# CO Outflow Candidates Toward the W3/4/5 Complex I: The Sample and its Spatial Distribution

## TL;DR

This large-scale survey identified 459 CO outflow candidates in the W3/4/5 complex and surroundings, revealing star formation activity concentrated in Galactic spiral arms, especially in the Perseus arm, with detailed spatial distribution insights.

## Contribution

The paper presents the first extensive CO outflow candidate catalog for the W3/4/5 complex and analyzes their spatial distribution across different Galactic arms.

## Key findings

- Most outflow candidates are in the Perseus arm, indicating active star formation.
- Star formation is concentrated in spiral arms, especially in the Perseus arm.
- Filamentary structures host many outflow candidates in interarm regions.

## Abstract

Using the Purple Mountain Observatory Delingha 13.7 m telescope, we conducted a large-scale $^{12}$CO $\left(J=1 \rightarrow 0\right)$ outflow survey (over $\sim$ 110 deg$^2$) toward the W3/4/5 complex and its surroundings. In total, 459 outflow candidates were identified. Approximately 62\% (284) were located in the Perseus arm, including W3/4/5 complex and its surroundings, while $\sim$ 35\% (162) were located in the Local arm, $\sim$ 1\% (5) in the Outer arm, and $\sim$ 2\% (8) in two interarm regions. This result indicated that star formation was concentrated in the Galactic spiral arms. The detailed spatial distribution of the outflow candidates showed that the Perseus arm presented the most active star formation among the study regions. The W3/4/5 complex is a great region to research massive star formation in a triggered environment. A key region, which has been well-studied by other researches, is in the eastern high-density W3 complex that neighbors the W4 complex. Two shell-like structures in the Local arm contain candidates that can be used to study the impact on star formation imposed by massive or intermediate-mass stars in relatively isolated systems. The majority of outflow candidates in the two interarm regions and the Outer arm are located in filamentary structures.