A Large Scale, Low Frequency Murchison Widefield Array Survey of Galactic HII regions between 260< l <\340

TL;DR

This paper presents a comprehensive low-frequency survey of 302 Galactic HII regions using the Murchison Widefield Array, providing detailed physical properties and spectral data to enhance understanding of these ionized regions.

Contribution

It offers the largest uniform low-frequency catalogue of Galactic HII regions, including spectral indices and physical parameters derived from multi-frequency observations.

Findings

Detected 302 HII regions between 260° and 340° longitude.

Derived physical properties like electron density and ionized gas mass.

Identified the transition from optically thin to thick regimes in HII regions.

Abstract

We have compiled a catalogue of HII regions detected with the Murchison Widefield Array (MWA) between 72 and 231MHz. The multiple frequency bands provided by the MWA allow us identify the characteristic spectrum generated by the thermal Bremsstrahlung process in HII regions. We detect 302 HII regions between 260 < l < 340 and report on the positions, sizes, peak, integrated flux density, and spectral indices of these HII regions. By identifying the point at which HII regions transition from the optically thin to thick regime we derive the physical properties including the electron density, ionised gas mass and ionising photon flux, towards 61 HII regions. This catalogue of HII regions represents the most extensive and uniform low frequency survey of HII regions in the Galaxy to date.