Nieddu Marco Giovanni
UniCa About Professors and Researchers Marco Giovanni Nieddu Research Research outcomes (IRIS)

Marco Giovanni Nieddu

Horizon-scale variability of M87* from 2017–2021 EHT observations

Ciriaco Goddi;Alejandro Mus;
2025-01-01

Abstract

We report three epochs of polarized images of M87* at 230 GHz using data from the Event Horizon Telescope (EHT) taken in 2017, 2018, and 2021. The baseline coverage of the 2021 observations is significantly improved through the addition of two new EHT stations: the 12 m Kitt Peak Telescope and the Northern Extended Millimetre Array (NOEMA). All observations result in images dominated by a bright, asymmetric ring with a persistent diameter of 43.9 ± 0.6 µas, consistent with expectations for lensed synchrotron emission encircling the apparent shadow of a supermassive black hole. We find that the total intensity and linear polarization of M87* vary significantly across the three epochs. Specifically, the azimuthal brightness distribution of the total intensity images varies from year to year, as expected for a stochastic accretion flow. However, despite a gamma-ray flare erupting in M87 quasi-contemporaneously to the 2018 observations, the 2018 and 2021 images look remarkably similar. The resolved linear polarization fractions in 2018 and 2021 peak at ∼5%, compared to ∼15% in 2017. The spiral polarization pattern on the ring also varies from year to year, including a change in the electric vector position angle helicity in 2021 that could reflect changes in the magnetized accretion flow or an external Faraday screen. The improved 2021 coverage also provides the first EHT constraints on jet emission outside the ring, on scales of .1 mas. Overall, these observations provide strong proof of the reliability of the EHT images and probe the dynamic properties of the horizon-scale accretion flow surrounding M87*.
2025
Inglese
ASTRONOMY & ASTROPHYSICS
704
A91
37
WOS:001645252600001
2-s2.0-105026133756
https://www.aanda.org/articles/aa/full_html/2025/12/aa55855-25/aa55855-25.html
Esperti anonimi
scientifica
Accretion, accretion disks; Black hole physics; Galaxies: active; Galaxies: individual: M87*; Galaxies: jets; Gravitation
sì
Akiyama, Kazunori; Albentosa-Ru??z, Ezequiel; Alberdi, Antxon; Alef, Walter; Carlos Algaba, Juan; Anantua, Richard; Asada, Keiichi; Azulay, Rebecca; B ...espandi
1.1 Articolo in rivista
info:eu-repo/semantics/article
1 Contributo su Rivista::1.1 Articolo in rivista
262
304
open
Files in This Item:
File Size Format  
2025_6_CP_aa55855-25_compressed.pdf

open access

Type: versione editoriale
Size 6.27 MB
Format Adobe PDF
View/Open
6.27 MB Adobe PDF View/Open

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Questionnaire and social

Share on:
Impostazioni cookie