YSO jets in the Galactic Plane from UWISH2: IV - Jets and outflows in Cygnus-X

TL;DR

This study used infrared survey data to identify over 570 outflows from young stars in Cygnus-X, significantly expanding the known sample and providing detailed statistical properties of these outflows and their sources.

Contribution

It presents the largest unbiased sample of outflows in Cygnus-X, revealing new outflows and detailed characteristics, and offers insights into the properties and evolution of young stellar objects.

Findings

Identified 572 outflows, with 465 new discoveries, increasing known objects by over 430%.

Most outflows are bipolar, with median length of 0.45pc and asymmetrical lobes.

Half of the driving sources are protostars, with some showing variability in the K-band.

Abstract

We have performed an unbiased search for outflows from young stars in Cygnus-X using 42 deg$^2$ of data from the UKIRT Widefield Infrared Survey for H$_2$ (UWISH2 survey), to identify shock-excited near-IR H$_2$ emission in the 1$-$0 S(1) 2.122 $\mu$m line. We uncovered 572 outflows, of which 465 are new discoveries, increasing the number of known objects by more than 430%. This large and unbiased sample allows us to statistically determine the typical properties of outflows from young stars. We found 261 bipolar outflows and 16% of these are parsec-scale. The typical bipolar outflow is 0.45pc in length and has gaps of 0.025 to 0.1pc between large knots. The median luminosity in the 1$-$0 S(1) line is 10$^{-3}$ L$_{\odot}$. The bipolar flows are typically asymmetrical, with the two lobes misaligned by 5$^{\circ}$, one lobe 30% shorter than the other, and one lobe twice as bright as the other. Of the remaining outflows, 152 are single-sided and 159 are groups of extended, shock-excited H$_2$ emission without identifiable driving sources. Half of all driving sources have sufficient WISE data to determine their evolutionary status as either protostars (80%) or classical T-Tauri stars (20%). One fifth of the driving sources are variable by more than 0.5mag in the K-band continuum over several years. Several of the newly-identified outflows provide excellent targets for follow up studies. We particularly encourage the study of the outflows and young stars identified in a bright-rimmed cloud near IRAS 20294$+$4255, which seems to represent a textbook example of triggered star formation.