# Looking for ultralight dark matter near supermassive black holes

## TL;DR

This study searches for ultralight dark matter cores near supermassive black holes using stellar and imaging data, setting limits on their properties and questioning previous theoretical extrapolations.

## Contribution

It provides new observational constraints on ultralight dark matter solitons near SMBHs and discusses the limitations of existing theoretical models.

## Key findings

- No positive evidence for ULDM solitons was found.
- Constraints exclude certain soliton masses predicted by naive models.
- Theoretical arguments suggest extrapolations may overestimate soliton masses.

## Abstract

Measurements of the dynamical environment of supermassive black holes (SMBHs) are becoming abundant and precise. We use such measurements to look for ultralight dark matter (ULDM), which is predicted to form dense cores ("solitons") in the centre of galactic halos. We search for the gravitational imprint of an ULDM soliton on stellar orbits near Sgr A* and by combining stellar velocity measurements with Event Horizon Telescope imaging of M87*. Finding no positive evidence, we set limits on the soliton mass for different values of the ULDM particle mass $m$. The constraints we derive exclude the solitons predicted by a naive extrapolation of the soliton-halo relation, found in DM-only numerical simulations, for $2\times10^{-20}~{\rm eV}\lesssim m\lesssim8\times10^{-19}~{\rm eV}$ (from Sgr A*) and $m\lesssim4\times10^{-22}~{\rm eV}$ (from M87*). However, we present theoretical arguments suggesting that an extrapolation of the soliton-halo relation may not be adequate: in some regions of the parameter space, the dynamical effect of the SMBH could cause this extrapolation to over-predict the soliton mass by orders of magnitude.