the specific angular momenta of galactic disks and typical halos.

Survival of molecular gas in a stellar feedback-driven outflow witnessed with the MUSE TIMER project and ALMA

“…Therefore extra-planar gas ejected from star forming regions -such as the spiral arms -is unlikely to reach the small radii which we consider here through a fountain flow (see e.g. Fraternali & Binney 2008;Pezzulli et al 2015;DeFelippis et al 2017). Furthermore, as discussed below in Section 4.2, the residual CO velocities are inconsistent with the CO gas in the transverse dust lane moving inwards.…”

On the Origin of Star–Gas Counterrotation in Low-mass Galaxies

“…Early numerical simulations were able to reproduce the main predictions from this tidal torque scenario for the origin of the dark matter halo spins (Efstathiou & Jones 1979;White 1984;Barnes & Efstathiou 1987) and further confirmation may be found in the orientations of the angular momentum of nearby disk galaxies with respect to the surrounding large scale structure (Navarro et al 2004). With the advent of more sophisticated hydrodynamical simulations it also became clear that baryons undergo a much more complex evolution than previously envisioned (van den Bosch et al 2002;Abadi et al 2003;Brook et al 2011;Scannapieco et al 2012;Bryan et al 2013;Übler et al 2014;Dubois et al 2014;Teklu et al 2015;Zavala et al 2016;Zjupa & Springel 2017;DeFelippis et al 2017;Jiang et al 2018;Garrison-Kimmel et al 2018).…”

Gas accretion and galactic fountain flows in the Auriga cosmological simulations: angular momentum and metal redistribution

“…Brook et al 2012b;Aumer et al 2013;Marinacci et al 2014;Wang et al 2015;Colín et al 2016;Grand et al 2017). The general picture now emerging from simulations is that the formation of discs is promoted because energetic feedback expels low angular momentum gas from the central regions that later re-accretes onto the galaxy, providing fuel for late-time star formation from gas with, on average, high angular momentum (Brook et al 2011(Brook et al , 2012aÜbler et al 2014;Teklu et al 2015;Zavala et al 2016;Christensen et al 2016;Agertz & Kravtsov 2016;DeFelippis et al 2017) that should be well-aligned with the disc (e.g. Sales et al 2012).…”

“…In what follows, we use a tracer particle analysis (DeFelippis et al 2017) to track the history of baryonic elements found in star particles at redshift zero (described in Section 2), and classify the type of accretion based on a set of criteria described in Section 3. In Section 4, we show that, in general, nearly all of the stars formed by redshift zero contain previously wind-recycled material, to which galactic fountain flows contribute significantly.…”