Detection of Infall in the Protostar B335 with ALMA
  Observations of the isolated globule B335 with ALMA have yielded absorption
features against the continuum that are redshifted from the systemic velocity
in both HCN and HCO$^+$ lines. These features provide unambiguous evidence for
infall toward a central luminosity source. Previously developed models of
inside-out collapse can match the observed line profiles of HCN and HCO$^+$
averaged over the central 50 AU. At the new distance of 100 pc, the inferred
infall radius is 0.012 pc, the mass infall rate is $3 \times 10^{-6}$ solar
masses per year, the age is 50,000 years, and the accumulated mass in the
central zone is 0.15 solar masses, most of which must be in the star or in
parts of a disk that are opaque at 0.8 mm. The continuum detection indicates an
optically thin mass (gas and dust) of only $7.5\times 10^{-4}$ solar masses in
the central region, consistent with only a very small disk mass.
