A Synthetic 21-cm Galactic Plane Survey of an SPH Galaxy Simulation

TL;DR

This paper presents a synthetic 21-cm Galactic Plane Survey generated from SPH galaxy simulations, aiming to study atomic gas dynamics and molecular cloud formation in the Outer Galaxy's Perseus Arm.

Contribution

It introduces a novel method of creating synthetic HI survey data from SPH simulations using radiative transfer, enabling detailed study of gas behavior at spiral arm interfaces.

Findings

Synthetic HI data reveals shock interactions in spiral arms.

Identification of HI self-absorption features at shock sites.

Insights into cold atomic gas role in molecular cloud formation.

Abstract

We have created synthetic neutral hydrogen (HI) Galactic Plane Survey data cubes covering 90 degrees < l < 180 degrees, using a model spiral galaxy from SPH simulations and the radiative transfer code TORUS. The density, temperature and other physical parameters are fed from the SPH simulation into TORUS, where the HI emissivity and opacity are calculated before the 21-cm line emission profile is determined. Our main focus is the observation of Outer Galaxy `Perseus Arm' HI, with a view to tracing atomic gas as it encounters shock motions as it enters a spiral arm interface, an early step in the formation of molecular clouds. The observation of HI self-absorption features at these shock sites (in both real observations and our synthetic data) allows us to investigate further the connection between cold atomic gas and the onset of molecular cloud formation.