We have used the Hydra fiber positioner and the bench spectrograph on the KPNO 4 m telescope to measure radial velocities for giants in the Draco (Dra) and Ursa Minor (UMi) dwarf spheroidal galaxies. The measurement uncertainties are 1–10 km s−1 per observation, with the median uncertainty being 3.6 km s−1. To date, we have reduced the data from two of our three runs. In UMi these have yielded 150 velocities for 85 member giants; 52 stars have two or more measurements. In Dra we have 108 velocities for 84 member giants and 20 stars have two or more measurements. There is good agreement between the repeat observations and with the Olszewski, Aaronson, & Hill (1995) MMT echelle velocities.

The catalogue is a cross-identification catalogue containing 11800 galactic and SMC member stars. It gives individual results of various authors before 1988, but no mean values. The best is to make statistics inside individual systems, comparing them afterwards. Fig.1 concerns the radial velocities obtained for BAF stars in 1963 by FLORSCH using an objective-prism. Since the largest gradient lies in a dirction near the north (FLORSCH 1972), we reported velocities to the declinations of the stars. It appears that the velocities belong to three groups separated by two empty strips showing each a gradient of about 30 km/s/deg falling down from north to south. The same structure appears for other homogeneous populations, like K type stars (fig.2). This gradient agrees with HINDMAN's HI measurements and was recently confirmed by the results obtained by Le COAR etal for HII, as shown by the crosses on figure 1 which represent mean values of HII velocities calculated by using Le COAER's values. In order to find out the structure by using the Cepheids and eventually confirm the great depth we announced in 1972, 73 and 81, we corrected their mean magnitudes by the formula m1=m+2.03 logP to calculate the fictive magnitudes they would have if their common period was one day. Fig.3 gives the result for the Bar of the Cloud. Out of an important thickness, it appears that the northern end is nearer than the southern by a mean value of about 20 kpc. If one consider the whole Cloud, out of the Wing, fig.4, one can see that the extreme northern Arm is folded and slightly extended.

We study here the dynamics of an extended shell of relatively low-mass (almost zero-mass) particles around massive binary systems by computer simulations in the framework of approximately restricted three-body problem. We examine a set of several initial conditions concerning the masses M1 and M2 of the binary components surrounded by N test particles in uniform random distribution on a spherical envelope of radius R expanding with a velocity V. We apply this model to binary galaxy systems with a halo of baryonic dark matter, e.g., massive black holes. It is shown that, initially, the shell expands isotropically with decreasing velocity and then, falls back into the system forming zones of compressed matter. At some moment of time there could be a collapse of these particles on to the heavier component of the binary. Further in time, a number of particles escape from the system. We consider a number of different models with different initial parameters. For models with smaller R and V, about one-half of the particles escape from the system; while for larger values the shell disrupts as a whole. The escaping particles form a collimated flow in the plane of the orbit of the binary. The position of the flow and the directions of motions depend on the position of the heavier component of the binary at the moment of the closest approach of the particles and on the ratio M1/M2.

The scale height of the disk stars in our Galaxy increases continously with age, which is also seen in the age-velocity dispersion relation of the solar vicinity. In external galaxies a similar evolution of stellar disks can be deduced from the colour distribution of the light in edge-on galaxies. Using physical disk models and stellar population synthesis we compute the luminosity and colour profiles in optical and infrared bands. For diffusion coefficient and SFR constant in time the vertical density profile is exponential. The colour profiles are mainly affected by dust extinction, and the age and metallicity distribution of the stars. The comparison of a basic model with the observed profiles of IC 2531 shows, that these influences can be disentangled by analyzing the systmatic deviations in the colour profiles.

Our chemical evolution models describe in detail the enrichment process of a number of individual elements from 12C to 56Fe, including delayed SNI contributions. Variation of the characteristic timescale of star formation (SF) t∗ not only results in differences in the abundance evolution but also changes abundance ratios of elements originating from different nucleosynthetic sites, as e.g. [C/O], [O/Fe], or [Mg/Fe].

As part of a large project to study the rate, distribution and history of star formation in the outer parts of galactic disks (Ferguson, PhD thesis), we have obtained very deep Hα and B-band images of the nearby face-on spiral NGC1058. Our images reveal extremely low surface brightness outer spiral arms in the B-band which extend well beyond the Holmberg radius and appear to be aligned with underlying HI spiral arms. These features contrast greatly to the flocculent appearance of the innermost regions of the disk and the complete absence of any well defined-arms in the Hα image. The surface brightness profile derived from the B-band image exhibits a sharp fall off in the inner regions of the disk followed by a much shallower decline beyond ~ R25 and consequently a single exponential disk cannot be fit to the entire profile.

Many observations point out the great difference in metallicities determined from broad band colors of various wavelength regimes.

We have fitted exponential, isothermal (“sech2”) and intermediate (“sech”) model distributions to the observed vertical light profiles in edge-on galaxies.

Magris et al. (1993, Proceedings of the ESO/OHP Workshop on Dwarf Galaxies, ed. G. Meylan) have combined the spectral evolution population synthesis code of Bruzual & Charlot (1993, ApJ 405, 538) with the multipurpose photoionization-shock code MAPPINGS (Binette et al. 1993, AJ 105, 797) in order to calculate self-consistently the evolution of the nebular emission corresponding to the ionizing spectra produced by the synthetic population. In this poster we compare the redshift dependence of the EW[OII]3727 predicted by the Magris et al. models with the observations available (Colles et al. 1990, MNRAS 244, 408; Kennicutt 1992, ApJS 79, 255; Le Fevre et al. 1994, ApJ 423, L89). Models in which stars form following the Salpeter IMF according to the SFR Ψ(t) = 1M⊙τ−1exp(–t/τ), for τ = 1, 2, 3, 5, 7, and ∞ Gyr have been considered. We assume Ho = 50, Ω = 0, tg = 16 Gyr. About 2/3 of the galaxies in these samples have EW[OII]3727 from 2 to 5 times larger than the ones predicted by our models for steadily decreasing or even constant (τ = ∞) SFR. To cover the range of observed values of EW[OII]3727 we assume that instantaneous bursts (Salpeter IMF) of star formation take place in these galaxies, superimposed on the steady SFR used in the models. The mass added by the bursts as newly formed stars per unit mass of stars in the underlying galaxy is in the range 1 – 4 × 10−4. Depending on the rest-frame wavelength, the color of the galaxies may remain unaffected or become considerably bluer as a consequence of the bursting activity.

We present an Optical, FIR and X-ray study of the low LFIR Sc galaxy, NGC 247. Global correlations (ie. B or X vs. Radio or FIR) in late-type spirals suggest that some luminosities do not scale linearly. We describe first results of a program to study emission in late-type spirals on local (kpc) scales to investigate this non-linear behaviour. Our data includes B, I, Hα+[Nii] CCD, IRAS 60, 100μm (Rice 1993), and ROSAT PSPC, (0.1-2.4keV) images. Since abstract submission we have added H I (Carignan and Puche 1990) and 1.49 GHz continuum (Condon 1987). The Hα+[Nii] is generally coextensive with the IRAS emission and H I. The brightest Hα+[Nii] region (log LHα~38.6 ergs s−1) in a region of low FIR flux, may possess a locally warm 60/100μm ratio suggesting a similarity with more luminous galaxies that have warm 60/100μm ratios globally. 1.49 GHz sources are not cospatial with bright X-ray sources, nor with Hα+[Nii]. Three extended 1.49 GHz sources are cospatial with very faint, soft X-ray emission, suggesting a SNR origin. We cannot rule out a direct 1.49 GHz/X-ray or 1.49 GHz/ H ii origin due to relativistic e− propagation. ROSAT PSPC results suggest 4 4σ (0.1-2.4 keV) X-ray sources are intrinsic. Their LX range of 1036–37 ergs s−1 is consistent with X-ray binaries, whilst the total LX = 3.0×1037 ergs s−1 is underluminous by ~3, compared to previous regression fits. A faint soft, LX ~ 1×1036 ergs s−1 nuclear X-ray feature may be a SNR outflow, and similar to plumes/outflows seen in starbursts, but 104 less luminous.

We selected a sample of dwarf galaxies in the Virgo cluster from the original catalog of Bingelli, Sandage and Tamman (1985), which have been measured at 21 cm by Hoffman et al. (1987). The original sample was selected to have both high surface brightness objects (classified as BCD or anything/BCD), and low surface brightness galaxies (classified as ImIII, ImIV or ImV). An additional selection was done on the total amount of HI, as given in Hoffman et al. We selected from each surface brightness group objects with high HI content (flux integral larger than a set threshold), and others with low HI content. We thus defined four samples differing in surface brightness level and total HI content.

The Hubble Space Telescope key project to determine the extragalactic distance scale aims to measure H0 to 10%. To achieve this goal will require Cepheid distance measurements for some 20 galaxies within a redshift of approximately 103 km/s. These galaxies in turn will calibrate five secondary distance indicators which will extend the volume over which the expansion rate has been measured to some 106 Mpc3.

The interpration of the interaction in galaxies is simplified in mixed pairs (E+S) because most or all of the cold gas can be traced to an origin in a single galaxy (S). We used spectroscopy, imaging, far–IR, and stellar population synthesis to study the stellar content and history of star formation in the nuclear region of the early–type galaxy in the mixed pair AM0327–285. We used the procedure for stellar population synthesis developed by Bica (1988) to estimate the star-formation history of the nucleus of the elliptical galaxy. The method uses a library of star clusters, and estimates the chemical evolution in a test population with two parameters: age and metallicity; no assumptions on gravity or details of stellar evolution are necessary, and the IMF is implicit in the cluster spectra. The procedure allows one to both determine the chemical enrichment and date successive generations of star formation. The result indicates that the dominant population is old and metal–rich ([Z/Z]⊙=0.3), while ~ 10% of the flux at 5870 Å arises from a young stellar population (age ≤ 5 × 108 yr), confirming that this early-type galaxy had recent star formation as suggested also by photometry and far–IR data (de Mello et al 1994). This age is close to several estimates of the characteristic timescale of the interaction, suggesting that the mass influx associated with this star formation occurred as a result of an earlier phase of the interaction and not as a result of the present geometry of the pair.

Polar ring galaxies, where rotation velocities can be measured in two orthogonal planes, are generally considered to be ideal objects for studies of the three-dimensional distribution of dark matter in galaxies.

The Surface Brightness Fluctuation (SBF) method introduced by Tonry & Schneider (1988) is known as a distance indicator. However, we focus on another aspect. Our aim is to obtain new information on the stellar population that constitutes an elliptical galaxy by comparing radial gradients in SBF magnitudes with traditional broad-band colours. We have obtained I–band images of NGC 3379 with the NTT/SUSI, 0″.8–1″.2 FWHM, Sodemann & Thomsen (1994). An analysis similar to that of Tonry & Schneider (1988) is applied. However, the smoothed galaxy is obtained from (Thomsen & Baum, 1989). For NGC 3379 we find a SBF signal of 3.39 ± 0.02 ADU, see Figure 1, corresponding to an object with apparent magnitude Ī = 28m.62 ± 0m.03. If the image is subdivided into 4 annular regions, we find the gradient in I in Figure 2. As both fluctuation ‘noise’ and photon noise raise towards the centre of the galaxy, it is difficult to correct for globular clusters in a position independent way. Dealing with gradients of the SBF signal, the task is even more delicate. The weakening of Ī towards the galaxy centre is foreseen by the stellar population models of Worthey (1994).

This work presents a new calibration of the metallicity scale for elliptical galaxies based on new observational data. I use my observations with the 1000-channel IPCS of the 6m telescope. The spectra for 100 galaxies are published elsewhere (Sil'chenko & Shapovalova, 1989; Sil'chenko, 1990). A subsample of 30 ellipticals has become a base for the new metallicity scale.

The central part of NGC 1052 has been observed at the prime focus of the 6m telescope with the Multi-Pupil Spectrophotometer equipped with a two-dimensional IPCS. Ninety-nine spectra over the central 14.5″x11″ are registered in the spectral range of λλ4700 – 5400 AA and are used to map ionized-gas velocities (by [OIII]λ5007) and to derive radial profiles of absorption-line equivalent width for MgIλA5175, FeIλ5270, and Hβ.

Our aim is to quantify the stellar population within the nuclear regions of AGN by means of long slit spectroscopic observations in the optical range (5000-10000Å), including MgI, NaI, TiO, CN, CaIIT. We wish to determine whether there is a relationship between central activity and stellar population, and to determine the nature of the featureless continuum.

In many hydrodynamical models of elliptical galaxies the absence of information about the detailed evolution of stars and the spectro-photometric output by hot gas and stars leads to a missing link between the data we obtain in observations (photons) and the internal behavior (dynamics) of a galaxy.

We have begun a program with the Low Resolution Imaging Spectrograph, operating with 30 multi-slits per exposure (Oke et al 1994, Cohen et al 1993) on the ten – meter W. M. Keck telescope located on Mauna Kea, Hawaii to observe the globular cluster systems of the Virgo ellipticals. We expect to learn about the dark matter content of galaxy halos, the formation of these halos and their cluster systems, possibly the formation of the galaxy's themselves, the interaction of the cluster system with the galaxy's gravitational potential (i.e. rotation and spinup), and the homogeneity of chemical evolution in various places. The metallicity of the globular clusters versus the metallicity of the underlying galaxy can also by analyzed. In addition the dynamics (i.e. in practice, the rotation and velocity dispersion) of the halo of the parent galaxy versus the globular cluster system can be determined.