The dynamical state of the First Hydrostatic Core Candidate Cha-MMS1
  Observations of First Hydrostatic Core candidates, a theoretically predicted
evolutionary link between the prestellar and protostellar phases, are vital for
probing the earliest phases of star formation. We aim to determine the
dynamical state of the First Hydrostatic Core candidate Cha-MMS1. We observed
Cha-MMS1 in various transitions with the APEX and Mopra telescopes. The
molecular emission was modeled with a radiative transfer code to derive
constraints on the envelope kinematics. We derive an internal luminosity of
0.08 - 0.18 Lsol. An average velocity gradient of 3.1(0.1) km/s/pc over 0.08 pc
is found perpendicular to the filament in which Cha-MMS1 is embedded. The
gradient is flatter in the outer parts and at the innermost 2000 - 4000 AU.
These features suggest solid-body rotation beyond 4000 AU and slower,
differential rotation beyond 8000 AU. The origin of the flatter gradient in the
innermost parts is unclear. The classical infall signature is detected in HCO+
3-2 and CS 2-1. The radiative transfer modeling indicates a uniform infall
velocity in the outer parts of the envelope. An infall velocity field scaling
with r^(-0.5) is consistent with the data for r < 9000 AU. The infall
velocities are 0.1 - 0.2 km/s at r > 3300 AU and 0.04 - 0.6 km/s at r < 3300
AU. Both the internal luminosity of Cha-MMS1 and the infall velocity field in
its envelope are consistent with predictions of MHD simulations for the first
core phase. There is no evidence for a fast, large-scale outflow stemming from
Cha-MMS1 but excess emission from the high-density tracers CS 5-4, CO 6-5, and
CO 7-6 suggests the presence of higher-velocity material at the inner core. Its
internal luminosity excludes Cha-MMS1 being a prestellar core. The kinematical
properties of its envelope are consistent with Cha-MMS1 being a first core
candidate or a very young Class 0 protostar.(abridged).
