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

Laura M. Fissel, Peter A.R. Ade, Francesco E. Angile, Peter Ashton, Steven J. Benton, Che Yu Chen, Maria Cunningham, Mark J. Devlin, Bradley Dober, Rachel Friesen, Yasuo Fukui, Nicholas Galitzki, Natalie N. Gandilo, Alyssa Goodman, Claire Elise Green, Paul Jones, Jeffrey Klein, Patrick King, Andrei L. Korotkov, Zhi Yun LiVicki Lowe, Peter G. Martin, Tristan G. Matthews, Lorenzo Moncelsi, Fumitaka Nakamura, Calvin B. Netterfield, Amanda Newmark, Giles Novak, Enzo Pascale, Frédérick Poidevin, Fabio P. Santos, Giorgio Savini, Douglas Scott, Jamil A. Shariff, Juan D. Soler, Nicholas E. Thomas, Carole E. Tucker, Gregory S. Tucker, Derek Ward-Thompson, Catherine Zucker

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53 Scopus citations


We compare the magnetic field orientation for the young giant molecular cloud Vela C inferred from 500 μm 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 12CO and 13CO 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 13CO and by C18O 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 103 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.

Original languageEnglish (US)
Article number110
JournalAstrophysical Journal
Issue number2
StatePublished - Jun 20 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Data behind figures
  • dust
  • Extinction-ISM: individual objects (Vela C)-ISM: magnetic fields-ISM: molecules-molecular data Supporting material: interactive figures


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