CARMA Large Area Star Formation Survey: Structure and Kinematics of
  Dense Gas in Serpens Main
  We present observations of N2H+(1-0), HCO+(1-0), and HCN(1-0) toward the
Serpens Main molecular cloud from the CARMA Large Area Star Formation Survey
(CLASSy). We mapped 150 square arcminutes of Serpens Main with an angular
resolution of 7 arcsecs. The gas emission is concentrated in two subclusters
(the NW and SE subclusters). The SE subcluster has more prominent filamentary
structures and more complicated kinematics compared to the NW subcluster. The
majority of gas in the two subclusters has subsonic to sonic velocity
dispersions. We applied a dendrogram technique with N2H+(1-0) to study the gas
structures; the SE subcluster has a higher degree of hierarchy than the NW
subcluster. Combining the dendrogram and line fitting analyses reveals two
distinct relations: a flat relation between nonthermal velocity dispersion and
size, and a positive correlation between variation in velocity centroids and
size. The two relations imply a characteristic depth of 0.15 pc for the cloud.
Furthermore, we have identified six filaments in the SE subcluster. These
filaments have lengths of 0.2 pc and widths of 0.03 pc, which is smaller than a
characteristic width of 0.1 pc suggested by Herschel observations. The
filaments can be classified into two types based on their properties. The first
type, located in the northeast of the SE subcluster, has larger velocity
gradients, smaller masses, and nearly critical mass-per-unit-length ratios. The
other type, located in the southwest of the SE subcluster, has the opposite
properties. Several YSOs are formed along two filaments which have
supercritical mass per unit length ratios, while filaments with nearly critical
mass-per-unit-length ratios are not associated with YSOs, suggesting that stars
are formed on gravitationally unstable filaments.
