NEW data about dwarfs: a few more metal-poor dwarfs have been observed for lithium at the CAT + CES at La Silla (ESO). These new results, together with a few new measurements in the literature show again a constant lithium abundance, confirming the trend previously found (the plateau). Let us note however that two metal-poor dwarfs have recently been reported with a low lithium abundance. Obviously, more observations are needed.

We describe a near-infrared imaging survey of interacting galaxies.

Planetary nebulae are one of the latest phases of evolution of low- and intermediate mass stars and can be used as probes of stellar populations and overall chemical evolution in galaxies. Bulge planetary nebulae offer the advantage of being a sample of objects at known distance. Therefore, their study is essential.

We report the first results of a multicolour (broad V,R,I and narrow [OIII] bands) surface photometry study of a small sample of HII galaxies.

The data were obtained at the 2.5m Nordic Optical Telescope (NOT) at La Palma, Canary Islands under subarcsecond seeing conditions. Part of the data has 0.55 arc seconds resolution (FWHM). The data will allow us to investigate the bi-parametric behaviour of the luminosity vs line-witdh relation.

We report IUE observations of two extremely low metallicity HII galaxies. Lyman alpha emission was detected in both galaxies.

Over the past decade, a very considerable amount of effort in the understanding of stellar populations has gone. Because a large number of analysed data is the basis of this understanding, our efforts concerning this subject matter presented in this poster are mainly:

–Conception of spectrograph

Multiaperture spectrograph is now a reality on large telescopes. The spectrograph SFM has been achieved in the Observatoire de Marseille and is now at Calar Alto (Baranne et al., 1992). It is used on the German 3.5 m telescope. Such an instrument multiplicates by a large factor the number of observed stars.

We present a luminosity function (LF) for the coolest stars in three POSSII fields - extending earlier LFs to much lower masses at higher precision than has been acheived previously.

Wolf-Rayet (W-R) galaxies are a subset of emission-line galaxies in whose integrated spectra a broad (i.e., stellar in origin) He II λ 4686 emission feature has been detected. This line is a prominent emission feature in the spectra of WN stars. The presence of 102 to 105 W-R stars in these galaxies has been inferred from a comparison of the luminosity and equivalent width of this feature in the integrated galaxy spectra with those of the corresponding line in the spectra of Galactic and LMC WN stars. Most W-R galaxies exhibit other properties indicative of a very young starburst population, such as a relatively “blue” continuum and a strong nebular emission line spectrum due to photoionization by large numbers of hot, early-type stars. Their spectra are therefore very similar to to those of giant H II regions. There are currently about 40 W-R galaxies known.

Based on the population synthesis results1 for the nuclear region of the elliptical galaxy NGC5044, possible theoretical Age Metallicity Relations (AMR) have been derived, reproducing the stellar luminosity distribution over age A and metallicity Z. A self-consistent method, used to constrain the star formation history and chemical evolution of a galaxy directly from its spectrum (i.e. from 3000 – 10000 å) is presented. This method is predominantly based on the modelling of stellar luminosity contributions obtained by spectral decomposition methods with those theoretically calculated using a conventional galactic evolution model, incorporating a parametrised Star Formation Rate (SFR) and Initial Mass Function (IMF). Related model parameters were constrained by minimizing the λ2– test defined by the corresponding luminosity distributions.

The HI surface density of 8 low surface brightness galaxies falls below the critical density for star formation. This may explain why these galaxies appear so unevolved and are generally deficient in molecular gas.

The study of abundances in HII regions along the disc of spiral galaxies has shown the existence of negative gradients with higher abundance towards the centre (e.g. Pagel & Edmunds 1981; McCall, Rybski & Shields 1985; Garnett & Shields 1987; Edmunds 1989). The origin of these gradients is unclear but various chemical models with inflow, radial flows or star-formation cut-offs can produce them (e.g. Pagel & Edmunds 1981; Güsten & Mezger 1982; Díaz & Tosi 1984; Mayor & Vigroux 1981; Pitts & Tayler 1989; Clarke 1989). In the present study we have collected the chemical data available in the literature for some 30 spiral galaxies and we have calculated the abundances in a consistent way. The purpose is to carry out a thorough study of possible correlations or trends of abundance with many other galaxian properties, that can be followed up with further observations until a clearer picture for the origin of the gradients emerges. We summarize here some of the main results, which are fully included in Vila & Edmunds (1991). There is no prefered scale length (e.g. R25, disc effective radius, etc) which reduces the apparent variation of gradients between galaxies. The central abundances of spirals are correlated with their mass, barred spirals have shallower gradients and non-barred spirals show a correlation of gradient slope with morphological type. The correlation of abundance with mass surface density is confirmed and a weaker correlation is found with surface brightness. For those 9 galaxies where information on their HI, H2, photometry and rotation curves is available, the gas fraction along the disc has been estimated. The initial results show an empirical yield uniformly decreasing with radius, possibly varying as a function of metallicity.

It is shown that the published colour-distributions of globular cluster systems surrounding nearby elliptical galaxies disagree with each other. While part of the discrepancies are introduced by zero-point errors, uncertainties in photometric transformations and other systematic differences between individual studies, independent measurements of the same cluster systems indicate that systematic errors are smaller than the observed off-sets. This implies that the latter differences are intrinsic.

We present the results of a spectroscopic study of planetary nebulae (PN) in the Magellanic Clouds. The optical survey of He, N, O, and Ne abundances by Monk et al. (1988) has been updated by higher S/N AAT optical data. In addition, carbon and other elemental abundances have been derived from the IUE spectra of 40 PN. Ionized nebular masses have been derived for 80 PN. The ionised mass versus nebular electron density plot shows that planetary nebulae become optically thin when their electron densities drop below 4500 cm−3. Below this density, the mean nebular hydrogen mass found for non-Type I PN is 0.22±0.08 M⊙. Using Zanstra and energy-balance methods, the mean central star mass found for 14 SMC and LMC PN is 0.59±0.02 M⊙.

Detailed observations of 103 IRAS Miras found in two strips across the Bulge with −15° < l < 15° and 7° < |b| < 8° were discussed by Whitelock et al. (1991). Among other things they derived distance moduli for each object. In this work (which will be reported in more detail by Whitelock and Catchpole 1991) we examine the number of Miras per 0.3 mag distance modulus bin as a function of distance modulus and as a function of galactic longitude. The important aspect of this approach is that it provides us with a probe of the depth and structure of the bulge. If the number distribution as a function of modulus is examined separately for the two sides of the bulge, then it is very clear that the distribution of the Miras with l > 0° is narrower and peaks in front of the distribution of Miras with l < 0°. This asymmetry can be understood if the Bulge is bar shaped, the bar is tilted at approximately 45° to the line of sight and the near end is in the first quadrant. This conclusion is consistent with those of Blitz & Spergel (1991) and Nakada et al. (1991). It is particularly interesting to note that Menzies' (1990) radial velocity data for a subset of the Miras discussed here show that the Bulge is rotating rapidly.

A comparison is made of the period distribution of Miras in the Bulge in fields centred at b = −3°.9 and b = −7°.5 The field centred at l = 0°.0 b = −7°.5, occupies 3.79 square degrees and is part of Baade/Plaut field 3. The Miras are those discussed by Wesselink (1987) and those discovered through follow up observations of IRAS objects. The sample is almost certainly incomplete as there are probably Miras of intermediate period which were not detected by either Wesselink or IRAS. The period distribution is shown in Fig 1a.

We have secured new optical spectra of 11 WR stars in M33 and M31 using the WHT+Faint Object Spectrograph, covering λλ4800–9800å at 14å and λλ3500–5000å at 7å resolution. In our M33 sample five stars are classified as WC4–5 from their C IV λ5800/C III λ5696 line strengths (viz MC 6, MC 53, MC 79, MC 24 and MC 71), one as WC6 (MC 65), one is a WNE-CE star (MC 48) and one is possibly an intermediate WC4-WO star (MC 78). Of the two stars observed in M31, one is classified as WC4–5 (MS 11) and the other as WC7-8 (MS 4).

An objective, automated group-finding algorithm has been used to re-identify the OB associations in the irregular galaxy NGC 6822. The properties of the OB associations, such as size, age, and mass, are compared with those of OB associations in M33 identified using similar data and techniques. These two data sets allow the first objective comparison to be made of the properties of OB associations in two quite different galaxies.

Preliminary single-burst population synthesis models are presented for weak and strong spectral features as a function of metallicity for old populations. Models agree with published globular cluster observations as well as theoretical calibrations. For small ellipticals, the galaxies and model predictions agree well in all indices. For the typical giant E, metallicity-insensitive features (G band, Hβ) continue to match the models, while the behavior of metallicity sensitive features (Fe, CN, Mg, Na D) diverges. In giant Es, with increasing metallicity, the light-element indices deepen relative to the iron-peak features far more rapidly than the models. This effect almost certainly indicates that, in the typical giant E, some light elements are enhanced with respect to the iron-peak elements compared to the solar ratios.

Data of 136 high velocity outflows listed in a comprehensive catalogue and maps of three dimensional distribution are presented. The distribution of collimation factors and the formation rate is estimated.

We present a study of the photometric and spectroscopic properties of elliptical galaxies in compact groups. We find that although some elliptical galaxies are affected by interactions and mergers, the current merger rate is small, even in compact groups of galaxies. We also find tentative evidence that the central velocity dispersions of elliptical galaxies in compact groups are lower than the velocity dispersions of similar galaxies in other environments.