Probing the Low Surface Brightness Dwarf Galaxy Population of the Virgo Cluster

TL;DR

This study uses the NGVS data and an optimized detection method to identify 443 dwarf galaxies in the Virgo cluster, including 303 new detections, and analyzes their luminosity function to compare with galaxy formation models.

Contribution

It introduces a refined detection algorithm for low surface brightness dwarf galaxies and provides a comprehensive catalog of new Virgo cluster dwarf galaxies.

Findings

Identified 443 dwarf galaxies, 303 of which are new detections.

Surface density of new detections decreases with distance from cluster center.

Faint end slope of the luminosity function is -1.35+/-0.03, consistent with previous studies.

Abstract

We have used public data from the Next Generation Virgo Survey (NGVS) to investigate the dwarf galaxy population of the Virgo cluster beyond what has previously been discovered. We initially mask and smooth the data, and then use the object detection algorithm Sextractor to make our initial dwarf galaxy selection. All candidates are then visually inspected to remove artefacts and duplicates. We derive Sextractor parameters to best select low surface brightness galaxies using g band central surface brightness values of 22.5 to 26.0 mag sq arc sec and exponential scale lengths of 3.0 - 10.0 arc sec to identify 443 cluster dwarf galaxies - 303 of which are new detections. These new detections have a surface density that decreases with radius from the cluster centre. We also apply our selection algorithm to 'background', non-cluster, fields and find zero detections. In combination, this leads us to believe that we have isolated a cluster dwarf galaxy population. The range of objects we are able to detect is limited because smaller scale sized galaxies are confused with the background, while larger galaxies are split into numerous smaller objects by the detection algorithm. Using data from previous surveys combined with our data, we find a faint end slope to the luminosity function of -1.35+/-0.03, which does not significantly differ to what has previously been found for the Virgo cluster, but is a little steeper than the slope for field galaxies. There is no evidence for a faint end slope steep enough to correspond with galaxy formation models, unless those models invoke either strong feedback processes or use warm dark matter.