Submillimeter Array High-angular Resolution Observations of the Monoceros R2 Star Forming Cluster

TL;DR

This study uses high-resolution submillimeter observations to analyze the MonR2 star-forming complex, revealing new outflows, chemical activity, and insights into the protostellar environment and cluster formation mechanisms.

Contribution

First high-angular resolution submillimeter study of MonR2, identifying new outflows, characterizing protostellar sources, and supporting the competitive accretion model of cluster formation.

Findings

Discovered 11 new molecular outflows in MonR2.

Identified IRS5 as a chemically active hot core with a protostar of ~7 M_Sun.

Outflows contribute to turbulence and support the cluster formation scenario.

Abstract

We present the first high-angular resolution study of the MonR2 star-forming complex carried out with the Submillimeter Array at (sub-)millimeter wavelengths. We image the continuum and molecular line emission toward the young stellar objects in MonR2 at 0.85mm and 1.3mm, with resolutions ranging from 0.5" to ~3". While free-free emission dominates the IRS1 and IRS2 continuum, dust thermal emission prevails for IRS3 and IRS5, giving envelope masses of ~0.1-0.3 M_Sun. IRS5 splits into at least two sub-arcsecond scale sources, IRS5B and the more massive IRS5A. Our 12CO(2-1) images reveal 11 previously unknown molecular outflows in the MonR2 clump. Comparing these outflows with known IR sources in the IRS5 and IRS3 subclusters allows for tentative identification of driving stars. Line images of molecular species such as CH3CN or CH3OH show that, besides IRS3 (a well-known hot molecular core), IRS5 is also a chemically active source in the region. The gas excitation temperature derived from CH3CN lines toward IRS5 is 144 \pm 15 K, indicating a deeply embedded protostar at the hot-core evolutionary stage. SED fitting of IRS5 gives a mass of ~7 M_Sun and a luminosity of 300 L_Sun for the central source. The derived physical properties of the CO outflows suggest that they contribute to the turbulent support of the MonR2 complex and to the gas velocity dispersion in the clump's center. The detection of a large number of CO outflows widespread across the region supports the competitive accretion scenario as origin of the MonR2 star cluster.