Ww Zeilinger

Stellar dynamical evidence for dark halos in elliptical galaxies - The case of NGC 4472, IC 4296, and NGC 7144

Extended and accurate major axis kinematical profiles and line strength gradients of the elliptical galaxies NGC 4472, IC 4296, and NGC 7144 have been measured using the ESO NTT in the EMMI long-slit spectroscopic mode. For NGC 7144 the stellar rotation curve and velocity dispersion profile extend to 75″ from the center (where the surface brightness is 24.4 B-mag arcsec −2 , 2.8 mag below the sky), with typical error bars of 10 km s −1 . The flat or slowly increasing velocity dispersion profiles of these galaxies indicate that massive dark halos might dominate their dynamics

On the origin of bursts in blue compact dwarf galaxies: clues from kinematics and stellar populations

Blue compact dwarf galaxies (BCDs) form stars at, for their sizes, extraordinarily high rates. In this paper, we study what triggers this starburst and what is the fate of the galaxy once its gas fuel is exhausted. We select four BCDs with smooth outer regions, indicating them as possible progenitors of dwarf elliptical galaxies. We have obtained photometric and spectroscopic data with the FORS and ISAAC instruments on the VLT. We analyse their infrared spectra using a full spectrum fitting technique, which yields the kinematics of their stars and ionized gas together with their stellar population characteristics. We find that the stellar velocity to velocity dispersion ratio ((nu/sigma)(star)) of our BCDs is of the order of 1.5, similar to that of dwarf elliptical galaxies. Thus, those objects do not require significant (if any) loss of angular momentum to fade into early-type dwarfs. This finding is in discordance with previous studies, which however compared the stellar kinematics of dwarf elliptical galaxies with the gaseous kinematics of star-forming dwarfs. The stellar velocity fields of our objects are very disturbed and the star formation regions are often kinematically decoupled from the rest of the galaxy. These regions can be more or less metal rich with respect to the galactic body and sometimes they are long lived. These characteristics prevent us from pinpointing a unique trigger of the star formation, even within the same galaxy. Gas impacts, mergers, and in-spiraling gas clumps are all possible star formation igniters for our targets.

On the dynamics of very flattened ellipticals.

Our aim is to study the generic phase-space structure of flattened ellipticals by investigating a few typical cases. Here we report on the E4 elliptical NGC 4697.

Formation and evolution of dwarf elliptical galaxies: Structural and kinematical properties

We confront predictions of the currently popular theories for dE formation and evolution with the observed position of dEs in

A triaxial model for the bulge of NGC 4697

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The intrinsic shapes of galactic discs

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A search for dark matter in elliptical galaxies: radially extended spectroscopie observations for 6 objects

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A SEARCH FOR DARK-MATTER IN ELLIPTIC GALAXIES - RADIALLY EXTENDED SPECTROSCOPIC OBSERVATIONS FOR 6 OBJECTS.

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THE DISTRIBUTION OF IONIZED-GAS IN EARLY-TYPE GALAXIES.

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THE INTERNAL DYNAMICS OF VERY FLATTENED NORMAL GALAXIES : STELLAR DISTRIBUTION FUNCTIONS FOR NGC 4697

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