Bar-driven evolution and quenching of spiral galaxies in cosmological simulations

TL;DR

This study uses high-resolution cosmological simulations to investigate how stellar bars form, evolve, and influence galaxy structure, gas distribution, and star formation, highlighting their role in galaxy quenching.

Contribution

It provides a detailed analysis of bar-driven evolution and quenching in a Milky Way-like galaxy within a cosmological context, including the formation of a boxy-peanut bulge.

Findings

Bar forms after z~1.4, grows significantly after z~0.4

Buckling instability leads to a boxy-peanut bulge at z=0

Bar-driven gas inflows enhance nuclear star formation and contribute to quenching

Abstract

We analyse the output of the hi-res cosmological zoom-in simulation ErisBH to study self-consistently the formation of a strong stellar bar in a Milky Way-type galaxy and its effect on the galactic structure, on the central gas distribution and on star formation. The simulation includes radiative cooling, star formation, SN feedback and a central massive black hole which is undergoing gas accretion and is heating the surroundings via thermal AGN feedback. A large central region in the ErisBH disk becomes bar-unstable after z~1.4, but a clear bar-like structure starts to grow significantly only after z~0.4, possibly triggered by the interaction with a massive satellite. At z~0.1 the bar reaches its maximum radial extent of l~2.2 kpc. As the bar grows, it becomes prone to buckling instability, which we quantify based on the anisotropy of the stellar velocity dispersion. The actual buckling event is observable at z~0.1, resulting in the formation of a boxy-peanut bulge clearly discernible in the edge-on view of the galaxy at z=0. The bar in ErisBH does not dissolve during the formation of the bulge but remains strongly non-axisymmetric down to the resolution limit of ~100 pc at z=0. During its early growth, the bar exerts a strong torque on the gas within its extent and drives gas inflows that enhance the nuclear star formation on sub-kpc scales. Later on the infalling gas is nearly all consumed into stars and, to a lesser extent, accreted onto the central black hole, leaving behind a gas-depleted region within the central ~2 kpc. Observations would more likely identify a prominent, large-scale bar at the stage when the galactic central region has already been quenched. Bar-driven quenching may play an important role in disk-dominated galaxies at all redshift. [Abridged]