Future Prospects for Constraining Black-Hole Spacetime: Horizon-scale Variability of Astrophysical Jet. (arXiv:2311.10141v1 [astro-ph.HE])

<a href="http://arxiv.org/find/astro-ph/1/au:+Moriyama_K/0/1/0/all/0/1">Kotaro Moriyama</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cruz_Osorio_A/0/1/0/all/0/1">Alejandro Cruz-Osorio</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mizuno_Y/0/1/0/all/0/1">Yosuke Mizuno</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fromm_C/0/1/0/all/0/1">Christian M. Fromm</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nathanail_A/0/1/0/all/0/1">Antonios Nathanail</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rezzolla_L/0/1/0/all/0/1">Luciano Rezzolla</a>

The Event Horizon Telescope (EHT) Collaboration has recently published the

first horizon-scale images of the supermassive black holes M87* and Sgr A* and

provided some first information on the physical conditions in their vicinity.

The comparison between the observations and the three-dimensional

general-relativistic magnetohydrodynamic (GRMHD) simulations has enabled the

EHT to set initial constraints on the properties of these black-hole

spacetimes. However, accurately distinguishing the properties of the accretion

flow from those of the spacetime, most notably, the black-hole mass and spin,

remains challenging because of the degeneracies the emitted radiation suffers

when varying the properties of the plasma and those of the spacetime. The

next-generation EHT (ngEHT) observations are expected to remove some of these

degeneracies by exploring the complex interplay between the disk-jet dynamics,

which represents one of the most promising tools for extracting information on

the black-hole spin. By using GRMHD simulations of magnetically arrested disks

(MADs) and general-relativistic radiative-transfer (GRRT) calculations of the

emitted radiation, we have studied the properties of the jet and the

accretion-disk dynamics on spatial scales that are comparable with the horizon.

In this way, we are able to highlight that the radial and azimuthal dynamics of

the jet are well correlated with the black-hole spin. Based on the resolution

and image reconstruction capabilities of the ngEHT observations of M87*, we can

assess the detectability and associated uncertainty of this correlation.

Overall, our results serve to assess what are the prospects for constraining

the black-hole spin with future EHT observations.

The Event Horizon Telescope (EHT) Collaboration has recently published the

first horizon-scale images of the supermassive black holes M87* and Sgr A* and

provided some first information on the physical conditions in their vicinity.

The comparison between the observations and the three-dimensional

general-relativistic magnetohydrodynamic (GRMHD) simulations has enabled the

EHT to set initial constraints on the properties of these black-hole

spacetimes. However, accurately distinguishing the properties of the accretion

flow from those of the spacetime, most notably, the black-hole mass and spin,

remains challenging because of the degeneracies the emitted radiation suffers

when varying the properties of the plasma and those of the spacetime. The

next-generation EHT (ngEHT) observations are expected to remove some of these

degeneracies by exploring the complex interplay between the disk-jet dynamics,

which represents one of the most promising tools for extracting information on

the black-hole spin. By using GRMHD simulations of magnetically arrested disks

(MADs) and general-relativistic radiative-transfer (GRRT) calculations of the

emitted radiation, we have studied the properties of the jet and the

accretion-disk dynamics on spatial scales that are comparable with the horizon.

In this way, we are able to highlight that the radial and azimuthal dynamics of

the jet are well correlated with the black-hole spin. Based on the resolution

and image reconstruction capabilities of the ngEHT observations of M87*, we can

assess the detectability and associated uncertainty of this correlation.

Overall, our results serve to assess what are the prospects for constraining

the black-hole spin with future EHT observations.

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