The MandelZoom project II: the impact of stellar feedback on black hole accretion through an $\alpha$-disc in dwarf galaxies with a resolved interstellar medium

TL;DR

This study uses high-resolution simulations to explore how stellar feedback influences the growth of intermediate-mass black holes in dwarf galaxies, emphasizing the importance of combined feedback processes.

Contribution

It introduces a simulation approach resolving the $ ext{α}$-disc scale and models combined stellar feedback effects on black hole accretion in dwarf galaxies.

Findings

Radiative feedback suppresses fragmentation and promotes massive circumnuclear discs.

Supernova feedback heats the ISM, reducing CND mass and black hole accretion.

Combined feedback causes intermittent CNDs, allowing significant black hole growth.

Abstract

We present a suite of high-resolution simulations to study how different stellar feedback channels regulate the growth of central intermediate-mass black holes (IMBHs) in dwarf galaxies hosting nuclear star clusters (NSCs). We employ a super-Lagrangian refinement scheme to resolve the self-gravity radius of the $\alpha$-accretion disc ($<0.01$~pc) and follow the gas inflows from the interstellar medium (ISM) to the black hole (BH), allowing for the self-consistent emergence of circumnuclear discs (CNDs). In the absence of stellar feedback, as expected, the galactic disc fragments excessively, producing a massive CND. When radiative stellar feedback is included, fragmentation is suppressed, with even more massive CNDs forming and feeding the IMBH. With supernova (SN) feedback only, clustered SNe strongly heat the ISM, yielding both the lowest CND masses and BH accretion rates. When both radiative stellar feedback and SNe are included, the CND becomes intermittent: it survives for $10$--$100$~Myr, and is then destroyed by feedback before being replenished by fresh galactic inflows, while substantial BH growth still takes place. These results highlight the critical importance of accurately modelling the combined effects of key stellar feedback processes to understand IMBH growth. Our simulation suite brackets the likely range of CND states, with IMBHs exhibiting significant growth and systematic spin-up in all dwarf galaxy models explored. These findings bode well for the detection of IMBHs with future observational facilities such as SKA, the Rubin Observatory, and LISA, and make them highly relevant progenitor candidates of the high-redshift supermassive BHs observed by JWST.