The orientation of elliptical galaxies

TL;DR

This paper presents a Bayesian method to determine the orientations of elliptical galaxies by combining photometric data with triaxial models, providing insights into their intrinsic alignments.

Contribution

It introduces a novel Bayesian approach that estimates galaxy orientations by integrating likelihoods over shape parameters using photometric profiles.

Findings

Orientation estimates depend on the position angle differences in photometric profiles.

Applied method to ten galaxies, revealing alignments of principal axes in some cases.

The position angle difference is crucial for constraining galaxy orientations.

Abstract

We determine the orientations of the light distribution of individual elliptical galaxies by combining the profiles of photometric data from the literature with triaxial models. The orientation is given by a Bayesian probability distribution. The likelihood of obtaining the data from a model is a function of the parameters describing the intrinsic shape and the orientation. Integrating the likelihood over the shape parameters, we obtain the estimates of the orientation. We find that the position angle difference between the two suitably chosen points from the profiles of the photometric data plays a key role in constraining the orientation of the galaxy. We apply the methodology to a sample of ten galaxies. The alignment of the intrinsic principle axes of the NGC 3379, 4486 and NGC 5638 are studied.