期刊
ASTROPHYSICAL JOURNAL
卷 878, 期 2, 页码 -出版社
IOP Publishing Ltd
DOI: 10.3847/1538-4357/ab1eb0
关键词
dust, extinction; ISM: individual objects (Vela C); ISM: magnetic fields; ISM: molecules; molecular data
资金
- NASA [NNX13AE50G, 80NSSC18K0481, NAG5-12785, NAG5-13301, NNGO-6GI11G, NNX0-9AB98G]
- Illinois Space Grant Consortium
- Canadian Space Agency
- Leverhulme Trust [F/00 407/BN]
- Natural Sciences and Engineering Research Council of Canada
- Canada Foundation for Innovation
- Ontario Innovation Trust
- US National Science Foundation Office of Polar Programs
- Australian Government
- European Research Council (ERC) under the Horizon 2020 Framework Program [CSF-648505]
- European Commission under the Marie Sklodowska-Curie Actions within the H2020 program [658499 PolAME H2020-MSCA-IF-2014]
- STFC [ST/R000786/1, ST/M001334/1, ST/S00033X/1] Funding Source: UKRI
- NASA [474373, NNX13AE50G] Funding Source: Federal RePORTER
We compare the magnetic field orientation for the young giant molecular cloud Vela C inferred from 500 mu m polarization maps made with the BLASTPol balloon-borne polarimeter to the orientation of structures in the integrated line emission maps from Mopra observations. Averaging over the entire cloud we find that elongated structures in integrated line-intensity or zeroth-moment maps, for low-density tracers such as (CO)-C-12 and (CO)-C-13 J -> 1 - 0, are statistically more likely to align parallel to the magnetic field, while intermediate- or high-density tracers show (on average) a tendency for alignment perpendicular to the magnetic field. This observation agrees with previous studies of the change in relative orientation with column density in Vela C, and supports a model where the magnetic field is strong enough to have influenced the formation of dense gas structures within Vela C. The transition from parallel to no preferred/perpendicular orientation appears to occur between the densities traced by (CO)-C-13 and by (CO)-O-18 J -> 1 - 0. Using RADEX radiative transfer models to estimate the characteristic number density traced by each molecular line, we find that the transition occurs at a molecular hydrogen number density of approximately 10(3) cm(-3). We also see that the Centre Ridge (the highest column density and most active star-forming region within Vela C) appears to have a transition at a lower number density, suggesting that this may depend on the evolutionary state of the cloud.
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