Population statistics of intermediate mass black holes in dwarf galaxies using the NewHorizon simulation

TL;DR

This study uses the NewHorizon simulation to analyze the evolution, occupation, and growth limitations of intermediate mass black holes in dwarf galaxies, revealing their limited growth and dynamic displacement from galaxy centers.

Contribution

It provides new insights into IMBH occupation fractions, growth patterns, and dynamical behaviors in dwarf galaxies using large-scale cosmological simulation data.

Findings

IMBH occupation fraction is at least 50% in dwarf galaxies with stellar mass down to 10^6 Msun.

IMBH growth is limited and more efficient at high redshift (z=3).

IMBHs often become dynamically displaced from galaxy centers, especially at lower redshifts.

Abstract

While it is well established that supermassive black holes (SMBHs) co-evolve with their host galaxy, it is currently less clear how lower mass black holes, so-called intermediate mass black holes (IMBHs), evolve within their dwarf galaxy hosts. In this paper, we present results on the evolution of a large sample of IMBHs from the NewHorizon simulation. We show that occupation fractions of IMBHs in dwarf galaxies are at least 50 percent for galaxies with stellar masses down to 1E6 Msun, but BH growth is very limited in dwarf galaxies. In NewHorizon, IMBH growth is somewhat more efficient at high redshift z = 3 but in general IMBH do not grow significantly until their host galaxy leaves the dwarf regime. As a result, NewHorizon under-predicts observed AGN luminosity function and AGN fractions. We show that the difficulties of IMBH to remain attached to the centres of their host galaxies plays an important role in limiting their mass growth, and that this dynamic evolution away from galactic centres becomes stronger at lower redshift.