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The SAO/ASIAA Submillimeter Array (SMA)
| The Magnetic Field Revealing the Inflow Structures in the Central 2 pc of the Galactic Center |
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Image Credit: Hsieh, Pei-Ying
(a) and (b): Color-composite image of SMA HCN(J = 4−3) tracing the circumnuclear disk in the Galactic center (blue; CND) and the 6 cm map tracing the mini-spiral (red). The B-field orientation of the JCMT data and the best-fit model are overlaid with the white segments in the (a) and (b), respectively. respectively. The SgrA* is labeled with the black cross. (c) The JCMT B-field segments (blue) and model (red) are overlaid on the CND (gray image) and the mini-spiral (contours). The B-field model is aligned with the CND well, which suggests that the same field lines, continuing inward, also align with the mini-spiral. (d) Azimuthal-plot of the B-field position angle (ΦB; red points) with the model overlaid (blue curve). The B-field shows a predominantly azimuthal field
being wrapped along with the CND. The systemetic deviation of the B-field in the NE-lobe (E), SW-lobe can be attributed to the accretion history. The clear connection of the neutral CND and ionized mini-spiral with the B-field is presented for the first time (Hsieh et al. 2018, accepted for publication in ApJ).
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| Utilizing James Clark Maxwell Telescope (JCMT) μm SCUPOL dust polarization data, we investigate the configuration of the magnetic (B-) field in the circumnuclear disk (CND) of the Galactic Center (GC). Overall on a large scale, the B-field shows a clear predominantly toroidal morphology. Compared to earlier 100 μm observations, the SCUPOL data show a hugely improved polarization coverage at a higher resolution. In general, the observed B-field morphology is well described by a self-similar axisymmetric disk model where the radial infall velocity is one quarter of the rotational velocity. A detailed comparison with higher-resolution interferometric maps from the Submillimeter Array (SMA) further reveals that the B-field aligns with the neutral gas streamers where they are connecting to the CND. Moreover, the innermost observed B-field structure also appears to trace and align with the ionized mini-spirals located inside the CND. This suggests that there might be one underlying B-field structure that is connecting the CND with its streamers and the inner mini-spirals. An estimate of βplasma ~1 -- based on the global B-field morphology that constrains the azimuthal-to-vertical field strength ratio to be around 40 combined with a measurement of the azimuthal velocity -- indicates that the B-field appears dynamically significant towards the CND and also onwards to the inner mini-spirals. The connection of the CND and the mini-spiral by the B-field is revealed for the first time (Hsieh et al. 2018, accepted for publication). |
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