Clumpy Disc and Bulge Formation

TL;DR

This study uses hydrodynamical simulations to explore how gas-rich galaxies form bulges through clump migration, influenced by supernova feedback, revealing multiple bulge formation pathways and their observable signatures.

Contribution

It demonstrates that clump migration significantly contributes to bulge formation in gas-rich galaxies, with supernova feedback regulating clump growth and bulge structure.

Findings

Clumps form and migrate to the galaxy center, building bulges.

Supernova feedback moderates clump mass and bulge profile.

Bulge formation occurs alongside other processes like bars and mergers.

Abstract

We present a set of hydrodynamical/Nbody controlled simulations of isolated gas rich galaxies that self-consistently include SN feedback and a detailed chemical evolution model, both tested in cosmological simulations. The initial conditions are motivated by the observed star forming galaxies at z ~ 2-3. We find that the presence of a multiphase interstellar media in our models promotes the growth of disc instability favouring the formation of clumps which in general, are not easily disrupted on timescales compared to the migration time. We show that stellar clumps migrate towards the central region and contribute to form a classical-like bulge with a Sersic index, n > 2. Our physically-motivated Supernova feedback has a mild influence on clump survival and evolution, partially limiting the mass growth of clumps as the energy released per Supernova event is increased, with the consequent flattening of the bulge profile. This regulation does not prevent the building of a classical-like bulge even for the most energetic feedback tested. Our Supernova feedback model is able to establish a self-regulated star formation, producing mass-loaded outflows and stellar age spreads comparable to observations. We find that the bulge formation by clumps may coexit with other channels of bulge assembly such as bar and mergers. Our results suggest that galactic bulges could be interpreted as composite systems with structural components and stellar populations storing archaeological information of the dynamical history of their galaxy.