Feedback from galactic stellar bulges and hot gaseous haloes of galaxies

TL;DR

This study uses hydrodynamical simulations to show how stellar bulge feedback influences the hot gaseous haloes of galaxies, potentially solving key issues like over-cooling and missing feedback in MW-like galaxies.

Contribution

It introduces a two-phase stellar feedback model demonstrating its role in shaping galaxy halo gas and preventing cooling, advancing understanding of galaxy evolution.

Findings

Starburst-driven blastwave heats halo gas beyond virial radius.

Long-lasting stellar feedback sustains hot gaseous haloes.

Feedback effects depend on environment and galaxy formation history.

Abstract

We demonstrate that the feedback from stellar bulges can play an essential role in shaping the halo gas of galaxies with substantial bulge components by conducting 1-D hydrodynamical simulations. The feedback model we consider consists of two distinct phases: 1) an early starburst during the bulge formation and 2) a subsequent long-lasting mass and energy injection from stellar winds of low-mass stars and Type Ia SNe. An energetic outward blastwave is initiated by the starburst and is maintained and enhanced by the long-lasting stellar feedback. For a MW-like galactic bulge, this blastwave sweeps up the halo gas in the proto-galaxy and heats up the surrounding medium to a scale much beyond the virial radius of the halo, thus the accretion of the halo hot gas can be completely stopped. In addition, the long-lasting feedback in the later phase powers a galactic bulge wind that is reverse-shocked at a large radius in the presence of surrounding intergalactic medium and hence maintains a hot gaseous halo. As the mass and energy injection decreases with time, the feedback evolves to a subsonic and quasi-stable outflow, which is enough to prevent halo gas from cooling. The two phases of the feedback thus re-enforce each-other's impact on the gas dynamics. The simulation results demonstrate that the stellar bulge feedback may provide a plausible solution to the long-standing problems in understanding the MW type galaxies, such as the "missing stellar feedback" problem and the "over-cooling" problem. The simulations also show that the properties of the hot gas in the subsonic outflow state depend sensitively on the environment and the formation history of the bulge. This dependence and variance may explain the large dispersion in the X-ray to B-band luminosity ratio of the low $L_X/L_B$ Es.