Studies of globular clusters in spiral galaxies are still available for only a few galaxies with a limited range of galactic types. We have identified (or set upper limits on) the cluster systems in several edge-on spirals ranging from the early-type spiral NGC 7814 to the late type NGC 5907. We discuss the properties of the cluster systems and their relationship to the properties of the parent galaxies.

We present a progress report for the ongoing study of the globular cluster (GC) system around the edge-on lenticular galaxy NGC 3115. This object is one of the best targets for this kind of investigation, due to its proximity (~ 10 Mpc) and favourable inclination (for a deep photometric study and a review of the properties of NGC 3115, see Capaccioli et al., 1986). Previously published data include a preliminary luminosity function of GC candidates, based on indirect calibration of KPNO photographs (Strom et al., 1977), and visual star counts on CFH and AAT deep plates (Hanes and Harris, 1986). Here we report on B-band photometry down to mB ~ 24, based on CCD calibration.

We have explored the use of maximum likelihood estimation techniques in the use of globular cluster luminosity functions (LFs) as distance indicators. In particular, we have tested size-of-sample effects through the analysis of Monte Carlo simulations of LFs drawn from an assumed universal population like that characterizing the globular clusters in the Local Group. Our working assumption, following others before us, is that the underlying LF is adequately well described by a Gaussian normal in a number vs. absolute magnitude representation.

For typically observable sample sizes in studies which are limited to the bright half of the LF, statistical limitations preclude a precise determination of the attributes which fully describe the LF, even in the absence of field object contamination. In particular, the intrinsic dispersion (the shape parameter of the LF) must be taken to be a universal constant, independent of galaxy type; only then may the turnover magnitude (which contains the distance information) be derived with good precision. Some data exist for nearby galaxies (including ellipticals) which permit an assessment of the universality of the intrinsic dispersion: they are not inconsistent with the hypothesis. However, it will be important to test this point in future as more data are secured.

Real globular clusters in remote galaxies are unresolved, and the samples are contaminated with foreground field stars and remote background objects. This contamination necessitates corrections which are statistical in nature, applicable to binned LFs. Through numerical simulations, we have tested the limitations imposed by realistic numbers of field objects in globular cluster LFs in remote galaxies, testing for systematic biases and assessing the attainable precision in derived distance as a function of the sample size and the limiting magnitude.

Our program is based on photographic and photoelectric UBV photometry of globular cluster stars with the Soviet 6 m telescope. M 10 = NGC 6254 remains, regretfully, the only cluster for which we were able to gain photoelectric observational material sufficient for calibration of the photographic photometry for faint stars. Samus and Shugarov (1983) presented for M 10 a V, (B - V) diagram showing an unusually large magnitude difference between the main sequence turn-off point and the horizontal branch, V(TO) - V(HB) ≍ 3.8 mag. It seemed of interest to compare M 10 and M 12 by their values of V(TO) - V(HB). A preliminary calibration of the faint star photographic photometry in M 12 leads to V(TO) - V(HB) ≍ 4 mag (Mironov et al., 1984). One may notice that in the classification introduced by Mironov and Samus (1974, 79), which is based mainly on the horizontal-branch morphology, both M 10 and M 12 belong to group I, presumably the older group. V, (B-V) diagrams were also published by us for NGC 288 and M 2 = NGC 7089 (Samus and Shugarov 1978, 79).

A new color-magnitude diagram for M 3 is presented. 10,000 stars have been measured down to V = 22 with an internal accuracy better than 0.03 mag to get complete and very accurate samples over well defined areas.

More than 10,000 stars have been measured down to V = 22 in two different areas. In the first, with 3.5 < r < 6.0 arcmin, photometric completeness has been achieved down to V = 21.5 and an algorithm to correct for losses due to unrecoverable crowding and blending has been experimentally computed. In the second, within a square field of 15 × 15 arcmin, completeness has been extended only to V = 18, well below the horizontal branch.

Many tests made on the data guarantee an internal photometric accuracy better than 0.03 mag at V = 21. Therefore, both the total population of each branch and the relative star-number ratios are “bona fide” representatives of the corresponding evolutionary time-scales. Here we simply present: 1) the color-magnitude diagram (see Fig. 1) obtained from the reduction of a wide collection of Palomar plates; 2) a table which presents the contribution of the various branches to the integrated cluster light; 3) the preliminary indication that, within the annulus we have considered, the blue stragglers seem to be slightly less centrally concentrated than the subgiants in the same magnitude interval.

Deep UBV CCD imagery has been obtained in three fields of the galactic globular cluster M5. The locations of these fields are at distances of 8, 21, and 58 core radii. In the middle field, which overlaps substantially with the deep photometry field of Arp, the CCD photometry reaches fainter than V = 26. Color-magnitude diagrams constructed from stars in the inner two fields are identical, to within the errors, and can be used to set an upper limit of 4% to any metallicity difference between these two fields. A U, (U - V) color-magnitude diagram is also shown for the inner field and compared with that of a more metal rich and more metal poor cluster. Major differences in the morphology of these three diagrams are present as a function of metal abundance. From the color-color diagram the reddening in the direction of M5 is determined (E(B - V) = 0.02) as well as its metallicity ([M/H] = −1.13). The distance to M5 is then established from fitting local subdwarfs to the lower main sequence of the cluster. This yields (m - M)V = 14.3. Using the observationally determined parameters, an overlay of the appropriate VandenBerg and Bell isochrones yields an age estimate of 18 Gyrs for M5. Luminosity functions constructed from the three fields show excellent agreement through the range V = 17 to 23. Fainter than V = 23 there is some evidence for mass segregation effects due to dynamical relaxation.

We present B and V photometry of ~ 4500 stars (V < 21.3 mag) within the region 2′.1 < r < 10′ centered on the southern globular cluster M 30 (NGC 7099), from two sets of four plates of the 4 m CTIO (CT) and the 2.5 m Dupont (LC) telescopes (Piotto 1986). Instrumental magnitudes (applying INVENTORY to PDS scans) are calibrated by four CCD exposures from the ESO 1.5 m Danish telescope. Our results removed the disagreement between previous photometry (Alcaino and Liller 1980) and the isochrones published by VandenBerg (1983).

For decades, star counts and HR diagrams extending below the main sequence turnoff in globular clusters meant the work of Sandage (1957). The advent of large CCD's at the foci of large telescopes has changed this (McClure et al. 1985, Harris & Hesser 1985, Christian & Heasley 1986, Heasley et al. 1986, Penny & Dickens 1986, Richer & Fahlman 1986, Smith et al. 1986) and made clear that clusters differ in the shapes of their luminosity functions and in the morphology of their HR diagrams. We return here to photographic methods, which can capture an order of magnitude more images and so possibly reveal new details.

About 30 deep B and V CCD images, obtained at the 3.6 m ESO telescope, with the EFOSC in the focal reducer option, have been used to obtain color-magnitude diagrams and luminosity functions for the main sequence of the globular clusters ω Cen and NGC 3201. Two fields per cluster, at different distances from the center (25′ − 30′ for ω Cen and 7′.5 − 9′ for NGC 3201) were observed and separately reduced.

This paper presents a color magnitude diagram for the enigmatic cluster ω Centauri (NGC 5139 = C1328 − 472) tracing the main sequence down to V ~ 21.5. The spread in color on the upper main sequence is confirmed as intrinsic to the cluster. The CCD observations were made using the SAAO 1 m telescope with the UCL CCD camera and the RGO CCD camera at the prime focus of the AAT.

Main sequence photometry has been obtained in the BV system for at least 36 galactic globular clusters (Peterson 1986). One of the most important objectives for these continued researches by several astronomical groups has been that of determining the ages of globular clusters. During the past five years, a general consensus has emerged that the spread in age among the known galactic globular clusters could be as small as 1 billion years; Burstein (1985) suggests that the average age of these objects lies between 14 and 17 Gys.

The way to arrive at (even relative) ages for globular clusters involves the determination of their (relative) distances. We would like to see a theory which would fit the absolute magnitudes of RR Lyrae stars as determined from observations (Sandage effect). We have examined a sample of 17 CM diagrams of galactic globular clusters, 11 of which were observed at ESO and reduced with the program, ROMAFOT and 6 of which were taken from the literature. In Fig. 1 the difference in bolometric magnitude between the turnoff point and the location of the zero-age horizontal branch (ZAHB), δV RRTO (bo1) is plotted versus [Fe/H]. It turns out that δV RRTO ≃ δ RRTO (bo1) + 0.1 = 3.56 ±0.15. We are faced with the problem of determining how the horizontal branch scales with metallicity in order to understand the constant value of 3.56 in this relation.

The aim of the present work is two-fold: 1) To study the effect of the tidal field of the Galactic bulge on a cluster in a high eccentricity plunging orbit with half-mass density nearly equal to the Roche density; 2) To estimate the tidal or limiting radius for such orbits.

Density curves of polytrope index 5 were fitted to the surface density distributions of 26 globular cluster systems. Though we have shown only two of them in Fig. 1, the remaining systems resemble the above cases. No differences exist between elliptical and spiral galaxies.

This paper describes a project whose aim is to study the dynamics of a globular cluster system using an N-body code modified to include the gravitational field of an isothermal galaxy model. The galaxy and the globular cluster system have the same radii, are spherically symmetric and non-rotating. The evolution is to be followed up to a Hubble time.

The existence of deviations of the observed photometric profiles with respect to the King models is a known fact (e.g., Newell and O'Neil, 1978; Aurière, 1983) and has been recently emphasized in the large survey by Kron et al., 1984. The origin of the light “excesses” (or defects) in the nuclear regions is, however, not very well understood. This work aims at clarifying this problem on the basis of multicolor (BVRIKC) CCD observations.

In order to test the prediction that many Galactic globular clusters have undergone core collapse (Lightman 1982, Cohn and Hut 1984) and should therefore have central surface brightness cusps, we have obtained UBVR CCD frames of the cores of 72 clusters. We present and analyze U-band surface brightness profiles for three clusters: one “control cluster” with a normal flat core profile — NGC 6388 — and two with central power law cusps — NGC 6624 and M15 (NGC 7078).

We report MMT Echelle radial velocity observations of 52 giants within 3 core radii of the center of NGC 6712. The mean radial velocity of these stars is −107.5 km/s, with a line of sight velocity dispersion of 4.0 km/s. We use these data, together with CCD photometry of the cluster, to derive a mass to light ratio for the center of the cluster of 0.7, an unusually low value.

We have used the Dominion Astrophysical Observatory radial velocity spectrometer on the 3.6m Canada-France-Hawaii telescope to obtain radial velocities, accurate to ~0.8 km/s, for ~20 stars in each of nine globular clusters. The stars are generally within three core radii of the cluster center. The cluster names and metallicities (the latter are averages of values in Zinn and West (1984), Pilachowski (1984), and Webbink (1985)) are given in Table I. This sample includes two clusters with cusps in their surface brightness profiles: NGC 6624 and 6681.