The Spitzer Gould Belt Survey of Large Nearby Interstellar Clouds: Discovery of a Dense Embedded Cluster in the Serpens-Aquila Rift

TL;DR

This paper reports the discovery of a dense, embedded young stellar cluster called Serpens South in the Serpens-Aquila Rift, using Spitzer infrared imaging and molecular line observations, revealing a high protostar fraction and detailed cluster structure.

Contribution

It presents the first identification and characterization of the Serpens South cluster, including its protostar-rich composition and spatial structure, based on infrared and molecular data.

Findings

Serpens South is a dense, protostar-rich embedded cluster.

The cluster is at a distance of approximately 260 pc.

It exhibits a high surface density and close protostar spacing.

Abstract

We report the discovery of a nearby, embedded cluster of young stellar objects, associated filamentary infrared dark cloud, and 4.5 micron shock emission knots from outflows detected in Spitzer/IRAC mid-infrared imaging of the Serpens-Aquila Rift obtained as part of the Spitzer Gould Belt Legacy Survey. We also present radial velocity measurements of the region from molecular line observations obtained with the Submillimeter Array (SMA) that suggest the cluster is co-moving with the Serpens Main embedded cluster 3 degrees to the north. We therefore assign it the same distance, 260 pc. The core of the new cluster, which we call Serpens South, is composed of an unusually large fraction of protostars (77%) at high mean surface density (>430 pc^-2) and short median nearest neighbor spacing (3700 AU). We perform basic cluster structure characterization using nearest neighbor surface density mapping of the YSOs and compare our findings to other known clusters with equivalent analyses available in the literature.