The photometric study of the Sagittarius dwarf galaxy by Marconi et al. (1998) has suggested the presence of a spread in metallicity (-0.7 ≤ [Fe/H] ≤ −1.6), which may result from different bursts of star formation. We present the results from a Multi Object Slit spectroscopy program carried out at the NTT with the aim to determine spectroscopic abundances of Sagittarius giants selected from the CCD photometry. From our intermediate resolution (R~1500) spectra, radial velocities are determined to confirm the membership and metallicities are derived by using spectral synthesis codes for stars down to V ~ 18, i.e. below the RGB clump. Out of 57 observed stars, 23 have a radial velocity consistent with Sagittarius membership; here we present results for 8 of these. No star with [Fe/H]< −1.0 is found, three stars are found to be metal-rich.

Coordinates are listed for 26 carbon stars which are radial velocity members of the Sagittarius Dwarf Galaxy (SDG). Their near-infrared properties indicate that most are on an extended Asymptotic Giant Branch (AGB), and the total number of such stars in the SDG is estimated at about 100. At least one-third of the C stars studied are large amplitude, i.e. Mira, variables; these are the first Miras to be found in a dSph galaxy. Surprisingly, the most luminous C star is not a Mira, but a low amplitude variable.

A comparison of the properties of C stars in the Bulge and in the SDG indicates that the two groups cannot be drawn from the same population. It is therefore highly unlikely that the Bulge C stars are, contrary to previous suggestions, related in any way to the SDG.

Our systematic searches for carbon stars in the Fornax dwarf spheroidal galaxy at the Canada-France-Hawaii Telescope have led to more than a doubling of the number of carbon stars known in this system, to 104. Furthermore, low-luminosity carbon stars resembling those we had previously found in the Small Magellanic Cloud have been identified in this system. We review the carbon star surveys carried out in the Fornax dwarf and present our main results. The Fornax carbon star population is compared to those of other Galactic halo dwarf systems.

We advance some results of our study of the star formation history of the Local Group dSph galaxy Leo I, obtained through the analysis of its deep HST color-magnitude diagram (CMD) using model CMDs computed from stellar evolutionary models. We conclude that most star formation (≃ 90%) took place in Leo I between 7 and 1 Gyr ago. It seems to have started at a very low rate ≃ 15 Gyr ago and continued, also at a very low rate, from 1 Gyr ago until the present time. A constant Z=0.0004 and a large fraction of binary stars are required to obtain the best agreement with both the distribution of stars across the CMD and with its morphology. An IMF like the one obtained by Kroupa et al. (1993) for the solar neighborhood, or steeper, is compatible with the data.

We have started a search for variable stars in Fornax, covering a area of 40′ x 40′. We have ~ 30 data points in both V and I. To detect variable stars, we use the variability index defined by Welch & Stetson (1993). We present here our first results.

Fornax shows a radial age gradient. The old population is the most extended one similar to what was found in other dwarf galaxies, while younger populations are more centrally concentrated. With ≈ −1.2 dex the dominant intermediate-age population is much more metal-rich than the oldest populations traced by Fornax's globular clusters (≈ −2 dex, 15–11 Gyr). Star formation appears to have proceeded continuously with decreasing rates rather than in distinct episodes. Fornax contains the youngest population ever found in a dwarf spheroidal galaxy, 100–200 Myr, which makes its apparent lack of gas even more puzzling.

We report on our new photometric surveys of star fields in the Fornax dwarf spheroidal (dSph) galaxy designed to investigate its star formation and chemical evolution histories.

Using observations from the Hubble Space Telescope archive, color-magnitude diagrams have been constructed for globular Cluster 4 in the Fornax dSph galaxy and its surrounding field. These diagrams extend below the main-sequence turnoffs and have yielded measurements of the ages of the populations. In particular, from our analysis Cluster 4 shows [Fe/H] ≃ 2.0, a value significantly lower than that derived for the Fornax field ([Fe/H] ≃ −1.40). Putting our results in the frame of the findings of Buonanno et al. (1998) for the Fornax clusters 1, 2, 3 and 5, a global analysis of the properties of Fornax stellar populations has been performed.

In this paper we present preliminary results of a wide field photometry survey of Ursa Minor and discuss the presence of an intermediate-age population and tidal tails in it.

28′ x 28′ deep V- and I-band images of the center and of the SE field of M33 have been obtained at the prime focus of the Canada-France-Hawaii 3.6m telescope. They allowed to map separately the young blue stars, the red supergiants, the red giants and the extreme AGB stars. The disk as traced by red giants has a surprisingly sharp edge. The young blue stars trace the spiral structure very well, but the detailed comparison with H I and CO maps does not show a very good correspondence. The simple spiral-shock model of star formation proposed for the South arm of M33 is not confirmed. On the edge of the galaxy, star formation starts at a column density of H I of about 3 x 1020 atom cm−2. The colour-magnitude diagram for the halo stars shows a broadened red giant branch with a mean metallicity [Fe/H] ≃ −1.0. The shape of the red giant branch confirms the distance modulus of 24.82±0.20 for M33.

We present Faint Object Camera (FOC) ultraviolet images of the central 14 x 14″ of Messier 31 and Messier 32. The hot stellar population detected in the composite UV spectra of these galaxies is partially resolved into stars, and we measure their colors and apparent magnitudes. We detect 433 stars in M31 and 138 stars in M32, down to limits of mF275W = 25.5 mag and mF175W = 24.5 mag. We investigate the luminosity functions of the sources, their spatial distribution, their color-magnitude diagrams, and their total integrated far-UV flux. Although M32 has a weaker UV upturn than M31, the luminosity functions and color-magnitude diagrams of M31 and M32 are surprisingly similar, and are inconsistent with a majority contribution from any of the following: post-AGB stars more massive than 0.56 M⊙, main sequence stars, or blue stragglers. The luminosity functions and color-magnitude diagrams are consistent with a dominant population of stars evolving from the extreme horizontal branch (EHB) along tracks of mass 0.47–0.53 M⊙. These stars are well below the detection limits of our images while on the zero-age EHB, but become detectable while in the more luminous (but shorter) post-HB phases. Our observations require that only a very small fraction of the main sequence population (2% in M31 and 0.5% in M32) in these two galaxies evolve though the EHB and post-EHB phases, with the remainder rapidly evolving through bright post-AGB evolution with few resolved stars expected in the small field of view covered by the FOC.

Our current knowledge of M31's dwarf spheroidal companions is reviewed. Two topics of recent interest constitute the bulk of this review. First, color-magnitude diagrams reaching below the horizontal branch have been constructed for two M31 dwarf spheroidals, based on images from HST/WFPC2. The horizontal branches are predominantly red in both galaxies, redder than expected for their metallicity based on Galactic globular clusters. Thus, the second parameter effect is seen in the M31 halo. Second, recent surveys have revealed three new dwarf spheroidal companions to M31. Thus, dwarf spheroidal galaxies are not as rare around M31 as previously thought and as a result, some properties of the M31 companion system have changed.

Unless the nearby universe is subtly anomalous, it should contain a relatively normal selection of galaxies whose histories are representative of field galaxies in general throughout the Universe. We can therefore take advantage of our ability to resolve the nearby galaxies into individual stars to directly, and accurately, measure star formation histories. The star formation histories are determined from model-fitting analysis, based on stellar evolution tracks, of colour-magnitude diagrams. The most accurate information on star formation rates extending back to the earliest epochs can be obtained from the structure of the main sequence. However, the oldest main sequence turnoffs are very faint, and it is often necessary to use the more evolved stars to infer the star formation history. These can then be compared with the properties of galaxies seen over a large range of lookback times at moderate to high redshifts. There is considerable evidence that the faint blue galaxies seen in large numbers in cosmological redshift surveys are the progenitors of the small late-type irregular galaxies seen in copious numbers in the Local Group, and we concentrate on these here.

We present a progress report on our ongoing HST WFPC2 study of globular clusters in NGC 185 and NGC 205. Most of the cluster candidates studied previously only from the ground are indeed globular clusters; however, several candidates turn out to be either foreground stars or background galaxies. In addition, we have discovered one new, previously unsuspected cluster. A complete knowledge of the globular cluster systems in even these nearby galaxies requires high spatial resolution data. We then derive preliminary I, (V – I) color-magnitude diagrams for some of the clusters, as well as for their surrounding fields. The clusters show the blue horizontal branches expected for the low metallicities we derive, which are in agreement with those derived from ground-based integrated spectra. The fields appear generally more metal-rich than indicated by previous ground-based studies. The field blue horizontal branch in NGC 185 is only a very minor component, while that in NGC 205 is even smaller. After all of our observations have been acquired, these data will allow a very accurate knowledge of the individual and composite properties of the globular cluster systems of these 2 galaxies, as well as those of their field stars.

Spectral and imaging results for the central region of M31 are presented. An analysis of absorption-index radial profiles involving Mg, Fe, and Ca lines reveals that the unresolved core of M31 is distinct from the inner bulge in having a higher metallicity; of the two nuclei of M31, it is the fainter in visible light and is located exactly in the dynamical center of the galaxy (and dynamically decoupled) which is chemically distinct. By including the Balmer absorption line Hβ in the analysis, we have disentangled metallicity and age effects; a stellar age difference by a factor of three is found between the nucleus and the bulge, the nucleus being younger. A morphological analysis of CCD images has shown the presence of an inner stellar-gaseous disk with a radius of some 80 pc which is embedded into the bulge.

Results of VRI photometry are presented, based on 1-m, 6-m and HST telescope frames taken in different parts of IC 10. From comparison of the location in CM diagrams of branches of blue supergiants it was found that E(B - V) = 0.98. The distance modulus estimation from TRGB is (m - M)I = 23.8 ± 0.1. The ages of brightest stars of the east star complex are derived from comparison with theoretical isochrones. It is possible that IC 10 is a galaxy with an extended red giant disk.

We present the results of a detailed BVRI and Hα study of the isolated nearby blue compact dwarf (BCD) galaxy NGC 6789. Judging from the literature the observed galaxy has not yet been resolved into stars up to now. On CCD frames obtained with 6m BTA telescope and 2.5m Nordic telescope the galaxy is well resolved. Its colour-magnitude diagram confirms the two component (core-halo) galaxy morphology, which consists of two stellar populations distinct in structure and colour: an inner high surface-brightness young population within 150 pc from the center of the galaxy, and a relatively low surface-brightness intermediate-age population extending out to at least 600 pc. The distance to the galaxy, estimated from the tip of the red giant branch (TRGB) is 2.1 Mpc which places NGC 6789 close to the Local Group. From the mean colour of the RGB, the mean metal abundance of the halo population is estimated as [Fe/H] ≃ −1 dex.

Deep UBV and JHK photometry of the stars in IC 1613 was used to investigate the stellar content in the H II regions of the northeast sector of the galaxy. The ages of nine of the associations outlined by Hodge (1978) were determined. A10 and A14 were found to be the youngest associations with ages of approximately 5 Myr, while A12, A18 and A19 were the oldest ones found, having a common age of approx. 20 Myr. Analysis of theoretical HR diagrams shows the presence of young massive stars in the associations, which have been born almost coeval. We have also found evidence of a difference between the slopes of the IMFs and differential LFs, between the group of associations embedded in gas and the group containing A12, A18 and A19, which are not affected by nebulosity.

We have been pursuing a program of hot star UV spectroscopy in local group galaxies over several years with HST. We have also obtained WFPC2 images in parallel and pointed exposures with several broad band filters.

• The imaging data have been used to generate colour-magnitude plots of central fields, clusters and halo fields in M31, M33 and NGC 6822. We have compared these with high-mass model isochrones from recent models, to examine the stellar populations that are indicated. M33 contains a substantial young cluster population whose mass and age appear to be related. The western outer wisps of NGC 6822 contain a relatively young population of stars.

• Most of the spectra have been reported and modelled in published papers: we note here the first comparison of stars in NGC 6822 with others from local group galaxies.

• We have also discussed the interstellar extinction in M31 and find it is similar to the Galaxy after allowance for comparable amounts of halo extinction that resembles that of the Magellanic Clouds.

Deep BVI CCD photometry of dwarf galaxy DD0 210 obtained in this study shows that the resolved stellar population in this galaxy consists of a dominant old red giant population and some young stars. We have estimated the distance to this galaxy using the I-band magnitude of the tip of the red giant branch, obtaining a value of 1030±50 kpc. This result combined with the velocity of DDO 210 shows that DDO 210 is a member of the Local Group.