Erlangen Centre for Astroparticle Physics

ECAP Seminar: Sebastian Böser
2019-11-07 12:00 - 13:00 (Europe/Berlin) | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Project 8 – towards a radio frequency measurement of the neutrino mass
While neutrino flavour oscillations are a clear indication that neutrinos do have non-vanishing rest masses, their values have so far not been established experimentally. The state-of-the-art experiment KATRIN has recently set a limit for the effective electron neutrino mass at mβ < 1.1 eV/c² @ 90%CL. However, cosmological observations indicate that Σm𝜈 < 0.12eV/c², well below KATRINs final projected sensitivity at m_𝜈 < 0.2 meV/c². As the MAC-E filter technology employed in KATRIN can not be scaled easily, new technologies are required to measure the neutrino mass in the lab. Towards this goal, the Project 8 collaboration has established Cyclotron Radiation Emission Spectroscopy as a new experimental method. In a four phased approach, this technique is employed in precision endpoint spectroscopy on tritium. For the final stage of the experiment, an atomic tritium setup is envisioned that allows a sensitivity of m_𝜈 < 0.04 meV/c²

ECAP Seminar: Markus Demleitner
2019-07-25 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
The VO And Why It Matters To You
In the most technical words, the Virtual Observatory (VO) is an effort to enable uniform and efficient access to astronomical data. With more glitz, it is like the Web and Google, only for data. In this talk I will try to convince you that what sounds tedious and boring in reality is exciting and useful to your research. Thus, after some motivation filling in the gaps in the above definitions, I will go on describing some of the key VO technologies and ways to use them – right now, from your desktop. I will close with an invitation to publish your data to the VO as well.
Slides available at http://docs.g-vo.org/er.pdf.

ECAP Seminar: Siegfried Glenzer
2019-07-18 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Exploring extreme states of matter with an ultra-bright X-ray free-electron laser
In this talk, we will review recent progress in high-energy density physics using the world’s brightest X-ray source, the Linac Coherent Light Source, SLAC’s free electron X-ray laser. These experiments investigate laser-driven matter in extreme conditions where powerful X-ray scattering and imaging techniques have been applied to resolve ionic interactions at atomic (Ångstrom) scale lengths and to visualize the formation of dense plasma states [1, 2]. The major research areas include dynamic compression experiments of solid targets to determine structural properties and characterize phase transitions at conditions approaching the interior of planets. Another area studies extreme fields produced by high-intensity radiation where fundamental questions of strongly excited solids can be investigated [3]. Each of these areas takes advantage of the unique properties of the probing beam. They include small foci for achieving high intensity or high spatial resolution, high photon or electron flux for dynamic structure factor measurements in single shots, and high spectral bandwidth to resolve plasmon (Langmuir) waves or ion acoustic waves in dense plasmas. We will present new experimental data demonstrating several novel studies that test our fundamental understanding of matter in extreme conditions with data of sufficient accuracy to support or refute theoretical approximations. These advances have led to significant international competition and laid out the path for facility upgrades to explore ever more extreme states of matter.
[1] P. Sperling, E. J. Gamboa, H. K. Chung, E. Galtier, H. J. Lee, Y. Omarbakiyeva, H. Reinholz, G. Röpke, U. Zas- trau, J. Hastings, L. B. Fletcher, and S. H. Glenzer, Phys. Rev. Lett. 115, 115001 (2015).
[2] B. B. L. Witte, L. B. Fletcher, E. Galtier, E. Gamboa, H. J. Lee, U. Zastrau, R. Redmer, S. H. Glenzer, and P. Sperling, Phys. Rev. Lett. 118, 225001 (2017).
[3] M. Mo, Z. Chen, R. K. Li, M. Dunning, B. B. L. Witte, J. K. Baldwin, L. B. Fletcher, J. B. Kim, A. Ng, R. Redmer, A. H. Reid, P Shekhar, X. Z. Shen, M. Shen, K. Sokolowski-Tinten, Y. Y. Tsui, Y. Q. Wang, Q. Zheng, X. J. Wang, and S. H. Glenzer, Science 360, 1451-1454 (2018).

ECAP Seminar: Sara Buson
2019-07-11 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
High-energy neutrinos from AGN?
With the advent of multi-messenger observatories, neutrino astronomy is turning into a helpful tool to investigate and put limits on the contribution of the known astrophysical objects to the diffuse neutrino background. Active Galactic Nuclei (AGN) have long been suggested among the candidate sources of cosmic high-energy neutrinos. If hadronic processes operate in the AGN jets, a lot can be learnt by combining neutrino observations with the putative accompanying electromagnetic information. This is motivated by the fact that both radiations may be pictured in the same astrophysical particle-cascades scenario, cascades that are ultimately originated by cosmic rays. While to date no neutrino point sources have been identified at high confidence, a promising ground for discovery could be the search for transient and variable neutrino/electromagnetic sources, in which case the atmospheric neutrino and muon backgrounds can be reduced by taking advantage of time- and space-coincidence. Recent outcomes in this field will be presented.

ECAP Seminar: Iris Gebauer
2019-07-04 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Indirect Dark Matter Searches and Cosmic Ray Transport in the Era of AMS
The Alpha Magnetic Spectrometer (AMS) is installed on the International Space Station (ISS) since May 2011. AMS is a complex particle detector designed to precisely measure the fluxes of cosmic rays between 0.5 GeV and a few TeV. The physics goals of the experiment include the search for possible signals of dark matter annihilation and hints for primordial antimatter in the fluxes of cosmic rays. As of recently, new calorimetric experiments like CALET and DAMPE begin to shed even more light on the matter component in cosmic rays with high statistics measurements up to TeV energies.
A plethora of precision results is emerging from these experiments. Many results challenge our understanding of galactic cosmic ray transport. This talk provides an overview over some of the most exiting and often surprising results from AMS, CALET and DAMPE. I will discuss their impact on our understanding of the origin and transport of galactic cosmic rays and their contribution to indirect dark matter searches.

ECAP Seminar: Andreas Haungs
2019-06-27 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Cosmic rays between the knee and the ankle
Investigations of the energy spectrum as well as the mass composition of cosmic rays in the energy range of PeV to EeV are important for understanding both, the origin of the galactic and the extragalactic cosmic rays. The multi-detector arrangement of KASCADE and its extension KASCADE-Grande was designed for observations of cosmic ray air showers in this energy range. Most important result from KASCADE is the proof that the knee feature at several PeV is due to a decrease in the flux of light atomic nuclei of primary cosmic rays. Results of KASCADE-Grande have now shown two more spectral features: a knee-like structure in the spectrum of heavy primaries at around 90 PeV and a hardening of the spectrum of light primaries at energies just above 100 PeV. These features are meanwhile confirmed by other experiments like Tunka, IceCube/IceTop, or TA/TALE. In this seminar the recent results on energy spectrum and composition are compared to each other and with astrophysical models for the energy range, where the transition from galactic to extragalactic origin of cosmic rays are expected. In addition, the effects of using different hadronic interaction models for interpreting the measured air-shower data will be discussed. Finally, the KASCADE Cosmic Ray Data Centre (KCDC) is discussed, which is a web-based platform to provide astroparticle physics data for the general public. The main purpose of KCDC is to archive original data to offer long-term scientific data for the high-energy astroparticle physics community as well as for students and the interested public via a sophisticated web portal. However, KCDC can only be a first step into a global analysis and data centre for multi-messenger astroparticle physics.

ECAP Seminar: Christian Glaser
2019-06-13 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Radio detection of ultra-high energy neutrinos
High energy neutrino astronomy is a powerful tool to study the high-energy universe. Neutrinos can escape dense source environments and point back to their sources with sub-degree accuracy. In particular, multi-messenger analyses that combine neutrino detection with electromagnetic (e.g. gamma ray) and gravitational-wave observations bear huge potential to probe the sources of neutrinos and cosmic rays. The detection of neutrinos is challenging because of their small flux and cross-section, and requires the instrumentation of huge volumes. Ultra-high energy neutrinos (E > 1e16 eV) can be efficiently measured using the radio technique, and the cold Antarctic ice is an optimal target material.
Before discussing the radio detection of neutrinos, I will briefly present the radio detection of cosmic rays, highlighting what we can learn from this mature field for neutrino detection. Then, I will report on the pilot neutrino detectors installed on the Ross ice shelf and at the South Pole, discuss how neutrinos can be measured with a radio detector and how their properties can be reconstructed from the short radio flash. At the end, I will present plans for a large-scale radio neutrino detector and discuss its prospects.

ECAP Seminar: Lee Thompson
2019-06-06 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
HyperKamiokande: a next generation long baseline neutrino experiment in Japan

The seminar will present the HyperKamiokande (HyperK) project which will build a large volume water Cerenkov detector for long baseline neutrino oscillation studies in Japan. A brief historical resume of the discovery of neutrino oscillations will be provided. The presentation will give an overview of the design of the HyperK detector and its main technical features. Details of the scientific programme to be undertaken will also be discussed. The prospects for the project to determine fundamental measurements such as CP violation and mass hierarchy will also be presented.

ECAP Seminar: Thorsten Enßlin
2019-05-02 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Information field theory – turning data into images
Charting the Universe from measurements is a challenging information theoretical problem. The finite data provided by instruments is never able to constraint the infinite degrees of freedom of the physical fields we are interested in astronomy or other areas. Additional information like physical laws and empirical correlations has to be folded into the field inference. Information field theory (IFT) is information theory for field inference enabling the consistent fusion of measurement data and theoretical concepts exploiting techniques developed for quantum field theory. IFT provides optimal methods to generate images exploiting all available information. Existing applications of IFT in astrophysics are galactic tomography, gamma- and radio- astronomical imaging, and the analysis of cosmic microwave background data. Applications in preparation are inferring the dynamics of an observed field and the fusion of measurements from complementary instruments into coherent pictures.

ECAP Seminar: Takaaki Tanaka
2019-02-14 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Recent Results from X-ray Studies of Supernova Remnants
X-ray emission from supernova remnants provides us with probes to high energy phenomena such as acceleration of cosmic-ray particles and nucleosynthesis in supernova explosions. In this talk, I will present some of recent results that I, with my students and collaborators, obtained from observations with Suzaku, Chandra, XMM-Newton, and NuSTAR satellites. I will mainly cover results related to particle acceleration and over-ionized plasma in Galactic supernova remnants. I will also talk about expectations brought about by high resolution spectroscopy with future X-ray observatories such as XRISM, which is scheduled to be launched in 2021.

ECAP Seminar: Marijke Haverkorn
2019-02-07 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
The Magnetic Field of the Milky Way
The Milky Way’s magnetic field has coherent structures on Galactic scales, following spiral arms but also Galactic outflows. It also has a turbulent component, which influences the galactic ecosystem in many ways, such as delaying star formation, isotropizing Galactic cosmic rays, and providing significant pressure component.
These magnetic field components can only be detected indirectly, through the signature they leave on various kinds of radiation and particles, observations of which are fitted to models of the Galactic magnetic field. Traditionally, radio polarimetry is most used to probe Galactic magnetic fields, with radio detectors in frequency ranges from LOFAR to Planck giving unique information.
I will discuss some of the recent progress in this field, and our new project called IMAGINE, which aims to combine all different observational tracers and prior information to build a next-generation model of the Galactic magnetic field.

ECAP Seminar: Joachim Puls
2019-01-31 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
On the difficulties to derive reliable CNO abundances in hot massive stars
Though low in number, massive stars play an essential role in the early and present Universe, due to their enormous energy output and production of metals. Moreover, the end-products of massive star evolution are among the most spectacular events/objects in our Cosmos: Supernovae, (long-duration) Gamma-Ray Bursters and Black Holes. Unfortunately, the evolution of massive stars is not as well understood as required for reliably predicting the different evolutionary channels, and problems already exist during the Main Sequence, related to mass loss and rotation. To constrain present evolutionary predictions, the observational analysis of CNO surface abundances is a prime tool, giving insight into rotationally-induced mixing processes and angular momentum transport. Such analyses, however, are hampered by many difficulties, increasing the measurement uncertainties significantly, compared to the low-mass case. In this talk, I will outline these difficulties, also with focus on problems arising from physically complex line transitions, and discuss the results and implications from more recent abundance studies of hot massive stars.

Digitizing the Sky: Prof. Dr. U. Heber
2019-01-10 19:15 - 20:45 | Zentrum für Medizinische Physik und Technik (ZMPT), Hörsaal: 01.020, Henkestraße 91, 91052 Erlangen, Henkestraße 91, Erlangen, 91058, Germany
Prof. Heber will present the FAU contributions to the APPLAUSE digitization project of astronomical photo negative at the Collegium Alexandrinum.
More on the project in our News Item and at the Collegium’s page.

ECAP Seminar: Klaus Helbing
2019-01-10 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Probing Particle Physics with IceCube
The IceCube observatory located at the South Pole is a cubic-kilometre optical Cherenkov telescope primarily designed for the detection of high-energy astrophysical neutrinos. IceCube became fully operational in 2010 and reached a milestone in 2013 by the first observation of cosmic neutrinos in the TeV-PeV energy range. This observation does not only mark an important breakthrough in neutrino astronomy, but it also provides a new probe of particle physics related to neutrino production, mixing, and interaction. An overview is given of the various possibilities how IceCube can address fundamental questions related to the phenomena of neutrino oscillations and interactions, the origin of dark matter, and the existence of exotic relic particles, like monopoles. Recent results are summarized and future avenues are highlighted.

ECAP Seminar: Florian Kühnel
2018-12-20 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Primordial Black Holes as Dark Matter
Primordial black holes are black holes that may have formed in the early Universe. Their masses potentially span a range from as low as the Planck mass up to many orders of magnitude above the solar mass. This, in particular, includes black holes of the order of 10 solar masses, like those recently discovered by LIGO. These may be of primordial origin. In order to qualitatively and quantitatively asses this and related scenarios, a profound understanding of the holes’ formation mechanism necessary. After a general introduction on primordial black holes, I will discuss the most consequential aspects of their formation, and elaborate on the observable imprints these may leave. I will give an overview about recent abundance limits, and comment on constraints of combined scenarios in which also particle dark matter is present.

ECAP Seminar: Thomas Heid (Phd defense)
2018-12-13 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Characterizing the diffuse neutrino flux with the future KM3NeT/ARCA detector

ECAP Seminar: Anna Franckowiak
2018-11-22 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Searching for electromagnetic counterparts to high-energy neutrinos
In September 2017, the detection of a high-energy neutrino in coincidence with a flaring gamma-ray blazar revealed the first compelling high-energy neutrino source candidate. At the same time gamma-ray blazars are disfavored as the dominant neutrino source class. Other plausible source candidates are tidal disruption events, low-luminosity gamma-ray bursts and supernovae. Combining neutrino data with electromagnetic measurements in a multi-messenger approach will increase the sensitivity to identify other neutrino sources and help to solve long-standing problems in astrophysics such as the origin of cosmic rays. I will review the recent progress in neutrino multi-messenger astronomy and highlight the potential of the novel optical survey instrument, Zwicky Transient Facility (ZTF), to probe various source classes as neutrino emitters.

ECAP Seminar: Andrea Santangelo
2018-07-11 13:00 - 14:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Fundamental Physics studies with X-ray spectral-timing-polarimetry and the eXTP mission
[ abstract not available yet ]

ECAP Seminar: Gisela Anton and Joern Wilms
2018-07-04 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Status report on IceCube-Gen2 and eROSITA
Gisela Anton and Joern Wilms will give us a brief status report on the IceCube-Gen2 and eROSITA projects.

ECAP Seminar: Bosco Oruru
2018-06-27 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Status of Astronomy in East Africa: Focus on Uganda
Astronomy and Cosmology are science disciplines that give an in-depth description and analysis of the structures and forms that characterize the universe. Although Astronomy and Cosmology are not yet fully developed in the East African region, several affirmative developments have been registered in the establishment of the disciplines in the region. These include, among others: postgraduate training of students from Uganda, Kenya, Rwanda and Ethiopia in South Africa since 2003, benefiting from the South African National Astrophysics and Space Science Programme (NASSP) and the Square Kilometre Array (SKA) Project. Some of these have since graduated with PhDs and returned to their home countries to contribute to the development of the disciplines. The Entoto Observatory in Ethiopia has been commissioned to provide infrastructure for Observational Astronomy and outreach activities. Kenya will host some Radio Astronomy telescopes under SKA. Most public universities in Ethiopia offer Astronomy at undergraduate level, while a few offer it at postgraduate level. In Kenya, Astronomy has been introduced at undergraduate level at the University of Nairobi and Kenyatta University, respectively. In Uganda, Mbarara University of Science and Technology leads by offering Astronomy as major components of Physics at both undergraduate and postgraduate levels, and many graduate students do projects/research in Astrophysics. In Rwanda, the National University of Rwanda also offers Astronomy as a component of Physics for undergraduate students. Since 2009, the East African Astronomical Society (EAAS) has been formed and workshops have been held in Kenya, Ethiopia, Uganda and Rwanda, respectively. In 2013, the East African Astronomical Research Network (EAARN) was formed by astrophysicists, with the sole aim of improving research capacity and collaboration in Astrophysics. Although Makerere University is the oldest public university in Uganda and among the top ranking universities in Africa, Astronomy is yet to be fully developed. An effort has been made to introduce it as taught components of Physics at undergraduate and postgraduate levels. This has created awareness among students and also cultivated much interest in pursuing further careers in Astrophysics. The university has at least employed on full-time one professional Astrophysicist who may spearhead the establishment of the field. Initially, part-time lecturers were being engaged to help teach astronomy related courses. Successful establishment of Astronomy at Makerere University will require adequate resources, which are lacking at the moment. However, with support, collaborations and graduate training, this can be achieved.

ECAP Seminar: Frank Haberl
2018-06-20 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
The XMM-Newton surveys of the Magellanic Clouds
Using the XMM-Newton observatory, we performed X-ray surveys of the Magellanic Clouds, the two star-forming galaxies nearest to the Milky Way. The images obtained from the EPIC instruments provide a wealth of information about the X-ray source populations in the Small and Large Magellanic Cloud. Due to their proximity we can resolve the emission from supernova remnants, and we have discovered many new X-ray binaries powered by accretion of matter. In particular the Small Magellanic Cloud is remarkable with respect to its large number of X-ray binaries with a high-mass donor star. These discrete sources are embedded in diffuse X-ray emission which originates in the hot phase of the interstellar medium of the clouds.

ECAP Seminar: Adrian Zink
2018-06-13 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Updates of the ECAP desktop computing system
New operating system, new hardware and new IT services for the ECAP desktop computing system will be presented and discussed.

ECAP Seminar: Michael Schulreich
2018-06-06 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Reconstructing the origin of the Local Bubble and Loop I via radioisotopic signatures on Earth
Deep-sea archives all over the world show an enhanced concentration of the radionuclide 60Fe, isolated in layers dating from about 2.2Myr ago. Since this comparatively long-lived isotope is not naturally produced on Earth, such an enhancement can only be attributed to extraterrestrial sources, particularly one or several nearby supernovae in the recent past. It has been speculated that these supernovae might have been involved in the formation of the Local Superbubble, our Galactic habitat. In this talk, I will summarize our efforts in giving a quantitative evidence for this scenario. Besides analytical calculations, I will present results from high-resolution hydrodynamical simulations of the Local Superbubble and its presumptive neighbor Loop I in different environments, including a self-consistently evolved supernova-driven interstellar medium. For the superbubble modeling, the time sequence and locations of the generating core-collapse supernova explosions are taken into account, which are derived from the mass spectrum of the perished members of certain, carefully preselected stellar moving groups. The release and turbulent mixing of 60Fe is followed via passive scalars, where the yields of the decaying radioisotope were adjusted according to recent stellar evolution calculations. The models are able to reproduce both the timing and the intensity of the 60Fe excess observed with rather high precision. I will close with a discussion of recent developments and give future perspectives.

ECAP Seminar: Oliver Hupe
2018-05-30 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Radiation Protection Dosimetry: Phantoms and measuring quantities
In this talk the concept of the radiation protection quantities will be explained. An overview about the different types and different applications of phantoms in radiation protection and their use for the definition of the different quantities is used for this. The phantoms can serve as a basis for the current definition and the calculation of conversion coefficients for the protection quantities according to ICRP 116. For the definition, the ICRU tissue 4-element phantoms are used. In practise, the the ISO calibration phantom for the current operational quantities such as ISO water slab, PMMA rod etc can be used for the calibration of personal dosemeters.

ECAP Seminar: Henning Gast
2018-05-23 11:30 - 12:30 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Latest results from the AMS experiment on the International Space Station
The Alpha Magnetic Spectrometer (AMS) is a detector designed for precision spectroscopy of cosmic rays that was installed on the International Space Station in May 2011. With dimensions of 5x4x3 cubic meters and a weight of 7.5 tons, AMS is the largest cosmic-ray spectrometer ever built. I will summarize the results from the first 6.5 years of operation of AMS. The energy spectra of positrons, electrons, anti-protons, and light nuclei measured by AMS challenge existing theories for the origin and propagation of cosmic rays.

ECAP Seminar: Thomas Janka
2018-05-16 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
3D core-collapse supernova modeling and applications to Cas A and other supernova remnants
First three-dimensional, first-principle simulations of core-collapse supernovae have become possible in the recent past. They demonstrate the basic viability of the neutrino-driven mechanism for powering the explosions of the majority of supernova progenitors. Although a number of open questions remain to be settled, the explosion models are now sufficiently mature to strive for detailed comparisons against observations, for example considering well studied, nearby supernovae and young supernova remnants. This talk will review our basic understanding of the explosion mechanism and report some results of such observational tests.

ECAP Seminar: News from the ECAP laboratory
2018-05-02 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
News from the ECAP laboratory
Kay Graf and Stefan Funk will report on the status of the ECAP laboratory building.

ECAP Seminar: Christoph Weniger
2018-04-25 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Dark matter searches with gamma rays
The Fermi Large Area Telescope has during its almost 10 years of mission time revolutionized our understanding of the gamma-ray sky. It enabled, e.g., the discovery of the Fermi bubbles, a surprisingly large number of gamma-ray emitting millisecond pulsars, dark gas in the Milky Way disk, and it performed some of the most sensitive searches for dark matter annihilation signals. An excess of GeV photons from the Galactic bulge and center has been found, which caused a lot of excitement since it is compatible with a self-annihilation signal from WIMP dark matter. Circumstantial evidence points now however in another direction, namely that the excess is caused by the combined emission of thousands of unresolved millisecond pulsars in the Galactic bulge. Furthermore, additional gamma-ray emission from star formation, from the activity of the central supermassive black hole, and gamma-ray emission associated with the Fermi bubbles can potentially play an important role for the bulge emission. I will present the current state of the discussion, results from the new analysis code SkyFACT that support the millisecond pulsar interpretation of the Fermi GeV excess, and plans for the future to further disentangle the various contributions to the gamma-ray emission from the Galactic bulge and center. A better understanding of this emission will shed further light on the history of the inner Galaxy and potentially the nature of dark matter.

ECAP Seminar: Thorsten Lisker
2018-02-01 14:00 - 15:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
Survival in galaxy clusters: from ultra-diffuse to ultra-compact objects
The diversity of low-mass cluster galaxies in terms of their size and stellar content is striking. So-called ultra-diffuse galaxies residing in the core of a massive galaxy cluster appear surprisingly intact and might be protected by a large dark matter content. Ultra-compact objects, on the other hand, were proposed to be remnant nuclei of disrupted dwarf galaxies, but no tidal debris is found in their vicinity. The stellar age gradients of “normal” cluster dwarfs suggest that ram pressure stripping played an important role in their evolution – yet that alone cannot explain the systematically different angular momentum content of late-type and early-type dwarfs. In this seminar talk I am going to present our latest observational efforts to tackle these problems, along with comparisons to simulations that can shed light upon the galaxies’ evolutionary history.

ECAP Seminar: Christian Motch
2018-01-31 12:00 - 13:00 | ECAP, room 307, Erwin-Rommel-Str 1, Erlangen, 91058, Germany
SVOM – Space-based multiband astronomical Variable Objects Monitor
The Chinese-French space mission SVOM (Space-based multi-band astronomical Variable Objects Monitor) is mainly designed to detect and localize Gamma-Ray Burst events (GRBs). The satellite, to be launched late 2021, embarks a set of gamma-ray, X-ray and optical imagers. Thanks to its pointing strategy, quick slew capability and fast data connection to earth, ground based observations with large telescopes will allow us to measure redshifts for an unprecedented number of GRBs. While the association of long GRBs with core-collapse SNe is well established, the recent detection of a kilonova and of a short GRBs in coincidence with GW170817 beautifully confirms predictions from NS-NS or NS-BH mergers models. I will present the SVOM instrumentation, its policy for alert distribution and will discuss the overall science goals and capability of the SVOM mission in the framework of the multi-wavelength and multi-messenger panorama of the next decade.
