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High signal-to-noise, low-resolution spectra have been obtained for 22 globular clusters (GCs) in NGC 4365. Some of these were selected as probable representatives of an intermediate-age (2-5 Gyr), extremely metal-rich GC subpopulation. The presence of such a subpopulation had been inferred from the unusual optical and near-IR color distributions of GCs in this otherwise typical Virgo elliptical galaxy. However, ages derived from Lick indices are consistent with uniformly old mean ages for all GCs in our sample. The metallicities of the clusters show some evidence for a trimodal distribution. The most metal-poor and metal-rich peaks are consistent with the values expected for an elliptical galaxy of this luminosity, but there appears to be an additional, intermediate-metallicity peak lying between them. New Hubble Space Telescope photometry is consistent with this result. A plausible scenario is that in earlier data these three peaks merged into a single broad distribution. Our results suggest that it is difficult to identify intermediate-age GC subpopulations solely with photometry, even when both optical and near-infrared colors are used., Comment: 30 pages, including 11 figures. AJ in press

We present spectroscopy for globular clusters (GCs) in the elliptical galaxy NGC 4365, obtained with the LRIS spectrograph on the Keck I telescope. Previous studies have shown that the optical color distribution of GCs in NGC 4365 lacks the bimodal structure that is common in globular cluster systems, showing only a single broad peak. Measurements of Balmer line indices (Hbeta, Hgamma and Hdelta) on the GC spectra support recent suggestions by Puzia et al., based on optical and near-infrared photometry, that some of the clusters in NGC 4365 are intermediate-age (2-5 Gyrs) and metal-rich (-0.4, Comment: 19 pages, including 6 figures and 3 tables. Accepted for publication in ApJ

Using high-dispersion spectra from the HIRES echelle spectrograph on the Keck I telescope, we measure velocity dispersions for 4 globular clusters in M33. Combining the velocity dispersions with integrated photometry and structural parameters derived from King-Michie model fits to WFPC2 images, we obtain mass-to-light ratios for the clusters. The mean value is M/LV = 1.53 +/- 0.18, very similar to the M/LV of Milky Way and M31 globular clusters. The M33 clusters also fit very well onto the fundamental plane and binding energy - luminosity relations derived for Milky Way GCs. Dynamically and structurally, the four M33 clusters studied here appear virtually identical to Milky Way and M31 GCs., Comment: 25 pages, including 7 figures and 4 tables. Accepted for AJ, Nov 2002

We analyze high signal-to-noise spectra for 14 globular clusters (GCs) in the Sombrero galaxy, NGC 4594 = M104, obtained with the LRIS spectrograph on the Keck I telescope. We find generally good agreement between spectroscopic metallicities and previous photometric metallicities based on V-I colors. Further, we use measurements of various Balmer line indices on co-added spectra of metal-poor and metal-rich GCs to estimate ages for the GC subpopulations and find ages of 10-15 Gyr, with preferred ages around 11-12 Gyr and no detectable differences between the metal-rich and metal-poor subpopulations. However, because of model and measurement uncertainties, age differences of a few (2-3) Gyrs cannot be be ruled out. We also measure alpha-to-iron abundance ratios from Mg and TiO features and find enhancements on the order of +0.4 dex relative to the Sun, similar to the alpha/Fe abundance ratios observed in other old stellar populations. Finally, we combined our sample with radial velocities for 34 GCs from Bridges et al. 1997 and obtain virial and projected masses for the Sombrero of M(Vir) = 8.1+/-1.8 x 10^11 M(sun) and M(P) = 5.3+/-1.0 x 10^11 Msun within 17 kpc, respectively. Using 12 clusters within the central 4.5 kpc, the corresponding numbers are M(Vir) = 2.1+/-1.1 x 10^11 Msun and M(P) = 2.0+/-1.3 x 10^11 Msun., Comment: 24 pages, including 9 figures and 3 tables. Accepted for publication in AJ

We present Keck/LRIS spectra for 11 old globular clusters in the S0-type galaxy NGC 1023 and 2 young blue clusters in the nearby companion NGC 1023A. Analysis of the spectra of 7 old clusters with sufficient S/N shows generally good agreement between spectroscopic and previous photometric metallicity estimates, but the integrated colors of two clusters are too blue for their spectroscopic metallicities. Although the cluster ages are not well constrained, they are most likely similar to those of Milky Way globular clusters and certainly older than about 5 Gyr. The brightest GC in the sample shows enhanced cyanogen, possibly indicating an abundance anomaly similar to that observed in some M31 globular clusters. For the two blue clusters in NGC 1023A we estimate ages between 125 and 500 Myr, based on their strong Balmer lines. The total masses are about 80000 Msun and 60000 Msun for a Miller-Scalo IMF and Z=0.004, making these objects similar to the young populous clusters in the LMC. It is suggested that the two young clusters might have formed during a period of enhanced star formation activity in NGC 1023A, stimulated by a close encounter with NGC 1023., 32 pages, including 7 figures and 6 tables. Accepted for publication in AJ

The structure of a very bright (MV = -10.9) globular cluster in NGC 1023 is analyzed on two sets of images taken with the Hubble Space Telescope. From careful modeling of King profile fits to the cluster image, a core radius of 0.55+/-0.1 pc, effective radius 3.7+/-0.3 pc and a central V-band surface brightness of 12.9+/-0.5 mag / square arcsec are derived. This makes the cluster much more compact than Omega Cen, but very similar to the brightest globular cluster in M31, G1 = Mayall II. The cluster in NGC 1023 appears to be very highly flattened with an ellipticity of about 0.37, even higher than for Omega Cen and G1, and similar to the most flattened clusters in the Large Magellanic Cloud., Comment: 14 pages, 3 figures, 1 table. Accepted for AJ, Oct 2001

We use the Panchromatic Hubble Andromeda Treasury (PHAT) survey dataset to perform spatially resolved measurements of star cluster formation efficiency ($\Gamma$), the fraction of stellar mass formed in long-lived star clusters. We use robust star formation history and cluster parameter constraints, obtained through color-magnitude diagram analysis of resolved stellar populations, to study Andromeda's cluster and field populations over the last $\sim$300 Myr. We measure $\Gamma$ of 4-8% for young, 10-100 Myr old populations in M31. We find that cluster formation efficiency varies systematically across the M31 disk, consistent with variations in mid-plane pressure. These $\Gamma$ measurements expand the range of well-studied galactic environments, providing precise constraints in an HI-dominated, low intensity star formation environment. Spatially resolved results from M31 are broadly consistent with previous trends observed on galaxy-integrated scales, where $\Gamma$ increases with increasing star formation rate surface density ($\Sigma_{\mathrm{SFR}}$). However, we can explain observed scatter in the relation and attain better agreement between observations and theoretical models if we account for environmental variations in gas depletion time ($\tau_{\mathrm{dep}}$) when modeling $\Gamma$, accounting for the qualitative shift in star formation behavior when transitioning from a H$_2$-dominated to a HI-dominated interstellar medium. We also demonstrate that $\Gamma$ measurements in high $\Sigma_{\mathrm{SFR}}$ starburst systems are well-explained by $\tau_{\mathrm{dep}}$-dependent fiducial $\Gamma$ models., Comment: 26 pages, 13 figures, Accepted by ApJ

We present the Snapshot Hubble U-band Cluster Survey (SHUCS), a project aimed at characterizing the star cluster populations of ten nearby galaxies (d, Accepted for publication in the Astronomical Journal. 31 pages, 18 figures. Paper I in a series