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Here is more detailed information about the research projects of our IMPRS students
(listed by student generation and in alphabetic order).
Check for students of our 7th, 6th, 5th, 4th, 3rd generation, or our IMPRS alumni. |
| 5th generation students (joined IMPRS-HD 2009) | ||
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Ellen Andrae
(Germany)
ellen.andrae @ mpi-hd.mpg.de Photometry with GALEX GAMA | Thesis abstract:
Supervisor: Richard Tuffs (MPIK) |
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Paul Boley
(USA)
boley @ mpia.de The inner regions of the youngest massive stars | Thesis abstract:
Massive stars are in many ways the most influential members of
star-forming clusters. Expanding ionized regions created by such stars
can trigger further star formation at the interface with the
surrounding ISM, while shocks and outflows associated with these
objects play important roles in grain reprocessing in the vicinity and
can trigger further collapse of surrounding molecular material.
However, despite being the most luminous stars, the most massive stars are often highly extincted, sometimes even entirely undetectable, at optical wavelengths during the youngest stages of their evolution. In studying such deeply-embedded objects, I will make extensive use of observations in the mid-infrared, including interferometric observations with the MIDI, high-resolution spectroscopy with CRIRES and direct imaging with VISIR -- all instruments at ESO Paranal. Such observations, when combined with radiative transfer modeling, will allow for a sounding of the inner-most regions of these massive stars. Supervisors: Thomas Henning / Roy van Boekel (MPIA) |
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Federica Capranico
(Italy)
capranico @ ari.uni-heidelberg.de Angular momentum correlations between galaxies | Thesis abstract:
My thesis is addressed to obtain a reconstruction of the matter density field exploiting intrinsic
alignments between galaxies. Galaxies acquire angular momentum because of tidal forces from the ambient large scale structure during their formation process. Apart from being the origin of rotating galaxies, this mechanism explains the presence of intrinsic alignments as well. In fact, neighbouring galaxies undergo to similar tidal torques (i.e. similar potentials) and thus will have correlated angular momenta. This correlation is reflected in the ellipticites of the galaxies too, since the spin is always perpendicular to the disk of the galaxy. The angular momenta are then linked to the tidal shear, and the latter to the density field by means of Poisson's equation. My project exploits this chain of dependencies in order to get a reconstruction of the density field by means of Bayesian inference. The project is divided in two parts: the 1st concerns the construction of a program that is able to create a density field, and from that both the angular momentum and the ellipticity fields. The 2nd step concerns the density field reconstruction, which is carried out by ARGO (Algorithm for the Reconstruction of Galaxy-traced Overdensities). ARGO tries to find the most suitable density field that is able to explain the ellipticity field by adjusting in an iterative way the density field. The most suitable density field is the one that maximises the Likelihood function. Supervisor: Bjoern-Malte Schaefer (ARI) |
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Gustavo Dopcke
(Brasil)
gustavo @ uni-hd.de The transition from Pop. III to Pop. II/I star formation | Thesis abstract:
We make use of numerical models to find the 'critical metallicity' for the
transition of Pop. III to Pop. II star formation. Making use of the Gadget2
SPH code, we successfully reproduced previous results in the literature for a
spherical symmetric collapse and then show results from a full 3D treatment.
We conclude that dust cooling affects the fragmentation of low metallicity
gas clouds and can determine the evolution of the stellar IMF. We address questions like: What is the expected mass spectrum of stars in metal-free and metal-poor conditions? At what metallicity do we expect to find the transition from forming predominantly high-mass stars to the IMF we observe today? What are the dominant physical processes that govern fragmentation and determine the mass spectrum? To answer those questions we investigate the effects of the cooling due to dust grains on the collapse of low metallicity star-forming clouds. Making use of 3D numerical models to follow the thermal evolution of clouds with different metallicities, we study self-consistently the evolution of the gas and dust temperatures during the collapse, and determine the properties of the cloud at the point at which it undergoes gravitational fragmentation. Supervisors: Simon Glover / Ralf Klessen (ITA) |
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Aram Giahi
(Germany)
aram @ ari.uni-heidelberg.de The interface between lensing and intrinsic alignment | Thesis abstract:
The primary lensing observable are correlations in the galaxy shapes, but these
correlations can also be induced by coupled angular momenta. There are statistical
methods for distinguishing the two. I'm working out and improving these methods
without discarding data.
Supervisor: Bjoern Schaefer (ARI) |
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Philipp Girichidis
(Germany)
philipp @ girichidis.com Fragmentation Properties of Massive Molecular Cloud Cores | Thesis abstract: We investigate the fragmentation behavior of massive cores with a focus on the initial conditions of a collapsing cloud. Two crucial quantities in the collapse process of dense cores are the initial mass distribution and the interplay with turbulent velocities. From our calculations we conclude that the mechanical initial conditions might have a much larger impact on the cloud evolution, the stellar mass distribution and the formation process of young stellar clusters as well as the accretion scenario than the different physical processes like radiation or magnetic fields. Supervisor: Robi Banerjee (ITA) |
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Alessandra Grassi
(Italy)
sandri @ ari.uni-heidelberg.de Detecting features in the DM distribution | Thesis abstract:
I'm investigating the possiblity of detecting features in the dark matter
distribution using 3d weak lensing methods.
These features can be important for carrying out tests on the geometry
of the universe. I'm have optimised the calculations related to
inference of parameters from weak lensing data and applies this software
now to the detection of localised features in the spectrum.
Supervisor: Bjoern-Malte Schaefer (ARI) |
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Oleksiy Golubov
(Ukraine)
golubov @ ari.uni-heidelberg.de Modelling the Milky Way disk | Thesis abstract:
Supervisor: Andreas Just (ARI) |
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Meiert Grootes
(Netherlands)
meiert.grootes @ mpi-hd.mpg.de Panchromatic investigation of the mass assembly history of galaxies using the GAMA ans ATLAS surveys | Thesis abstract:
Supervisors: Richard Tuffs (MPIK) |
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Raoul Haschke
(Germany)
haschke @ ari.uni-heidelberg.de Structure and evolution of the Magellanic Clouds | Thesis abstract:
The metallicities and three-dimensional structure of the old stellar
populations in the Magellanic Clouds (MCs) are mostly unknown. RR Lyrae
are excellent tracers of Population II stars and can therefore be used
to examine these properties. In addition, we are using Cepheids in order
to study the structure of the young populations and the recent star
formation history of the MCs. Moreover, these studies yield detailed
extinction maps.
Supervisor: Eva Grebel (ARI) |
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Mathias Jaeger
Austria
mjaeger @ mpia.de Evolution of the galaxy population since redshift z=2 | Thesis abstract:
To get better information about the evolution and creation of
blue and red galaxies at high redshifts the COMBO17+4 survey is going to
be reduced and analysed. Therefore the MPIAPHOT pipeline is used which is
based on MIDAS. Depending on the results of the first reductions, further
observations of interesting objects are possible.
Supervisor: Klaus Meisenheimer (MPIA) |
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Ervin Kafexhiu
(Albania)
ervin.kafexhiu @ mpi-hd.mpg.de Nuclear processes in accretion flows | Thesis abstract:
Supervisor: Felix Aharonian (MPIK) |
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Fazeel Mahmood Khan
(Pakistan)
khan @ ari.uni-heidelberg.de Dynamics and evolution of supermassive black hole binaries in merging galaxies | Thesis abstract:
Supervisor: Andreas Just (ARI) |
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Natalia Kudryavtseva
(Russia)
natkud @ mpia.de Micro-arcsecond astrometry of exoplanet host stars and starburst clusters | Thesis abstract:
The 2nd generation Very Large Telescope Interferometer instrument GRAVITY
aims at achieving micro-arcsecond accuracy astrometry. In a study of the
GRAVITY science cases I investigate the astrometric detection of
exoplanets around very low mass stars. This includes defining the actual
sample of M-dwarfs to be surveyed and doing simulations to identify the
"best" survey strategy. The second science case involves astrometric detection of intermediate mass black holes in starburst clusters. As a starting point I want to measure proper motions and internal velocity dispersions for starburst cluster Westerlund 1. It is a massive young cluster, which might not be in virial equilibrium. The data for Westerlund 1 was obtained with the VLT adaptive optics system NAOS-CONICA. Analysis and interpretation of this data will help us to understand formation and evolution of starburst clusters and to study the motion of the stars around black holes. Supervisors: Wolfgang Brandner/Stefan Hippler (MPIA) |
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Eva Lefa
(Greece)
eva.Lefa @ mpi-hd.mpg.de Synchrotron-Compton emission from AGN jets | Thesis abstract:
The formation and propagation of relativistic jets is expected to
lead to an internal flow profile that could have a significant impact
on its non-thermal emission properties. Based on theoretical and
empirical techniques, we will analyze possible spectral characteristics
for AGNs at high energies and calculate the synchrotron-Compton
emission of stratified relativistic jets.
Supervisors: Frank Rieger / Felix Aharonian (MPIK) |
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Chia-Chun Lu
(Taiwan)
chia-chun.lu @ mpi-hd.mpg.de High-energy observations with the HESS telescope system | Thesis abstract:
Supervisor: Werner Hofmann (MPIK) |
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Johannes Ludwig
(Germany)
ludwig @ ari.uni-heidelberg.de TBD | Thesis abstract:
Supervisor: Eva Grebel (ARI) |
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Iwona Mochol
(Poland)
iwona.mochol @ mpi-hd.mpg.de Pair cascades in black hole magnetospheres | Thesis abstract:
Vacuum gaps of spinning supermassive black holes threaded by
externally supported magnetic fields are promissing sites of particle
acceleration up to ultra-high energies. Such processes are accompanied by
emission of TeV curvature photons, which can in turn create subsequent
pairs e+e- if the magnetic field is strong enough. The whole process is
self-supporting until the vacuum is discharged. In our work we model this
cascade production and acceleration, taking into account energy losses
resulting from radiation damping forces.
Supervisor: John Kirk (MPIK) |
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Faviola Molina
(Venezuela)
molina @ stud.uni-heidelberg.de Statistical analysis of simulated molecular clouds | Thesis abstract:
The aim of my thesis is to analyze the CO, density and temperature distributions in a large
suite of simulated molecular clouds in order to help us understand how to interpret emission
maps from real molecular clouds. The simulations were performed using a fully dynamical 3D model
of magnetized turbulence coupled to a chemical network simplified with a particular focus on the
formation and destruction of CO and H_2. Currently, we have performed CO(1-0) synthetic emission
maps. We find that most of the CO is located at densities over 10^3 cm^-3 where the temperature
is roughly 10-40 K independently of the mean density, metallicity and UV field strength.
Although most of the volume is in warmer and less dense regions, CO photodisociation is more
efficient there making the CO abundance small. It follows that CO observations alone give a
misleading view of the physical conditions in the clouds. Our next step is to extend the
analysis to higher CO transitions and other chemical species.
On the density analysis, we first focus on simulations of supersonic, isothermal and magnetized gas in order to study the roll of magnetic fields on the density variance--Mach number relation. We found a a one-to-one relation between the Mach number, the thermal to magnetic pressure ratio and the density variance. The second step is to extend this study in the simulations that include the chemical network. Supervisors: Simon Glover / Ralf Klessen (ITA) |
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Natalie Raettig
(Germany)
raettig @ mpia.de The global baroclinic instability: physical conditions and implication on planet formation | Thesis abstract:
Turbulence is known to play an important role in accretion disks: as source of angular
momentum transport as well as transporting the dust in disks. I will analyze the so
called baroclinic instability, which is of purely hydrodynamical nature. In numerical
simulations carried out with the PENCIL-code I will look at general properties like angular
momentum transport, but I will also use the BI as a method to trap small particles.
With that I want to form planetesimals instantaneously and thus bypass one of the great
obstacles in planet formation. Supervisors: Hubert Klahr / Thomas Henning (MPIA) |
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Daniel Seifried
(Germany)
dseifried @ hs.uni-hamburg.de Evolution of large scale outflows from collapsing molecular cloud cores | Thesis abstract:
Magnetic fields are known to have a great impact on the formation of stars.
This can be in particular seen in the powerful objects like outflows and jets
generated by forming protostars and their surrounding protostellar disks. In
my work I focus on the influence of magnetic fields on the formation process
of massive stars. In particular, I'm interested how magnetic fields affect
the formation and stability of massive protostellar disks and the formation
of large-scale protostellar outflows. By means of large computer simulations
performed with the astrophysical code FLASH we study the physical details of
the mechanism responsible for outflow launching as well as the effects of disk
properties on the accretion history of massive protostars.
Supervisor: Robi Banerjee (ITA, Hamburg) |
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Jochen Tackenberg
(Germany)
tackenberg @ mpia.de The early evolution of high-mass star formation | Thesis abstract:
The formation of stars more massive than 8 Msun is hardly understood.
Still, no consistent concept exists explaining how such objects evolve
from the diffuse gas to such massive and luminous objects.
In order to understand which conditions are required and will allow the
formation of massive stars, we study their initial stages. As a first step we want to build a statistical significant sample of starless clumps, the potential prenatal phase. Starting from ATLASGAL, a continuum survey at 870um tracing the cold dust and gas, we search 20 square degrees of the sky for dense clumps and search within them for mid-IR tracers of ongoing star formation. Using kinematic distance estimates we will be able to characterize their column density, mass, physical size, and general distribution. Including additional tracers connected to the evolution of massive stars, such as the existence of compact HII regions or bright IRAS sources, we will classify all detected clumps and may establish an evolutionary sequence. But even more tempting will be to derive relative time scales of the different evolutionary phases, which can be translated into absolute timescales. In order to characterize the initial conditions inside the most massive, and therefore most promising, clumps, detailed studies of individual objects are required. We will use both the incredible imaging capabilities of HERSCHEL and ground based molecular line studies (single dish and interferometry) to determine their physical properties such as temperature, density, and virial mass, search for outflows or signatures of infall, or indications of turbulent support. This project will provide reliable initial conditions for future numerical studies and will help to improve their quality. Supervisors: Henrik Beuther / Thomas Henning (MPIA) |
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Tessel van der Laan
(Netherlands)
vdlaan @ mpia.de Formation and evolution of nuclear starburst rings | Thesis abstract:
My research focusses on the formation and evolution of circumnuclear starburst rings
in galaxies. These starburst rings can occur anywhere between 50pc and 1kpc distance
from the nucleus. They have star formation rates of up to 5% of the total star formation
in a galaxy, which makes them an important part of the secular evolution of the galactic
nuclear region. The general theoretical picture on the formation of nuclear rings is
fairly clear, the detailed mechanism of how star formation occurs and proceeds within
the ring is not. Are there preferred locations for star formation within the ring, or
is star formation randomly distributed throughout the ring? How does stellar evolution
affect the ring? Are starburst rings short lived phenomena and what happens to their
stars? Observational tests for these questions are basically non-existent, due to the
difficulties associated with the small angular size of most circumnuclear rings and the
need to obtain a complete inventory of high quality datasets. For the nearby galaxies
NGC5248 and NGC6951 we have managed to get suchs datasets together. The former is a
SAB spiral galaxy at a distance of 15Mpc. It harbors two (!) prominent starburst rings
at radii 180pc and 1kpc from the nucleus, respectively. The latter, also an SAB galaxy
at a distance of 24Mpc, has a single starburst ring at 580pc radius. For each galaxy we
have obtained subarcsecond 3-dimensional data of the stellar, ionized and molecular gas
in the circumnuclear rings. Together with state-of-the-art modelling, we hope to use
these datasets to get a detailed understanding of circumnuclear starburst rings.
Supervisors: Eva Schinnerer / Hans-Walter Rix (MPIA) |
| 4th generation students (joined IMPRS-HD 2008) | ||
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Alexander Hansson
(Sweden)
hansson @ ari.uni-heidelberg.de The origin of the local early-type dwarf galaxy population | Thesis abstract:
Early-type dwarf galaxies (dEs) are the most abundant type of galaxies in clusters though only
a small number of these objects are known in the field so far. This suggests that many cluster
dEs are products of their environment.
We are conducting a study of the local dE population which will reveal important clues
regarding the formation and evolution of these systems, including an assessment of the role of
the environment in which these objects reside.
Supervisor: Torsten Lisker (ARI) |
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Hagen Meyer
(Germany)
hmeyer @ ari.uni-heidelberg.de Identifying the progenitors of early-type dwarf galaxies | Thesis abstract:
In the local universe dwarf galaxies form 80 % of the galaxy population.
It is therefore reasonable to assume that they are the most numerous
type of galaxies in the universe.
Dwarf galaxies can roughly be divided into star-forming dwarf galaxies
(e.g. Blue Compact Dwarfs, Dwarf Irregulars)
and passive (red and dead), early-type dwarfs (dwarf ellipticals)
with (almost) no star-formation and only little gas.
The latter are most
commonly found in galaxy clusters, like the Virgo-Cluster. Candidate mechanisms to explain the transformation of star-forming dwarfs into passive dwarf galaxies are ram-pressure stripping, or fast gravitational perturbations of the dwarf by other cluster members. Details of these transformation processes are, however, currently not well understood. To answer these questions we use a optical multi-wavelength sample from the SDSS and additional UV/NIR-data to study dwarf galaxies in the nearby Virgo-Cluster. We will investigate structural properties and colours of likely progenitors of early-type dwarf galaxies as well the early-type galaxies themselves. Supervisor: Torsten Lisker (ARI) |
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Milica Micic
(Serbia)
milica @ uni-hd.de Molecular cloud formation in convergent flows | Thesis abstract:
Stars form within massive clouds of molecular gas known as giant molecular clouds, or
GMCs. Understanding how these clouds are formed is therefore a crucial part of the study of the
birth of stars. A promising theory for GMC formation suggests that these clouds form in places
where streams of warm atomic gas collide. The collision compresses the gas, which becomes
thermally unstable, breaking up into cold, dense clumps embedded within a largerscale turbulent
flow. However, current studies of this process have a number of drawbacks that limit their
usefulness. They use a highly simplified treatment of the thermal energy balance of the gas,
and have ignored its chemical evolution. It has therefore been difficult to directly compare
the clouds formed in these simulations with observations of real GMCs in a meaningful fashion,
and hence difficult to properly test the predictions of the theory. We will address this
problem by performing threedimensional adaptive mesh refinement simulations of cloud assembly
with the FLASH code. These simulations will for the first time selfconsistently model the
assembly of the clouds, the thermal energy balance within them, and the chemical transition
from atomic to molecular gas.
Supervisor: Ralf Klessen (ITA) |
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Dading Nugroho
(Indonesia)
nugroho @ mpia.de Star formation properties and kinematics of nearby AGN host galaxies | Thesis abstract:
My thesis work centers on a study of star formation and kinematics of the
Active Galactic Nuclei (AGN) host galaxies at nearby universe (z < 0.2).
There are two spectroscopic data sets that will form basis of my thesis.
The first is data from observation using VIMOS-Integral Field Unit mounted
at VLT-Melipal and second from observation with FORS2 instrument at
VLT-Kueyen. The study will help constrain the fuelling mechanisms of AGN and relation between AGN activity with star formation in host galaxies to understand the role of AGN to the transition of galaxies from blue cloud to the red sequence population in the color magnitude diagram. In more general, this study is a part of our effort to understand the relation of the Supermassive Black Hole (SMBH) and their host galaxies. Supervisor: Knud Jahnke / Hans-Walter Rix (MPIA) |
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Xiaoying Pang
(China)
xiaoying @ ari.uni-heidelberg.de Galactic and extragalactic star cluster evolution | Thesis abstract:
NGC3603 which is one of the most compact star clusters in the Milky Way
and is considered as a Galactic starburst cluster.NGC3603 is an arena of
star formation in which we can find very luminous OB stars, and pre-main
sequence stars which are still undergo formation of which pro-disk are
observed, and aslo molecular clouds. Depite the young age of NGC3603
which is only about 1Myr old, it already shows distinct mass
segregation. My work is to research on the dynamical evolution of the it
which is based on HST-WFPC2 data of 1997 (PI.Drissen) and
2007 (PI.Brandner). Then estimate dynamical timescels of NGC3603 to see
whether it is already undergone dynamical disolution, which is also
another way to see whether primodial mass segregation or dynamical
evolution plays more important role in initial mass funcion(IMF).
Supervisor: Eva Grebel (ARI) |
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Ana Uribe Uribe
(Colombia)
uribe @ mpia.de Interaction between circumstellar disks and embedded protoplanets. | Thesis abstract:
Circumstellar disks are a natural and necessary outcome of the process of
star formation due to angular momentum conservation in the collapse of
molecular cloud cores. Understanding the mechanisms by which matter is
accreted into the central young star is not only of fundamental importance
in star formation theory but also in acquiring a complete picture of the
properties and evolution of circumstellar disks themselves, which are
believed to be the birthplaces of planets. The problem of planet formation
is one that encompasses many orders of magnitude and thus involves a broad
range and sequence of physical processes. In this project we concentrate
on studying, form a theoretical and numerical approach, properties of
circumstellar disks such as angular momentum transport, general structure
and the interaction of the disk with embedded protoplanets.
Supervisor: Thomas Henning / Hubert Klahr (MPIA) |
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Kasper Borello Schmidt
(Denmark)
kschmidt @ mpia.de Identifying the multiply-imaged and strongly magnified QSOs in PS1 | Thesis abstract:
Lensed QSOs (at various luminosities) have proven over the last years to be a productive astrophysical
tool: the separation statistics is a powerful and independent tool to probe the concentration of
potential wells (galaxies and groups); the relative image brightnesses may be one of the best ways to
constrain dark-matter sub-halos; and the high magnifications that occur allow studies of the host
galaxies at unprecedented flux sensitivity and physical resolution. Drawing on the sample of
photometrically-identified QSO candidates, we plan to devise a statistically well-defined sample of
multiply-images QSO candidates, and to follow-up the most promising candidates. Following the
experience with SDSS (14), we will employ two separate approaches, one to identify “small separation
lenses” (< few arcsec); and one to search for wide-separation lenses (> few arcsec). In the first case,
the underlying assumption is that IPP only detects on source, that the subsequent analysis shows that
this source has QSO-like colors, but that the source shape is not consistent with the PSF; subsequent
multi-band deblending exercises can help remove QSO–star projection pairs. In the second,
’wide-separation’ case the approach will be to search for separate “catalog entries” or sources, that
have similar, QSO-like colors and that lie within < 20" of each other. We expect dozends of
wide-separation candidates, and many hundreds of small separation candidates
Using the PMAS IFU spectrometer at CAHA we then plan to get follow-up spectra for all wide-separation
candidates, and selected small-separation candidates (e.g. very high redshift objects)
Supervisor: Hans-Walter Rix / Sebastian Jester (MPIA) |
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Ana Valente
(Portugal)
avalente @ uni-heidelberg.de Cross-correlation studies between weak lensing and the Sunyaev-Zel'dovich effect | Thesis abstract:
We use the halo model of large scale structure in order to compute the angular
power spectrum of both wear shear and Sunyaev-Zel'dovich effect. While the weak
shear constrains the classical cosmological parameters, a model for the SZ effect
which has an empirical parameterization for the mass-temperature relation can be
used. A more sophisticated approach involving the baryon fraction and an entropy
floor is also possible. By correlating both signals, we aim to answer questions
regarding measurability, constraints on baryonic physics and biasing model.
Supervisor: Matthias Bartelmann (ITA) |
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Stephanie Schwemmer
(Germany)
S.Schwemmer @ lsw.uni-heidelberg.de Identification of Galactic Gamma-ray sources | Thesis abstract:
The H.E.S.S. experiment is a system of four Imaging Atmospheric Cherenkov Telescopes
located in Namibia, which detects gamma-rays above a treshold of 100 GeV. In 2004
and 2005 H.E.S.S. observed the Galactic Plane between +/- 30 degree Galactic longitude
and +/- 3 degree Galactic latitude. Many of the new sources detected in the scan are
not yet identified and therefore the nature of the sources is unknown. My PhD project
focuses on the identification of these Galactic gamma-ray sources, using observations
in other wave bands, especially in X-rays. I investigate the spatial and morphological
coincidences of possible counterparts and the different radiation processes within the
sources.
Supervisor: Stefan Wagner (LSW) |
