Great progress has been made in recent years in understanding the large-scale structure of the universe. Recall that it is only within this century that we have even come to realize the existence of other galaxies as separate entities. Until the 1920’s the universe did not extend beyond the Milky Way. Novae and Cepheid variables changed that picture, and for the past 75 years extragalactic astronomy has been one of the most active and fertile areas of science. The concept of an expanding universe and its beginning in a Big Bang all derive from the discovery of external galaxies.

Distant galaxies are faint and have small angular sizes, therefore their study has remained the province of the largest telescopes. Before the launch of Hubble Space Telescope, ground-based telescopes had succeeded in detecting distant galaxies out to redshifts of z ~ 1, and in establishing certain of their characteristics. But, there was uncertainty as to how much further HST could push the study of distant galaxies given its modest 2.4m diameter mirror and the fact that the surface brightnesses of cosmologically distant objects decrease as (1 + z)4.

For this reason, one of the early observations that was scheduled immediately after the first servicing mission of HST in December 1993 to repair spherical aberration was the re-imaging of the cluster of galaxies 0939+4713 at z = 0.4 that had been observed previously by Dressier et al. (1994) from both the ground and with the aberrated HST. The ten-orbit WFPC2 image demonstrated HST’s ability to resolve structure in distant galaxies, showing spiral and elliptical galaxies with a clarity approaching that achieved for the Coma cluster from the ground. Spirals are seen to be relatively abundant in 0939+4713, although they generally show an anomalous morphology.

The evolution of single stars on and away from the main sequence is well understood. A degenerate core is formed in a star as the star leaves the main sequence and expands to a giant with a radius typically 50 - 500 Ro . Observationally it is known that most stars are members of binary systems, and among these many have orbital periods less than 100 y. It can happen, therefore, that the expanding envelope of the primary of a binary system can reach to the secondary. As this happens, the primary fills its Roche tidal lobe and transfers matter to the secondary; if the primary has a radiative envelope the rate at which this occurs exceeds the Eddington limit of the secondary, which therefore repels the incoming gas, forming a common envelope around the two stars. Friction within the envelope causes the stars to spiral towards each other until the energy and angular momentum extracted from the binary orbit and transferred to the envelope are sufficient to eject the common envelope as a planetary nebula, leaving a short period binary comprising a white dwarf and a main sequence star.

This mechanism of producing short period binaries containing white dwarfs, proposed by Ostriker and by Paczynski (1976), is the probable origin of the class of objects known as Cataclysmic Variable Stars (CVs), which encompass the classical novae, dwarf novae, novalike variables and a variety of related objects. Evidence has been accumulating for forty years (Crawford & Kraft 1956, Warner 1995a) that every CV consists of a secondary star (usually a dwarf, but a few systems contain giants) filling its Roche lobe and transferring mass to a white dwarf primary. In systems of normal chemical composition the orbital periods lie between 75 mins and ~250 d, with the majority having . A few hydrogen-free systems are known for which 17 mins < Porb < 50 mins. It should be noted that CVs are very compact binary systems: for h such a binary would fit inside the Sun.

Some 30 years ago very few scientists thought that black holes may really exist. Attention focussed on the black hole hypothesis after neutron stars had been discovered. It was rather surprising that astrophysicists immediately ‘welcomed’ black holes. They found their place not only in the remnants of supernova explosions but also in the nuclei of galaxies and quasars.

Joint Discussion 1 was supported by Division IV (Stars) and Commission 29 (Stellar Spectra), and co-supported by Commissions 28 (Galaxies), 36 (Theory of Stellar Atmospheres) and 37 (Stellar Clusters and Associations). Members of the scientific organizing committee were: N. Arimoto (Japan), B. Barbuy (Brazil), T. Beers (USA), J. Bergeron (Germany), M. Bessell (Australia), R. Cayrel (France), G. Gilmore (UK), B. Gustafsson (Sweden), F. Matteucci (Italy), P. Nissen (Den-mark), and M. Rich (USA).

The inspiration for this meeting was the growing overlap and connections between previously separate areas of astrophysical research, namely, studies of stellar abundances, the bulges of galaxies, the gaseous components of nearby galaxies and the clouds (some of which may be primordial) responsible for the narrow absorption lines in quasars.

The signature of the early chemical evolution of our Galaxy is imprinted in the abundance ratios of the oldest stars. We recall that element ratios are determined by a mix of the relative rates of different types of supernovae, the stellar IMF, and the relative histories of star formation rates and gaseous flows, and thus encapsulate much of the history of star formation and ISM evolution in galaxies. Hence, abundance ratios in stars are a primary probe for testing theories of galaxy formation and evolution.

We do not know how the Galaxy formed: both the Eggen, Lynden-Bell & Sandage (1962) and the Searle & Zinn (1978) scenarios may be accommodated in the recent proposal of van den Bergh (1993) where the inner Galaxy follows ELS, whereas the outer Galaxy formation conforms to the Searle-Zinn proposition. A combination of abundance ratios, ages derived from colour-magnitude diagrams, and kinematical properties, can give us the required information to trace the past history of our Galaxy. We note here, that although stellar evolution and model atmospheres are not discussed in the proceedings both topics are of fundamental underlying importance. Model atmospheres are used to derive temperatures, colors and bolometric corrections of stars that are used not only in abundance analyses but also in deriving the ages of stars by comparing CM diagrams with HR diagrams. This process is under close scrutiny because of the apparent difference between the ages of the oldest stars and the expansion age of the universe.

Early abundance studies (e.g. Pagel 1968) showed that neutron-capture heavy elements (Z > 30) are present in halo stars, but deficient relative iron. Truran (1981) argued that at low [Fe/H] the chemical enrichment time scale was shorter than the lifetime of low-mass AGB progenitors, which are the main source of solar system heavy elements. He proposed that in the halo the heavy elements were produced by high mass stars, in type II supernova events (SNII), by rapid neutron capture nucleosynthesis (the r-process).

Spite & Spite (1978) investigated the trend of heavy element abundances with metallicity, from a small sample of halo stars. They found that at [Fe/H]~ -1.5 the halo [heavy element/Fe] ratio is approximately solar; but at lower [Fe/H] there is a roughly linear decrease of [heavy element/Fe] with declining [Fe/H]. Subsequent observations confirmed the general trend of heavy elements in the halo: [M/Fe]~0 down to [Fe/H]~ -2, followed by a linear decline in [M/Fe] to lower [Fe/H] (e.g. Gilroy et al 1988, Lambert 1987).

Additional evidence for the role of SNII in halo heavy element synthesis comes from the trend of [Eu/Fe] with [Fe/H]. Europium is an almost pure r-process element (Käppeler et al. 1989) and its abundance trend with metallicity is similar to the α element trend (e.g. O and Mg made in massive stars). The element ratios show an increase in [M/Fe] as [Fe/H] decreases from 0 to —1; below this point [Eu/Fe] and [α/Fe] remain constant at ~+0.3 dex. For α elements this behavior is thought to be due to the change in the relative contributions from type II SN and type la SN in the disk and halo (Tinsley 1979). The trend for Eu also indicates production by massive stars (e.g. SNII). Near [Fe/H]~ -2.5 Eu appears to decline relative to [Fe/H] (like other heavy elements, but unlike the α elements). This abundance trend has been used to constrain the numerous proposed astrophysical sites of the r-process (e.g. Mathews & Cowan 1990).

Only a bit more than 25 years ago, it seemed possible to assume that all Galactic globular clusters were chemically homogeneous. There were indications that star-to-star Fe abundance variations existed in ω Cen, but this massive cluster appeared to be unique. Following Osborn’s (1971) initial discovery, Zinn’s (1973) observation that M92 asymptotic giant branch (AGB) stars had weaker G-bands than subgiants with equivalent temperatures provided the first extensive evidence that there might be variations in the abundances of the light elements in an otherwise “normal” cluster. Since then star-to-star variations in the abundances of C, N, O, Na, Mg and Al have been observed in all cases in which sample sizes have exceeded 5-10 stars, e.g., in clusters such as M92, M15, M13, M3, ω Cen, MIO and M5. Among giants in these clusters one finds large surface O abundance differences, and these are intimately related to differences of other light element abundances, not only of C and N, but also of Na, Mg and Al (cf. reviews by Suntzeff 1993, Briley et al 1994, and Kraft 1994). The abundances of Na and O, as well as Al and Mg, are anticorrelated. Prime examples are found among giants in M15 (Sneden et al 1997), M13 (Pilachowski et al 1996; Shetrone 1996a,b; and Kraft et al 1997) and ω Cen (Norris & Da Costa 1995a,b).

These observed anticorrelations almost certainly result from proton- capture chains that convert C to N, 0 to N, Ne to Na and Mg to Al in or near the hydrogen fusion layers of evolved cluster stars. But which stars? An appealing idea is that during the giant branch lifetimes of the low-mass stars that we now observe, substantial portions of the stellar envelopes have been cycled through regions near the H-burning shell where proton-capture nucleosynthesis can occur. This so-called “evolutionary” scenario involving deep envelope mixing in first ascent red giant branch (RGB) stars has been studied by Denissenkov & Denissenkova (1990), Langer & Hoffman (1995), Cavallo et al (1996, 1997) and Langer et al (1997). The mixing mechanism that brings proton-capture products to the surface is poorly understood (Denissenkov & Weiss 1996, Denissenkov et al 1997, Langer et al 1997), but deep mixing driven by angular momentum has been suggested (Sweigart & Mengel 1979, Kraft 1994, Langer & Hoffman 1995, Sweigart 1997).

Measurement of the abundances of the light and heavy elements in stars of the Milky Way galaxy is the cornerstone for the study of numerous aspects of chemical evolution in galaxies and the Universe. We stand poised to enter an era of rapid understanding, as new-generation telescopes with apertures in the 8m-10m class enable astronomers to obtain high-resolution, high-signal-to-noise near-UV, optical, and IR spectra of the stars which have locked up the chemical history of our Galaxy in their outer atmospheres. It is thus appropriate to review present surveys for the low-metallicity stars of our Galaxy, as the stars we uncover today will be studied so intensively in the coming decades.

The origin of the elements in the early Galaxy has been thought to be fairly well understood as primordial matter polluted by ejectae of type II supernovae. Some recent observational results have led to reconsider in more detail this statement. As a result, it is confirmed in some respects, but curiously, when the same metallicity can be found both in the halo and in the thick disk, the stars contaminated by SN la ejectae are more the halo stars than the thick disk stars.

I review the current status of measurements of element ratios in metal rich stars. These include giants in the Galactic bulge, metal rich Galactic globular clusters, and high velocity dwarfs in the Solar vicinity. There is evidence for enhancement of Mg and Ti in the bulge. While s-process elements have Solar abundance in bulge giants, they are deficient in the metal rich, high velocity dwarfs. There are no secure measurements of oxygen abundance in the bulge, but present data indicate no evidence either for extremely low or high [O/Fe] in bulge giants. The current data are limited by resolution and S/N, and I outline goals for observations with the next generation of ground-based telescopes.

If the central bulge of the Milky Way formed rapidly, one would expect that enrichment could occur only through massive star SNe, with little or no contribution from core deflagration SNe. In this scenario, one expects alpha-capture elements to be enhanced at a given [Fe/H] compared to the Solar vicinity: element abundance ratios may record something of the history of star formation. The idea is developed in Wheeler, Sneden & Truran (1989) and its application to bulges and elliptical galaxies is developed in Matteucci & Brocato (1990). As Kraft reviews in this volume, the stellar evolution effects that modify surface abundances in globular cluster stars do not appear to be a problem for field giants.

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.

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.

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 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.

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

“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.

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.

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 (~ 109 M ʘ ) 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 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.