First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole

Abstract

We present measurements of the properties of the central radio source in M87 using Event Horizon Telescope data obtained during the 2017 campaign. We develop and fit geometric crescent models (asymmetric rings with interior brightness depressions) using two independent sampling algorithms that consider distinct representations of the visibility data. We show that the crescent family of models is statistically preferred over other comparably complex geometric models that we explore. We calibrate the geometric model parameters using general relativistic magnetohydrodynamic (GRMHD) models of the emission region and estimate physical properties of the source. We further fit images generated from GRMHD models directly to the data. We compare the derived emission region and black hole parameters from these analyses with those recovered from reconstructed images. There is a remarkable consistency among all methods and data sets. We find that >50% of the total flux at arcsecond scales comes from near the horizon, and that the emission is dramatically suppressed interior to this region by a factor >10, providing direct evidence of the predicted shadow of a black hole. Across all methods, we measure a crescent diameter of 42±3 μas and constrain its fractional width to be <0.5. Associating the crescent feature with the emission surrounding the black hole shadow, we infer an angular gravitational radius of GM/Dc 2 =3.8±0.4 μas. Folding in a distance measurement of -+ 16.8 Mpc 0.7 0.8 gives a black hole mass of =  ´ | | M M 6.5 0.2 0.7 10 stat sys 9. This measurement from lensed emission near the event horizon is consistent with the presence of a central Kerr black hole, as predicted by the general theory of relativity.

The Structure of Radiatively Inefficient Black Hole Accretion Flows

“…In a given simulation, we find that there is no clear convergence of d log ρ /d log r to a particular value in the steady state flow exterior to the inner 10-30 GM/c 2 , as might be expected if there were a unique self-similar solution for the structure of RIAFs. By contrast, such a well-defined radial profile is seen in hydrodynamic α models of RIAFs (e.g., Stone et al 1999;Yuan et al 2012). It is unclear if this difference between the hydrodynamic and MHD models reflects the very different angular momentum and energy transport physics in the two different simulations or if our simulations still do not have sufficient dynamic range to reach a quasi self-similar state.…”

“…Stone et al (1999),, andYuan et al (2012) studied the radial structure of RIAFs using axisymmetric hydrodynamic simulations with an α viscosity, with outcomes differing with the details of that viscosity. The differences between hydrodynamic and magnetohydrodynamic (MHD) simulations make it difficult to know how to connect the results of those simulations to the MHD problem considered here.…”

Shadow and quasinormal modes of a rotating loop quantum black hole

“…Recently, the EHT Collaboration announced their first image concerning the detection of an event horizon of a supermassive black hole at the center of a neighboring elliptical M87* galaxy [1][2][3][4][5][6]. With this image, it was found that the diameter of the center black hole shadow is (42 ± 3) µas with a deviation 10% from circularity, which leads to a measurement of the center mass, M = (6.5 ± 0.7) × 10 9 M [1].…”

“…The calculations of the shadow size and shape, and their observational implications from different black hole spacetimes or spacetimes of compact objects with exotic matters ether in general relativity or in modified theories of gravity have been extensively studied, see, for example, . Recently, the first observational data of the shadow image captured by EHT [1][2][3][4][5][6] have been used for constraining the black hole parameters and deviations from the Kerr metric [49][50][51][52][53]. Although these constraints are still not stringent enough, these works do show that the observational data does have the capacity for constraining black hole parameters beyond those presented in GR.…”

Shadow of a spinning black hole in an expanding universe

“…In recent years, various kinds of astronomical observations strongly reveal that black holes do exist in our universe. The evidences so far are not limited to gravitational wave detection by LIGO and Virgo, but also include the images of black holes by Event Horzion Tecescope (EHT) [1][2][3][4][5][6]. However, compared to the precision of LIGO and Virgo, the pictures of black holes captured by EHT are not clear enough.…”