Characterizing the outer disk of eXtended-UV galaxies in the optical domain with deep surveys

TL;DR

This study analyzes the optical properties of nine XUV galaxies using deep survey data to classify their outer disks and explore their relation to GLSB galaxies, revealing three distinct families with different characteristics.

Contribution

It introduces a method to classify XUV galaxies based on optical surface brightness profiles and compares their properties to GLSBs, providing new insights into their nature and diversity.

Findings

One third of XUV galaxies meet GLSB criteria.

Remaining XUV galaxies show diverse outer disk profiles.

Color profiles suggest a merger history for NGC1140.

Abstract

Aims : Extended-UV (XUV) galaxies are galaxies presenting an extended outer ultraviolet disks. Although some Giant Low Surface Brightness (GLSB) galaxies are also XUV, their relation has been seldom studied. This work aims to determine whether a sample of nine XUV galaxies can be classified as GLSBs, by analyzing their photometric properties in deep optical images. Method : The method presented here uses optical data from the Dark Energy Survey (DES) to construct surface brightness (SB) profiles for each galaxy. A characteristic UV radius is defined to examine the XUV disks. The surface brightness profiles are fitted using simple exponential functions, and the extracted parameters are compared with the literature to identify possible GLSB galaxies. We examined also other diagnostics, including color profiles. Results : The analysis of the optical surface brightness profiles of XUV galaxies reveal that they can be classified into three different families. One third meet the GLSB criteria in terms of diffuseness, another third are regular, and the remaining have a stronger decline in the outer disk than in the inner disk, opposite to GLSBs. The color profiles allowed us, in addition to distinguish one of the galaxy, NGC1140, likely resulting from a rare dwarf-dwarf merger.