The metal-rich dwarf stars in the solar neighbourhood have historically not attracted as much attention as the metal-poor (halo) stars which tell us about the early phases of the chemical evolution of our galaxy. The properties of metal-rich stars are highly important when we try to interpret integrated spectra from metal-rich stellar populations, such as the Bulge and elliptical galaxies. A small group of so called super metal rich stars (SMR) have played a significant role in shaping the conceptions of such populations. Famous examples are the dwarf HR1614 and the giant μ Leonis. In the review by Taylor (1996) SMR stars are discussed in great detail, in particular the reality of extremly high [Fe/H]. Taylor (1996) find that no giant stars fulfil the criteria fulr SMR-ness that he sets and only a handful of dwarf stars do, and most of them are possible candidates rather than firm detections.

A few recent studies have studied known SMR candidates and stars with high [M/H] (as derived from photometry), Feltzing & Gustafsson (1997), Castro et al. (1997), Gonzalez (1997), McWilliam & Rich (1994), Castro et al. (1996). A first conclusion is that there are indeed quite a few stars with [Fe/H] > 0.2 dex (the definition of SMR, see Taylor 1996). We will here review these studies in some detail.

The combination of abundance ratios with kinematical data can detail the picture even further. For example we can study stars on highly eccentric orbits which trace the evolution in the galactic disk closer to the galctic centre. Not much is known about these stars but we did have some very intriguing observations; Barbuy & Grenon (1990) (hereafter BG90) found that dwarf stars on very eccentric orbits contained much more oxygen than what was expected from standard models of galactic chemical evolution of the disk, Edvardsson et al.(1993) (hereafter E93) found large spreads and “upturns” for certain elements, Na, Si, Ti, Al, for stars with 0.0dex < [Fe/H] < 0.2 dex.

Stellar populations of elliptical galaxies were studied extensively in the recent past (eg., Arimoto & Yoshii 1987; Buzzoni et al. 1992; Worthey 1994; Kodama & Arimoto 1997). However, colours and line-strengths analysed by these approaches came mainly from central regions of galaxies and possible variations of stellar population structure within a galaxy were entirely ignored. Kodama & Arimoto (1997) recently show that a colour-magnitude (CM) relation of ellipticals in Coma cluster (Bower, Lucey, & Ellis 1992), and the CM relation of cluster ellipticals in general, should originate from a difference in mean stellar metallicities, as suggested by Arimoto & Yoshii (1987), and cannot be due to an increase of mean stellar age towards luminous galaxies as claimed by Worthey (1994). It is quite often stated that any theory of galaxy formation should explain the origin of CM relation, or in other words, the mass (luminosity) - metallicity relation of elliptical galaxies. However, one should not forget the fact that the CM relation is defined only for stars in the central regions of galaxies; it is possible that the CM relation itself is an observational artifact, since ellipticals show in general radial gradients of metallic-line strengthes, decreasing from a centre towards outer regions (eg., Faber 1977; Davies, Sadler, & Peletier 1993; Gonzalez 1993; Carollo & Danziger 1994). Indeed, Gorgas & Gonzalez (1996) found that ellipticals with larger central Mg2 indices tend to have steeper Mg2 gradient, which suggests that global metallicities of ellipticals are perphaps universal and are independent of galaxy luminosities.

The Keck 10-m telescope has begun to produce many new findings in a field of stellar spectroscopy with the help of the High Resolution Spectrograph (HIRES). The other large telescopes such as the Subaru, VLT, and Gemini are now being constructed and expected to perform high-resolution spectroscopy in a near future within several years or so. These highresolution spectroscopic studies will be carried out based on studies which have been made mainly with existing telescopes with aperture smaller than 4 m.

Abundance Ratios are observed in a wide variety of instances addressed in this volume: in Gas and Stars, Simple Stellar Populations (SSPs) like star clusters, and, finally, in Composite Stellar Populations (CSPs) like E/SO galaxies (Bulges, spheroidal galaxies, Merger Remnants, etc.) on which the focus of this contribution will be. I’ll briefly review the observational situation and the current interpretation and then cast some doubt on the latter from our own chemically consistent spectrophotometric modelling results.

I can compute arbitrary-abundance models and spectra at high resolution using millions of atomic and diatomic molecular lines. Examples are given for Sakurai’s object and for a λBoo star. I am continuing to improve the input line data.

For the past seven years a large, international team of astrophysicists and atomic physicists has been engaged in the systematic exploration and analysis of the extraordinary spectrum of one chemically-peculiar star, chi Lupi (B9.5pHgMn + A2 Vm). The observational data consist of 345 Ã of the star’s ultraviolet spectrum acquired with the Goddard High Resolution Spectrograph (GHRS) on board the Hubble Space Telescope (HST) at a resolving power of approximately 90,000 and an average S/N ratio of about 75 in the continuum. These data were supplemented with new optical-wavelength echelle spectra obtained at the AAT and at KPNO[l]. We have named this study “The x Lupi Pathfinder Project”, because it is in many respects similar to the initial exploration of a strange new land – never before has the ultraviolet spectrum of an ultra-sharp-lined star been observed at this level of detail and accuracy.

The merger model for elliptical galaxy formation has received increasing attention since it was first suggested by Toomre & Toomre (1972). Van den Bergh (1984) pointed out a problem with the idea that elliptical galaxies were formed by simply combining two, or more, spiral galaxies. He noted that the specific frequency (SN, number of globular clusters per unit galaxy light) is systematically lower for spirals than for ellipticals. Schweizer (1987) suggested that globular clusters (GCs) might be expected to form in the merger process, thereby alleviating or possibly eliminating the SN problem. Ashman & Zepf (1992) developed this idea into a merger model for GC formation with testable predictions.

We recently examined this model in the light of new HST and ground-based imaging data on the blue and red sub-populations of GCs in elliptical galaxies (Forbes, Brodie & Grillmair 1997). We concluded that the merger model for GC formation has serious problems, particularly in explaining the characteristics of GCs in giant elliptical galaxies with high SN. A multi-phase collapse scenario was suggested as more consistent with the available evidence.

The purpose of this paper is to define a set of “standard”, “reference” or “comparison” stars, according to their use, of spectral type A0V in order to be used for further studies in the domain of peculiar stars as well as normal stars of this Teff and luminosity range.

The well measured gas-phase abundances in the low halo suggest that this region of the Galaxy has total (gas plus dust) metal abundances which are close to those in the solar neighborhood. The gas-phase abundances in the halo are generally higher than those seen in the disk, however, this affect is likely due to the destruction of dust in the halo clouds. Observations of high velocity clouds (HVCs) in the halo suggest that these clouds have metal abundances which are substantially lower than those measured for the local interstellar medium. These determinations, however, are often of lower quality than those for the low halo because of uncertainties in the hydrogen abundances along the sightlines, in the incorporation of elements into dust, and in the partial ionization of the clouds.

The quest for accurate fundamental parameters (M, R, Teff log g, v sin i) of CP stars has been a lasting problem ever since the nature and origin of these stars has been discussed. The main reason for the difficulty lies in the anomalous colours of these stars, linked with their abundance anomalies which are responsible for complicated blocking and backwarming effects. In the following, we review the Teff determinations proposed so far, and show how the Hipparcos results improve the radius and log g determinations of nearby Ap stars.

We discuss elemental abundances in quasar absorption line systems and their implications for galaxy formation and chemical evolution.

The NLTE abundance analyses concerning late-B through A stars carried out before 1990 have been well summarized by Takada-Hidai (1991), which may be consulted for details; about 10 elements had been studied in NLTE by that time.

“It takes little talent to see clearly what lies under one’s nose, a good deal of it to know in which direction to point that organ.” W. H. Auden

Listening to the sequence of fine talks that have made up this Joint Discussion, I have been impressed by the veritable flood of new observations that bear on the question of the abundance ratios in the oldest stars. The flood is marked by depth and diversity, as ‘noses’ are being pointed in highly profitable directions. As an example of depth, I would note the extensive investigations reviewed by Andy McWilliam of the chemical compositions of very metal-poor stars where [Fe/H] ≃ -3 marks the upper end of the range defining the class. To characterize diversity, I draw attention to the analyses of quasar absorption line systems so ably discssed by Limin Lu who showed that the abundance ratios for the gas in such high z systems resemble ratios found from Galactic metal-poor stars. Of course, to many at this Joint Discussion the wealth and diversity did not come as a surprise. Indeed, I suspect that many of us pursue the topic of the composition of the first generations of stars because of the wealth and diversity of observational constraints that may now spawn a unified interpretation. Hopefully, the marvellous talks given here will pull in a few new minds - young and old - to ponder nucleosynthesis in very young galaxies and in our Galaxy in particular.

In an attempt to make the present summary comprehensible yet sufficiently concise I will risk some over-simplification: further details are given in Seaton (1997, 1998 — Papers I and II).

In a star let Fv dv be the outward flux of radiant and let an atom of element k present an effective area of σv(k) for absorption of radiation. Then the momentum absorbed per atom and per-unit area and unit time is G(k) = (1/c) ∫ Fvσv(k) dv which is just the force acting on the atom. The radiative acceleration is grad(k) = G(k)/M(k) where M(k) is the atom’s mass.

UGCA 86 is an irregular dwarf galaxy in the 1C 342 / Maffei I group, just next to the Local Group. It was first mentioned by Zwicky (1968) as VII Zw 009, but not contained in his “Catalogue of Selected Compact Galaxies and of Post-eruptive Galaxies” (1971). It was independently rediscovered by Nilson (1974) and Rots (1979) as UGCA 86 and A 0355 resp. Rots found it by HI observations, and from peculiarities in the HI morphology and kinematics he suspected that it was interacting with 1C 342. Thus, the tentatively interesting items: a starforming, low surface brightness dwarf galaxy in an interacting system (one of the nearest), triggered us to engage in more detailed studies.

In a first step, we made detailed surface photometry in U, B and V (Richter et al. 1991). UGCA 86 proved to be one galaxy (which was not trivial; Saha & Hoessel 1991 discussed if it could be a chance superposition or a collision of two independent galaxies, due to the very different appearence of the southern and the central starburst; Miller & Hodge 1992 and the distance measurements of Karachentsev & Tikhonov 1993 support our result) with the typical exponential brightness profile of a spheroidal dwarf galaxy, and contains at least two starburst regions of very different color: a central red one and a blue one in the southern outskirts. There is an infrared source in the IRAS Point Source Catalogue coincident with UGCA 86. The amount of dust indicated by this source is in very good quantitative agreement with what would be required to redden the central starburst by the observed color difference compared to the southern burst. Nevertheless, the straightforward hypothesis, that the color of the central burst is due to dust extinction, is contradicted by the improved, higher resolution data.

In the light of recent results from helioseismology, the abundance anomalies seen at the surface of Bp, Ap, Am and Fm stars appear as the measurable superficial effect of a process that has much more general impact.

Two important questions are connected to the evolutionary history of blue compact dwarf galaxies (BCDs): the triggering mechanism of the starburst and the properties of the precursor(s) and successor. The halos of many BCDs show red colours indicating that the host galaxy is in fact of early type. But where did the gas come from? Was it there from the start in a quiescent mode or was it fed by a merger with an intergalactic gas cloud or a gas-rich dwarf? Is there a general answer to this question or are there different families of BCDs?

The BCDs generating most of the interest are those with low chemical abundances, typically 10% solar. The only plausible precursors in this case are metal-poor dis, LSBGs or pure HI clouds (e.g. Thuan & Seitzer 197, ApJ 231, 680). In a comparison between LSBGs and BCDs Taylor et al. (e.g. 1997, ApJ 480, 524; 1996, ApJS 107, 143) found an excess of HI rich companions in the environments of BCDs which they interpret as a support of tidal triggering. We have studied a few massive (~ 109Mʘ ) metal- poor blue compact galaxies (BCGs). These are too bright to be classified as dwarfs but define an extension of the BCD family. For simplicity we will in the following use the common abbrevation BCD. In a search for possible precursors we have studied a sample of blue LSBGs with metallicities similar to BCDs (5-15%).

We present a brief review about recent progresses concerning the study of diffusion processes in CP stars. The most spectacular of them concerns the calculation of radiative accelerations in stellar envelopes for which an accuracy better than 30% can now be reached for a large number of ions. This improvement is mainly due to huge and accurate atomic and opacity data bases available since the beginning of the 90’s. Developments of efficient computational methods have been carried out to take advantage of these new data. These progresses have, in turn, led to a better understanding of how the element stratification is building up with time. A computation of self-consistent stellar evolution models, including time-dependent diffusion, can now be within the scope of the next few years. However, the progresses previously mentioned do not apply for stellar atmospheres and upper layers of envelopes.

We attempt to solve the question of star formation triggers and star formation laws by studying samples of simple objects and defining carefully the possible external effects. Among the star formation (SF) triggers there are some that can operate only in large disk galaxies. These are shear instabilities and density waves, and we can eliminate them if we restrict the sample to diskless objects of low mass. Such galaxies, which do show star formation, are late-type dwarf galaxies (DGs).

Other SF triggers are related to the neighborhood a galaxy finds itself in. Such triggers are galaxy-galaxy collisions and galaxy-intracluster matter interactions (stripping, shocks, etc.). These also can be eliminated by properly choosing the sample to study; one selects galaxies from neigh-borhoods of widely different densities (of galaxies) and compares their SF parameters.

We selected our first samples in a region of relatively high galaxy density, where a complete morphological classification of objects was available, and suitable depth in brightness sampling could readily be achieved. This is the Virgo cluster, where Binggeli, Sandage and Tammann (1985, BST) provide a sample of more than 2000 DGs. Among those, some 25% are of late type and are classified by BST as blue compact dwarfs (BCDs), as Magellanic irregulars (Im) of five possible sub-classes, or as combinations of those two classifications.