RESEARCH
1. Galactic star formation
1.1 Detection and investigation of protostars
(mm/submm/FIR)
We are performing 1.3mm surveys of regions of ongoing star
formation in order to detect protostellar objects. Our search strategy
has turned out to be extremely succesfull and has led to the detection
of more than a dozen protostars. These objects are observed subsequently
in the submm and FIR range for the determination of their physical properties
like mass, temperature and density profile.
1.2 Investigation of young stellar objects (NIR/MIR/FIR)
Infrared surveys of young stellar clusters show evidence for
deeply embedded ClassI objects, i.e. stars which are surrounded by relicts
of their protostellar dust cocoons and/or circumstellar disks. The circumstellar
environment is investigated by variuos infrared techniques in order to
study the formation of protoplanetary disks.
1.3 Reddening and IMF of young stellar clusters
(UBVRI, JHKLM)
Young open clusters are ideal places to investigate the law of
interstellar extinction, which allows to study the properties of dust
grains. Furthermore, we address the question whether high and low mass
stars are formed simultaneously within the same molecular cloud.
1.4 Dust polarization at 1.3mm
During the protostellar collapse the magnetic fields also condense
and thus should cause highly polarized emission at mm wavelengths. We
plan to detect this emission from newly discovered protostars for the
first time.
2.1 Dust and CO content of dwarfs, normal spirals
and active galaxies
The dust and gas content of various samples of galaxies is investigated
by mm/submm continuum and CO(1-0)/(2-1) observations. The parallel data
sets allow the determination of the total amount of the interstellar medium,
the gas-to-dust ratio and the conversion factor between CO and H_2.
2.2 Global star formation efficiency in galaxies
The star formation efficiency and the activity of galaxies in general
can be basically reduced to the conversion of gas into luminosity. We
study the different activity stages between various galaxy types by determining
their ratio of total luminosity vs. total gas mass.
3. Interacting galaxies
3.1 The interstellar medium in interacting galaxies
(mm/submm/FIR)
Interacting galaxies are relatively strong emitters at FIR and mm
wavelengths. We investigate the amount and the spatial distribution of
gas and dust in these active systems in order to understand the process
of triggered star formation.
3.2 Induced star formation and starbursts (optical
spectroscopy)
Optical follow-up observations of our mm-studies are performed to locate
individual regions of star formation and to determine the dynamical state
of the interstellar medium in interacting galaxies.
4. Quasars and high-z radio galaxies
4.1 Emission mechanisms in quasars (mm/submm/FIR)
Observations between 60 and 1300mu have turned out to be a very
efficient tool to distinguish between synchrotron radiation and thermal
emission from dust. We are involved in several long term projects (ground-based
and satellite) to investigate the emission mechanisms of various class
of quasars, including radio-quiet, radio-loud (steep and flat radio sources)
and high-z objects.
4.2 Optical Variability of quasars (UBVRI)
A long term study on the variability of quasars has been
started at our 87cm telecope on Cerro Armazones, Chile. The variability
studies are performed with a 2k CCD camera at UBVRI.
4.3 Polarization of quasars at 1.3mm
A sytematic monitoring of the 1.3mm polarization of quasars
is planned. The aim of this program is to distinguish between synchrotron
radiation and thermal emission from dust.
4.4 The interstellar medium in radio galaxies
of high redshift (mm/submm/FIR)
We observe high-z radio galaxies from the ground at mm/submm
wavelengths and have complementary ISO data for a number of sources. This
and future data allow to study the interstellar medium at the earliest
phases of galaxy formation and give insight into the star formation efficiency
at early cosmic epochs.