YSO jets in the Galactic Plane from UWISH2: V - Jets and Outflows in M17

TL;DR

This study uses UWISH2 survey data to identify and analyze 48 outflows in the M17 complex, revealing that most are driven by actively accreting protostars, with many being newly discovered and concentrated in the star-forming M17SWex region.

Contribution

First comprehensive analysis of H2 emission outflows in M17 using UWISH2 data, identifying 48 new outflows and characterizing their driving sources and spatial distribution.

Findings

93% of outflows are new discoveries.

90% of driving sources are protostars.

Outflows are concentrated in the M17SWex region.

Abstract

Jets and outflows are the first signposts of stellar birth. Emission in the H2 1-0S(1) line at 2.122 micron is a powerful tracer of shock excitation in these objects. Here we present the analysis of 2.0 x 0.8 square degrees data from the UK Widefield Infrared Survey for H2 (UWISH2) in the 1-0S(1) line to identify and characterize the outflows of the M17 complex. We uncover 48 probable outflows, of which, 93 per cent are new discoveries. We identified driving source candidates for 60 per cent of the outflows. Among the driving source candidate YSOs: 90 per cent are protostars and the reminder 10 per cent are Class II YSOs. Comparing with results from other surveys, we suggest that H2 emission fades very quickly as the objects evolve from protostars to pre-main-sequence stars. We fit SED models to 14 candidate outflow driving sources and conclude that the outflows of our sample are mostly driven by moderate-mass YSOs that are still actively accreting from their protoplanetary disc. We examined the spatial distribution of the outflows with the gas and dust distribution of the complex, and observed that the filamentary dark-cloud "M17SWex" located at the south-western side of the complex, is associated with a greater number of outflows. We find our results corroborate previous suggestions, that in the M17 complex, M17SWex is the most active site of star formation. Several of our newly identified outflow candidates are excellent targets for follow up studies to better understand very early phase of protostellar evolution.