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