John P. Blakeslee

The Next Generation Virgo Cluster Survey (NGVS) is a deep, high-resolution imaging campaign that used the 1 deg ² MegaCam instrument on the Canada–France–Hawaii Telescope to carry out a comprehensive optical survey of the Virgo cluster, from its core to its virial radius. The NGVS covers a contiguous area of 104 deg ² (8.63 Mpc ² at the 16.5 Mpc distance of Virgo) in the u *, g , i , and z bands, with additional limited coverage in r . In this paper, we present the final catalog of Virgo galaxies across the entire NGVS area. The catalog includes 3680 galaxies considered to be bona fide members of the cluster, spanning a factor of 2.5 million in luminosity, from g = 8.42 mag to g = 24.41 mag ( M _g = −22.67 mag to M _g = −6.68 mag). With 2100 previously uncataloged galaxies, the NGVS catalog augments the number of known Virgo members by a factor of 2.3. The catalog is complete down to g = 18.6 mag ( M _g = −12.5 mag, corresponding to a stellar mass M _⋆ ∼ 1.6 × 10 ⁷ M _⊙ for an old stellar population) and 50% complete at g = 22.0 mag ( M _g = −9.1 mag, M _⋆ ∼ 6.2 × 10 ⁵ M _⊙ ), 3 mag deeper than the venerable Virgo Cluster Catalog (VCC), which for over 40 yr has served as the reference standard for Virgo. Photometric and structural parameters are derived for all NGVS galaxies and presented in a series of tables, alongside nuclear and morphological classification, as well as stellar masses and, when available, radial velocities.

We present the methods and data for a detailed structural analysis of over 600 ultracompact dwarf (UCD) galaxy candidates in the Virgo Cluster, based on deep ground-based imaging from the Next Generation Virgo Cluster Survey and archival Hubble Space Telescope (HST) Advanced Camera for Surveys imaging. Our goal is to test two main formation scenarios—whether UCDs are massive globular clusters (GCs) or the remnant nuclei of tidally stripped dwarf galaxies (nucleated dwarf elliptical galaxies, dEs)—by analyzing their morphologies and searching for extended stellar envelopes. We find that over 10% of Virgo UCD candidates exhibit two-component profiles with extended outer structures of R _e ∼ 30–300 pc that cannot be well fitted by standard King or Sérsic models, indicating the presence of diffuse envelopes (eUCDs). High-resolution HST imaging is essential for resolving compact eUCDs that are unresolved in ground-based data. We also present results of the Gemini/Gemini Multi-Object Spectrograph spectroscopy follow-up programs to confirm the Virgo Cluster membership for eUCD candidates. The full catalog consists of a near-complete spectroscopic sample of 68 Virgo eUCDs, as well as properties for 51 strongly nucleated dEs that resemble eUCDs. Together, this constitutes the largest and most comprehensive sample thus far of eUCDs and other possible nucleated dE–GC transition objects. This is a companion paper to K. Wang et al., which was based in large part on the data we present here. Future wide-field space-based surveys will offer unprecedented opportunities to identify eUCDs across a range of environments.

Observations with JWST in the F090W band provide a powerful tool for determining galaxy distances based on tip of the red giant branch (TRGB) measurements. It is a great convenience that the TRGB lies at an almost constant absolute magnitude level at low metallicities. However, the TRGB becomes fainter at high metallicities in the F090W filter. Details of this break in slope are critical for precision applications in the acquisition of distances. With an absolute scaling set by the maser distance to NGC 4258 (but excluding the uncertainty in that distance), the value M F090W TRGB = − 4.40 ± 0.03 mag (traditional Vega) is found for (F090W − F150W) ₀ < 1.65 mag. The theoretical RGB isochrone that reaches the color 1.65 at the RGB tip corresponds to metallicity [M/H] = −0.57 for a 10 Gyr population. The calibration is used to derive distances for 16 galaxies relative to the megamaser host NGC 4258. Revised distances are on average slightly closer than literature values derived from the same data.

We present a study of morphologies, based on deep u * g ′ i ′ z ′ imaging of the Virgo Cluster from the Next Generation Virgo Cluster Survey, for 3689 Virgo cluster members spanning a mass range of ∼10 ¹¹ –10 ⁵ M _⊙ . Our analysis introduces a new, two-component visual classification scheme developed to capture the morphological diversity of galaxies over more than 6 orders of magnitude in stellar mass. Our morphological classifications use two parameters to describe the global structure and star formation activity of each galaxy. Structural subcodes denote features such as spiral arms, bars, disks, shells, and streams, while star formation subcodes indicate the form and location of the current star formation activity (e.g., in cores, clumps, filaments). These visual classifications rely on deep g ′ -band images, supplemented by u * g ′ i ′ ­ color images, as well as unsharp-masked images for a subset of objects. We compare our classifications to previous results for bright member galaxies that used more established schemes, finding good agreement. We also measure quantitative classification statistics (e.g., CASGM ₂₀ ) for a subset of the brighter galaxies, and present catalogs for some galaxy types of special interest, including structurally compact galaxies, ultradiffuse galaxies, candidate ultracompact dwarf transition objects, as well as candidate postmerger systems. These morphological classifications may be useful as a training set in the application of machine learning tools to the next generation of wide-field imaging surveys.

The integral-field unit mode of the Near-Infrared Spectrograph (NIRSpec+IFU) mounted on the James Webb Space Telescope has now enabled kinematic studies of smaller and less massive compact stellar systems in which to search for central massive black holes (BHs) than ever before. We present here the first such detection using NIRSpec+IFU in its highest resolution (R ∼ 2700) mode. We report the detection of a central BH with mass M BH = 2.1 ± 1.1 × 10⁶ M _⊙ (1σ uncertainties) in UCD736 orbiting within the Virgo galaxy cluster. Schwarzschild modeling of the 1D kinematic profile rules out a zero-mass central BH at the 3σ level; however, two other independent modeling approaches fail to rule out a zero-mass BH at >1σ significance. The presence of such a massive BH strongly argues against a globular cluster origin of this ultracompact dwarf galaxy (UCD), and rather suggests a tidally stripped formation route from a former ≳10⁹ M _⊙ dwarf galaxy host. This represents the detection of a BH in the most compact (r _h ≈ 15 pc) stellar system to date, with a M BH corresponding to ∼8% of the system’s stellar mass, roughly in line with previously reported UCD BH detections and comparable to the BH detected in the compact elliptical galaxy NGC4486B.

The TRGB−SBF Project team is developing an independent distance ladder using a geometrical calibration of the tip of the red giant branch (TRGB) method in elliptical galaxies that can, in turn, be used to set the surface brightness fluctuation (SBF) distance scale independent of Cepheid variables and Type Ia supernovae. The purpose of this project is to measure the local expansion rate of the Universe independently of the methods that are most at odds with the theoretically predicted value of the Hubble–Lemaître constant H ₀, and therefore isolate the influence of potential systematic observational errors. In this paper, we use JWST TRGB distances calibrated using the megamaser galaxy NGC 4258 to determine a new Cepheid-independent SBF zero-point with the Hubble Space Telescope. This new calibration, along with improved optical color measurements from Pan-STARRS and DECam, gives an updated value of H ₀ = 73.8 ± 0.7 (statistical) ±2.3 (systematic) km s⁻¹ Mpc⁻¹ that is virtually identical to the SBF Hubble–Lemaître constant measured by J. P. Blakeslee et al.

The Virgo Cluster is the nearest substantial cluster of galaxies to the Milky Way and a cornerstone of the extragalactic distance scale. Here, we present JWST/NIRCam observations that simultaneously cover the cores and halos of 10 galaxies in and around the Virgo Cluster and are designed to perform simultaneous measurements of the tip of the red giant branch (TRGB) and surface brightness fluctuations (SBF). Seven of the targets are within the Virgo Cluster and where we are able to resolve some of the cluster’s substructure, while an additional three provide important constraints on Virgo infall. The seven galaxies within Virgo itself all have SBF measurements from the Advanced Camera for Surveys Virgo Cluster Survey (ACSVCS). After adjusting the ACSVCS measurements for the offset from our new JWST TRGB measurements, we determine a distance to the Virgo Cluster of d = 16.17 ± 0.25 (stat) ± 0.47 (sys) Mpc. The work presented here is part of a larger program to develop a Population II distance scale through the TRGB and SBF that is completely independent of the prominent Cepheid + Type Ia supernova ladder. The TRGB distances to the galaxies presented here, when combined with future SBF measurements, will provide a crucial step forward for determining whether or not systematic errors can explain the well-known “Hubble tension” or if there is significant evidence for cracks in the ΛCDM model.

We present an analysis of the spatial distribution of globular cluster (GC) systems of 118 nearby early-type galaxies in the Next Generation Virgo Cluster Survey and Mass Assembly of early-Type GaLAxies with their fine Structures survey programs, which both used MegaCam on the Canada–France–Hawaii Telescope. We describe the procedure used to select GC candidates and fit the spatial distributions of GCs to a two-dimensional Sérsic function, which provides effective radii (half number radii) and Sérsic indices, and estimate background contamination by adding a constant term to the Sérsic function. In cases where a neighboring galaxy affects the estimation of the GC spatial distribution in the target galaxy, we fit two two-dimensional Sérsic functions, simultaneously. We also investigate the color distributions of GCs in our sample by using Gaussian mixture modeling. For GC systems with bimodal color distributions, we divide the GCs into blue and red subgroups and fit their respective spatial distributions with Sérsic functions. Finally, we measure the total number of GCs based on our fitted Sérsic function, and calculate the GC specific frequency.

We present an analysis of the spatial distribution of globular cluster (GC) systems of 118 nearby early-type galaxies in the Next Generation Virgo Cluster Survey (NGVS) and Mass Assembly of early-Type GaLAxies with their fine Structures (MATLAS) survey programs, which both used MegaCam on the Canada-France-Hawaii Telescope. We describe the procedure used to select GC candidates and fit the spatial distributions of GCs to a two-dimensional Sérsic function, which provides effective radii (half number radii) and Sérsic indices, and estimate background contamination by adding a constant term to the S'ersic function. In cases where a neighboring galaxy affects the estimation of the GC spatial distribution in the target galaxy, we fit two 2D Sérsic functions, simultaneously. We also investigate the color distributions of GCs in our sample by using Gaussian Mixture Modeling. For GC systems with bimodal color distributions, we divide the GCs into blue and red subgroups and fit their respective spatial distributions with Sérsic functions. Finally, we measure the total number of GCs based on our fitted Sérsic function, and calculate the GC specific frequency.