IMPRS projects at MPE/HEG

The High Energy Astrophysics group at MPE has its major scientific emphasis on the study of extreme processes mostly via X-ray observations, but also extending to other wavebands. Our main astrophysical themes are: 1) Investigating physical processes including strong gravity around black holes and other compact objects; 2.) The cosmic history of black hole growth and its relationship to galaxy evolution; 3) Large scale structure, as probed hot gas in clusters and groups of galaxies, and the related cosmological implications; 4) gamma-ray bursts. Research fields for which PhD projects are offered specifically for 2013/14 include:

Supermassive black holes in the high redshift Universe
Accreting supermassive black holes (SMBH) in active galactic nuclei (AGN) may play a significant role
in shaping the formation and evolution of the first galaxies, and their radiative output can also be
important for the reionization of the Universe. One of the best ways of finding growing SMBH is using
X-ray surveys, where the contrast between the accretion power and stellar output of the galaxies is high,
and because the X-rays can penetrate any surrounding obscuring gas and dust. Despite this, the number of
X-ray-selected AGN currently known at high redshift is very small. The aims of this project are to search
for such objects in both deep and wide X-ray surveys, identify them with multiwaveband data, and ideally
confirm them via longer-wavelength spectroscopy. This will provide the first census of the accretion power
in the Universe during this early epoch in the formation of black holes and galaxies. The project will lead
naturally into the exploitation of the eROSITA all sky survey, expected to uncover numerous high redshift AGN
into the epoch of reionization at redshift larger than 6.
Supervisors: K. Nandra, A. Georgakakis, A. Merloni, M. Salvato


The point source component of the extended ROSAT All-Sky Survey
The extended ROSAT All-Sky Survey (Boller, Freyberg, Trümper 2014) provide
the deepest X-ray All-Sky Survey of point sources before eROSITA data will become available.
The number of sources is 124401. X-ray images, X-ray spectra and X-ray light curves have been produced.
The scientific analysis is presently limited to the brightest objects. The main task is to work out
the X-ray timing and spectral properties of different sources classes for the bright end of the population,
down to lower flux limits and an analysis of the multiwavelength properties.
The successful candidate is expected to have a strong background in AGN physics as well in basic stellar astrophysics.
The PhD work is of basic interest for the upcoming eROSITA survey. The science themes will be supervised by Prof. Thomas Boller and Dr. Mara Salvato.


Population properties of AGN in observations and simulations: toward a physical description of accretion history of the Universe.
The physical mechanisms that are responsible for the growth of
super-massive black holes at the centres of galaxies are still not
well understood. Progress can be achieved by relating the properties
of black holes (e.g. Eddington ratio, mass) to diagnostics of the
physical conditions on larger scales e.g. morphology or
star-formation history of the galaxies that host active black
holes. Comparison of these observations with the predictions
of simulations on the cosmological evolution of AGN can guide the
interpretation to make inferences about the key physical processes
at play. The Ph.D. project will compare directly
the predictions of recent cosmological simulations with the latest
observational constraints on the population properties of Active
Galactic Nuclei (i.e. supermassive black holes in their growth
phase). The latter include the star-formation history, host galaxy
morphology, accretion rate distribution and large scale environment of
AGN, as obtained from the groups' direct involvement in a number of
large multi-wavelength extragalactic survey programs.
Supervisors: A. Georgakakis, A. Merloni, K. Nandra


Study of the Structure of Galaxy Clusters with X-ray Observations
Galaxy clusters are interesting astrophysical laboratories and cosmological
probes. To use galaxy clusters for astrophysical or cosmological studies we
need to understand the structure and matter composition. With detailed
X-ray observations by the modern X-ray observatories XMM-Newton and
Chandra we can obtain detailed insight into the structure, matter
composition and dynamical state of galaxy clusters. The Ph.D. project
will be devoted to the detailed analysis of X-ray observations of
galaxy clusters.




Studying stellar feedback into the ISM through X-ray emission
Massive star impacts on their surrounding interstellar medium affects its ability for formation of new stars.
Ionising radiation, winds and supernovae lead to formation of cavities and bubbles filled with gas at X-ray
emitting temperatures. It is unclear how much massive-star energy is thus transferred into the interstellar
medium, or radiated away. This ''feedback'' scenario is one of the main astrophysical issues in the context of
galaxy and cosmic chemical evolution. Observations with ROSAT have shown diffuse X-ray emission from several
nearby cavities of the ISM, with interesting morphologies following, in some cases, the HI-delineated cavity
boundaries. We will investigate how energy is imparted from massive-star groups towards interstellar medium
on My time scales, combining 3D simulations with observations of interstellar gas in HI, X-ray, and gamma-ray emission.
Supervisor: R. Diehl (with inclusion of several HEG collaborators)


Exploring the interplay between star formation and interstellar dust with GRBs
Gamma-ray bursts (GRBs) are the most energetic events known, and shed light on the darkest and
farthest side of the Universe in unprecedented detail.
Their confirmed link to massive stars, their vast cosmological distances, and their highly
luminous emission, offer an effective and unique probe of the
interstellar properties and chemical composition of star-forming galaxies in the young Universe,
which for the most part would otherwise remain undetected. Understanding the contribution from
such galaxies in the cosmic star formation rate, and studying the role that interstellar dust and atomic
and molecular gas play in driving the star-formation are key aspects of galaxy and stellar evolution models,
and can be uniquely addressed with GRBs. This PhD project will combine large imaging and spectroscopic
GRB afterglow and host galaxy datasets to study the emission, attenuation and depletion properties
of the interstellar medium in distant, star-forming galaxies in relation to other environmental
characteristic properties. The distinct and relatively unexplored view provided by GRBs on distant
galaxies will form an important building-block to our understanding on the conditions of star-formation
in the very early Universe. Supervisors: P. Schady


Testing the GRB fireball model
Analytical descriptions of the evolution of the GRB fireballsuggest that the cooling frequency (typically
between the X-rays and optical) should move with a specified speed depending on the density profile of the surrounding.
Previous GROND data have shown that this picture is too simplistic: neither does the speed of the cooling frequency
movement matches, nor the direction. Recent hydrodynamical relativistic simulations have revealed a number of effects
which change the expectations. The succesful applicant shall work within the GROND team and in close collaboration
with one of the authors of these simulations (now Humboldt fellow in the HEG) to (i) test the new models against observations,
and (ii) derive further constraints on the model.
Supervisor: J. Greiner (with inclusion of several HEG collaborators)


X-ray transients
As part of an international collaboration entitled "Exploring the X-ray Transient and variable Sky", funded through the 7th framework
programme of the EU, the full Newton-XMM archive will be analysed for transient sources. The succesful applicant shall perform a
multi-wavelength characterisation of all kinds of X-ray transients with their wide variety of time-scales. The final goal is to establish
a classification engine for X-ray transients which are expected to be observed in the upcoming eROSITA all-sky survey. This work will be
based on the existing expertise in, and activities of the GROND group in the area of gamma-ray, X-ray and optical transients.
Supervisor: J. Greiner (with inclusion of several HEG collaborators)


Development of Silicon Detectors for X-ray astronomy


Mara Salvato, Last update: 16/10/2013[Disclaimer]