Interferometric Measurements of Variable 340 GHz Linear Polarization in Sagittarius A*

2005/11/22 by D. P. Marrone, Daniel P. Marrone, J. M. Moran +4 · 8 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #Galaxy #Linear polarization #Optics #Physics #Polarization (electrochemistry) #Position angle #Wavelength #astro-ph

paper · pdf · doi:10.1086/500106

published as Astrophys.J.640:308-318,2006 · 12 pages, 4 figures. To appear in ApJ

arxiv created 2005/11/22 · openalex publication_date 2006/03/13 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

Using the Submillimeter Array, we have made the first high angular resolution measurements of the linear polarization of Sagittarius A* at submillimeter wavelengths and the first detection of intraday variability in its linear polarization. We detected linear polarization at 340 GHz (880 μm) at several epochs. At the typical resolution of 1 4 × 2 2, the expected contamination from the surrounding (partially polarized) dust emission is negligible. We found that both the polarization fraction and the position angle are variable, with the polarization fraction dropping from 8.5% to 2.3% over 3 days. This is the first significant measurement of variability in the linear polarization fraction in this source. We also found variability in the polarization and total intensity within single nights, although the relationship between the two is not clear from these data. The simultaneous 332 and 342 GHz position angles are the same, setting a 1 σ rotation measure (RM) upper limit of 7 × 10 5 rad m -2 . From position angle variations and comparison of "quiescent" position angles observed here and at 230 GHz, we infer that the RM is a few times 10 5 rad m -2 , a factor of a few below our direct detection limit. A generalized model of the RM produced in the accretion flow suggests that the accretion rate at small radii must be low, below 10 -6 -10 -7 M ☉ yr -1 depending on the radial density and temperature profiles, but in all cases below the gas capture rate inferred from X-ray observations.

Citations

• The Proper Motion of Sagittarius A*. II. The Mass of Sagittarius A*
• Intraday Variation of Sagittarius A* at Short Millimeter Wavelengths
• Confirmation and Analysis of Circular Polarization from Sagittarius A*
• A size of ∼1 au for the radio source Sgr A* at the centre of the Milky Way
• The Submillimeter Array
• Intraday Variability of Sagittarius A* at 3 Millimeters
• SINFONI in the Galactic Center: Young Stars and Infrared Flares in the Central Light‐Month
• Stellar Dynamics in the Central Arcsecond of Our Galaxy
• SCUBA: a common-user submillimetre camera operating on the James Clerk Maxwell Telescope
• Galactic Centre stellar winds and Sgr A* accretion
• The Nature of the 10 kilosecond X-ray flare in Sgr A*
• First simultaneous NIR/X-ray detection of a flare from Sgr A*

Cited by

• Linearly and Circularly Polarized Emission in Sagittarius A*
• Interpreting the time variable RM observed in the core region of the TeV blazar Mrk 421
• Very High-Energy Emission from the Direct Vicinity of Rapidly Rotating Black Holes
• The Galactic Center massive black hole and nuclear star cluster
• PAGAN I: MULTI-FREQUENCY POLARIMETRY OF AGN JETS WITH KVN
• Multiwavelength Light Curves of Two Remarkable Sagittarius A* Flares
• Polarimetric Properties of Event Horizon Telescope Targets from ALMA
• Revealing the Accretion Flow in M87*: Insights from Faraday Rotation