Elevated ratios of [S II]/Hα relative to those typical of H II regions have been used to identify supernova remnants (SNRs) and also characterize the diffuse Galactic background (Reynolds 1985) and gas observed on the large scale in other galaxies (e.g., Lehnert & Heckman 1994). We explore the implications for these regions of the fact that ionized sulfur may exist both in gas that is predominantly neutral as well as fully ionized.

The possibility to study magnetic field of the Galaxy calculating correlation or structure functions of synchrotron background radio emission have been known long ago (Kaplan and Pikel'ner (1963); Getmantsev (1958)). But this method had not been as popular as other methods of magnetic field studies. However theoretical calculations made by Chibisov and Ptuskin (1981) showed that correlation functions of intensity of synchrotron background radio emission can give a lot of valuable information about galactic magnetic fields because of the intensity of synchrotron background radio emission depends on H⊥. According to this theory correlation C(θ, φ) and structure S(θ, φ) functions of intensity, as functions of angular separation θ between two lines of sight and position angle φ on the sky between this two lines of sight, can be presented as a sum of isotropic (not dependent from angle φ) and anisotropic parts:

The interstellar bubbles are generally the result of the interaction of strong stellar winds with the surrounding material. HI voids and shells have been disclosed around several WR stars in our Galaxy (e.g. Niemela & Cappa de Nicolau 1991, Dubner et al. 1992). We report here an analysis of the interstellar medium in the vicinity of the WR star HD 192163 = WR 136 and the optical ring nebula NGC 6888 based on HI observations. Our aim is to look for the traces left in the cold interstellar gas by the action of the stellar winds of HD 192163.

The interaction of strong stellar winds with the interstellar medium creates large cavities or interstellar bubbles surrounded by expanding outer shells. 21-cm line (HI) observations have revealed the presence of such neutral gas bubbles around several WR stars (e.g. Niemela & Cappa de Nicolau 1991 and references therein; Dubner et al. 1992).

Continuing our search for HI bubbles around WR stars, we have analyzed the neutral hydrogen distribution in the vicinity of the Wolf-Rayet star WR149, a highly reddened WN6-7 star located at 6.5 kpc in the direction (l,b) = (89.°53,+0.°65).

The expansion of shocked interstellar medium around an OB association is an example of the astrophysical blastwave (Ostriker and McKee, 1988). The thin, cold, shell-like structure expanding supersonically accumulates the ambient medium. We assume that the shell has the zero thickness at radius of the shockwave rs and that it expands at velocity vs. The shell is divided into elements described with equations of motion: d/dt(Mv s ) = dS[(P–Po ) + novo (v s –vo )]–Mg(R,z), where M and dS are the mass and the surface of it, P, Po are the inside and outside pressures, no,vo are density and velocity of the ambient medium and g(R,z) is the gravitational acceleration in the Galaxy. R, z are the galactocentric cylindrical coordinates. The mass of an element increases as long as the expansion velocity component normal to the shell, v⊥ exceeds the velocity of sound in the ambient medium M = v ⊥ nodS. The 3D model using the above infinitesimally thin shell approximation was developed by Palouš (1990, 1992) and Silich (1992).

The giant bubble in Cepheus was discovered by Kun et al. (1987) in the IRAS maps. It has an angular diameter of about 9° and connects several well-known star forming regions such as IC1396, S140, NGC7129. All these regions have nearly the same distances of about 800 pc permitting a good distance and linear size estimate for the bubble. Figure 1 shows the surface distribution of IRAS 100 μ optical depths, obtained from the 60 and 100 μ data and smoothed to the resolution of the HI survey. Although the bubble was discovered in the IRAS data base it is well pronounced in the integrated HI map obtained from the observations of Heiles & Habing (1974) and Weaver & Williams (1973). Figure 2 shows the HI line area map.

The observational tests to check the concept of nonthermal particle generation in the vicinity of OB associations embedded in a superbubble (SB) are discussed. Acceleration of nonthermal charged particles is expected to be very efficient due to powerful energy release by supernovae and colliding stellar winds. The distinctive features of the SB's emission spectra due to nonthermal particle interaction with gas, dust and electromagnetic fields are summarized.

G54.4–0.3 is an extended shell-type supernova remnant (SNR) in the Galactic plane. We selected this source as a candidate for the interaction of SNRs with the interstellar medium on the base of an investigation of cool IRAS point sources in the direction of SNRs. We found a statistical excess of IRAS sources with FIR spectra similar to young stellar objects (T d ≈ 25 − 45 K) in the vicinity of G54.4–0.3 and a number of other SNRs in the northern hemisphere (Junkes & Fürst 1992).

From our recent Faint Object Spectrograph (FOS) observations of the Orion Nebula obtained with the Hubble Space Telescope, we present preliminary results that address the nitrogen abundance. The list of detected lines and their identifications included the first measurement of the N II] 2142 Å line in an H II region. This measurement in conjunction with [O II] 2471 Å permits a new assessment of the important N/O ratio in Orion. Unfortunately, the measurements of the N III] 1747-54 Å multiplet and the O III] 1660-66 Å multiplet have poor signal-to-noise, precluding another independent derivation of N/O.

In a well known paper written a quarter century ago, cosmology was described as a search for two numbers (Sandage 1970). As those of you who have attended any of the parallel sessions of Symposium 167 surely appreciate, today's cosmologists find more than just two numbers interesting. It is likewise clear from the present symposium that the number of interesting parameters associated with the Milky Way is very much greater than two.

The rotation curves of spiral galaxies indicate that most of them have massive dark coronas, and it seems likely that our Galaxy also has a dark corona. Our position in the galactic disk makes it difficult to measure the galactic rotation curve beyond about 20 kpc from the galactic center, but it does allow us to use several other indicators of the total galactic mass out to very large distances. I will review some of these indicators. The conclusion is that the Galaxy does indeed have a massive dark corona: the data are consistent with the enclosed mass within radius R increasing like M(R) ≈ R(kpc) × 1010 M ⊙, out to a radius of more than 100 kpc, and a total galactic mass of at least 12 × 1011 M ⊙.

I review the dynamical measurements of mass in the solar neighborhood and show that, within 1 kpc, ∼ 40% is unaccounted for by known stars and gas. I discuss several interpretations of the data including the ‘standard model’ where the extra mass is due to a spherical dark halo. I argue that the evidence for a radically different picture of an ultra-flat distribution is at least as compelling as the standard model.

We have measured radial velocities for a large number of classical cepheids of the Galaxy, particularly in the outer disc. We determine the rotation curve up to a galactocentric radius of 16 kpc. The results are then compared to similar studies using HII regions. We also consider some possible complications.

The spatial distribution of the outlying satellites of the Galaxy has been determined by fitting a three dimensional surface to the positions of 10 companion galaxies and 13 distant globular clusters. Both groups show a highly flattened distribution whose minor axes are aligned to within ∼ 5°. The combined group of 23 objects shows a triaxial distribution with semimajor axis extending ∼ 400 kpc. The minor axis is inclined at ∼ 76° to the Galactic poles. There is a suggestion of a nested hierarchy consisting of satellite galaxies, globular clusters, and distant halo field stars, in order of decreasing spatial extension.

As part of a stellar population sampling program, a series of photometric probes at various field sizes and depths have been obtained in a low extinction window in the galactic anticentre direction. Very deep CCD frames probe the most external parts of the disc, providing strong evidence that the galactic density scale length for the old disc population is rather short (2.5 kpc) and drops abruptly beyond 5.5-6 kpc.

Deeper frames in the I band allow to estimate photometric distances and confirm the position of the disk edge. A few stars are found at larger distances. Their number is exactly what we expect if the thick disk does not have any cutoff. We discuss the implications for the formation and evolution of the disc, for the star formation threshold, and for the origin of the thick disc population.

The galactic rotation curve has been determined using the space velocities of 197 OB stars associated with 59 HII regions.

We present here a new analytical Galactic potential. We used the constraint of galactic globular cluster dynamics compared to their spatial distribution. This was done with the help of the globular clusters' proper motions. The result for the clusters dynamics show a better agreement between orbital parameters and statistical distribution of the studied globular clusters than in previous published potentials. The globular cluster dynamics constrain the mass distribution on a large scale, until 40 kpc from the centre. In this model, the total mass for the Milky Way is 7.9 1011 M⊙.

The Galactic rotation law provides critical information for estimating the distribution of mass in the Galaxy, for tying the distance of the Sun from the Galactic center to local distance scales, and, if determined over large enough distances, for estimating the total mass of the system and the amount of nonluminous matter present. Interior to the Sun velocities are well defined by observations of the ISM, particularly HI. These techniques are not available for points exterior to the Sun and we must rely on observations of velocities of objects whose distances can be estimated. Notable among these are the Cepheids (Pont et al 1994) and the combination of CO velocities and OB cluster distances (Brand & Blitz 1993) where the two are found to coexist. Adding a new class of objects, particularly bright, relatively common objects to this effort is of importance.

A new homogeneous catalog of photographic RGU star count and three-color data in seven high-galactic latitude fields has been used to determine the structural parameter values from a large number of multi-component population models of the Galaxy. The data provide strong evidence of a prominent thick disk component coexisting with a canonical thin disk and a low-density spheroidal halo.

A system of galactic constants is proposed. Due to the intention of basing it on stellar dynamics, the working hypothesis is the assumption that the Galaxy is in a steady state characterized with axial symmetry. Then, as easy to see, one reaches a system containing seven independent constants typical for the present assumption. The current knowledge concerning the amounts of these constants is discussed.