The Bulge has been mapped in the infrared both coarsely from balloon platforms and in detail from the IRAS satellite and the ground. The information revealed by each type of survey is discussed. Particular attention is given to surveys of the Sgr I clear field, its content of long-period variables and their implications for distance determination and the high end of the Bulge luminosity function.

The review covers the properties of red variables in globular clusters and the Galactic Bulge. Details are given of our current understanding of the Mira evolutionary phase. There is evidence that Miras in the LMC and the Bulge occupy different parts of the instability strip but obey the same PLC relation. The Bulge contains at least 2 × 104 Miras of which 100 or so have luminosities in excess of Mbol = — 5 mag. The Mira phase lasts more than 105 yr. These objects originate from stars with a wide range of metallicity, but it is currently unclear if the most metal-rich stars reach the top of the AGB to become Miras. Preliminary data suggest that the distribution of the Miras along the minor axis of the Bulge is different from that of the late-M stars but similar to the 2.4 μm luminosity.

Our knowledge of the Bulge carbon stars is briefly reviewed. It is suggested that, by analogy with the carbon-rich dwarfs, these stars are probably best understood as the products of binary evolution.

I discuss observable quantities of OH/IR stars and their interpretation. The strong 1612 MHz maser is found in about 1/2 of all the stars that reach the AGB and then have the following properties: they are oxygen–rich, of high–luminosity (3,000 → 30,000L ⊙), vary in luminosity with a long period (P>500 d), lose mass rapidly and have a metallicity high enough to form sufficient amounts of dust (the metallicity of the LMC is probably the lowest value sufficient to produce OH/IR stars). OH/IR stars can be several Gyr old. There are at least three different populations each characterized by different galactic orbits. (1) OH/IR stars in the galactic disk on almost circular orbits; (2) OH/IR stars in the galactic bulge on orbits of lower angular momentum; (3) OH/IR stars within 150 pc from the galactic center forming a rapidly rotating system.

The available kinematical data on OH/IR stars is discussed, and dynamical models for the OH/IR stars are presented.

Several independent studies of the abundances and kinematics of K and M giants in the inner Galaxy (R < 2 kpc) are assembled to trace out this region's global properties. The mean metal abundance is [M/H] ≈ +0.3 at R = 0.5 kpc, and declines by about 1.2 dex out to R = 2 kpc. The line-of-sight velocity dispersion at R = 0.5 kpc is σr ≈ 115 km sec—1 for all population tracers, and declines by d log σr /d log R = —0.4. It now seems fairly clear that only the most metal-poor K giants become RR Lyrae variables, while the more metal-rich ones become late M stars. There is some evidence that the most metal-rich stars are in a flatter, more rapidly rotating system. Metal abundance ratios for a few K giants suggest that the inner Galaxy may have formed rapidly.

After a discussion of the methods used to derive the physical parameters of planetary nebulae and their central stars, the global properties of planetary nebulae in the Galactic bulge are reviewed, and compared to those of planetary nebulae in different contexts.

The stellar populations give traces of the formation history of the bulges. The metallicity distribution of K-giants in the Galactic bulge resembles to that of the giant ellipticals. There seems to be no conspicuous colour-magnitude relation intrinsic to the bulges. This can be explained if the bulges formed by the dissipative collapse of central regions of proto-galaxies followed by the supernova-driven bulge wind which was induced later than the dwarf ellipticals of the similar mass (the biased wind). Unfortunately, the observational data available at present of stellar populations of the bulges are not yet sufficient to get a firm conclusion on the origin of the bulges.

A fair fraction of stars in the Galactic Bulge (a possibly in bulges in general) appears to be more metal rich than the sun. Some of the current limitations in quantitatively modelling such super metal rich (SMR) stars are briefly recalled, including the question of the helium enrichment, of the metallicity dependence of mass loss, and of the metal opacity. Recent color-magnitude diagrams for stars in the Galactic Bulge are show that the bulk of Bulge stars must be very old, although current data do not allow to determine the age with sufficient accuracy to establish the relative age of the Halo and of the Bulge. The question of the nature of the most luminous (AGB) stars in bulges and in M32 is then addressed in some detail, discussing a series of methodological aspects which would need careful consideration before using bright AGB stars as age indicators. It is concluded that — for the time being — none of the claims for the presence of an intermediate age component in the Galactic Bulge, in M32, and in the bulge of M31 is completely exempt from ambiguities, and ways for elimitating such ambiguities are suggested. Finally, from the evidence that bulges are dominated by a very old stellar population it is concluded that star formation in bulges probably started and was essentially completed before the completion of star formation in the halo: bulges are likely to on average older than halos.

The central 200 pc of the Galaxy is obscured by 5-30 visual magnitudes of extinction and therefore may be studied only in the infrared. The central parsec consists of a mostly red star cluster (IRS 16) and a cluster of ≈ 10 HeI Wolf-Rayet or Of-like stars; this cluster is the best evidence for star formation in this region. The central 5 pc has an extended giant branch (to M bol /=−6) and long period variables. These stars are not extraordinarily bright; in the central 200 pc luminous asymptotic giant branch (AGB) stars (M bol < −5) concentrate toward the nucleus in a distribution more flattened than the general light. Candidates for relatively young objects include a rapidly rotating population of high outflow velocity OH/IR stars. The AGB luminosity function in the central 200 pc resembles that recently found in M32 and M31 bulge fields. Depending on how one interprets the extended giant branch, the population may be intermediate age with some ongoing star formation, or mostly old and metal rich, with star formation confined to the nucleus.

Recent work on the intrinsic shape, the internal kinematics of stars and gas, and the dynamics of the Galactic Bulge is discussed. Starcounts, measurements of the integrated light and the kinematics of the atomic and molecular gas all provide strong evidence that the Bulge is triaxial, and is rotating fairly rapidly. To date, there is little evidence for triaxiality in the stellar kinematics: the available stellar velocities are consistent with Kent's (1992) oblate model. This unsatisfactory situation is expected to improve rapidly.

Recent work on the dynamics of galaxy bulges has been dominated by two themes. (1) Bulges share the richness in kinematic structure that is currently being discovered in elliptical galaxies. This includes kinematic evidence for triaxiality and for accretion (counterrotating gas and stellar components). (2) The main subject of this paper is observational and theoretical evidence that some “bulges” are built secularly out of disk material. Many bulges show photometric and kinematic evidence for disklike dynamics. This includes (i) velocity dispersions σ much smaller than those predicted by the Faber-Jackson σ — M B correlation, (ii) rapid rotation V(r) that implies V/σ values well above the “oblate line” describing rotationally flattened, isotropic spheroids in the V/σ — ellipticity diagram, and (iii) spiral structure dominating the r 1/4 part of the galaxy. In these galaxies, the steep, r1/4-law central brightness profiles belong not to bulges but to disks. That is, some galaxy disks have central brightness profiles that are much steeper than the inward extrapolation of an exponential fit to the outer parts. These observations and n-body simulations of gas flow in nonaxisymmetric galaxies imply that high-central-concentration, flat components can be formed out of disk gas that is transported toward the center by bars and oval distortions. The n-body models suggest further that some “bulges” are built of disk stars heated in the axial direction by resonant scattering off of bars. These effects are signs that important secular evolution processes are at work in galaxy disks.

The structure of bulges and ellipticals, and their relation to galaxy halos are reviewed. Since many ellipticals contain faint disks, the qualitative distinction between bulges and ellipticals is more accurately described as a quantitative variation in Bulge/Disk ratio. The exception may be the brightest ellipticals, which are usually Bright (est) Cluster Members. The available evidence suggests that the spheroid properties are determined by more than halo properties alone. This is clearest for systems with low B/D ratio, where bulge velocity dispersions are similar to disk velocity dispersions. Constraints on the stellar formation scenarios are discussed.

Without attempting to cover all of the topics discussed at this meeting, I plan to talk briefly about some of the major achievements and ideas that came up here, and then mention a few of the important open questions and some work that might be done to answer them.

Depending on the nature of the various components (stars, gas) present in triaxial stellar systems (elliptical galaxies, bulges and bars), the dynamics is expected to be rather different. The stars are collisionless, dissipationless, and dynamically hot; they are mainly trapped by quasi-periodic or chaotic orbits. On the contrary, the gas is collisional, dissipational, and dynamically cold; the cold or warm gas (≲ 104 K) is a powerful orbital tracer, however shocks prevent it from following self-crossing orbits. The hot gas (≲ 106 K) is influenced by “repulsive” pressure forces which prevent in close encounters the flow from being strongly shocked; it rather follows chaotic trajectories. By means of fully self-consistent 3D simulations with stars and gas using PM (Pfenniger & Friedli 1992) and SPH (Friedli & Benz 1992) techniques, we investigate the response of gaseous components in the following situations: 1) slow or fast pattern speed Ωp , 2) direct or retrograde gas motion with respect to the stars, and 3) warm or hot gas temperature T. Initial parameters and final characteristics of each runs are reported in Table I.