We present UBVI CCD photometry of the stellar contents and globular cluster(GC) candidates in the spiral galaxy NGC 300 in the Sculptor group. Color-magnitude diagrams for 18 OB associations having more than 30 member stars are presented. The slope of the initial mass function for the bright stars in NGC 300 is estimated to be Γ = -2.6 ± 0.3. Assuming the distance to NGC 300 of (m - M)o = 26.53 ± 0.07, the mean absolute magnitude of three brightest blue stars is obtained to be < MvBSG (3) > = -8.95 mag. We have performed search for GCs in NGC 300 and have found 17 GC candidates in this galaxy. Some characteristics of these GC candidates are discussed.

CN and CH band strengths for ten new bright giants in the globular cluster M15 have been measured from archival spectra obtained with the Multiple Mirror Telescope. Using published indices for other bright M15 giants, a CN-CH band strength anticorrelation is found for bright red giants. However, stars that do not follow the CN-CH anticorrelation are also found. They seem to show a positive correlation between the two indices. Among them, all the AGB and HB stars of the sample are included. Stars I-38 and X6, which are located near the RGB fiducial line in the CMD, have low measured CH(G) indices compared with other RGB stars. Stars IV-38, S4, and S1, which are all near the RGB tip, have strong measured CH(G) indices. Therefore, most of their evolutionary states are suspected to be different from those of a normal single RGB star.

Many models of globular cluster formation assume the presence of cold dense clouds in early universe. Here we re-examine the Fall & Rees (1985) model for formation of proto-globular cluster clouds (PGCCs) via thermal instabilities in a protogalactic halo. We first argue, based on the previous study of two-dimensional numerical simulations of thermally unstable clouds in a stratified halo of galaxy clusters by Real et al. (1991), that under the protogalactic environments only nonlinear (δ≳1) density inhomogeneities can condense into PGCCs without being disrupted by the buoyancy-driven dynamical instabilities. We then carry out numerical simulations of the collapse of overdense douds in one-dimensional spherical geometry, including self-gravity and radiative cooling down to T = 10 4 K. Since imprinting of Jeans mass at 10 4 K is essential to this model, here we focus on the cases where external UV background radiation prevents the formation of H2 molecules and so prevent the cloud from cooling below 10 4 K. The quantitative results from these simulations can be summarized as follows: 1) Perturbations smaller than Mmin ~(10 5.6 M⊙)(nh/0.05cm-3)-2 cool isobarically, where nh is the unperturbed halo density, while perturbations larger than Mmax ~(10 8 M⊙)(nh/0.05 cm-3)-2 cool isochorically and thermal instabilities do not operate. On the other hand, intermediate size perturbations (Mmin < Mpgcc < Mmax) are compressed supersonically, accompanied by strong accretion shocks. 2) For supersonically collapsing clouds, the density compression factor after they cool to Tc = 10 4 K range 10 2.5 - 10 6, while the isobaric compression factor is only 10 2.5. 3) Isobarically collapsed clouds (M < Mmin) are too small to be gravitationally bound. For supersonically collapsing clouds, however, the Jeans mass can be reduced to as small as 10 5.5 M⊙(nh/0.05 cm-3)-1/2 at the maximum compression owing to the increased density compression. 4) The density profile of simulated PGCCs can be approximated by a constant core with a halo of p∝ r-2 rather than a singular isothermal sphere.

The VI CCD photometry is made for stars in the globular cluster M22 down to V ≈ 19m, I ≈ 18m. In the color-magnitude diagram (CMD), red giant branch (RGB), asymtotic giant branch (AGB) and blue horizontal branch (BHB) are well defined. The luminosity functions (LF) of RGB, AGB and BHB stars are derived, discussing deficient gaps and bumps in the CMD. The anomalously wide RGB seen in the BV photometric system is found to disappear in the VI photometric system.