Monitoring the morphology of M87* in 2009–2017 with the Event Horizon Telescope
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Date
Authors
Wielgus, Maciek
Akiyama, Kazunori
Blackburn, Lindy
Chan, Chi-kwan
Dexter, Jason
Doeleman, Sheperd S.
Fish, Vincent L.
Issaoun, Sara
Johnson, Michael D.
Krichbaum, Thomas P.
Journal Title
Journal ISSN
Volume Title
Publisher
IOP Publishing
Abstract
The Event Horizon Telescope (EHT) has recently delivered the first resolved images of M87*
, the supermassive black
hole in the center of the M87 galaxy. These images were produced using 230 GHz observations performed in 2017
April. Additional observations are required to investigate the persistence of the primary image feature—a ring with
azimuthal brightness asymmetry—and to quantify the image variability on event horizon scales. To address this need,
we analyze M87* data collected with prototype EHT arrays in 2009, 2011, 2012, and 2013. While these observations
do not contain enough information to produce images, they are sufficient to constrain simple geometric models. We
develop a modeling approach based on the framework utilized for the 2017 EHT data analysis and validate our
procedures using synthetic data. Applying the same approach to the observational data sets, we find the M87*
morphology in 2009–2017 to be consistent with a persistent asymmetric ring of ∼40 μas diameter. The position angle
of the peak intensity varies in time. In particular, we find a significant difference between the position angle measured
in 2013 and 2017. These variations are in broad agreement with predictions of a subset of general relativistic
magnetohydrodynamic simulations. We show that quantifying the variability across multiple observational epochs has
the potential to constrain the physical properties of the source, such as the accretion state or the black hole spin.
Description
Keywords
Black holes, Galaxy accretion disks, Galaxy accretion, Supermassive black holes, Event Horizon Telescope (EHT), Active galactic nuclei (AGN), Low-luminosity active galactic nuclei, Very long baseline interferometry (VLBI), Astronomy data modeling, Radio interferometry
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Citation
Wielgus, M., Akiyama, K., Blackburn, L. et al. 2020, 'Monitoring the morphology of M87* in 2009–2017 with the Event Horizon Telescope', Astrophysical Journal, vol. 901, no. 1, art. 67, pp. 1-28.