Chairs
Professor Malcolm Fairburn, King's College London, UK
Professor Malcolm Fairburn, King's College London, UK
Malcolm Fairbairn works at the intersection of particle physics, astrophysics and cosmology. His interests include dark matter, dark energy, inflation and astroparticle physics. He obtained his PhD from the University of Sussex in 2002 before postdocs in Brussels, Stockholm and at CERN. He has been at King's College London for a decade.
09:05-09:30
The current status of 3.5 keV line and sterile neutrino dark matter
Professor Alexey Boyarsky, Leiden University, The Netherlands
Abstract
Professor Boyarsky will review the current status of the attempts to figure our the origin of the 3.5 kev line and of sterile neutrino as dark matter candidate.
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Professor Alexey Boyarsky, Leiden University, The Netherlands
Professor Alexey Boyarsky, Leiden University, The Netherlands
Professor Boyarsky graduated from MIPT in 1995 and got my PhD in 1999. He worked at the Niels Bohr Institute, EPFL (Lausanne), ETH (Zurich) and CERN. Currently he is a professor at Leiden University. He is a theoretical physicist, working in particle and astroparticle physics and cosmology. He is a part of the SHiP collaboration and scientific associate at CERN.
09:45-10:15
Plasma models and charge exchange
Professor Jelle Kaastra, SRON and Leiden University, The Netherlands
Abstract
Charge exchange (CX) is the process where an electron is transferred from one atom to another. Here Professor Kaastra considers CX between cold, neutral hydrogen gas and hot plasma. The CX process can give rise to line radiation in the X–ray and other spectral bands. The spectrum for this process is quite different from the normal X–ray emission spectrum from the hot plasma. CX with oxygen ions has been seen in many spectra from Solar System objects. Professor Kaastra shows that the CX process in clusters of galaxies occurring between the hot intracluster gas and cold gas filaments is very effective and produces significant line radiation near 3.5 keV due to interaction with sulphur. Additional evidence for this process in clusters comes from grating spectra of clusters in the oxygen band, as well as from UV spectroscopy. Professor Kaastra concludes this presentation with a brief summary of atomic physics, spectral modelling and calibration issues related to the 3.5 keV band.
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Professor Jelle Kaastra, SRON and Leiden University, The Netherlands
Professor Jelle Kaastra, SRON and Leiden University, The Netherlands
Jelle obtained his master's degree in 1981 and his PhD in astronomy at the same university in 1985 with a thesis on Solar Flares.After that he joined SRON, the Netherlands Institute for Space Research in Leiden, first as a postdoc and from 1988 as a permanent staff member. He moved in 1994 with the Leiden branch to Utrecht. He is now senior scientist at SRON, and since 2014 adjunct full professor of high-energy astrophysics at Leiden University. His specialism is high-resolution X-ray spectroscopy of extragalactic sources. He is acting PI of the XMM-Newton Reflection Grating Spectrometer and the Chandra Low Energy Transmission Grating Spectrometer. In addition he has been an ESA-selected member of the Astro-H Science Advisory Council.
11:00-11:30
X–ray probes of dark matter
Professor Tesla Jeltema, University of California, Santa Cruz, USA
Abstract
Professor Jeltema will discuss the use of X–ray observations to constrain particle dark matter models. In particular, she will review searches for X–ray lines including observations of and constraints on the 3.5 keV line. She will also discuss the use of X–ray observations of galaxies and clusters to constrain dark matter self–interaction.
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Professor Tesla Jeltema, University of California, Santa Cruz, USA
Professor Tesla Jeltema, University of California, Santa Cruz, USA
Tesla is an Associate Professor of Physics at University of California, Santa Cruz. She received her BSc from The College of William and Mary and her PhD in Physics from the Massachusetts Institute of Technology. Her research focuses on observational cosmology and particle astrophysics, including constraints on the nature of dark matter and dark energy and studies of the evolution of galaxies.
11:45-12:00
Laboratory X–ray astrophysics with highly charged ions
Dr Chintan Shah, Max Planck Institute for Nuclear Physics, Heidelberg, Germany
Abstract
X–ray observations provide insight into the state and dynamics of a variety of astrophysical plasmas. Its interpretation relies on synthetic spectra which are based on plasma models. Those models, in turn, depend heavily on the accurate knowledge of the underlying atomic processes. A recent Hitomi observation of the Perseus cluster [1] provided an unprecedented high–resolution spectrum. It revealed not only well–resolved lines originating from most abundant highly charged ions, but also uncovered significant shortcomings of present spectral packages SPEX and AtomDB, namely inaccurate energies and atomic–scale processes completely missing from the models. For example, a weak line feature around 3.5 keV found in the spectra of galaxy clusters sparked tremendous interest when it was attributed to a possible dark matter decay process [2]. However, charge exchange between bare sulphur ions and hydrogen, a process not included in spectral models, was found to be a more plausible explanation. This talk will report on laboratory electron beam ion trap experiments that compellingly supported charge–exchange mechanism for 3.5 keV X–ray line [3]. It will further underpin how the incomplete knowledge of atomic processes limits the amount of information that can be extracted from current and next–generation X–ray satellites such as Athena and XRISM.
REFERENCES:
[1] Hitomi Collaboration, Nature 535, 117–121 (2016)
[2] E Bulbul et al, Astrophys. J 789, 13 (2014)
[3] C Shah et al, Astrophys. J 833, 52 (2016)
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Dr Chintan Shah, Max Planck Institute for Nuclear Physics, Heidelberg, Germany
Dr Chintan Shah, Max Planck Institute for Nuclear Physics, Heidelberg, Germany
Chintan Shah obtained his BSc and MSc in Physics from the M. S. University of Baroda, India, in 2011. After working as an assistant scientist at the Institute for Plasma Research for a year in India, he moved to Germany to obtain his PhD from Heidelberg University. He received his PhD in 2015 where his focus was on the development of X-ray Compton polarimeters and on implementing techniques to study plasma anisotropies. Currently, Chintan is working as a postdoctoral fellow at Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg, Germany. His primary focus is on laboratory astrophysics experiments with an Electron Beam Ion Trap (EBIT) to study underlying atomic processes responsible for the X-ray line formation such as collisional excitation, dielectronic recombination, and charge exchange. Chintan's present interests include benchmarking atomic theory and providing empirical data to improve present spectral models which will be critical in interpreting the high-resolution X-ray spectra that current and future missions such as XRISM and Athena, will yield.
12:00-12:15
Sterile neutrino constraints from Chandra to eROSITA
Dr Florian Hofmann, Max Planck Institute for Extraterrestrial Physics (MPE), Germany
Abstract
There is an ongoing debate on the nature of the 3.55 keV emission line in X-ray spectra of astronomical objects. One possible explanation is the decay of 7.1 keV sterile neutrinos, which have been proposed as a candidate for dark matter. The authors performed an independent search for the emission line in X-ray spectra of galaxy clusters obtained from the Chandra observatory data archive. They will also discuss future capabilities of the eROSITA observatory in the search for dark matter.
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Dr Florian Hofmann, Max Planck Institute for Extraterrestrial Physics (MPE), Germany
Dr Florian Hofmann, Max Planck Institute for Extraterrestrial Physics (MPE), Germany
Florian obtained his master’s degree in physics from the Technical University of Munich (TUM) in 2013. In 2016 he obtained his PhD in astronomy within the International Max Planck Research School on Astrophysics (IMPRS) at the Ludwig Maximilians University (LMU) in Munich. Currently he is working as a Postdoc at the Max Planck Institute for Extraterrestrial Physics (MPE). He has been working on X–ray observations of Galactic and extragalactic X–ray binaries, clusters of galaxies, and most recently the Galactic center with the Chandra and XMM–Newton observatories. He is a member of the galaxy cluster working groups of the eROSITA (planned launch 2019) and ATHENA X–ray observatories.