A simple model for global H i profiles of galaxies

¹ Argelander Institut für Astronomie, Universität Bonn, auf dem Hügel 71, 53121 Bonn, Germany
e-mail: ims@astro.uni-bonn.de
² Astrophysics, Cosmology and Gravity Centre, Department of Astronomy, University of Cape Town, Private Bag X3, 7701 Rondebosch, South Africa
³ Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, The Netherlands
⁴ Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands

Received: 9 February 2014
Accepted: 28 April 2014

Abstract

Context. Current and future blind surveys for H i generate large catalogs of spectral lines for which automated characterisation would be convenient.

Aims. A 6-parameter mathematical model for H i galactic spectral lines is described. The aim of the paper is to show that this model is indeed a useful way to characterise 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.