The link between turbulence, magnetic fields, filaments, and star formation in the central molecular zone cloud G0.253+0.016
- Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia)
- CSIRO Astronomy and Space Science, P.O. Box 76, Epping NSW, 1710 (Australia)
- Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF (United Kingdom)
- Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, D-69120 Heidelberg (Germany)
- CASA, University of Colorado, 389-UCB, Boulder, CO 80309 (United States)
- Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands)
- Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago (Chile)
- Institute for Astrophysical Research, Boston University, Boston, MA 02215 (United States)
- European Southern Observatory, Karl-Schwarzschild-Straße 2, D-85748 Garching bei München (Germany)
Star formation is primarily controlled by the interplay between gravity, turbulence, and magnetic fields. However, the turbulence and magnetic fields in molecular clouds near the Galactic center may differ substantially compared to spiral-arm clouds. Here we determine the physical parameters of the central molecular zone (CMZ) cloud G0.253+0.016, its turbulence, magnetic field, and filamentary structure. Using column density maps based on dust-continuum emission observations with ALMA+Herschel, we identify filaments and show that at least one dense core is located along them. We measure the filament width W{sub fil}=0.17±0.08 pc and the sonic scale λ{sub sonic}=0.15±0.11 pc of the turbulence, and find W{sub fil}≈λ{sub sonic}. A strong velocity gradient is seen in the HNCO intensity-weighted velocity maps obtained with ALMA+Mopra. The gradient is likely caused by large-scale shearing of G0.253+0.016, producing a wide double-peaked velocity probability distribution function (PDF). After subtracting the gradient to isolate the turbulent motions, we find a nearly Gaussian velocity PDF typical for turbulence. We measure the total and turbulent velocity dispersion, 8.8±0.2 km s{sup −1} and 3.9±0.1 km s{sup −1}, respectively. Using magnetohydrodynamical turbulence simulations, we find that G0.253+0.016's turbulent magnetic field B{sub turb}=130±50 μG is only ≲1/10 of the ordered field component. Combining these measurements, we reconstruct the dominant turbulence driving mode in G0.253+0.016 and find a driving parameter of b=0.22±0.12, indicating solenoidal (divergence-free) driving. We compare this to spiral-arm clouds, which typically have a significant compressive (curl-free) driving component (b>0.4). Motivated by previous reports of strong shearing motions in the CMZ, we speculate that shear causes the solenoidal driving in G0.253+0.016 and show that this reduces the star-formation rate by a factor of 6.9 compared to typical nearby clouds.
- OSTI ID:
- 22868416
- Journal Information:
- Astrophysical Journal, Vol. 832, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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