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 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 2023 include:

eROSITA Cosmology in the Big Data Era

Clusters of galaxies, located at the peaks in the cosmic density field, offer an independent and powerful probe of the growth of structure. The properties of galaxy clusters, being sensitive underlying cosmological, can be utilized to extract valuable information on the underlying cosmological model. With the advent of the new eROSITA All-Sky Survey, we are in the verge of discovering more than 100,000 clusters of galaxies. Combined with the other multi-wavelength wide area surveys, e.g., Dark Energy Survey, eROSITA will constrain the cosmological parameters at a percent level precision at the end of its All-Sky Survey. Complimentary to the traditional analysis methods, deep machine learning techniques provide a revolutionary way to optimally extract cosmological parameters using the data from large-scale multi-wavelength surveys. In this Ph.D. project, the successful candidate will develop machine learning techniques to model the large structure formation of the Universe with a complementary approach to facilitate new discoveries, interpret, and extract new cosmological features from existing large datasets. The new techniques will open a new window to estimating cosmology with higher accuracy than before.

Supervisors: E. Bulbul, K. Nandra

The X-ray transient sky from eROSITA through Einstein Probe to Athena

The exploration of the X-ray time domain sky is entering its golden age. The SRG/eROSITA all-sky survey (started in 2019 and continuing until 2023) is already providing a wealth of transient and variable phenoma and changing our understanding of some of these populations along the way. The Chinese Einstein Probe (slotted for launch in early 2023) will be a dedicted transient discovery and follow-up mission with unprecedented all-sky sensitivity and coverage. Athena, the next large X-ray observatory of ESA planned for launch in the early 2030ies, will offer breakthrough capabilities to study the variable sky out to larger distances and fainter populations. The MPE HEG is playing major roles in all three satellite projects, from building and operating eROSITA, to contributing detectors and optics experience to the FXT on Einstein Probe, to leading the development of the WFI for Athena. The aim of this PhD project is to connect the three mission by exploring the eROSITA transient sky as it is being observed, turning the results into a forecast for Einstein Probe, studying the first sources found with Einstein Probe, and assessing Athena's opportunities for achieving the next step in studying the transient and variable X-ray sky.

Supervisors: A. Rau, K. Nandra

The role of the hot circum-galactic medium in galaxy formation and evolution

Galaxy formation and evolution studies the processes that shape galaxies over time. How the quenched galaxy population has emerged in the context of hierarchical galaxy formation is a puzzle in this field. The key to understand quenching is to establish with observations a complete census of the existing gas within reach of galaxies: the circum-galactic medium (CGM). The cold, cool and warm phases of the CGM have been extensively studied and are now well charted. To attain a complete picture of the co-evolution between the galaxy population and its CGM, its hot phase, currently poorly known, needs to be explored. In this project, the PhD candidate will explore how the hot CGM emission, as observed by eROSITA, is related to the properties of the galaxies and host dark matter halo population. The candidate will confront observations to the latest hydro-dynamical simulations to tackle quantitatively the relation between hot CGM, quenching and AGN feedback.

Supervisors: J. Comparat, K. Nandra

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. eROSITA, 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 launched in 2019. In the soft band (0.5-2 keV), it is 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. An example is the recently identify SNR Hoinga (in the picture).

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 search 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
Composite X-ray and radio image of Hoinga. The X-rays discovered by eROSITA are emitted by the hot debris of the exploded progenitor, whereas the radio antennae detect synchrotron emission from relativistic electrons, which are decelerated at the outer remnant layer.(Credit: eROSITA/MPE (X-ray), CHIPASS/SPASS/N. Hurley-Walker, ICRAR-Curtin (Radio))

Mara Salvato, Last update: 27/09/2022[Disclaimer]