Feedback from Central Black Holes in Elliptical Galaxies: Two-dimensional Models Compared to One-dimensional Models

TL;DR

This study compares 1D and 2D hydrodynamical models of black hole feedback in elliptical galaxies, finding similar overall growth patterns but more irregular and higher accretion rates in 2D due to instabilities.

Contribution

It extends black hole feedback models to two dimensions and systematically compares their effects with one-dimensional models, highlighting the impact of instabilities.

Findings

2D models show Rayleigh-Taylor instabilities leading to fragmentation.

Overall black hole growth and duty cycle are similar in 1D and 2D.

2D models exhibit more irregular accretion and feedback patterns.

Abstract

We extend the black hole (BH) feedback models of Ciotti, Ostriker, and Proga to two dimensions. In this paper, we focus on identifying the differences between the one-dimensional and two-dimensional hydrodynamical simulations. We examine a normal, isolated $L_*$ galaxy subject to the cooling flow instability of gas in the inner regions. Allowance is made for subsequent star formation, Type Ia and Type II supernovae, radiation pressure, and inflow to the central BH from mildly rotating galactic gas which is being replenished as a normal consequence of stellar evolution. The central BH accretes some of the infalling gas and expels a conical wind with mass, momentum, and energy flux derived from both observational and theoretical studies. The galaxy is assumed to have low specific angular momentum in analogy with the existing one-dimensional case in order to isolate the effect of dimensionality. The code then tracks the interaction of the outflowing radiation and winds with the galactic gas and their effects on regulating the accretion. After matching physical modeling to the extent possible between the one-dimensional and two-dimensional treatments, we find essentially similar results in terms of BH growth and duty cycle (fraction of the time above a given fraction of the Eddington luminosity). In the two-dimensional calculations, the cool shells forming at 0.1--1 kpc from the center are Rayleigh--Taylor unstable to fragmentation, leading to a somewhat higher accretion rate, less effective feedback, and a more irregular pattern of bursting compared to the one-dimensional case.