Publication Date:
2014-01-29
Description:
Accurate parametrization of galaxies detected in the 21-cm H i emission is of fundamental importance to the measurement of commonly used indicators of galaxy evolution, including the Tully–Fisher relation and the H i mass function. Here, we propose a new analytic function, named the ‘busy function’, that can be used to accurately describe the characteristic double-horn H i profile of many galaxies. The busy function is a continuous, differentiable function that consists of only two basic functions, the error function, erf( x ), and a polynomial, | x | n , of degree n ≥ 2. We present the basic properties of the busy function and illustrate its great flexibility in fitting a wide range of H i profiles from the Gaussian profiles of dwarf galaxies to the broad, asymmetric double-horn profiles of spiral galaxies. Applications of the busy function include the accurate and efficient parametrization of observed H i spectra of galaxies and the construction of spectral templates for simulations and matched-filtering algorithms. We demonstrate the busy function's power by automatically fitting it to the H i spectra of 1000 galaxies from the HI Parkes All-Sky Survey (HIPASS) Bright Galaxy Catalog, using our own c / c ++ implementation, and comparing the resulting parameters with the catalogued ones. We also present two methods for determining the uncertainties of observational parameters derived from the fit.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
Permalink
