# The Southern HII Region Discovery Survey (SHRDS): Pilot Survey

## TL;DR

The SHRDS pilot survey used radio observations to confirm and estimate distances of HII regions in the southern Galactic plane, demonstrating the effectiveness of infrared and radio selection methods.

## Contribution

This study presents the first pilot survey of the SHRDS, validating candidate HII regions and demonstrating the survey's capability to detect radio recombination lines in the southern sky.

## Key findings

- Detected radio recombination lines from 36 of 53 candidates
- Confirmed candidates as true HII regions
- Estimated distances to HII regions

## Abstract

The Southern HII Region Discovery Survey (SHRDS) is a survey of the third and fourth quadrants of the Galactic plane that will detect radio recombination line and continuum emission at cm-wavelengths from several hundred HII region candidates using the Australia Telescope Compact Array. The targets for this survey come from the WISE Catalog of Galactic HII Regions, and were identified based on mid-infrared and radio continuum emission. In this pilot project, two different configurations of the Compact Array Broad Band receiver and spectrometer system were used for short test observations. The pilot surveys detected radio recombination line emission from 36 of 53 HII region candidates, as well as seven known \hii regions that were included for calibration. These 36 recombination line detections confirm that the candidates are true HII regions, and allow us to estimate their distances.