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

Abstract

We analyse the output of the hi-res cosmological "zoom-in" hydrodynamical 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 as well as on the central gas distribution and star formation. The simulation includes radiative cooling, star formation, SN feedback and a central massive black hole wich 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 stabilizes and 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 it is long-lived and is 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, as the bar reaches its maximum length and strength, the infalling gas is nearly all consumed into stars and, to a lesser extent, accreted onto the central black hole, leaving behind a gasdepleted 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. AGN feedback is instrumental in this scenario not because it directly leads to quenching, but because it promotes a strong bar by maintaining a flat rotation curve, suppressing the density of baryons within the central kpc in the early stages of the formation of the galaxy.

Understanding the scatter in the spatially resolved star formation main sequence of local massive spiral galaxies

“…In the core region, barred galaxies have lower sSFR than nonbarred galaxies. It has been suggested that a bar structure can quench star formation of galaxies (Cheung et al 2013;Gavazzi et al 2015;Zhou et al 2015;Spinoso et al 2017). Numerical simulation of a bar formation in a galaxy shows that gas is rapidly transferred toward the central region on the onset of the bar structure, and that the gas transfer triggers a burst of star formation in the central region of the galaxy.…”

“…Numerical simulation of a bar formation in a galaxy shows that gas is rapidly transferred toward the central region on the onset of the bar structure, and that the gas transfer triggers a burst of star formation in the central region of the galaxy. As the gas being transferred to the central region, gas within the bar's corotation radius is consumed and SFR within the radius can be suppressed finally (Spinoso et al 2017).…”

Bar quenching in gas-rich galaxies

“…An analysis of the ErisBH simulation demonstrated that the formation of a bar in a galaxy with a quiet merger history can quench its star formation on kiloparsec scales (Spinoso et al 2017). They showed that gas can be removed rapidly by the bar in the inner region, preventing any further strong star formation.…”

Structural and photometric properties of barred galaxies from the Auriga cosmological simulations

“…For instance, Scannapieco & Athanassoula (2012) studied the properties of two bars of Milky Way-mass galaxies at z = 0, a subsample of the simulations described in Scannapieco et al (2009). Subsequent work developed by Goz et al (2015), Okamoto et al (2015), and Spinoso et al (2017), focused on the evolution of bar properties for one or two galaxies. Although the aforementioned works were generally in good agreement with both previous idealised simulations and observations, they lacked of a statistically representative sample to verify if these cosmological simulations could reproduce the statistical properties of barred galaxies.…”