Cosmological evolution of gas and supermassive black holes in idealized isolated halos

TL;DR

This study models the evolution of baryonic gas and supermassive black holes in isolated dark matter halos, incorporating realistic density profiles, feedback mechanisms, and cosmological effects to understand galaxy formation processes.

Contribution

It introduces a novel simulation approach with a smooth transition in dark matter profiles and detailed feedback modeling, advancing understanding of halo core dynamics and SMBH growth.

Findings

Halo cores exhibit heating and cooling cycles influenced by feedback.

Central SMBH growth slows after an initial exponential phase.

Baryon fraction decreases with feedback efficiency and lower halo mass.

Abstract

We study the evolution of baryonic gas in cosmologically growing dark matter halos. To accurately model both the inner and outer regions of the halos, we use a dark matter density profile that transitions smoothly from the NFW profile within the virial radius to a more realistic flat profile far beyond the halo. We construct a dark matter gravitational potential consistent with this density profile, and we use a "cosmological" potential that accounts for gas evolution consistent with Hubble expansion at large radii. Gas is initialized with a density $\approx$ 0.2 times the dark matter density, consistent with the universal baryon fraction $\rho_{\rm g}/(\rho_{\rm g}+\rho_{\rm DM}) \approx 0.17$. We study the formation of the virial shock and evolution of the baryon fraction, including the effects of radiative cooling and AGN jet feedback. The feedback is powered by the accretion of cold gas onto a central supermassive black hole (SMBH). The cores of the halo exhibit heating and cooling cycles, whose strength and duration depend on the feedback efficiency and the halo mass. The central SMBH initially grows exponentially with time in the early quasar phase, but the growth slows down at later times. The baryon fraction in the core decreases with increasing feedback efficiency and decreasing halo mass. While the halo outskirts evolve self-similarly, the core density is non-evolving, in agreement with cluster observations. We analyze the correlations between the properties of the gas and the central SMBH, and explore the existence of a fundamental plane.