http://arxiv.org/abs/2111.07735
The first image of the black hole (BH) M87* obtained by the Event Horizon Telescope (EHT) has the shape of a crescent extending from the E to WSW position angles, with a tentative ‘ESE hotspot’. Assuming that the BH spin vector is aligned with both the inner accretion axis and the projected direction of the kpc-scale relativistic jet, the position of the ESE hotspot is inconsistent with the axisymmetric accretion flow. Recent polarimetric EHT images of M87* show that the ESE hotspot is essentially unpolarized, which strongly supports its distinct origin. If the hotspot emission is due to the synchrotron radiation, its depolarization requires either isotropically tangled magnetic fields or an additional Faraday dispersion measure. The 6-day EHT observing campaign in April 2017 allowed in principle to detect orbital motions advancing by up to ~60 deg. The apparent rotation rate of the major axis of the EHT crescent image is consistent with the rotation rate of the Faraday-corrected polarization angle measured by the ALMA. However, the counterclockwise (CCW) sense of these rotations is opposite to the clockwise (CW) rotation of the plasma flows implied by the N-S brightness asymmetry, which might indicate that accretion in M87 is retrograde.
K. Nalewajko
Tue, 16 Nov 21
14/97
Comments: 5 pages, 1 figure, to appear in the proceedings of the Sixteenth Marcel Grossmann Meeting (MG16)