The Way We Measure: Comparison of Methods to Derive Radial Surface Brightness Profiles

TL;DR

This study compares three methods for deriving radial surface brightness profiles in face-on spiral galaxies, finding that equivalent profiles closely match elliptical averaging, while principle axis summation aligns better with edge-on galaxy profiles.

Contribution

It introduces and evaluates a new method, principle axis summation, and compares it with traditional elliptical averaging and equivalent profiles for galaxy surface photometry.

Findings

Equivalent profiles match well with elliptical averaging.

Principle axis summation aligns better with edge-on galaxy profiles.

Elliptical averaging remains a valid method for face-on galaxies.

Abstract

The breaks and truncations in the luminosity profile of face-on spiral galaxies offer valuable insights in their formation history. The traditional method of deriving the surface photometry profile for face-on galaxies is to use elliptical averaging. In this paper, we explore the question whether elliptical averaging is the best way to do this. We apply two additional surface photometry methods, one new: principle axis summation, and one old that has become seldom used: equivalent profiles. These are compared to elliptically averaged profiles using a set of 29 face-on galaxies. We find that the equivalent profiles match extremely well with elliptically averaged profiles, confirming the validity of using elliptical averaging. The principle axis summation offers a better comparison to edge-on galaxies.