|
|
|
Very Long Baseline Interferometry Group
Director: Prof. Dr. J. Anton Zensus
Group
website
|
|
|
|
|
Code:
AZ01
|
TANAMI (Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry)
TANAMI is an international project done in collaboration with
the Universities of WŸrzburg and Valencia and NASA's
Goddard Space Flight Center to monitor the parsec-scale structures of
relativistic jets in active galactic nuclei in the Southern Hemisphere. The
jets south of -30 deg declination
are being monitored at 1.3 cm and 3.6 cm radio wavelengths by means of
very-long-baseline interferometry. TANAMI uses the Australian Long
Baseline Array complemented with additional stations extended towards South
Africa, the Antarctica and Chile. Observations started in 2007, prior to
the launch of the gamma-ray Fermi satellite, which
is also probing those sources in the other extreme of the spectrum, with
the aim of relating the emission in the radio and at high energies.
Correlated multiwavelength observations are being
done with modern X-ray telescopes (XMM-Newton, Swift, INTEGRAL) as well as
in the NIR/optical regime. The PhD project will investigate the nature of
active galactic nuclei, their supermassive black holes and relativistic
jets, making use of unprecedented data across the whole electromagnetic
spectrum.
Project Aims:
The most powerful
extragalactic jets of the Southern Hemisphere are being probed by Fermi in
the gamma-ray regime, and by single-dish and interferometric
TANAMI observations in the radio band. The imaging and further
analysis of individual sources and of the complete data set is planned in
this PhD project: data debugging, image analysis, spectral studies of the
jets, correlation study of the morphological and brightness variation in
the context of a multi-band approach are the main goals of the project.
The data being collected are unique, for its quality and for coming
from the relatively unexplored Southern skies. The project guarantees
integration in the NASA Fermi/LAT collaboration, high-impact publications
and a long time baseline for collaboration, since Fermi/LAT will operate
for the next 5-10 years, and TANAMI is expected to keep collecting data
during this time.
Bibliography:
Ojha et
al. A&A, 519, A45 (2010)
MPIfR Press Release (June 2011): http://www.mpifr-bonn.mpg.de/public/pr/pr-cena-may2011-dt.html
See full publication list at http://pulsar.sternwarte.uni-erlangen.de/tanami/pubs/
Contact: Prof. Dr. Anton Zensus (azensus@mpifr-bonn.mpg.de) and
Prof. Dr. Matthias Kadler (matthias.kadler@astro.uni-wuerzburg.de),
Prof. Dr. Eduardo Ros (ros@mpifr-bonn.mpg.de)
Site: Bonn, Max-Planck-Institut fŸr Radioastronomie, VLBI group In collaboration with the
University of WŸrzburg, Germany
Back to AZ
project list -
Back to top
|
|
|
|
|
Code:
AZ02
|
Monitoring of Jets in Active Galactic Nuclei with VLBA
Experiments
About ten percent
of the active galactic nuclei (AGN) eject jets of plasma at relativistic
speeds from their central regions. The rapidly variable non-thermal emission
and apparent superluminal motions in the jets imply that they contain
highly energetic plasma moving nearly directly at us at speeds approaching
that of light. Understanding the acceleration, collimation, and stability
properties of these flows is one of the central topics in the modern
relativistic astrophysics. High-dynamic-range, high-resolution radio
imaging of (sub-)parsec-scale structures in the
jets is essential to derive observational constraints for the physical
conditions in the jets close their launching site.
Very long baseline interferometry (VLBI) imaging with its
unsurpassed angular resolution allows direct studies of the innermost
parsecs of the jets. The MOJAVE program (Monitoring of Jets in Active
Galactic Nuclei with VLBA Experiments) monitors structural changes in the
parsec-scale jets of over 300 AGN making it one of the largest VLBI
monitoring programs to date. The program is unique in its extent,
time-sampling, and statistical completeness of the sample. Many of the
monitored sources have over 15 years of well-sampled observations providing
an unprecedented data set for studying the evolving jet structures.
The PhD candidate will join the international MOJAVE program
team and use the survey data to analyze the properties of magnetized plasma
jets in AGN. According to his/her interests, the candidate can concentrate
e.g., on a statistical analysis of the observed structures of the jet and
its magnetic field, or carry out an in-depth study of the time-evolution of
the shocked regions in the jets of a few selected sources.
Contact: Prof. Dr. Anton Zensus (azensus@mpifr-bonn.mpg.de), Dr.
Tuomas Savolainen (tsavolainen@mpifr-bonn.mpg.de),
Prof. Dr. Eduardo Ros (ros@mpifr-bonn.mpg.de)
Site: Bonn, Max-Planck-Institut fŸr Radioastronomie, VLBI group
Back to AZ
project list -
Back to top
|
|
|
|
|
Code:
AZ03
|
From Black Holes to Jets: Active Galactic Nuclei
Very Long Baseline Interferometry in the radio regime (VLBI)
provides highest resolution images of the central regions of Active Galactic
Nuclei (AGN). In these inner parts of the most energetic objects of the
Universe jets are created and collimated. The role of the accretion disk
and the black hole in the launching of jets is still a matter of debate.
Unification scenarios – relying on the same Jet/Accretion disk/Black
Hole-system in all objects - explain different types of AGN as due to
orientation effects. However, this cannot explain all observed
jet-phenomena.
Project aims: The research for the PhD
project concentrates on unusual phenomena in the jets of AGN in the
vicinity of black holes. The current paradigm of
"simple" outward motion is being questioned in a number of AGN.
To investigate this unexpected behavior in more detail and to study the physical
emission processes in jets in general and the connection between the
central engine and jet launching, is the subject of this PhD project.
Contact: PD Dr. Silke Britzen (sbritzen@mpifr-bonn.mpg.de)
Site: Bonn, Max-Planck-Institut
fŸr Radioastronomie,
VLBI Group
Back to AZ
project list -
Back to top
|
|
|
|
|
Code:
AZ04
|
Supermassive Binary Black Holes & Merging Galaxies
The expected frequent mergers of galaxies over the course of
their formation and cosmological evolution must lead to the formation of
supermassive binary black holes. Black hole binary mergers could be
responsible for many quasars. Detecting more such binary systems is
therefore of great interest for key topics in astrophysics ranging from
galaxy formation to activity in galaxies. A number of phenomena were
attributed to the presence of binary systems, including X-shaped radio
galaxies and double-double radio galaxies, precession of a jet emitted by
one of the binary components, wiggling of a jet due to the orbital motion,
periodic variations in the luminosity due to perturbation of an accretion
disk around one of the holes, binary galaxies with radio-jet cores, and
binary quasars, etc.
Project aims: The research planned for
the PhD project focuses on the investigation of the connection between
galaxy interactions and active galactic nuclei with particular emphasis on the
proof of the existence and analysis of supermassive binary systems in the
centers of AGN.
Contact: PD Dr. Silke Britzen (sbritzen@mpifr-bonn.mpg.de)
Site: Bonn, Max-Planck-Institut
fŸr Radioastronomie,
VLBI Group
Back to AZ
project list -
Back to top
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Millimeter and Sub-millimeter Group
Director: Prof. Dr. Karl Menten
Group website
|
|
|
|
|
Code:
KM01
|
The Intimate Connection between radio and gamma-ray emission
from the Gamma-ray Binary LSI +61303
Recent progress in gamma-ray astronomy has
established gamma-ray binaries
as a new class of sources. In
these stellar systems gamma-ray emission results from the interaction
between a normal star and a compact object, that can either be a neutron
star or a black hole.
LSI+61303 among the other gamma-ray binaries is the only
source having in addition
periodical radio outbursts. The
radio outbursts occur with orbital occurrence and are modulated by a long-term periodicity. Both periodicities seem to be present
also in the equivalent width (EW) of the Halpha
emission line of the decretion disk of the Be companion star. In addition,
Fermi-LAT data show that some modulation seems to be present also in the gamma-ray
emission. The prime goals of this PhD project are to investigate, by timing
analysis, eventual periodicities present in the three data bases: radio data, Halpha data and Fermi-Lat
observations. To investigate the physical processes behind
the observed emission. To improve an existing model of a precessing
conical jet by considering Inverse Compton and adiabatic losses for the
relativistic electrons.
Contact: Dr. Maria Massi (mmassi@mpifr-bonn.mpg.de)
Site: Bonn, Max-Planck-Institut
fŸr Radioastronomie,
Millimeter and Submillimeter Astronomy Group
Back to KM project list-
Back to top
|
|
|
|
|
|
|
|
Fundamental Physics in Radio Astronomy Group
Director: Prof. Dr. Michael Kramer
Group website
|
|
|
|
|
Code:
MK01
|
Common Envelope Evolution
Most of the stars in our Galaxy are gravitationally coupled with
a close companion in a binary star system. Because stars expand as they
age, many in binaries interact by transferring of matter from one star to
the other. Often this mass transfer runs out of control and, when the
material cannot be accreted onto the companion star, a common envelope
forms around both stars. The common envelope is either ejected or becomes
the envelope of a new, merged star. This is one of the most important --
but least understood -- phenomena in stellar astrophysics. To understand the
outcome of common-envelope evolution is critical to many branches of
stellar astrophysics. For example, close white dwarf binaries
which may explode as Type Ia supernovae,
the standard candles of cosmology, can only form from common envelope
ejection. Other related phenomena include novae and the beautiful planetary
nebulae.
For the first time, a full theoretical prediction of the
outcome of common-envelope evolution is possible and this is the aim of the
project. State-of-the-art 3D hydrodynamical simulations
will be used to construct a model of common-envelope evolution in a stellar
evolution code. This approach has many advantages: the initial conditions
for mass transfer are modelled correctly, the
stellar evolution can be followed indefinitely including accurate
energy-transfer and mixing physics, and binary stars across the whole
parameter space can be simulated. This project has the potential to be a
major breakthrough with ramifications in many fields of astronomy,
including the formation of exotic stars (e.g. Wolf-Rayet
stars), stellar explosions (type Ia/b/c
supernovae and novae) and double white dwarf binaries. These are exciting
times for stellar astrophysics in Bonn: the expert help required to carry
out such an ambitious project is available in one place for the first time.
Contact: , Robert Izzard (izzard@astro.uni-bonn.de), Prof.
Dr. Michael Kramer (mkramer@mpifr.de)
Site: Bonn, Argelander Institute
for Astronomy,
University of Bonn
Reading: http://www.astro.uni-bonn.de/~izzard/doc/papers/2011/comenv_2011-Izzard.pdf
Project
funding pending: please contact Robert Izzard to determine current status.
Back to MK project list-
Back to top
|
|
|
|
|
Code:
MK02
|
Monitoring the Interstellar Weather with Pulsars
Our Galaxy is a dynamical and constantly evolving system. The
interstellar medium (ISM) appears constant at large scales (~kpc) but is turbulent at small scales (~pc). These
changes impact on many of the observed properties of astronomical objects
but rarely does one have the opportunity to monitor those changes as
accurately as with pulsars. The amount of pulse
dispersion by the ISM across our observing band is given by the Dispersion
Measure (DM), which is equal to the integrated amount of
interstellar matter between the pulsar and the observer. The wide observing
bands of modern instruments and the low observing frequencies attainable
with telescopes like LOFAR conspire towards very accurately measured
dispersion delays and, hence, DMs. Also, the pulsed emission from pulsars
is highly polarised and the magnetic field of the
ISM causes the plane of polarisation to rotate as
those pulses travel through the Galaxy. The integrated amount of this
rotation is expressed with the Rotation Measure (RM) and, again, can be
measured with great accuracy across wide frequency bands. Both DM and RM
should remain constant with time in a static system but are constantly
changing in the dynamical Milky Way. Using a high number of bright, polarised pulsars we
can closely track those changes and interpret them as changes of the matter
distribution in the Galaxy and changes in the Galactic Magnetic field.
The LOFAR station at Effelsberg as
well as the 100m Effelsberg single-dish radio telescope will provide excellent frequency coverage from
several GHz to tens of MHz, thus providing the means to monitor pulsar DMs
and RMs with unprecedented accuracy. Both instruments incorporate very
large bandwidths, with LOFAR having 96 MHz at 150 MHz (high band) and 50
MHz (low band), and Effelsberg reaching up to 3
GHz of bandwidth at ~ 1 GHz, with the newly installed Ultra-Broad-Band
(UBB) receiver. The telescopes will be easily accessible from MPIfR and are
expected to generate a large amount of total-flux and polarisation
data from regularly monitored pulsars, which will be analysed
by the project's investigators.
The project will be
conducted within the Fundamental Physics in Radio Astronomy group of the
MPIfR lead by Prof. Michael Kramer. His team's research
concentrates on various aspects of fundamental physics, namely here the
Galactic population of neutron stars, their use for precision tests of
general relativity and alternative theories of gravity, the detection of
low-frequency gravitational waves and the structure and properties of
super-dense matter".
Contact: , Dr. Aristeidis
Noutsos (anoutsos@mpifr-bonn.mpg.de) ,
Prof. Dr. Michael Kramer (mkramer@mpifr-bonn.mpg.de)
Site: Bonn, Max-Planck-Institut
fuer Radioastronomie,
Fundamental Physics in Radio Astronomy Group
Back to MK project list-
Back to top
|
|
|
|
|
Code:
MK02
|
Searching the Galaxy for pulsars
The
largest telescopes in the world are currently undertaking surveys to search
for pulsars. The group in Bonn is leading surveys using the 64-m Parkes telescope in Australia and our 100-m Effelsberg telescope near Bonn. Their locations allow
these telescopes cover the whole sky. Although nearly 2000 pulsars have
been discovered it is the most unusual
pulsars that really push forward research areas such as, general
relativity, pulsar evolution and emission mechanisms. In addition to using
large telescopes these new surveys use cutting edge hardware. New receivers
and a new generation of data recording 'backends'
have increased the sensitivity of these surveys dramatically over previous
efforts, allowing us to search deep into the Galaxy for the periodic pulsar
signals.
The successful applicant would take part in the observations
and data taking. They would be involved in the processing using powerful computer
clusters (in Bonn and at partner institutions) including using Einstein@Home from the AEI (similar to SETI@Home). Finally they would be expected to lead the
follow up observations and analysis of interesting discoveries.
The project will be
conducted within the Fundamental Physics in Radio Astronomy group of the
MPIfR lead by Prof. Michael Kramer. His team's research
concentrates on various aspects of fundamental physics, namely the Galactic
population of neutron stars, their use for precision tests of general
relativity and alternative theories of gravity, the detection of
low-frequency gravitational waves and the structure and properties of
super-dense matter.
Contact: , Dr. David Champion(davidjohnchampion@gmail.com)
, Prof. Dr. Michael Kramer (mkramer@mpifr-bonn.mpg.de)
Site: Bonn, Max-Planck-Institut
fuer Radioastronomie,
Fundamental Physics in Radio Astronomy Group
Back to MK project list-
Back to top
|
|
|
|
|
|
|
|
|
|
|
University of Bonn
Argelander
Institute for Astronomy
Group website
|
|
|
|
|
Code:
UB01
|
The Stellar Initial Mass Function
Investigate (theoretically) how unresolved multiple stellar systems
affect an observed mass or luminosity function of stars, and extract the
true underlying mass distribution. The full-scale modelling
of Galactic-field populations requires treatment of ages, stellar
evolution, metallicity distributions and multiplicity
of stars as well as Galactic structure. The shape of the IMF below the
hydrogen burning mass limit remains uncertain with the possibility of a
discontinuity near the stellar/sub-stellar transition region. This is to be
studied theoretically using available observational data.
Contact: Prof. Dr. Pavel Kroupa (pavel@astro.uni-bonn.de), Prof. Dr. Karl Menten (kmenten@mpifr- bonn.mpg.de)
Site: Bonn, Argelander
Institute for Astronomy, University of Bonn
Back to Uni. Bonn project list -
Back to top
|
|
|
|
|
Code:
UB02
|
The dynamical evolution of young and old star clusters
Star clusters are known to be the fundamental building blocks of
galaxies as most stars form in clusters. The physical processes driving
early cluster evolution are to be studied with the aim of increasing our
understanding of the formation and survival of clusters and the impact on
the morphology of entire galaxies of these processes. Theoretical and
computational methods will be used to investigate the physics of internal
cluster evolution as a result of binary-star activity, stellar evolution
and gas expulsion. External influences resulting from time-varying tidal fields
of various strengths are to be studied with the aim of better understanding
the observed cluster radius-age data including the outer reaches of the
Milky Way and in extragalactic systems.
Contact: Prof. Dr. Pavel Kroupa (pavel@astro.uni-bonn.de), Prof. Dr. Karl Menten (kmenten@mpifr- bonn.mpg.de)
Site: Bonn, Argelander
Institute for Astronomy, University of Bonn
Back to Uni. Bonn project list -
Back to top
|
|
|
|
|
Code:
UB03
|
The mass function of star clusters
The physical processes leading to early and old cluster
evolution influence the observable mass distribution of star clusters. This
is to be studied using semi-analytical and numerical methods in order to
map-out the dependency of the cluster mass function on the host
environment.
Contact: Prof. Dr. Pavel Kroupa (pavel@astro.uni-bonn.de)
Site: Bonn, Argelander
Institute for Astronomy, University of Bonn
Back to Uni. Bonn project list - Back
to top
|
|
|
|
|
Code:
UB04
|
Dwarf galaxies and dark matter
Fundamental physical principles (energy and angular-momentum
conservation) imply that during early cosmological times when gas-rich
pre-galactic rotationally supported structures merged to form the
present-day galaxies, tidal tails were expelled and locally fragmented to
form tidal-dwarf galaxies (TDGs). Cosmological arguments suggest this
population of non-traditional dwarfs to be possibly very significant and
that it may dominate the low-luminosity end of the galaxy luminosity
function. These TDGs would not contain dark matter and may thus pose a
major "contaminant" of the classical or cosmological galaxy
population. The dynamical evolution of TDGs in host potentials is to be
studied numerically and semi-analytically with the special attention on the
Milky-Way satellite population to see if any of the satellites may be
ancient TDGs.
Contact: Prof. Dr. Pavel Kroupa (pavel@astro.uni-bonn.de)
Site: Bonn, Argelander
Institute for Astronomy, University of Bonn
Back to Uni. Bonn project list -
Back to top
|
|
|
|
|
Code:
UB05
|
The dynamical evolution of the brown-dwarf population in star
forming regions
Recent work suggests that brown dwarfs form together with
stars but that they follow a different mass distribution
which is disjoint from the stellar initial mass function. The fraction
of binary systems among brown dwarfs (15 per cent) is also much lower than
for stars (50 per cent or more), and their binding energy distributions are
very different such that the brown dwarf binaries have an energy truncation
at a higher level than stars. This project aims to bring this evidence
together to investigate various formation mechanisms of brown dwarfs, and
to study theoretically how they disperse throughout their birth cluster
comparing their binary, spatial and kinematical properties with those of
stars. The work will be performed with the GPU-based supercomputing
platforms stationed at the Argelander-Institut
and with dedicated codes.
Contact: Prof. Dr. Pavel Kroupa (pavel@astro.uni-bonn.de), Prof. Dr. Karl Menten (kmenten@mpifr- bonn.mpg.de)
Site: Bonn, Argelander
Institute for Astronomy, University of Bonn
Back to Uni. Bonn project list -
Back to top
|
|
|
|
|
Code:
UB06
|
The star-formation rates of dwarf galaxies and the origin of
matter
Recent work in Bonn has been showing that dwarf galaxies
appear to have the same short (3 Gyr) gas-
consumption timescales as major galaxies. The aim of this project is to
extend this finding to spectro- photometric
modeling of dwarf galaxies and to study the possible origin of the matter
that must be replenishing the star-forming material.
Contact: Prof. Dr. Pavel Kroupa (pavel@astro.uni-bonn.de)
Site: Bonn, Argelander
Institute for Astronomy, University of Bonn
Back to Uni. Bonn project list -
Back to top
|
|
|
|
|
Code:
UB07
|
Development and testing of a new cosmological model
Assuming energy conservation to be valid on a cosmological
scale, a new cosmological model can be derived which leads to good
agreement with the SNIa data and other recent
observational findings such as the star formation behaviour
of galaxies of different mass. In this project, the student will work on
the growth of structure in this new cosmology and further tests of it.
Contact: Prof. Dr. Pavel Kroupa (pavel@astro.uni-bonn.de)
Site: Bonn, Argelander
Institute for Astronomy, University of Bonn
Back to Uni. Bonn project list -
Back to top
|
|
|
|
|
Code:
UB08
|
Pair-instability supernovae in the local universe
The most massive stars, assuming mass loss is not too strong,
are thought not to form iron cores, but rather to become unstable due to
electron-positron-pair formation before central oxygen burning. The
collapsing oxygen-rich core will then ignite oxygen explosively, which may
lead to pair-instability supernovae, leaving no compact remnant. While such
explosions have been predicted since 50 years ago, they were often assumed
to only occur in the early universe. However, very recently, pair-
instability supernovae have been found observationally in the local
universe. This PhD project aims at constructing the first progenitor and
explosion models for local, i.e., finite metallicity
pair-instability supernovae, using our most modern hydrodynamic stellar
evolution code. The idea is to characterize the observable properties of
the progenitor and of the supernovae, and to make predictions for the nucleosynthesis yields of pair-instability, which could
well dominate the metal production in their host galaxies.
Bibliography:
Gal-Yam, A., et al., 2009, Nature, 462, 624
Langer, N., 2009, Nature, 462, 579
Contact: Prof. N. Langer (nlanger@astro.uni-bonn.de)
Site: Bonn, Bonn, Argelander
Institute for Astronomy, University of Bonn
Back to Uni. Bonn project list -
Back to top
|
|
|
|
|
Code:
UB09
|
Physics of galaxy clusters from SZ and X-ray data
Understanding the physical properties of the hot, ionized
intra-cluster medium (ICM) is a central theme of galaxy clusters cosmology.
The ICM mass and temperature relates to the total gravitational mass of the
dark matter in clusters, and morphological features like shock fronts show
how clusters are assembled. The ICM is typically observed through its X-ray
emission or the Sunyaev-Zel'dovich (SZ) effect,
but a combination of these two data provides an even more powerful
technique to analyze the cluster properties. The APEX-SZ team at the
University of Bonn is actively involved in this field of which the
prospective student will become a member. The preliminary task will be to
analyze some data taken from the APEX-SZ experiment and compare it
available X-ray and optical data. The central theme of this project will be
to develop a model independent method for studying cluster morphology, based
on APEX-SZ, Planck SZ and X-ray data. This project will also prepare the
student for future high-resolution SZ observation and analysis using the
CCAT telescope, which will start operating in the year 2017 and for which
Bonn University will have access through guaranteed time.
Contact: Dr. Kaustuv moni Basu (kbasu@astro.uni-bonn.de),
Prof. Dr. Frank Bertoldi (bertoldi@astro.uni-bonn.de)
Site: Bonn, Bonn, Argelander
Institute for Astronomy, University of Bonn
Back to Uni. Bonn project list -
Back to top
|
|
|
|
|
Code:
UB10
|
The mystery of galaxy cluster radio halos
Giant radio halos inside galaxy clusters are Mpc scale diffuse synchrotron emissions whose formation
processes are still poorly understood. These radio halos are associated
with galaxy cluster collisions, but we do not know how many of these
objects are in the sky or what impact they may have on our understanding of
other cluster properties. We have initiated a project to correlate cluster
radio halo measurements with X-ray and SZ effect data to understand the
powering mechanism and mass dependence of radio halos, as well as
determining their true abundance in the sky. New data from several radio
telescopes (EVLA, GMRT,..) have been collected and
being analyzed. The goal of this PhD project will be to take a leading
position in this work and measure the radio halo properties in several new
clusters using this state-of-the-art radio data, aiming towards a
comprehensive picture of radio halo origin.
Contact: Dr. Kaustuv moni Basu (kbasu@astro.uni-bonn.de),
Prof. Dr. Frank Bertoldi (bertoldi@astro.uni-bonn.de)
Site: Bonn, Bonn, Argelander
Institute for Astronomy, University of Bonn
Back to Uni. Bonn project list -
Back to top
|
|
|
|
|
Code:
UB11
|
Panoramic and detailed millimeter-radio views onto the
cosmic history of star formation
Among the most pressing questions in modern galaxy evolution
studies is how stellar mass assembled over cosmic time. Our current
understanding of the main drivers of star formation within galaxies is
still sparse but over the last years a picture emerged in which the
build-up of new stars is tightly connected to the existing stellar mass
(e.g. Karim et al. 2011 and references therein).
This possibly suggests that simple self-regulated gas-exchange of galaxies
and their respective haloes is capable of describing the very localized and
highly inefficient process of star formation via simple self-regulated
gas-exchange of galaxies and their respective haloes using only a few
parameters (Lilly et al. 2013). Given the highly hierarchical, violent
assembly of the large scale dark matter component of the Universe this link
is surprising and awaits detailed observational confirmation. Similarly, it
has been suggested that the effects different galaxy
environments cause are fully separable with respect to the star
formation-mass link (e.g. Peng et al. 2011), a
conclusion that clearly awaits observational confirmation at earlier cosmic
epochs than probed so far.
High angular resolution radio continuum observations of
cosmological deep fields can play an important role in dissecting all these
effects and shed light on the related open questions. Radio observations
have been highly successful in providing tight constraints for our
understanding of star formation over large cosmic timescales (e.g. Karim et al. 2011). The PhD project suggested here will
make use of the unique data sets currently observed at the Jansky-VLA in the 2 square degree COSMOS deep field
(see Schinnerer et al. 2010 for earlier COSMOS
radio observations using the VLA). The angular resolution achieved in this
survey will allow us to explore the extent of the star forming regions
within galaxies and help to dissect them from the active nuclear regions.
Particularly, recently obtained detailed environmental information in the
COSMOS field will allow to study the link of star formation and mass in a
wide range of galaxy environments, such as clusters, groups and filaments
of the large-scale matter distribution in unprecedented detail. The successful candidate will also
have the opportunity to use the radio data in combination with newly
obtained mm-data (from single-dish as well as interferometric
observations, partially from ALMA) to study star formation at very high
redshifts z>4 and to explore further research avenues within the vast
panchromatic COSMOS survey data sets. Alexander Karim
and Frank Bertoldi are full members of the
international COSMOS consortium and have access to all the latest deep
observations from a large variety of instruments. Critically, they play
leading roles in the ongoing field observations using the expanded Very
Large Array (Jansky-VLA; USA) as well as the 2mm
GISMO bolometer array operating at the IRAM 30m telescope on Pico Veleta (Spain).
Bibliography
Karim et al. 2011, ApJ,
730, 61
Lilly et al. 2013, ApJ (in press.), arXiv:1303.5059
Peng et al. 2010, ApJ,
721, 93
Schinnerer et al. 2010, ApJS, 188, 384
Contact: Prof. Dr. Frank Bertoldi
(bertoldi@astro.uni-bonn.de), Dr.
Alexander Karim (karim@astro.uni-bonn.de), Dr. Benjamin Magnelli (magnelli@astro.uni-bonn.de)
Site: Bonn, Bonn, Argelander
Institute for Astronomy, University of Bonn
Back to Uni. Bonn project list -
Back to top
|
|
|
|
|
|
|
|
|
|
|
|
|
|
University of Cologne
1st Physikalisches Institut
Group website
|
|
Code:
UK01
|
Physics of Low-Luminosity Radio Nuclei
Aim of this project is to address the global radio and molecular
gas properties of a representative sample of galaxies hosting
low-luminosity quasi-stellar objects. An abundant supply of gas is
necessary to fuel both the active galactic nucleus and any circum-nuclear star-burst
activity of quasi-stellar objects (QSOs). The connection between
ultra-luminous infrared galaxies and the host properties of QSOs is a
subject to a controversial debate. Nearby low-luminosity QSOs are ideally
suited to study the properties of their host galaxies because of their higher
frequency of occurrence compared to high-luminosity QSOs in the same
commoving volume and because of their small cosmological distance.
Representative samples are selected from QSO and radio surveys. The
abundance of molecular gas and the importance of star formation is being
probed through infrared- and
mm-spectroscopy. The nuclear activity is tested through radio interferometric observations that aim at distinguishing
between contributions from non-thermal nuclei and super nova remnants in
these low luminosity nuclei.
Contact: Prof. Dr. Andreas Eckart
(eckart@ph1.uni-koeln.de),
Prof. Dr. J. Anton Zensus (azensus@mpifr-bonn.mpg.de)
Site: Cologne, 1st Physics Institute, University of
Cologne
Back to Uni. Cologne project list - Back
to top
|
|
|
|
|
Code:
UK02
|
NIR Studies of the Black Hole at the Center of our Galaxy
The compact source Sgr A* that can
be associated with the massive black hole at the center of the Milky Way shown
a strong variability from the radio to the X-ray wavelength domain. The
most recent results from a near-infrared observations revealed polarized
NIR flare emission of Sgr A*. This can be
interpreted as emission from spots which are on
relativistic orbits around Sgr A*. Emission from
a possible jet or outflow from such a disk can also contribute. We also
find that the variable NIR emission of Sgr A* is
highly polarized and consists of a contribution of a non- or weakly
polarized main flare with highly polarized sub-flares. The flare activity
shows a possible quasi-periodicity of 20±3 min consistent with previous
observations. The highly variable and polarized emission supports that the
NIR emission is non-thermal and is consistent with emission from a jet or
temporary disk. Alternative explanations for the high central mass
concentration involving boson or fermion balls are increasingly unlikely.
Observations with the VLT, VLTI and in future with the LBT will allow us to
better discriminate Sgr A* from the surrounding
stars, to register the light curves with a higher signal to noise, and to
further develop the theoretical models.
Contact: Prof. Dr. Andreas Eckart
(eckart@ph1.uni-koeln.de), Dr.
Thomas P. Krichbaum (tkrichbaum@mpifr-bonn.mpg.de)
Site: Cologne, 1st Physics Institute, University of
Cologne
Back to Uni. Cologne project list -
Back to top
|
|
|
|
|
Code:
UK03
|
VLBI Studies of the Black Hole in the Center of our Galaxy
The compact radio source in the center of our Galaxy,
Sagittarius A* (Sgr A*), is probably the best
candidate of a super-massive black hole (with approx. 3.5 - 4 million solar
masses). At centimeter wavelengths, the radio image of Sgr
A* is scatter broadened, not allowing a direct view into the nucleus. At
short millimeter-wavelengths, however, the scatter broadening vanishes and
the underlying source begins to shine through. With Very Long Baseline
Interferometry (VLBI) at 3 mm wavelengths and below, it is therefore
possible to study the immediate environment of a super-massive black hole.
With a spatial resolution of a few ten Schwarzschild radii, one is not too
far from the scale, where general relativistic effects should become
visible. Direct signatures of the metric near the black hole, e.g. a shadow
(with possible distortion, depending on whether the black hole is rotating
or not), are expected to become observable. A first VLBI observation at 1
mm already indicated a size of < 20 Schwarzschild radii. Clearly more
data are needed to confirm and improve this first estimate. The new project
focuses on more extensive mm-VLBI monitoring of Sgr
A* in order to search for possible signatures of the black hole and for
variations in its source structure, the latter likely being related to the
observed quasi-periodic brightness variations in the infrared bands. In
addition to the 3mm-VLBI monitoring of Sgr A*, it
is further planned to perform new VLBI experiments at shorter wavelengths
(2mm, 1mm), adding new mm-telescopes, as they now become available for
VLBI.
Contact: Prof. Dr. Andreas Eckart
(eckart@ph1.uni-koeln.de), Dr.
Thomas P. Krichbaum (tkrichbaum@mpifr-bonn.mpg.de)
Site: Cologne, 1st Physics Institute, University of
Cologne and VLBI Group at the Max Planck Institute for Radio Astronomy,
Bonn
Back to Uni. Cologne project list -
Back to top
|
|
|
|
|
Code:
UK04
|
Near-Infrared Instrumentation for Large Interferometric
Observatories
The 1st Physics Institute of the University of Cologne is
participating in two international collaborations to develop near-infrared
detector systems for leading interferometric
telescopes. For the Very Large Telescope Interferometer in Chile the
institute is contributing two spectrometers to the GRAVITY project, a
six-baseline interferometric camera for the K
band. For the Large Binocular Telescope in Arizona the institute is
developing the fringe and flexure tracking unit
for the LINC-NIRVANA project, a direct imaging interferometric
camera for JHK bands. Both local project teams consist of senior
scientists, post docs, PhD students and technicians. The student can get
involved in either of the the two projects by
designing and testing of actual hardware components in the laboratories of
the institute, by writing of control software, or by building and operating
accompanying laboratory experiments which demonstrate crucial sub-functions
of the final instrument. The student will actively take part and experience
the work of a distributed multi-national consortium of scientists,
engineers, and technicians. Complementary to the instrumentation work and
in collaboration with the MPIfR (Prof. Anton Zensus),
the student will participate in the observational astronomy projects of the
workgroup of Prof. Andreas Eckart covering
sources that are active from the radio to the infrared wavelength domain.
Contact: Prof. Dr. Andreas Eckart
(eckart@ph1.uni-koeln.de)
Site: Cologne, 1st Physics Institute, University of
Cologne
Back to Uni. Cologne project list -
Back to top
|
|
|
|
|