Dense Clumps and Candidates for Molecular Outflows in W40

TL;DR

This study uses CO and HCO+ observations to analyze the complex velocity structure of W40, identifying dense clumps and candidate outflows, and proposing an updated 3D model of the region's molecular environment.

Contribution

The paper provides the first detailed analysis of molecular outflows and dense clumps in W40 using multiple molecular lines and presents an updated 3D model of the region.

Findings

Identified 13 high-velocity gas regions as candidate outflows.

Detected six dense clumps with estimated physical parameters.

Found complex velocity components indicating interactions with the HII region.

Abstract

We report results of the CO(J=3-2) and HCO+(J=4-3) observations of the W40 HII region with the ASTE 10 m telescope (HPBW~22 arcsec) to search for molecular outflows and dense clumps.We found that the velocity field in the region is highly complex, consisting of at least four distinct velocity components at V LSR ~ 3, 5, 7, and 10 km/s. The ~7 km/s component represents the systemic velocity of cold gas surroundingthe entire region, and causes heavy absorption in the CO spectra over the velocity range 6 <V LSR< 9 km/s. The ~5 and ~10 km/s components exhibit high CO temperature (>40 K) and are found mostly around the HII region, suggesting that these components are likely to be tracing dense gas interacting with the expanding shell around the HII region. Based on the CO data, we identified 13 regions of high velocity gas which we interpret as candidate outflow lobes. Using the HCO+ data, we also identified six clumps and estimated their physical parameters. On the basis of the ASTE data and near-infrared images from 2MASS, we present an updated three-dimensional model of this region. In order to investigate molecular outflows in W40, the SiO (J=1-0, v=0) emission line and some other emission lines at 40 GHz were also observed with the 45 m telescope at the Nobeyama Radio Observatory, but they were not detected at the present sensitivity.