# Radiation pattern and outflow geometry: a new probe of black hole spin?

## TL;DR

This paper investigates how the spin of a black hole influences the shape of galactic outflows through radiative feedback, proposing a new method to infer black hole spin from large-scale galaxy observations.

## Contribution

It introduces a novel approach linking black hole spin to outflow morphology, enabling spin estimation from galaxy-scale features.

## Key findings

- Low BH spins produce polar outflows due to vertically focused radiation.
- High BH spins lead to more isotropic radiation and quasi-spherical outflows.
- Black hole spin significantly impacts galactic feedback and obscuration.

## Abstract

We explore the impact of the central black hole (BH) spin on the large-scale properties of the host galaxy, by considering radiative feedback. The BH spin determines the radiation pattern from the accretion disc, which directly imprints on the geometry of the radiation-driven outflows. We show that for low BH spins, the emission is vertically focused, giving rise to polar/prolate outflows; while for high BH spins, the radiation pattern is more isotropic, leading to quasi-spherical/oblate outflows. Reversing the argument, we can potentially deduce the spin of the central BH from the observed morphology of galactic outflows. In principle, this may provide a novel way of constraining the central BH spin from galaxy-scale observations. Indeed, the BH spin can have significant macroscopic effects on galactic scales, ultimately shaping the large-scale feedback and the resulting obscuration.