Research - S. Hüttemeister

Research Interests

S. Hüttemeister

My research mostly (but not exclusively) concerns the interstellar medium (ISM to the experts) in the central regions of galaxies, including starbursting systems, barred galaxies, and (almost) normal objects like our own Milky Way or the nearby Grand Design spiral galaxy M51. I am especially interested in the relation between the physical parameters of the gas, mainly its temperature and density, its chemistry and the dynamical conditions it is subject to.

It becomes progressively clear that the ISM in the central region of galaxies is very different from what astronomers are used to seeing in the disks of galaxies. The gas often has a hot, diffuse molecular component that may not be bound in `classical' clouds. Wrongly assuming that it is sets off e.g. mass determinations by up to an order of magnitude.

Barred Galaxies: Laboratories for studies of diffuse gas

Starburst Systems: Extreme cases

Dwarf Galaxies: Small but typical

Tidal Tails: Galactic rebirth

M51: Exceedingly orderly

Our Galactic center: almost normal

A topic of special interest right now:

Intermediate Luminosity Mergers

A few details:
Infrared luminous (L(IR) > 10^11 L(sun)) and ultraluminous galaxies (ULIRGS, L(IR) > 10^12 L(sun)) are believed to mergers of massive, gas-rich galaxies. They are spectacular systems, related to super-starburst and Active Galactic Nuclei (AGN) activity, attracting the attention of a large number of researchers. Their molecular gas distribution is almost always found to be concentrated into a few 100 pcs within the center, often in rotating disk ar tori, while the atomic gas extends into enormous tidal tails. In the tails, tidal dwarfs galaxies can form, and the formation of elliptical galaxies may be tied to these cosmic fireworks.

Still, galaxies will collide and merge which do not have the necessary properties to produce spectacular ULIRGs and AGNs, either because the masses of the two progenitors are too small are unequal, or because they simply are not gas-rich enough, or because the orbital and/or internal properties of the galaxies do not allow am efficient funneling of the gas to the very heart of the merger.

These intermediate mergers and interactions also represent an ongoing change and development of the galaxies in the universe - even if the change appears more modest, it may well be the normal, more likely (and posisbly more important?) mechanism of galaxy evolution. Since the ULIRGs have captured the imagination of the majority of the researchers, these galaxy interactions remain to a large degree unexplored. Their contribution to the evolution of galaxies is not well understood - in particular not the relation to the major mergers and ULIRGs.

Knowledge of the parameters that govern the extent and efficiency of a starburst resulting from a merger and its connection to the progenitors can onlt be gained if the moderate luminosity mergers are investigated along with the high luminosity counterparts. If galaxy formation at high z happened through mergers, it is essential to understand the different types of mergers in the local unioverse, where the systems can be resolved with present techniques.

Currently active Projects
(quite a few!)
and current collaborators, plus the telescopes we use!

A very high resolution CO map of M51
Susanne Aalto, Nick Scoville, Pat Thaddeus - OVRO interferometer
UGC 2855: The second longest gaseous bar ever seen
Susanne Aalto, Bill Wall - OVRO interferometer, upcoming: Calar Alto
More barred galaxies: NGC 7479 and NGC 5218
Susanne Aalto, Mousoumi Das, Bill Wall - OVRO interferometer
High density tracers in the starburst galaxy NGC 253
Susanne Aalto, Per Bergman, Rainer Mauersberger- OVRO interferometer
IMC 0953 - a nearby tidal protogalaxy?
Sven Kohle, Christian Henkel, Jonathan Braine - IRAM interferometer
Mrk 297: A non-central starburst in a merger
Uli Klein, Albert Greve - IRAM interferometer
NGC 1569: molecular gas in a post-starburst dwarf galaxy
Chris Taylor, Albert Greve, Uli Klein - IRAM interferometer
The dynamics of the molecular gas in the Galactic center region
Wolfgang Duschl, Susanne v. Linden, Gereon Dahmen (now at Fernbach Software S.A.)
theory, based on 1.2m CTIO and SEST
The excitation of HNCO in the Galactic center region
Davide Rizzo, Gereon Dahmen - SEST
The silicon isotope ratio in the galaxy
Claudia Lemme - SEST
The oxygen isotope ratio in the Galaxy
Tom Wilson, Bill Langer, Gereon Dahmen - SEST
Highly excitad ammonia - whereever it can be found
Christian Henkel - Effelsberg



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