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 extends to other wavebands. Our main astrophysical themes are:
1.) Large scale structure, as probed hot gas in clusters and groups of galaxies, and the related cosmological implications;
2.) The cosmic history of black hole growth and its relationship to galaxy evolution;
3.)Investigating physical processes including strong gravity around black holes and other compact objects;
4) gamma-ray bursts.
Research fields for which PhD projects are offered specifically for 2018 include:
Observational Cosmology with Galaxy Clusters
Galaxy clusters are great probes of the structure formation, providing competitive constraints on the matter content of the Universe and the gravity models. Their properties reflect their small and large scale environment. With the large sample of galaxy clusters at hand, and through a combination of multi-wavelength properties of galaxy clusters, we aim to both understand the link between the cluster formation and their properties and obtain the cosmological constraints. The project relies on the large area X-ray cluster spectroscopy project, SPIDERS lead by MPE, existing deep photometric data yielding weak lensing mass measurements and galaxy properties, submillimeter cluster observations using SZ effect. Finally, we plan to include eROSITA data (upcoming X-ray all-sky survey) in this work.
Supervisors: A. Finoguenov, J. Comparat , G. Erfanianfar, D. Eckert, K. Nandra
Examples of Clusters in AEGIS field
Evolution of Supermassive Black Hole Accretion at High Redshift
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, identifying them with multiwaveband data. The aim is to contrain the X-ray luminosity function at high redshifts to 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. Merloni, M. Salvato
Jet opening angles and energetics of Gamma-ray bursts
Gamma ray bursts (GRBs) are the electromagnetic signatures of exploding
massive stars (long-duration sub-type) or the merger of two neutron stars
(short-duratino sub-type). Due to their huge energy release, these events
produce bright X-ray to radio afterglows, due to the interaction with the
circumburst and interstellar medium. Relativistic hydrodynamical models
have now reached a state which allows us to deduce several physical
parameters of the explosion and subsequent jet emission when compared
to observational data. The aim of this thesis is to perform a systematic
analysis of the large GRB afterglow data set collected at the MPE/HEG
over the last decade using these models. Among the physical parameters
to be deduced, the jet opening angle distribution for short-duration GRBs
will be of prime interest, allowing better predictions of the NS-NS merger
rate which in turn has important implications on the detection rate of
gravitational waves with aLIGO/VIRGO.
Supervisor: J. Greiner
X-ray sources in the cosmic web
The connection between galaxies and their host halos is an important issue in galaxy evolution and cosmology.
Past work has used a combination of two techniques to characterise this relationship: galaxy clustering and
galaxy-galaxy lensing, but this previous work, based on optical data, was limited to relative small sky areas.
We propose a PhD project work on both the measurement and the modeling of the halo occupation distribution of
extragalactic X-ray sources. The combination of the upcoming eRosita X-ray survey with deep and wide optical imaging,
and spectroscopic follow-up will enable a robust measurement of both the AGN-halo and the cluster-halo connections.
This project involves working with both observations and simulations to develop the optimal tools to measure
and interpret the clustering and galaxy-galaxy lensing signals. These measurements will shed light on the role
of the environment on the evolution of galaxies in dense and energetic environments.
Supervisor: J. Comparat, A. Merloni
Constraining cosmology and galaxy cluster physics using the X-ray background radiation
Since the 1970s, we know that a diffuse and roughly homogeneous source of X-rays, the X-ray background (XRB), is present at every position in the sky. Deep X-ray surveys have shown that the XRB is not actually diffuse. Instead, it is constituted of a large number of faint, unresolved active galactic nuclei (AGN) and galaxy clusters. The amplitude of fluctuations of the XRB on small scales carries important information on the structural properties of galaxy clusters. On large scales, XRB fluctuations are sensitive to the clustering of X-ray sources (both clusters and AGN), which strongly depend on the parameters governing the growth of structures in the Universe. The project will be carried out in two phases. First, we will develop tools to estimate the power spectrum of XRB fluctuations and model it as a function of the relevant cosmological and astrophysical parameters. Second, we will exploit the data of the upcoming eROSITA mission to measure the power spectrum of XRB fluctuations and set constraints on cosmology and cluster physics.
Supervisor: D. Eckert, A. Merloni
Examples of SNR morphology (Curtesy: NASA CXC Photo album)
A multi-wavelength study of supernova remnants and neutron stars
The PhD project is in the field of exploring stellar endpoints, e.g. supernova
remnants and neutron stars. The candidate shall make use of various data from current
radio, optical and high energy observatories(e.g. XMM-Newton, Chandra and Fermi).
The PhD candidate shall take active part in the preparation of observing proposals
for the current optical, radio and high-energy observatories and shall be familiar
with the common data analysis tools. Typically, a PhD research project develops by
its own during the course of the PhD. However, a starting point could be the
identification campaign of SNR candidates.
Identified radio supernova remnants (SNRs) in the Galaxy comprise an incomplete
sample of the SNR population due to various selection effects. ROSAT performed
the first All-Sky Survey (RASS) with an imaging X-ray telescope and thus provided
another window for finding SNRs and compact objects that may reside within them.
eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the core
instrument on the Russian Spektrum-Roentgen-Gamma (SRG) mission which is currently
scheduled for launch in fall 2017. In the soft band (0.5-2 keV), it will be about
30 times more sensitive than ROSAT, while in the hard band (2-8 keV) it will provide
the first ever true imaging survey of the sky. It supports to continue the previous
SNR identification campaign and to search for new supernova remnants and neutron
stars with a much higher sensitivity than was possible before. In the course of
the PhD research the current identification campaign of SNR candidates and neutron
stars shall be continued using existing multi-wavelength data from optical, radio
and X-ray missions as well as from eROSITA once the mission is up. Along that research
there will also be the possibility to look into the open questions on the internal
structure of neutron stars, on the equation of state of super-nuclear matter, on the
cooling of neutron stars as well as on their emission mechanisms for non-thermal
radiation and on particle acceleration mechanisms in supernova remnants.
Supervisor: W. Becker
