Extragalactic Globular Clusters are useful tracers of galaxy formation and evolution. Photometric studies of globular cluster systems beyond the Local Group are still the most popular method to investigate their physical properties, such as their ages and metallicities. However, the limitations of optical photometry are well known. The better wavelength sampling of the underlying cluster's SED using K-band photometry combined with optical passbands allows us to create colors which reduce the age-metallicity degeneracy to the largest extent. Here we report on the very first results of our near-IR photometric survey of globular cluster systems in early-type galaxies outside the Local Group.

We present preliminary results on the shape of the globular cluster luminosity function and the colors and inferred metallicities of the clusters in dwarf elliptical galaxies imaged with HST. The luminosity function (LF) of the GC candidates is consistent with a Gaussian-shaped LF similar to that in giant ellipticals. Also, with a mean color of (V - I) = 0.94, most of the GCs appear to be old and metal-poor ([Fe/H] = −1.4) like GCs in the Galaxy and in nearby giant ellipticals. This suggests that the bulk of the clusters were formed more than 10 Gyr ago.

The Hubble Space Telescope Wide Field and Planetary Camera 2 was used to image at high resolution the core region of the nearby, heavily obscured massive elliptical galaxy Maffei 1. We report on the discovery of 19 diffuse objects in the WFPC2 field that are likely to be globular clusters associated with Maffei 1. We present some preliminary data on the luminosities, colors, and sizes of these candidates.

We have obtained CMR photometry for a roughly 1° square region centered on NGC 5128. Preliminary results indicate that the limiting magnitude of the images is ≳ 1 magnitude fainter than the peak of the globular cluster luminosity function (GCLF) at R ⋍ 21.

We have conducted a wide-field optical survey of NGC 5128 (Cen A), the nearest large elliptical galaxy (3.5 Mpc). From UBVRI imaging and spectroscopic follow-up, we have identified and obtained kinematics for 125 new globular clusters out to a projected radius of 40 kpc. We also extend our survey of field star kinematics in NGC 5128, and now possess a total of 736 radial velocities for planetary nebulae out to a projected radius of 80 kpc.

1. • The PNe sample along the photometric major axis shows significant rotational support out to 80 kpc.

2. • The blue globular clusters seem to possess little or no angular momentum.

3. • The kinematics of the red globular cluster sample show some evidence for rotation around an axis common to that of the field stars.

On the basis of high resolution ground-based images, taken with VLT and FORS1, 71 bona fide globular clusters were discovered in the halo of NGC 5128. Only 5 of these clusters were previously known. In a UV color-magnitude diagram for the complete sample of 71 clusters and a (U—V)0vs. (V—Ks)0 color-color diagram for a subsample of 23 clusters, the objects span a similar magnitude and color range as the globular clusters in the MW and M31. The GCLFs spanning −10.1 < MV < −4.9 and −9.3 < MU < −3.3 have been constructed. These are the deepest GCLFs of in a gE made so far. The Kolmogorov-Smirnov statistics show that GCLF of the giant elliptical NGC 5128 is consistent with the ones of spiral galaxies like the MW and M31.

We have derived ages and metallicities from co-added spectra of 131 globular clusters (GCs) associated with the giant Virgo elliptical NGC 4472. ¿From their metal-line indices, we find that our sample of GCs span a metallicity range of approximately −1.6 ≤ [Fe/H] ≤ 0 dex. The SSP models of Worthey (1994; W94) predict that the metal-poor population of GCs has an age of 14.5 ± 4 Gyr and that the metal-rich population is 13.8 ± 6 Gyr old, whilst the models of Kurth, Fritze-v. Alvensleben & Fricke (1999; KFF99) predict ages of 6.0 ± 2 and 8.0 ± 5 respectively. We conclude that, within the uncertainties, the GCs are old and coeval, and that the bimodality seen in the broadband colours primarily reflects metallicity and not age differences.

We have studied the Globular Cluster System of the merger galaxy NGC 1316 in Fornax, using CCD BV I photometry. Dividing the sample into red (presumably metal-rich) and blue (metal-poor) subpopulations at B - I = 1.75, we find that they follow strikingly different angular distributions. The red clusters show a strong correlation with the galaxy elongation, but the blue ones are circularly distributed. An astonishingly low specific frequency for NGC 1316 of only SN = 0.9±0.2 is derived, which confirms with a larger field a previous finding by Grillmair et al. (1999). Assuming a “normal” SN of ∼ 4 for early-type galaxies, we use stellar population synthesis models to estimate the merger age to about 2 Gyr, if an intermediate-age population were to explain the low SN we observe. By fitting t5 functions to the Globular Cluster Luminosity Function (GCLF), we derive the following turnover magnitudes: and . They support that NGC 1316, in spite of its outlying location, is at the same distance as the core of the Fornax cluster.

We investigate the outer halo globular cluster population of NGC 1399. This study uses wide-field imaging of this cluster system, which covers the largest area studied with CCD photometry until now. The cluster system of NGC 1399 is found to extend further than 100 kpc from the galaxy. A population of metal-rich, as well as metal-poor clusters has been identified at these large radii. At radii smaller than 55 kpc the specific frequency of the red cluster system remains constant, while that of the blue clusters increases proportional to r0.8±0.2. For larger radii, the uncertainty of the galaxy light profile does not permit any reliable statement.

We describe an ongoing program to measure structural parameters for globular clusters with a range of ages in early-type galaxies. Using deep, optimally-dithered HST WFPC2 observations of NGC 3597, NGC 1316, and NGC 1399, we apply a χ2 minimization method to the determination of cluster sizes. The goals include studying the structure spectrum of stellar clusters at birth, and determining the rate at which tidal and evaporative destruction mechanisms operate to alter luminosity functions and specific frequencies to what we see in ellipticals today.

We present a preliminary analysis of HST-WFPC2 observations of globular cluster systems in the two brightest galaxies, UGC 9799 (cD) and NGC 1129 (non-cD), located in the center of rich clusters.

We have undertaken a survey of the globular cluster systems of a large sample of elliptical and spiral galaxies in order to test predictions of elliptical galaxy formation models. Here we outline the survey and present a summary of our results for the Virgo elliptical NGC 4472.

One of the most promising avenues for exploring the dynamics of the outer parts of elliptical galaxies involves using bright discrete objects as kinematical tracers: globular clusters and planetary nebulae. As large data sets are becoming available, rigorous dynamical analyses are needed to interpret them. To this end, we have developed an extension of orbit modeling methods, which we apply to the dynamics of the giant ellipticals M87 and M49. We find that a sample of ∼ 200 globular clusters velocities is effective at demonstrating the presence of a dark halo and providing hints about the detailed distribution of the dark matter.

We describe and celebrate the use of the MOS instrument at the Canada-France-Hawaii Telescope in a multi-object spectroscopic study of the rich globular cluster system (GCS) of the giant elliptical galaxy M87.

We have obtained deep photometry of NGC 1199 (in HCG 22) and NGC 6868 (in the Telescopium group). Both galaxies are the optically brightest galaxies of their groups. Our analysis of B and R images taken with the Keck II and the VLT/ESO telescopes, detected a population of globular clusters around both galaxies, with total specific frequencies SN = 1.7 ± 0.6 for NGC 1199 and SN = 1.3 ± 0.6 for NGC 6868. The color distributions of the globular cluster systems shows bimodal peaks centered at (B - R)0 = 1.13 ± 0.10 and 1.42 ± 0.10 (NGC 1199) and (B - R)0 = 1.12 ± 0.10 and 1.42 ± 0.10 (NGC 6868).

We present the results of a search for globular clusters in the surroundings of 15 low surface brightness dwarf galaxies in the Fornax cluster, on CCD images in the C and T1 bands. Globular cluster candidates show a clear bimodal color distribution. Their surface density distribution shows no concentration towards the respective dwarf galaxies but it does show concentration towards the center of the Fornax cluster. We suggest that the potential globular clusters might not be bound to the dwarf galaxies, but might instead belong to the intra-cluster medium.

Globular cluster systems (GCSs) have been observed in 17 elliptical galaxies located in Coma. Surface brightness fluctuations (SBF) and a 2.5-m ground-based telescope (INT, La Palma) have been used to determine total populations of Globular clusters (GCs) and specific frequency (SN) has been evaluated for each individual galaxy.

Red supergiants and bright AGB stars have been detected in NGC 1313, a galaxy outside of the Local Group, using NIR data obtained at ESO-NTT in La Silla Observatory. The derived color-magnitude diagram (CMD) compared with synthetic CMD strongly support the existence of an intermediate age stellar population.

Stellar Clusters are identified in images and in the spectra of these star forming dwarf galaxies. These Stellar Clusters have properties similar to those observed in other violent star forming galaxies and may the elementary entities of a starburst.

Five populations of young, massive, compact star clusters have been identified in the “Antennae galaxies”, the nearest and youngest example of a prototypical merging galaxy. The brightest of these clusters have all the attributes expected of young globular clusters, hence allowing us to study the formation and evolution of globular clusters in the local universe. Comparisons between the different populations and a variety of multi-wavelength observations are providing new insights into the formation of the clusters. For example, the very red clusters originally identified by Whitmore and Schweizer (1995) appear to be the youngest population, just emerging from their dust cocoon. The cluster luminosity functions for a wide variety of galaxies (i.e., mergers, starbursts, barred galaxies, spirals) appear to follow a “universal” power law, with index ≈ −2. The primary difference between the different galaxies is the normalization, with roughly a tenfold increase in the number of clusters in merging and starbursting galaxies. Hence, the fact that the brightest clusters are in mergers may be largely a statistical result. Simulations are now showing how the initial power law distribution for the clusters will evolve toward the peaked distribution found for old globular clusters, via a combination of processes including two-body evaporation, disk shocking, and stellar mass loss.