Radio continuum emission and water masers towards CB 54

TL;DR

This study uses high-resolution radio observations to identify water masers and free-free emission in CB 54, revealing protostars and their associated outflows, and proposing shock-ionization as the emission mechanism.

Contribution

First high-resolution radio and water maser observations of CB 54, linking masers to protostars and outflows, and suggesting shock-ionization as the origin of radio emission.

Findings

Detected a compact radio source aligned with a mid-IR object.

Water masers are associated with two mid-IR sources, indicating protostars.

Proposed shock-ionization as the mechanism for radio emission.

Abstract

We present high angular resolution observations of water masers at 1.3 cm and radio continuum emission at 1.3, 3.6 and 6 cm towards the Bok globule CB 54 using the Very Large Array. At 1.3 cm, with subarsecond angular resolution, we detect a radio continuum compact source located to the south-west of the globule and spatially coincident with a mid-infrared embedded object (MIR-b). The spectral index derived between 6 and 1.3 cm (alpha=0.3+/-0.4) is flat, consistent with optically thin free-free emission from ionized gas. We propose the shock-ionization scenario as a viable mechanism to produce the radio continuum emission observed at cm frequencies. Water masers are detected at two different positions separated by 2.3'', and coincide spatially with two mid-infrared sources: MIR-b and MIR-c. The association of these mid-IR sources with water masers confirms that they are likely protostars undergoing mass-loss, and they are the best candidate as driving sources of the molecular outflows in the region.