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Arrays of imaging atmospheric Cherenkov telescopes (IACTs) probe the very highenergy (VHE) gamma-ray sky. Their working principle consists of the simultaneous observation of air showers initiated by the interaction of VHE gamma rays and cosmic rays with the atmosphere. Cherenkov photons induced by a given shower are focused onto the camera plane of the telescopes in the array, producing a stereoscopic record of the event. This image contains the longitudinal development of the airshower, together with its spatial, temporal, and calorimetric information. The properties of the originating VHE particle (type, energy, and incoming direction) can be inferred from those images by reconstructing the whole event using machine learning techniques. In this thesis, a purely deep learning (DL) driven full-event reconstruction of simulated, stereoscopic IACT events of the future Cherenkov Telescope Array (CTA) is presented. In addition, we apply DL algorithms on real observational IACT data, utilizing Crab Nebula observations by the MAGIC telescopes. In order to conduct all necessary research to achieve the former milestones we developed CTLearn, a package that includes modules for loading and manipulating IACT data and for running DL models, using pixel-wise camera data as input...
This thesis presents the results of indirect dark matter searches in the gamma-ray sky of the near Universe, as seen by the MAGIC Telescopes. The author has proposed and led the 160 hours long observations of the dwarf spheroidal galaxy Segue 1, which is the deepest survey of any such object by any Cherenkov telescope so far. Furthermore, she developed and completely characterized a new method, dubbed “Full Likelihood”, that optimizes the sensitivity of Cherenkov instruments for detection of gamma-ray signals of dark matter origin. Compared to the standard analysis techniques, this novel approach introduces a sensitivity improvement of a factor of two (i.e. it requires 4 times less observation time to achieve the same result). In addition, it allows a straightforward merger of results from different targets and/or detectors. By selecting the optimal observational target and combining its very deep exposure with the Full Likelihood analysis of the acquired data, the author has improved the existing MAGIC bounds to the dark matter properties by more than one order of magnitude. Furthermore, for particles more massive than a few hundred GeV, those are the strongest constraints from dwarf galaxies achieved by any gamma-ray instrument, both ground-based or space-borne alike.
Searching for Dark Matter with Cosmic Gamma Rays summarizes the evidence for dark matter and what we can learn about its particle nature using cosmic gamma rays. It has almost been 100 years since Fritz Zwicky first detected hints that most of the matter in the Universe that doesn't directly emit or reflect light. Since then, the observational evidence for dark matter has continued to grow. Dark matter may be a new kind of particle that is governed by physics beyond our Standard Model of particle physics. In many models, dark matter annihilation or decay produces gamma rays. There are a variety of instruments observing the gamma-ray sky from tens of MeV to hundreds of TeV. Some make deep, focused observations of small regions, while others provide coverage of the entire sky. Each experiment offers complementary sensitivity to dark matter searches in a variety of target sizes, locations, and dark matter mass scales. We review results from recent gamma-ray experiments including anomalies some have attributed to dark matter. We also discuss how our gamma-ray observations complement other dark matter searches and the prospects for future experiments.
This is a report on the findings of the dark matter science working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper was commissioned by the American Physical Society, and the full white paper can be found on astro-ph (arXiv:0810.0444). This detailed section discusses the prospects for dark matter detection with future gamma-ray experiments, and the complementarity of gamma-ray measurements with other indirect, direct or accelerator-based searches. We conclude that any comprehensive search for dark matter should include gamma-ray observations, both to identify the dark matter particle (through the characteristics of the gamma-ray spectrum) and to measure the distribution of dark matter in galactic halos.
An important, open research topic today is to understand the relevance that dark matter halo substructure may have for dark matter searches. In the standard cosmological model, halo substructure or subhalos are predicted to be largely abundant inside larger halos, for example, galaxies such as ours, and are thought to form first and later merge to form larger structures. Dwarf satellite galaxies—the most massive exponents of halo substructure in our own galaxy—are already known to be excellent targets for dark matter searches, and indeed, they are constantly scrutinized by current gamma-ray experiments in the search for dark matter signals. Lighter subhalos not massive enough to have a visible counterpart of stars and gas may be good targets as well, given their typical abundances and distances. In addition, the clumpy distribution of subhalos residing in larger halos may boost the dark matter signals considerably. In an era in which gamma-ray experiments possess, for the first time, the exciting potential to put to test the preferred dark matter particle theories, a profound knowledge of dark matter astrophysical targets and scenarios is mandatory should we aim for accurate predictions of dark matter-induced fluxes for investing significant telescope observing time on selected targets and for deriving robust conclusions from our dark matter search efforts. In this regard, a precise characterization of the statistical and structural properties of subhalos becomes critical. In this Special Issue, we aim to summarize where we stand today on our knowledge of the different aspects of the dark matter halo substructure; to identify what are the remaining big questions, and how we could address these; and, by doing so, to find new avenues for research.
The research program in gamma-ray astronomy focuses on increasing our knowledge of the nature and origin of galactic and extragalactic gamma rays, and understanding high-energy processes in the Sun, celestial objects, interstellar medium, and extragalactic space. This book not only provides an overview of the latest research and future plans for space-borne and ground-based experiments dedicated to the observation of the gamma-ray sky, but also addresses the topic of variable gamma-ray sources from the perspective of their identification and counterparts at different wavelengths. It further gives an overview of the theory related to the most qualified emission processes that take place in these sources and of the nature of their variability. Sample Chapter(s). Integral: 4 Years in Orbit (767 KB). Contents: The Suzaku Mission (K Yamaoka); Gamma-Ray Astrophysics with AGILE (F Longo et al.); The GLAST Mission (J E McEnery); Recent Results from CANGAROO (M Mori); VERITAS: Status and Performance (J Holder); Gamma Ray Pulsars in the GLAST Era (M Razzano); Supernovae and Gamma-Ray Burst (M Della Valle); Solving GRBs and SGRs Puzzles by Precessing Jets (D Fargion et al.); Multiwavelength Observations and Theories of Blazars (G Tosti); Gamma Ray Bursts (L Amati); X-Rays and GeV Flares in GRB Light Curves (A Galli et al.); The Online Monitor for the GLAST Calibration Unit Beam Test (L Baldini et al.); Gamma-Ray Burst Physics with GLAST (N Omodei); The Global Fit Approach to Time-Resolved Spectroscopy of GRBs (A Chernenko); and other papers. Readership: Gamma-ray astronomers; astrophysicists; students and researchers involved in gamma-ray astronomy, both theoretical and experimental; researchers in the development of new gamma-ray detectors.
In this talk I review recent progress made in ground-based gamma-ray astronomy and illustrate the capabilities of present day observatories, such as the Very Energetic Radiation Imaging Telescope Array System (VERITAS), for Indirect Dark Matter searches and detection of cosmological diffuse visible and infrared radiation. I use these examples to provide scientific motivations for the next generation instrument, the Advanced Gamma Ray Imaging System (AGIS), and explain some new technological approaches to the AGIS design, currently under development.
Indirect detection of particle dark matter relies upon pair annihilation of Weakly Interaction Massive Particles (WIMPs), which is complementary to the well known techniques of direct detection (WIMP-nucleus scattering) and collider production (WIMP pair production). Pair annihilation of WIMPs results in the production of gamma-rays, neutrinos, and anti-matter. Of the various experiments sensitive to indirect detection of dark matter, the Gamma-ray Large Area Space Telescope (GLAST) may play the most crucial role in the next few years. After launch in late 2007, The GLAST Large Area Telescope (LAT) will survey the gamma-ray sky in the energy range of 20MeV-300GeV. By eliminating charged particle background above 100 MeV, GLAST may be sensitive to as yet to be observed Milky Way dark matter subhalos, as well as WIMP pair annihilation spectral lines from the Milky Way halo. Discovery of gamma-ray signals from dark matter in the Milky Way would not only demonstrate the particle nature of dark matter; it would also open a new observational window on galactic dark matter substructure. Location of new dark matter sources by GLAST would dramatically alter the experimental landscape; ground based gamma ray telescopes could follow up on the new GLAST sources with precision measurements of the WIMP pair annihilation spectrum.
This book provides a comprehensive review of the methodologies and searches for dark matter (DM) annihilation signals using very-high-energy gamma rays (VHE, E > 100 GeV), utilizing data from current Imaging Atmospheric Cherenkov Telescopes (IACTs) in the pre-Cherenkov Telescope Array (CTA) era. It presents the state-of-the-art statistical analysis methods and theoretical models related to TeV DM, applied to data from the H.E.S.S. telescope array, which is currently the most sensitive IACT array for observing the Galactic Center (GC), where the brightest DM annihilation signals are expected. The authors delve into the astrophysics of VHE gamma-ray production through cosmic ray acceleration. They explain the Imaging Atmospheric Cherenkov technique, describe the H.E.S.S. array, and discuss possibilities for DM annihilation-induced gamma-ray spectra and DM distribution profiles. By employing advanced statistical methods, they search for weak signals in the GC region using the H.E.S.S. Inner Galaxy Survey dataset and address systematic uncertainties. The authors present and debate the most constraining results on TeV dark matter models. Finally, this book presents the sensitivity of current IACTs to DM annihilation signals using IGS mock datasets, accounting for systematic and instrumental uncertainties. Detection prospects for canonical TeV DM models, such as the Wino, Higgsino, and quintuplet, are discussed. Sensitivity benchmarks on indirect DM searches with IACTs using H.E.S.S. as an example are provided, setting the stage for future developments in the CTA era. It serves as a consolidated resource for graduate students and researchers, presenting methodologies that could lead to significant advancements in the quest to understand dark matter.
The contributions in this volume provide a snapshot of the latest research and future plans for space-borne and ground-based experiments dedicated to the observation of the gamma-ray sky. The articles are authored by both seasoned veterans of the first dedicated gamma-ray missions, and young scientists entering the fascinating field of gamma-ray astrophysics.With the advent of gamma-ray instrumentation on spacecraft and large and sensitive ground-based detectors, new and unexpected phenomena have been discovered, such as gamma-ray bursts and gamma-ray emission from blazars. The immense vitality of the field in the current “post-EGRET era” is witnessed by the numerous ongoing and forthcoming gamma-ray experiments documented here, complementary to various cosmic-ray, neutrino, astroparticle and X-ray projects.