Different molecular filament widths as tracers of accretion onto
  filaments
  We explore how dense filament widths, when measured using different molecular
species, may change as a consequence of gas accretion toward the filament. As a
gas parcel falls into the filament, it will experience different density,
temperature, and extinction values. The rate at which this environment changes
will affect differently the abundance of different molecules. So, a molecule
that forms quickly will better reflect the local physical conditions a gas
parcel experiences than a slower-forming molecule. Since these differences
depend on how the respective timescales compare, the different molecular
distributions should reflect how rapidly the environment changes, i.e., the
accretion rate toward the filament. We find that the filament widths measured
from time-dependent abundances for C2H, CO, CN, CS, and C3H2, are sensitive the
most to this effect, being those molecules the ones presenting also the wider
filament widths. On the contrary, molecules such as N2H+, NH3, H2CO, HNC or
CH3OH are not so sensitive to accretion and present the narrowest filament
widths. We propose that ratios of filament widths for different tracers could
be a useful tool to estimate the accretion rate onto the filament.
