The internal Faraday screen of Sagittarius A
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F47813059%3A19630%2F24%3AA0000403" target="_blank" >RIV/47813059:19630/24:A0000403 - isvavai.cz</a>
Result on the web
<a href="https://www.aanda.org/articles/aa/full_html/2024/02/aa47772-23/aa47772-23.html" target="_blank" >https://www.aanda.org/articles/aa/full_html/2024/02/aa47772-23/aa47772-23.html</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1051/0004-6361/202347772" target="_blank" >10.1051/0004-6361/202347772</a>
Alternative languages
Result language
angličtina
Original language name
The internal Faraday screen of Sagittarius A
Original language description
We report on 85-101 GHz light curves of the Galactic Center supermassive black hole, Sagittarius A* (Sgr A*), observed in April 2017 with the Atacama Large Millimeter /submillimeter Array (ALMA). This study of high-cadence full-Stokes data provides new measurements of the fractional linear polarization at a 1-2% level resolved in 4 s time segments, and stringent upper limits on the fractional circular polarization at 0.3%. We compare these findings to ALMA light curves of Sgr A* at 212-230 GHz observed three days later, characterizing a steep depolarization of the source at frequencies below about 150 GHz. We obtain time-dependent rotation measure (RM) values, with the mean RM at 85-101 GHz being a factor of two lower than that at 212-230 GHz. Together with the rapid temporal variability of the RM and its di fferent statistical characteristics in both frequency bands, these results indicate that the Faraday screen in Sgr A* is largely internal, with about half of the Faraday rotation taking place inside the inner 10 gravitational radii, contrary to the common external Faraday screen assumption. We then demonstrate how this observation can be reconciled with theoretical models of radiatively ine fficient accretion flows for a reasonable set of physical parameters. Comparisons with numerical general relativistic magnetohydrodynamic simulations suggest that the innermost part of the accretion flow in Sgr A* is much less variable than these models predict; in particular, the observed magnetic field structure appears to be coherent and persistent.
Czech name
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Czech description
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Classification
Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
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OECD FORD branch
10308 - Astronomy (including astrophysics,space science)
Result continuities
Project
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Continuities
I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace
Others
Publication year
2024
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
ASTRONOMY & ASTROPHYSICS
ISSN
0004-6361
e-ISSN
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Volume of the periodical
682
Issue of the periodical within the volume
February 2024
Country of publishing house
FR - FRANCE
Number of pages
12
Pages from-to
„A97-1“-„A97-12“
UT code for WoS article
001161364400009
EID of the result in the Scopus database
2-s2.0-85184951610