Filaments and ridges in Vela C revealed by Herschel: from low-mass to high-mass star-forming sites

TL;DR

This study uses Herschel observations to analyze the Vela C molecular complex, revealing how different sub-regions and filaments exhibit distinct physical properties and star formation activities, especially highlighting the role of ridges in high-mass star formation.

Contribution

First detailed Herschel-based analysis of Vela C revealing sub-region differences and the significance of ridges in high-mass star formation.

Findings

Vela C is divided into five sub-regions with distinct PDFs.

The Centre-Ridge shows a bimodal temperature PDF and flatter column density PDF.

High-mass stars tend to form in high-density filaments called ridges.

Abstract

We present the first Herschel PACS and SPIRE results of the Vela C molecular complex in the far-infrared and submillimetre regimes at 70, 160, 250, 350, and 500 um, spanning the peak of emission of cold prestellar or protostellar cores. Column density and multi-resolution analysis (MRA) differentiates the Vela C complex into five distinct sub-regions. Each sub-region displays differences in their column density and temperature probability distribution functions (PDFs), in particular, the PDFs of the `Centre-Ridge' and `South-Nest' sub-regions appear in stark contrast to each other. The Centre-Ridge displays a bimodal temperature PDF representative of hot gas surrounding the HII region RCW 36 and the cold neighbouring filaments, whilst the South-Nest is dominated by cold filamentary structure. The column density PDF of the Centre-Ridge is flatter than the South-Nest, with a high column density tail, consistent with formation through large-scale flows, and regulation by self-gravity. At small to intermediate scales MRA indicates the Centre-Ridge to be twice as concentrated as the South-Nest, whilst on larger scales, a greater portion of the gas in the South-Nest is dominated by turbulence than in the Centre-Ridge. In Vela C, high-mass stars appear to be preferentially forming in ridges, i.e., dominant high column density filaments.