Investigating the role of magnetic fields in star formation using molecular line profiles

Charles Yin, Felix D. Priestley, James Wurster

Published 2021-04-08Version 1

Determining the importance of magnetic fields in star forming environments is hampered by the difficulty of accurately measuring both field strength and gas properties in molecular clouds. We post-process three-dimensional non-ideal magnetohydrodynamic simulations of prestellar cores with a time-dependent chemical network, and use radiative transfer modelling to calculate self-consistent molecular line profiles. Varying the initial mass-to-flux ratio from sub- to super-critical results in significant changes to both the intensity and shape of several observationally important molecular lines. We identify the peak intensity ratio of N$_2$H$^+$ to CS lines, and the CS $J=2-1$ blue-to-red peak intensity ratio, as promising diagnostics of the initial mass-to-flux ratio, with N$_2$H$^+$/CS values of $>0.6$ ($<0.2$) and CS blue/red values of $<3$ ($>5$) indicating subcritical (supercritial) collapse. These criteria suggest that, despite presently being magnetically supercritical, L1498 formed from subcritical initial conditions.