Galaxy formation and evolution

Abstract:

The morphological features of the early-type disk galaxy NGC 4672 are discussed as well as the velocity curves and velocity dispersion profiles of stars and ionized gas along both its major and minor axes. We conclude that NGC 4672 has structural (i.e. a bulge elongated perpendicularly to the disk) and kinematical (i.e, a stellar core rotating perpendicularly to the disk) properties similar to those of the Sa NGC 4698. The presence of the isolated core suggests that the disk component is the end result of the acquisition of external material in polar orbits around a pre-existing oblate spheroid, as in the case of the ring component of AM 2020-504, the prototype of polar ring ellipticals.

Abstract:

LUCIFER (LBT NIR-Spectroscopic Utility with Camera and Integral-Field Unit for Extragalactic Research) is a full cryogenic NIR spectrograph and imager (lambda 0.9 mu - 2.5 mu, zJHK-bands) to be built by a consortium of five institutes (Landessternwarte Heidelberg (LSW), Max Planck Institut fur Astronomie in Heidelberg (MPIA), Max Planck Institut fur Extraterrestrische Physik (MPE) in Garching, Astronomisches Institut der Ruhr Universitat Bochum (AIRUB) and Fachhochschule fur Technik und Gestaltung (FHTG) in Mannheim). The instrument has been selected as one of three first-light instruments for the Large Binocular Telescope (LBT) on Mt. Graham, Arizona which first mirror becomes available to the community in early 2003. The second mirror and a second more or less identical spectrograph/imager follows 18 month later. Both LUCIFER instruments will be mounted at the bent Gregorian foci of the two individual LET-mirrors and include six observing modes: seeing and diffraction limited imaging, seeing and diffraction Limited longslit spectroscopy, seeing limited multi-object spectroscopy (MOS) and integral-field spectroscopy (IFU). The detector will be a Rockwell HAWAII-2 HgCdTe-array with a pixel-size of 18 mu.

Abstract:

LUCIFER-MOS is a liquid nitrogen cooled near infrared multi object spectrograph imaging 20 freely selectable sub-fields of about 2.2" x 1.8" and 6 x 4 image elements each on the entrance slit of the LUCIFER spectrograph. The image elements are re-arranged by 480 fused silica fibers of 50 mu m core diameter and 100 mu m total diameter with integrated, hexagonal lenslets of 0.6 mm width corresponding to a 0.3" field. The pre-optics magnifies the telescope image by a factor 3.3, thus adapting the telescope plate scale to the lenslet scale, and additionally providing a cold stop. The post-optics converts the f/3 fiber output beam to the f/15 beam accepted by the spectrograph. Each of the 20 6 x 4 fiber arrays together with its pre-optics is mounted in a spider arm which can be freely positioned within the 200 mm diameter field of view by a cryogenic robot. The robot performs three rotational movements to position the spider arms and is driven by cold stepper motors. The spider arms are locked in their positions by two permanent magnets each. Their magnetic field can be compensated by coils to unlock the arms and move them across the field of view.

Abstract:

I apply constant-anisotropy spherical dynamical models to a sample of 18 round ellipticals to look for evidence of dark halos. All 18 lie along a Tully-Fisher relation parallel to that for spirals, but fainter at given upsilon(c) by about 1 mag. By constructing more general, flattened models, I show there is a degeneracy between anisotropy and flattening, and discuss its implications.