Ultralight Boson Dark Matter and Event Horizon Telescope Observations of $\mathrm{M}{87}^{*}$

The initial data from the Event Horizon Telescope (EHT) on $\mathrm{M}{87}^{*}$, 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 provides evidence that $\mathrm{M}{87}^{*}$ has a mass $\sim 6.5\times {10}^9{M}_{\odot }$. EHT also inferred the dimensionless spin parameter $|a^{*}|\gtrsim 0.5$ from jet properties; a separate recent analysis using only the light from near $\mathrm{M}{87}^{*}$ as measured by the EHT Collaboration found $|a^{*}|=0.9\pm 0.1$. These determinations disfavor ultralight bosons of mass ${\mu }_b\in (0.85,4.6)\times {10}^{-21}\mathrm{eV}$ for spin-one bosons and ${\mu }_b\in (2.9,4.6)\times {10}^{-21}\mathrm{eV}$ for spin-zero bosons, within the range considered for fuzzy dark matter, invoked to explain dark matter distribution on approximately kiloparsec scales. Future observations of $\mathrm{M}{87}^{*}$ could be expected to strengthen our conclusions.

Figure 1

Regions of parameter space constrained by observations of SMBHs. The orange (blue) region is ruled out for vector (scalar) bosons by $\mathrm{M}{87}^{*}$. Note that the constraints apply to both parity even and parity odd particles. Each constraint is derived using the $1\sigma$ conservative values for the mass and spin, and the shaded band on the left of each region represents the size of the theoretical uncertainty. The green region is the constraint on vector bosons from Ark 120 [18], which cannot constrain scalars. The region preferred by fuzzy DM (FDM) is shown in gray.

Figure 2

The constraints on light bosons as a function of the spin of $\mathrm{M}{87}^{*}$. The region constrained for scalar bosons (blue) is also constrained for vector bosons (orange). The characteristic fuzzy DM range is shown in gray, and the $1\sigma$ inference region of the spin is shown in khaki [33].