On the stellar kinematics and mass of the Virgo ultradiffuse galaxy VCC 1287

Abstract

Here, we present a kinematical analysis of the Virgo cluster ultradiffuse galaxy (UDG) VCC 1287 based on data taken with the Keck Cosmic Web Imager (KCWI). We confirm VCC 1287’s association both with the Virgo cluster and its globular cluster (GC) system, measuring a recessional velocity of 1116 ± 2 km s−1. We measure a stellar velocity dispersion (19 ± 6 km s−1) and infer both a dynamical mass ($1.11^{+0.81}_{-0.81} \times 10^{9} \ \mathrm{M_{\odot }}$) and mass-to-light ratio (M/L) ($13^{+11}_{-11}$) within the half-light radius (4.4 kpc). This places VCC 1287 slightly above the well-established relation for normal galaxies, with a higher M/L for its dynamical mass than normal galaxies. We use our dynamical mass, and an estimate of GC system richness, to place VCC 1287 on the GC number–dynamical mass relation, finding good agreement with a sample of normal galaxies. Based on a total halo mass derived from GC counts, we then infer that VCC 1287 likely resides in a cored or low-concentration dark matter halo. Based on the comparison of our measurements to predictions from simulations, we find that strong stellar feedback and/or tidal effects are plausibly the dominant mechanisms in the formation of VCC 1287. Finally, we compare our measurement of the dynamical mass with those for other UDGs. These dynamical mass estimates suggest relatively massive haloes and a failed galaxy origin for at least some UDGs.

Implications for Galaxy Formation Models from Observations of Globular Clusters around Ultra-Diffuse Galaxies

“…The large population of UDGs in Coma and their survival in the cluster environment suggested large total masses, 𝑀 total , despite their modest stellar masses (van Dokkum et al 2015a). Further investigations and estimations of the total mass of UDGs using stellar kinematics (van Dokkum et al 2019;Chilingarian et al 2019;Müller et al 2020;Gannon et al 2020;Forbes et al 2021), globular clusters (GCs) dynamics Toloba et al 2018), H I kinematics (Trujillo et al 2017;Leisman et al 2017;Papastergis et al 2017;Mancera Piña et al 2020;Poulain et al 2021), weak ★ E-mail: teymur.saif@gmail.com gravitational lensing (Sifón et al 2018), UDG abundance in clusters (Amorisco 2018), scaling relations (Zaritsky 2017), and X-ray observations (Lee et al 2020) found that most UDGs are dark matter dominated objects with halo masses similar to those of dwarf galaxies and dynamical mass-to-light ratios that span a wide range between a few tens to a few thousands. The most massive known UDGs have 𝑀 total ∼ 10 11 𝑀 , comparable to the most massive dwarf galaxies, such as the LMC (Erkal et al 2019).…”

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

“…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).…”

“…The data were initially reduced using the KCWI data reduction pipeline (KDERP). Following this we took the non-sky subtracted, differential atmospheric refraction corrected and standard star calibrated 'ocubes' and performed the trimming and extra flat fielding steps described in Gannon et al (2020). Based on fits such as these we measure the recessional velocities and velocity dispersions as reported in Table 2.…”

“…In order to extract stellar kinematics from our spectra we fitted the spectra using the method described in Gannon et al (2020) which utilises the code pPXF (Cappellari 2017). Briefly, the spectrum was fitted with the high resolution Coelho (2014) synthetic spectral library using 241 differing input configurations for pPXF.…”

“…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.…”