The Distance and Dynamical History of the Virgo Cluster Ultradiffuse Galaxy VCC 615

Abstract

We use deep Hubble Space Telescope imaging to derive a distance to the Virgo Cluster ultradiffuse galaxy (UDG) VCC 615 using the tip of the red giant branch (TRGB) distance estimator. We detect 5,023 stars within the galaxy, down to a 50% completeness limit of F814W = 28.0, using counts in the surrounding field to correct for contamination due to background sources and Virgo intracluster stars. We derive an extinction-corrected F814W tip magnitude of $m_{\mathrm{tip},0}=27.19_{-0.05}^{+0.07}$, yielding a distance of $d=17.7_{-0.4}^{+0.6}$ Mpc. This places VCC 615 on the far side of the Virgo Cluster ($d_{\mathrm{Virgo}}=16.5Mpc$), at a Virgocentric distance of 1.3 Mpc and near the virial radius of the main body of Virgo. Coupling this distance with the galaxy's observed radial velocity, we find that VCC 615 is on an outbound trajectory, having survived a recent passage through the inner parts of the cluster. Indeed, our orbit modeling gives a 50% chance the galaxy passed inside the Virgo core (r<620 kpc) within the past Gyr, although very close passages directly through the cluster center (r<200 kpc) are unlikely. Given VCC 615's undisturbed morphology, we argue that the galaxy has experienced no recent and sudden transformation into a UDG due to the cluster potential, but rather is a long-lived UDG whose relatively wide orbit and large dynamical mass protect it from stripping and destruction by Virgo cluster tides. Finally, we also describe the serendipitous discovery of a nearby Virgo dwarf galaxy projected 90 arcseconds (7.2 kpc) away from VCC 615.

18 pages, 10 figures, accepted for publication in The Astrophysical Journal

References in corpus (25)

• Array Programming with NumPy
• Statistical applications of the multivariate skew-normal distribution
• Forty-Seven Milky Way-Sized, Extremely Diffuse Galaxies in the Coma Cluster
• NIHAO XI: Formation of Ultra-Diffuse Galaxies by outflows
• emcee v3: A Python ensemble sampling toolkit for affine-invariant MCMC
• A High Stellar Velocity Dispersion and ~100 Globular Clusters for the Ultra Diffuse Galaxy Dragonfly 44
• The Panchromatic Hubble Andromeda Treasury X. Ultraviolet to Infrared Photometry of 117 Million Equidistant Stars
• A second galaxy missing dark matter in the NGC1052 group
• The Burrell Schmidt Deep Virgo Survey: Tidal Debris, Galaxy Halos, and Diffuse Intracluster Light in the Virgo Cluster
• Tip of the Red Giant Branch Distances. I. Optimization of a Maximum Likelihood Algorithm
• Still Missing Dark Matter: KCWI High-Resolution Stellar Kinematics of NGC1052-DF2
• Extensive Globular Cluster Systems Associated with Ultra Diffuse Galaxies in the Coma Cluster
• The Next Generation Virgo Cluster Survey (NGVS). XXX. Ultra-Diffuse Galaxies and their Globular Cluster Systems
• The Metallicity Distribution of Intracluster Stars in Virgo
• The brightness of the Red Giant Branch tip: Theoretical framework, a set of reference models, and predicted observables
• The Tip of the Red Giant Branch Distances to Type Ia Supernova Host Galaxies. IV. Color Dependence and Zero-Point Calibration
• The ALFALFA "Almost Darks" Campaign: Pilot VLA HI Observations of Five High Mass-to-Light Ratio Systems
• Sharpening the Tip of the Red Giant Branch
• Stellar Kinematics and Structural Properties of Virgo Cluster Dwarf Early-Type Galaxies from the SMAKCED Project II. The Survey and a Systematic Analysis of Kinematic Anomalies and Asymmetries
• A Tip of the Red Giant Branch Distance of $22.1\pm 1.2$ Mpc to the Dark Matter Deficient Galaxy NGC1052-DF2 from 40 Orbits of Hubble Space Telescope Imaging
• Dwarf galaxies in the MATLAS survey: Hubble Space Telescope observations of the globular cluster system in the ultra-diffuse galaxy MATLAS-2019
• Stellar Velocity Dispersion and Dynamical Mass of the Ultra-Diffuse Galaxy NGC 5846_UDG1 from the Keck Cosmic Web Imager
• Globular clusters as tracers of the dark matter content of dwarfs in galaxy clusters
• The Fate of Gas rich Satellites in Clusters
• HST Imaging of the Local Volume Dwarf Galaxies Pisces A&B: Prototypes for Local Group Dwarfs

Cited by in corpus (6)

• An evolutionary continuum from nucleated dwarf galaxies to star clusters
• The Next Generation Virgo Cluster Survey (NGVS). XXXV. First Kinematical Clues of Overly-Massive Dark Matter Halos in Several Ultra-Diffuse Galaxies in the Virgo Cluster
• Keck Spectroscopy of the Coma Cluster Ultra-Diffuse Galaxy Y358: Dynamical Mass in a Wider Context
• Looking into the faintEst WIth MUSE (LEWIS): Exploring the nature of ultra-diffuse galaxies in the Hydra-I cluster II. Stellar kinematics and dynamical masses
• Looking into the faintEst WIth MUSE (LEWIS): Exploring the nature of ultra-diffuse galaxies in the Hydra I cluster III. Untangling UDG 32 from the stripped filaments of NGC 3314A with multi-wavelength data
• Looking into the faintEst WIth MUSE (LEWIS): on the nature of ultra-diffuse galaxies in the Hydra I cluster. V. Integrated stellar population properties