Monitoring the Morphology of M87* in 2009-2017 with the Event Horizon Telescope

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2020-09-20
Major/Subject
Mcode
Degree programme
Language
en
Pages
28
Series
Astrophysical Journal, Volume 901, issue 1
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- A nd 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, Active galactic nuclei, Low-luminosity active galactic nuclei, Very long baseline interferometry, Astronomy data modeling, Radio interferometry
Other note
Citation
Event Horizon Telescope Collaboration 2020, ' Monitoring the Morphology of M87* in 2009-2017 with the Event Horizon Telescope ', The Astrophysical Journal, vol. 901, no. 1, 67 . https://doi.org/10.3847/1538-4357/abac0d