PhD Thesis Projects
Offered Projects
Sensitive measurements in background sources using
gravitational lensing Description: Gravitational lens systems
offer an important opportunity to study the lensed sources, nearly
always very distant quasars, in unprecedented detail. This happens
because the foreground galaxy acting as the lens increases the
brightness of the source and also magnifies lengths; this means
that intrinsic changes in the lensed source, or relative motions
between foreground galaxy and lensed source, which would otherwise
be undetectable, are available for study. This study will be done
using multi-epoch observations of gravitational lenses to reveal
structural changes in the lensed images and measure possible shifts
in the relative positions of the components. The student would
analyse observing data from MG J0414+0534 and B1422+231, among
other sources, to address the above described points and to improve
the lens modeling by comparing the same features as lensed in
different manner to each one of the sub-images.
Physics of the central regions of
AGN
Description:
VLBI imaging allows us to study the phenomenon whereby a radio jet
is ejected close to the massive black hole at the centres of active
galaxies. Due to its extremely high resolution (50 times the HST)
VLBI is the only technique which provides images of the regions
close to the central black hole, and can with repeated observations
follow the expulsion of matter along the radio jets and therefore
give important information about the physics of the AGN phenomenon.
To this end, more than 170 radio sources have been monitored since
the mid 1990s via 15 GHz observations using the US Very Long
Baseline Array. The goal of these observations is the to follow the
evolution of these jets and work out jet velocities, compositions
and details of interaction with the medium around the nucleus in a
huge sample of more than 1000 images of radio- loud AGN. The
student would explore the data of the survey sample, with special
attention to the relationship of the physical properties of the
studied objects between radio and other wavelengths, the
variability and brightness temperature and the presence of
acceleration and curvature in the relativistic
jet.
Collaborative
Partner Institutions: The member institutes of the MOJAVE/2cm
Survey collaboration
Radio and High-Energy Observations of
Relativistic Jets in Blazars and Active
Galaxies
Description: GLAST, the Gamma-Ray Large Area Space Telescope, is
NASA's next big space mission to explore the universe. GLAST
will study gamma-ray radiation, the most energetic form of
radiation, billions of times more energetic than the type of light
visible to our eyes. Such gamma-ray radiation is produced in
streams of hot gas moving close to the speed of light and beamed
relativistically into narrow cones around the jets ejected from the
very centers of active galactic nuclei. If these so- called jets
are pointed almost directly towards earth, they are called blazars
and their gamma-ray emission is relativistically enhanced, making
blazars a key-science topic for GLAST. Jets can be imaged
with sub-parsec resolution at the other end of the electromagnetic
spectrum: the radio regime. Via Very-Long-Baseline Interferometric
techniques, we can see the smallest possible scales in blazar jets
and study the relation to their high-energy gamma-ray
emission.
This PhD project will
be conducted in collaboration with NASA's Goddard Space Flight
Center in Greenbelt, Maryland (USA). The successful applicant will
work with an international group of scientists on the analysis and
interpretation of VLBI and GLAST data from blazars. Parts of
the project may be conducted at Goddard Space Flight Center during
several short or one extended visit.
Collaborative
Partner Institutions: Goddard Space Flight Center/NASA,
Greenbelt, MD, USA & Bamberg Observatory
Exploring the Southern Blazar Sky with
Multi-Wavelength Astronomy
Description:TANAMI (Tracking Active Galactic
Nuclei with Australian-South-African Milliarcsecond Interferometry)
is a new program to image and monitor the parsec- scale structures
of relativistic jets in active galactic nuclei (AGN) of the
Southern Hemisphere with the Long Baseline Array (LBA).
Complementary to existing programs in the Northern Hemisphere,
TANAMI is tracking the jets of sources south of -30 degrees
declination with milliarcsecond resolution at 8.4GHz and 22GHz.
TANAMI observations track fast superluminal moving jet features and
transient events in sources of special interest, in particular
blazars found by the new NASA gamma-ray mission GLAST to be flaring
at gamma-rays. The extreme ends of the electromagnetic spectrum
(radio and gamma-ray energies) will be bridged with supplementary
optical- to-UV and X-ray observations with the NASA mission Swift.
The correlated multi- wavelength analysis of individual sources
(e.g., sources in outburst) will be an important component of this
PhD project. The successful applicant will participate in the
planning and conduction of the LBA observations and their data
reduction and in multiwavelength observations of sources of special
interest. This PhD project will be conducted in collaboration with
the Dr. Remeis Sternwarte Bamberg (Universitaet
Erlangen-Nuernberg), the NASA Goddard Space Flight Center in
Greenbelt, MD, and with the US Naval Research Observatory in
Washington, DC.
Collaborative
Partner Institutions: Goddard Space Flight Center/NASA,
Greenbelt, MD, USA, Naval Research Observatory, Washington DC, USA
& Bamberg Observatory
Diploma Thesis Projects
As student of the
University of Bonn you can perform your Diploma or Master Thesis
project at the neigbouring Max Planck Institute for Radio
Astronomy, in our group. You can work in the topics mentioned
above for a PhD, or on more specific topics with a shorter time
plan, tailored for an undergraduate work. Here one example of
such a project:
The Flare in the
Quasar CTA 102
Description:
The high-redshift quasar CTA102 has experienced a major radio flare
inlate 2005, reaching historic flux density maxima. The
structure and spectral evolution in the jet emanating from the
black hole powering the central active galactic nucleus can be
probed at different wavelengths via Very-Long-Baseline
Interferometry (VLBI). Complementary X-ray and IR
observations performed quasi- simultaneously complete the spectral
energy distribution. The offered project aims to test the jet
models and the nature of the high energy radiation at the extreme
conditions of a rising state in activity. The main part of
the work will be based in the radio astronomy analysis, to be
combined with the other bands in the spectrum. This project is
performed in the framework of an international collaboration (see
below).
Collaborative
partners: Goddard Space Flight Center/NASA, University of
Michigan, and the National Radio Astronomy Observatory in the USA,
as well as the Tuorla Observatory in Finland,
Research Topics
