An improved method for statistical studies of the internal kinematics of HII regions: the case of M 83

TL;DR

This study analyzes the internal kinematics of 157 HII regions in galaxy M 83 using Halpha emission profiles, emphasizing the importance of instrumental response characterization and revealing a non-linear luminosity-velocity dispersion relation.

Contribution

It introduces an improved method for analyzing HII region kinematics, highlighting the non-linear luminosity-velocity dispersion relation and reinforcing the use of HII regions as standard candles.

Findings

No linear relation in the log(L)-log(sigma) plane, but an upper envelope.

Upper envelope follows log(L)=0.9*log(sigma)+38.1.

Supports HII regions as standard candles at L=10^38.5 ergs.

Abstract

We present the integrated Halpha emission line profile for 157 HII regions in the central 3.4' x 3.4' of the galaxy M 83 (NGC 5236). Using the Fabry-Perot interferometer GHaFaS, on the 4.2 m William Herschel on La Palma, we show the importance of a good characterization of the instrumental response function for the study of line profile shapes. The luminosity-velocity dispersion relation is also studied, and in the log(L)-log(sigma) plane we do not find a linear relation, but an upper envelope with equation log(L)=0.9 *log(sigma)+38.1. For the adopted distance of 4.5 Mpc, the upper envelope appears at the luminosity L=10^38.5 ergs, in full agreement with previous studies of other galaxies, reinforcing the idea of using HII regions as standard candles.