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Relative alignment between the magnetic field and molecular gas structure in the vela c giant molecular cloud using low and high density tracers

Fissel, Laura M, Ade, Peter A. R ORCID:, Angilè, Francesco E., Ashton, Peter, Benton, Steven J, Chen, Che-Yu, Cunningham, Maria, Devlin, Mark J, Dober, Bradley, Friesen, Rachel, Fukui, Yasuo, Galitzki, Nicholas, Gandilo, Natalie N, Goodman, Alyssa, Green, Claire-Elise, Jones, Paul, Klein, Jeffrey, King, Patrick, Korotkov, Andrei L., Li, Zhi-Yun, Lowe, Vicki, Martin, Peter G, Matthews, Tristan G, Moncelsi, Lorenzo, Nakamura, Fumitaka, Netterfield, Calvin B, Newmark, Amanda, Novak, Giles, Pascale, Enzo, Poidevin, Frédérick, Santos, Fabio P, Savini, Giorgio, Scott, Douglas, Shariff, Jamil A, Soler, Juan D, Thomas, Nicholas E, Tucker, Carole E ORCID:, Tucker, Gregory S, Ward-Thompson, Derek and Zucker, Catherine 2019. Relative alignment between the magnetic field and molecular gas structure in the vela c giant molecular cloud using low and high density tracers. Astrophysical Journal 878 (2) , pp. 1-26. 10.3847/1538-4357/ab1eb0

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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 $^{12}$CO and $^{13}$CO~$J$\,$\rightarrow$\,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 happen between the densities traced by $^{13}$CO and by C$^{18}$O~$J$\,$\rightarrow$\,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....

Item Type: Article
Date Type: Published Online
Status: Published
Schools: Physics and Astronomy
Publisher: American Astronomical Society
ISSN: 1538-4357
Date of Acceptance: 22 March 2019
Last Modified: 28 Apr 2023 01:15

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