ALMA Observations of SMM11 Reveal an Extremely Young Protostar in Serpens Main Cluster

TL;DR

This paper reports the discovery of SMM11, an extremely young Class 0 protostar in Serpens Main, observed with ALMA, showing a bipolar outflow, cold temperature, and features indicating it is a transitional object just after the second collapse.

Contribution

First ALMA observation of SMM11 revealing its extremely young protostellar stage with detailed outflow and envelope characteristics.

Findings

SMM11 is a Class 0 protostar with a collimated bipolar outflow.

The protostar is extremely cold with T_bol=26 K and low luminosity.

High outflow velocity suggests it is a transitional object after second collapse.

Abstract

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.