Brought to Light. III. Colors of Disk and Clump Substructures in Dwarf Early-type Galaxies of the Fornax Cluster

Abstract

It has been well established that dwarf early-type galaxies (ETGs) can often exhibit a complex morphology, whereby faint spiral arms, bars, edge-on disks, or clumps are embedded in their main, brighter diffuse body. In our first paper (“Brought to Light I”), we developed a new method for robustly identifying and extracting substructures in deep imaging data of dwarf ETGs in the Virgo galaxy cluster. Here we apply our method to a sample of 23 dwarf ETGs in the Fornax galaxy cluster, out of which 9 have disk-like and 14 have clump-like substructures. According to Fornax Deep Survey (FDS) data, our sample constitutes 12% of all dwarf ETGs in Fornax brighter than M r = − 13 mag, and contains all cases that unequivocally exhibit substructure features. We use g- and r-band FDS images to measure the relative contribution of the substructures to the total galaxy light and to estimate their g − r colors. We find that the substructures typically contribute 8.7% and 5.3% of the total galaxy light in the g and r bands, respectively, within two effective radii. Disk substructures are usually found in dwarf ETGs with redder global colors, and they can be either as red as or bluer than their galaxy’s diffuse component. In contrast, the clump substructures are found in comparatively bluer dwarf ETGs, and they are always bluer than their galaxy’s diffuse component. These results provide further evidence that dwarf ETGs can hide diverse complex substructures, with stellar populations that can greatly differ from those of the dominant diffuse light in which they are embedded.

Evidence for globular cluster collapse after a dwarf-dwarf merger: A potential nuclear star cluster in formation

“…Additionally, by analyzing the residual images after the subtraction of the models we find what look like remnants of an interaction in the form of streams or shells. In this regard, we comment on the presence of substructures with spiral patterns in early-type dwarfs in the recent work by Michea et al (2021Michea et al ( , 2022. These structures are found underneath the main smooth component of dwarf galaxies in the Virgo and Fornax clusters, and Smith et al (2021) propose that they are due to tidal forces causing an underlying disk component to emerge.…”

“…First, UGC 7346 has two clearly distinct stellar components, and not only one dominant smooth component. In addition, the residual substructure in UGC 7346 is considerably more asymmetric than the earlytype dwarf structures by Michea et al (2021Michea et al ( , 2022, which are fairly symmetric. We consider the possibility that the residuals could be a potential dust lane.…”

Evidence for globular cluster collapse after a dwarf-dwarf merger: A potential nuclear star cluster in formation

“…Additionally, by analyzing the residual images after the subtraction of the models we find what look like remnants of an interaction in the form of streams or shells. In this regard, we comment on the presence of substructures with spiral patterns in early-type dwarfs in the recent work by Michea et al (2021Michea et al ( , 2022. These structures are found underneath the main smooth component of dwarf galaxies in the Virgo and Fornax clusters; Smith et al (2021) have proposed that they are due to tidal forces causing an underlying disk component to emerge.…”

“…First, UGC 7346 has two clearly distinct stellar components and not only one dominant smooth component. In addition, the residual substructure in UGC 7346 is considerably more asymmetric than the earlytype dwarf structures by Michea et al (2021Michea et al ( , 2022, which are fairly symmetric. We considered the possibility that the residuals could be a potential dust lane.…”

The Discovery of Blue-cored Dwarf Early-type Galaxies in Isolated Environments

“…They show only a simple appearance of elliptical shape and are thought to be dominated by a homogeneous, old stellar population. However, unexpected complexity and diversity in their characteristics have recently become evident (e.g., Lisker et al 2006bLisker et al , 2006aPaudel et al 2010;Janz et al 2012;Toloba et al 2014;Ann et al 2015;Michea et al 2022).…”