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Cited by 298Astrophysical Phenomena and ObservationsAstrophysics and Cosmic PhenomenaAstrophysics and Star Formation Studies

An Unambiguous Detection of Faraday Rotation in Sagittarius A*

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Marrone, Daniel P., Moran, James M., Zhao, Jun-Hui, Rao, Ramprasad·2007·The Astrophysical Journal
DOI 10.1086/510850
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Abstract

The millimeter/submillimeter wavelength polarization of Sgr A* is known to be variable in both magnitude and position angle on timescales down to a few hours. The unstable polarization has prevented measurements made at different frequencies and different epochs from yielding convincing measurements of Faraday rotation in this source. Here we present observations made with the Submillimeter Array polarimeter at 227 and 343 GHz with sufficient sensitivity to determine the rotation measure at each band without comparing position angles measured at separate epochs. We find the 10-epoch mean rotation measure to be (-5.6 ± 0.7) × 10 5 rad m -2 ; the measurements are consistent with a constant value. We conservatively assign a 3 σ upper limit of 2 × 10 5 rad m -2 to rotation measure changes, which limits accretion rate fluctuations to 25%. This rotation measure detection limits the accretion rate to less than 2 × 10 -7 M ☉ yr -1 if the magnetic field is near equipartition, ordered, and largely radial, while a lower limit of 2 × 10 -9 M ☉ yr -1 holds even for a subequipartition, disordered, or toroidal field. The mean intrinsic position angle is 167 ° ± 7 ° and we detect variations of 31 deg. These variations must originate in the submillimeter photosphere, rather than arising from rotation measure changes.

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  • Observations of polarization and its variability in mm, sub-mm, and near IR wavelengths within the central 0.1 pc of Sgr A* have been instrumental in determining the mass accretion rate of the SMBH.

    “Observations of polarization and its variability in mm, sub-mm, and near IR wavelengths within the central 0 . 1 pc of the Sgr A ∗ have been instrumental in determining the mass accretion rate of the SMBH (Aitken et al. 2000; Marrone et al. 2007; Eckart et al. 2012; Brinkerink et al. 2016; Bower et al. 2018; Do et al. 2019; Michail et al. 2023).”

    From The Fermi/eROSITA bubbles: a look into the nuclear outflow from the Milky Way (2024) · cites this paper as Marrone et al. 2007

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Authors
Marrone, D. P., Moran, J. M., Zhao, J.-H., & Rao, R.
Affiliations
  • University of Chicago (US)
  • Center for Astrophysics Harvard & Smithsonian (US)
  • Institute of Astronomy and Astrophysics, Academia Sinica (TW)
ORCID
Venue
The Astrophysical Journal
Publisher
American Astronomical Society
Published
2006-12-15
Volume
654
Issue
1
Pages
L57-L60
ISSN
  • 0004-637X (ISSN-L)
  • 1538-4357
DOI
10.1086/510850
OpenAlex
W2034547856
Cited by
298
References
26
Citations by year
2026: 10 · 2025: 14 · 2024: 17 · 2023: 13 · 2022: 14 · 2021: 14 · 2020: 14 · 2019: 20 · 2018: 20 · 2017: 18 · 2016: 21 · 2015: 22 · 2014: 14 · 2013: 17 · 2012: 13
FWCI
7.09
Type
journal article
Language
en
Open access
Locations
  • The Astrophysical Journal (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • Digital Access to Scholarship at Harvard (DASH) (Harvard University) (submittedVersion, cc-by)
  • arXiv (Cornell University)
Funders
Harvard University
Topics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysical Phenomena and Observations
  • Physical Sciences › Physics and Astronomy › Nuclear and High Energy Physics › Astrophysics and Cosmic Phenomena
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysics and Star Formation Studies
Keywords
Sgr A*, Faraday rotation, rotation measure, black hole accretion, accretion rate, magnetic field, supermassive black holes

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