A Simple Model for Global HI Profiles of Galaxies

TL;DR

This paper introduces a simple 6-parameter model for characterizing HI spectral lines in galaxies, demonstrating its effectiveness in fitting data and estimating key properties more accurately than traditional methods.

Contribution

The paper presents a new, simple parametric model for HI galaxy spectral lines and validates its utility across different observational scenarios.

Findings

Model fits nearly all THINGS survey profiles.

Model remains robust with added noise.

Provides superior estimates of linewidth and flux.

Abstract

Context. Current and future blind surveys for HI generate large catalogs of spectral lines for which automated characterization would be convenient. Aims. A 6-parameter mathematical model for HI galactic spectral lines is described. The aim of the paper is to show that this model is indeed a useful way to characterize such lines. Methods. The model is fitted to spectral lines extracted for the 34 spiral galaxies of the recent high-definition THINGS survey. Three scenarios with different instrumental characteristics are compared. Quantities obtained from the model fits, most importantly line width and total flux, are compared with analog quantities measured in more standard, non-parametric ways. Results. The model is shown to be a good fit to nearly all the THINGS profiles. When extra noise is added to the test spectra, the fits remain consistent; the model-fitting approach is also shown to return superior estimates of linewidth and flux under such conditions.