A photometric and kinematic analysis of UDG1137+16 (dw1137+16): Probing ultradiffuse galaxy formation in a group environment

Abstract

The dominant physical formation mechanism(s) for ultra-diffuse galaxies (UDGs) is still poorly understood. Here, we combine new, deep imaging from the Jeanne Rich Telescope with deep integral field spectroscopy from the Keck II telescope to investigate the formation of UDG1137+16. Our new analyses confirm both its environmental association with the low density UGC 6594 group, along with its large size of 3.3 kpc and status as a UDG. The new imaging reveals two distinct stellar components for UDG1137+16, indicating that a central stellar body is surrounded by an outer stellar envelope undergoing tidal interaction. Both the components have approximately similar stellar masses. From our integral field spectroscopy we measure a stellar velocity dispersion within the half-light radius (15 ± 4 km s−1) and find that UDG1137+16 is similar to some other UDGs in that it is likely dark matter dominated. Incorporating literature measurements, we also examine the current state of UDG observational kinematics. Placing these data on the central stellar velocity dispersion – stellar mass relation, we suggest there is little evidence for UDG1137+16 being created through a strong tidal interaction. Finally, we investigate the constraining power current dynamical mass estimates (from stellar and globular cluster velocity dispersions) have on the total halo mass of UDGs. As most are measured within the half-light radius, they are unable to accurately constrain UDG total halo masses.

Formation of an ultra-diffuse galaxy in the stellar filaments of NGC 3314A: Caught in the act?

“…However, a larger DM amount was inferred for several UDGs (e.g. van Dokkum et al 2019;Forbes et al 2020a;Gannon et al 2021). In contrast, some UDGs with very low DM content have also been discovered (e.g.…”

Ultra-Diffuse Galaxies in the Perseus Cluster: Comparing Galaxy Properties with Globular Cluster System Richness

“…In the case of cored halos, lone dynamical masses at a single radius poorly constrain the total halo mass of the UDG (see further Gannon et al 2021). For example, it is clear that our dynamical mass measurement for R84 agrees well with cored halos of both mass 10 10 M and 10 11 M and so cannot constrain the total halo mass of the UDG (Figure 7, bottom panel).…”

“…Mass measurements coming from stellar, and GC velocity dispersions, for many GC-rich UDGs confirm their dark matter dominated nature (van Dokkum et al 2016;Toloba et al 2018;van Dokkum et al 2019b;Martín-Navarro et al 2019;Forbes et al 2021;Gannon et al 2020Gannon et al , 2021. When used in comparison to a total halo mass estimate coming from GC numbers they can be used to infer basic halo properties (e.g., cusp vs. core) (Toloba et al 2018;Gannon et al 2020Gannon et al , 2021Forbes et al 2021).…”

“…Literature UDG properties, barring GC counts, are from appendix A of Gannon et al (2021) and the references therein. For the Virgo cluster UDG VCC 1287 we use the GC system counts of 𝑁 GC = 22 ± 8).…”

“…A 10" bar is also included in each panel. Danieli et al 2019;Martín-Navarro et al 2019;Müller et al 2020;Gannon et al 2020Gannon et al , 2021Forbes et al 2021), to look for differences in their dark matter mass as expected by their GC numbers. We use their recessional velocities to place them in the phase space diagram for the Perseus cluster in order to explore differences in their infall times.…”