ALMA Observations of SMM11 Reveal an Extremely Young Protostar in
  Serpens Main Cluster
  We report the discovery of an extremely young protostar, SMM11, located in
the associated submillimeter condensation SMM11 in the Serpens Main cluster
using the Atacama Large Millimeter/submillimeter Array (ALMA) during its Cycle
3 at 1.3 mm and an angular resolution of ~0.5"~210 AU. SMM11 is a Class 0
protostar without any counterpart at 70 um or shorter wavelengths. The ALMA
observations show 1.3 mm continuum emission associated with a collimated 12CO
bipolar outflow. Spitzer and Herschel data show that SMM11 is extremely cold
(T_bol=26 K) and faint (L_bol<~0.9 Lsun). We estimate the inclination angle of
the outflow to be ~80 deg, almost parallel to the plane of the sky, from simple
fitting using wind-driven-shell model. The continuum visibilities consist of
Gaussian and power-law components, suggesting a spherical envelope with a
radius of ~600 AU around the protostar. The estimated low C18O abundance,
X(C18O)=1.5-3x10^-10, is also consistent with its youth. The high outflow
velocity, a few 10 kms^-1 at a few 1000 AU, is much higher than theoretical
simulations of first hydrostatic cores and we suggest that SMM11 is a
transitional object right after the second collapse of the first core.
