Interferometric Detection of Linear Polarization from Sagittarius A* at 230 GHz

By G. Bower, Melvyn Wright, Heino Falcke, D. Backer. 2003

200 citations recorded by the source corpus.

We measured the linear polarization of Sagittarius A* to be 7.2% ± 0.6% at 230 GHz using the BIMA array with a resolution of 3.″6 × 0.″9. This confirms the previously reported detection with the James Clerk Maxwell Telescope (JCMT) 14 m antenna. Our high-resolution observations demonstrate that the polarization does not arise from dust but from a synchrotron source associated with Sgr A*. We see no change in the polarization position angle and only a small change in the polarization fraction in four observations distributed over 60 days. We find a position angle of 139° ± 4°, which differs substantially from what was found in earlier JCMT observations at the same frequency. Polarized dust emission cannot account for this discrepancy, leaving variability and observational error as the only explanations. The BIMA observations alone place an upper limit on the magnitude of the rotation measure of 2 × 106 rad m-2. These new observations, when combined with the JCMT observations at 150, 375, and 400 GHz, suggest that the rotation measure = -4.3 ± 0.1 × 105 rad m-2. This RM may be caused by an external Faraday screen. Barring a special geometry or a high number of field reversals, this RM rules out accretion rates greater than ~10-7 M☉ yr-1. This measurement is inconsistent with high accretion rates necessary in standard advection-dominated accretion flow and Bondi-Hoyle models for Sgr A*. It argues for low accretion rates as a major factor in the overall faintness of Sgr A*.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/33658d0abe0596f645cc24a2ea149c2fb8f3eed0

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In Astronomy and Astrophysics

1. Ramesh Narayan
2. P. Hopkins
3. L. Hernquist
4. F. Yuan
5. R. Genzel
6. E. Quataert
7. D. M. Alexander
8. T. Johannsen

In Nuclear and High Energy Physics

1. Ramesh Narayan
2. F. Yuan
3. A. Sa̧dowski
4. T. Johannsen
5. L. Hernquist
6. J. McKinney
7. A. Merloni
8. P. Hopkins

Citations in the corpus

• Chandra X-Ray Spectroscopic Imaging of Sagittarius A* and the Central Parsec of the Galaxy (2001, background): “This result has recently been confirmed by Bower et al. (2003) using higher angular resolution observations with the BIMA array.”
• Flaring Activity of Sagittarius A* at 43 and 22 GHz: Evidence for Expanding Hot Plasma (2006, background): “More recently, detection of radio and sub-millimeter polarization from Sgr A* (Bower et al. 2003; Marrone et al. 2006) has allowed estimates of the integrated electron density in the accretion region from ∼10 to 1000 Schwarzschild radii.”
• Nonthermal Electrons in Radiatively Inefficient Accretion Flow Models of Sagittarius A* (2003, methodology): “We wish to explain all these facts while also satisfying the upper limit on the density of the gas near the black hole as deduced from the linear polarization data of Aitken et al. (2000) and Bower et al. (2003).”
• Two‐dimensional adiabatic flows on to a black hole – I. Fluid accretion (2003, background): “Furthermore, Aitken et al. (2000) (cf. Bower et al. 2003) have measured millimetre linear polarization, which suggests that the plasma density close to the black hole is much less than would be associated with a conservative inflow (Agol 2000).”
• DETECTING FLARING STRUCTURES IN SAGITTARIUS A* WITH HIGH-FREQUENCY VLBI (2008, background): “Nevertheless, following the detection of polarization from Sgr A* above 100 GHz (Aitken et al. 2000; Bower et al. 2001, 2003; Marrone et al. 2006), and subsequent measurements of the Faraday rotation measure (Macquart et al. 2006; Marrone et al. 2007), the accretion rate near the black hole has…”
• IPOLE - semi-analytic scheme for relativistic polarized radiative transport (2017, background): “It is therefore natural that EHT targets have substantial linear polarization, and indeed the linear polarization fraction in Sgr A* is ∼ 7 per cent1 (Bower et al. 2003, 2005; Marrone et al. 2007, 2008) and in M87 it is < 1 per cent (Kuo et al. 2014).”
• GRMHD simulations of magnetized advection‐dominated accretion on a non‐spinning black hole: role of outflows (2012, methodology): “Yuan et al. (2003) attempted to constrain the mass loss in Sgr A∗ using radio data on Faraday rotation (Agol 2000; Aitken et al. 2000; Quataert & Gruzinov 2000a; Bower et al. 2003; Marrone et al. 2007).”
• THE LEGACY OF SCUPOL: 850 μm IMAGING POLARIMETRY FROM 1997 TO 2005 (2009, unknown): “Publication(s) Emission Publication(s) L183 SC/PC 43 0.15 Ward-Thompson et al. (1999) N Ward-Thompson et al. (2000); Crutcher et al. (2004) ρ Oph A SFR 44 0.139 Mamajek (2008) N Tamura (1999); Green et al. (2004) Holland et al. (1996); Greaves et al. (1994) ρ Oph C SFR 45 0.139 Mamajek (2008) Y ρ Op”
• On the Nature of the Variable Infrared Emission from Sagittarius A* (2004, background): “…black hole by a factor ∼ (RS/Rout) s is in good agreement with the high level of linear polarization detected at 230 GHz (e.g., Aitken et al. 2000; Bower et al. 2003), which puts an upper limit on the density of gas near the BH and thus the accretion rate onto the hole (Quataert & Gruzinov…”
• An X-Ray, Infrared, and Submillimeter Flare of Sagittarius A* (2007, background): “Flare Polarization Although linear polarization has been detected in Sgr A* at submillimeter and near-IR wavelengths (e.g. Aitken et al. 2000; Bower et al. 2003; Marrone et al. 2006a; Eckart et al. 2006a), of the observations presented here only the 2006 July 17 SMA observations were designed to…”
• Polarimetry of near-infrared flares from Sagittarius A* (2006, background): “B-5019(A). polarization from Sgr A* (see also Bower et al. 2003; Melia & Falcke 2001; Bower et al. 1999a; Marrone et al. 2006).”
• NUMERICAL SIMULATION OF HOT ACCRETION FLOWS. III. REVISITING WIND PROPERTIES USING THE TRAJECTORY APPROACH (2015, background): “One is the detection of radio polarization at a level of 2 − 9% (e.g., Aitken et al. 2000; Bower et al. 2003; Marrone et al. 2007).”
• THE EVENT HORIZON OF SAGITTARIUS A* (2009, background): “Finally, below roughly 3 mm, Sgr A* is linearly polarized (Aitken et al. 2000; Bower et al. 2003; Macquart et al. 2006; Marrone et al. 2006, 2007).”
• Measuring the kinetic power of active galactic nuclei in the radio mode (2007, background): “…radii (∼ 0.025” at the distance of the galactic center) and an inner accretion rateṀa(rin) = Ṁoutξp ≃ 4 × 10−9 M⊙/yr, also consistent with the gas density in the inner accretion flw implied by linear polarization measurements (Aitken et al.2000; Bower et al. 2003; Bower et al. 2005).”
• Hot Accretion Flows Around Black Holes (2014, background): “The radio emission at submillimeter and millimeter wavelengths is linearly polarized at a level of 2−9% (Aitken et al. 2000; Bower et al. 2003; Marrone et al., 2006, 2007), and the mean rotation measure between 227 and 343 GHz is −5.6± 0.7× 105 radm−2.”
• EVIDENCE FOR LOW BLACK HOLE SPIN AND PHYSICALLY MOTIVATED ACCRETION MODELS FROM MILLIMETER-VLBI OBSERVATIONS OF SAGITTARIUS A* (2010, background): “However, the detection of linear polarization in Sgr A* above 100GHz (Aitken et al. 2000; Bower et al. 2001, 2003; Marrone et al. 2006) and subsequent measurements of the Faraday rotation measure (Macquart et al. 2006; Marrone et al. 2007), have implied that the accretion rate near the black hole…”