# On the Possibility that Ultra-Light Boson halos host and form Super-massive Black Holes

## TL;DR

This paper explores the hypothesis that ultra-light boson dark matter halos could collapse to form super-massive black holes at galactic centers, providing a potential alternative formation mechanism.

## Contribution

It extends scalar field collapse theory to galactic halos with SMBHs, modeling their interaction and deriving observable stellar kinematics for testing.

## Key findings

- Derived stellar velocity profiles influenced by ultra-light boson halos.
- Provided a framework to distinguish dark matter models via galactic center observations.
- Connected theoretical models with upcoming observational data from the Event Horizon Telescope.

## Abstract

Several observations suggest the existence of super-massive black holes (SMBH) at the centers of giant galaxies. However the mechanism under which these objects form remains non completely understood. In this work we review an alternative mechanism of formation of galactic SMBHs. This is, the collapse of ultra-light scalar field configurations playing the role of dark matter halos. Several works have studied this scenario and investigated its plausibility. The theory of collapse of scalar field configurations into compact objects has been extensively studied regarding to boson stars, in this work we extrapolate such results for models of galactic halos hosting central SMBHs. We construct the simplest setup of an ultra-light scalar field configuration laying in a Schwarzschild space-time for modeling a galactic system with a SMBH in the quasi-static limit. This model is applicable to systems either out of their accretion-phase at late times or either for those undergoing into a very slow accretion-phase, such as some early-type giant elliptic galaxies and bulges. On the other hand, very recent direct observation of Sagittarius A by the Event Horizon Telescope will open an era of explorations of the deep-inner galactic region of the Milky Way that will enable us to test and distinguish various dark matter models. Thus we use our model to give a very first step towards that direction. We derive the stellar kinematics induced by this sort dark matter to obtain information of the black hole's influence into the observable features of the velocity field of visible matter deep inside the galaxy. Thus we compute the radial velocity, acceleration and velocity dispersion densities for some realistic cases.