The Fornax Deep Survey (FDS) with VST XII: Low surface brightness dwarf galaxies in the Fornax cluster

TL;DR

This study uses advanced detection techniques to identify 265 new low surface brightness dwarf galaxies in the Fornax cluster, expanding the catalog and analyzing their properties and distribution to understand their evolution and contribution to the cluster's luminosity function.

Contribution

The paper introduces the application of Max-Tree Objects (MTO) for improved detection of LSB dwarfs, increasing catalog completeness and accuracy in the Fornax cluster.

Findings

Detected 265 new LSB dwarf galaxies, increasing the total to 821.

Extended the luminosity function with a faint-end slope of -1.38.

Found higher LSB galaxy concentration in the cluster center, supporting tidal interaction theories.

Abstract

In this work we use Max-Tree Objects, (MTO) on the FDS data in order to detect previously undetected Low surface brightness (LSB) galaxies. After extending the existing Fornax dwarf galaxy catalogs with this sample, our goal is to understand the evolution of LSB dwarfs in the cluster. We also study the contribution of the newly detected galaxies to the faint end of the luminosity function. We test the detection completeness and parameter extraction accuracy of MTO. We then apply MTO to the FDS images to identify LSB candidates. The identified objects are fitted with 2D S\'ersic models using GALFIT and classified based on their morphological appearance, colors, and structure. With MTO, we are able to increase the completeness of our earlier FDS dwarf catalog (FDSDC) 0.5-1 mag deeper in terms of total magnitude and surface brightness. Due to the increased accuracy in measuring sizes of the detected objects, we also add many small galaxies to the catalog that were previously excluded as their outer parts had been missed in detection. We detect 265 new LSB dwarf galaxies in the Fornax cluster, which increases the total number of known dwarfs in Fornax to 821. Using the extended catalog, we show that the luminosity function has a faint-end slope of -1.38+/-0.02. We compare the obtained luminosity function with different environments studied earlier using deep data but do not find any significant differences. On the other hand, the Fornax-like simulated clusters in the IllustrisTNG cosmological simulation have shallower slopes than found in the observational data. We also find several trends in the galaxy colors, structure, and morphology that support the idea that the number of LSB galaxies is higher in the cluster center due to tidal forces and the age dimming of the stellar populations. The same result also holds for the subgroup of large LSB galaxies, so-called ultra-diffuse galaxies.