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| Main Authors: | , , , , , |
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| Format: | Preprint |
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2024
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| Online Access: | https://arxiv.org/abs/2407.05093 |
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| _version_ | 1866929411719168000 |
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| author | Sato, Kazuki Shinnaga, Hiroko Furuya, Ray S. Suzuki, Takeru K. Kakiuchi, Kensuke Ott, Jürgen |
| author_facet | Sato, Kazuki Shinnaga, Hiroko Furuya, Ray S. Suzuki, Takeru K. Kakiuchi, Kensuke Ott, Jürgen |
| contents | We showcase a study on the physical properties of the Circumnuclear Disk surrounding the Sgr A* of the Galactic Center, emphasizing the role of magnetic field (B field) with 0.47 pc spatial resolution, based on the sensitive λ = 850 μm polarization data taken with the JCMT. The B field within the CND exhibits a coherent spiral pattern. Applying the model described by Wardle and Ko\ddot{o}nigl 1990 (WK model) to the observed B field pattern, it favors gas-pressure-dominant models without dismissing a gas-and-B field comparable model, leading us to estimate the B-field strength in the ionized cavity around Sgr A* as 0.24 + 0.05 mG. Analysis -0.04 based on the WK model further allows us to derive representative B-field strengths for the radial, azimuthal, and vertical components as (Br,Bϕ,Bz) = (0.4 \pm 0.1,-0.7 \pm 0.2,0.2 \pm 0.05) mG, respectively. A key finding is that the |ϕ| component is dominant over Br and Bz components, consistent with the spiral morphology, indicating that the CND' s B-field is predominantly toroidal, possibly shaped by accretion dynamics. Considering the turbulent pressure, estimated plasma \{beta} values indicate the effective gas pressure should surpass the magnetic pressure. Assessing the CND of our MWG in the toroidal-and-vertical stability parameter space, we propose that such an "effective" magnetoro-tational instability (MRI) may likely be active. The estimated maximum unstable wavelength, λmax = 0.1 \pm 0.1 pc, is smaller than the CND' s scale height (0.2 \pm 0.1 pc), which indicates the potential for the effective MRI intermittent cycles of \sim 10^{6} years, which should profoundly affect the CND's evolution, considering the estimated mass accretion rate of 10^{-2}M_{\odot} yr^{-1} to the Sgr A*. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2407_05093 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Spiral Magnetic Field and Their Role on Accretion Dynamics in the Circumnuclear Disk of Sagittarius A*: Insight from λ = 850 μm Polarization Imaging Sato, Kazuki Shinnaga, Hiroko Furuya, Ray S. Suzuki, Takeru K. Kakiuchi, Kensuke Ott, Jürgen Astrophysics of Galaxies We showcase a study on the physical properties of the Circumnuclear Disk surrounding the Sgr A* of the Galactic Center, emphasizing the role of magnetic field (B field) with 0.47 pc spatial resolution, based on the sensitive λ = 850 μm polarization data taken with the JCMT. The B field within the CND exhibits a coherent spiral pattern. Applying the model described by Wardle and Ko\ddot{o}nigl 1990 (WK model) to the observed B field pattern, it favors gas-pressure-dominant models without dismissing a gas-and-B field comparable model, leading us to estimate the B-field strength in the ionized cavity around Sgr A* as 0.24 + 0.05 mG. Analysis -0.04 based on the WK model further allows us to derive representative B-field strengths for the radial, azimuthal, and vertical components as (Br,Bϕ,Bz) = (0.4 \pm 0.1,-0.7 \pm 0.2,0.2 \pm 0.05) mG, respectively. A key finding is that the |ϕ| component is dominant over Br and Bz components, consistent with the spiral morphology, indicating that the CND' s B-field is predominantly toroidal, possibly shaped by accretion dynamics. Considering the turbulent pressure, estimated plasma \{beta} values indicate the effective gas pressure should surpass the magnetic pressure. Assessing the CND of our MWG in the toroidal-and-vertical stability parameter space, we propose that such an "effective" magnetoro-tational instability (MRI) may likely be active. The estimated maximum unstable wavelength, λmax = 0.1 \pm 0.1 pc, is smaller than the CND' s scale height (0.2 \pm 0.1 pc), which indicates the potential for the effective MRI intermittent cycles of \sim 10^{6} years, which should profoundly affect the CND's evolution, considering the estimated mass accretion rate of 10^{-2}M_{\odot} yr^{-1} to the Sgr A*. |
| title | Spiral Magnetic Field and Their Role on Accretion Dynamics in the Circumnuclear Disk of Sagittarius A*: Insight from λ = 850 μm Polarization Imaging |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2407.05093 |