Ultra Light Boson Dark Matter and Event Horizon Telescope Observations of M87*

Abstract: The initial data from the Event Horizon Telescope (EHT) on M87$^*$, the supermassive black hole at the center of the M87 galaxy, provide direct observational information on its mass, spin, and accretion disk properties. A combination of the EHT data and other constraints provide evidence that M87$^*$ has a mass $\sim 6.5 \times 10^9\,M_\odot$ and dimensionless spin parameter $|a^*|\gtrsim 0.5$. These determinations disfavor ultra light bosons of mass $\mu_b\sim 10^{-21}$ eV, within the range considered for fuzzy dark matter, invoked to explain dark matter distribution on $\sim$ kpc scales. Future observations of M87$^*$ could be expected to strengthen our conclusions.