A MAGIC picture of our Galactic Center A MAGIC picture of our Galactic Center Christian Fruck fruck@mpp.mpg.de Max-Planck-Institut für Physik PPMSC - München - 2015 1 / 33
A MAGIC picture of our Galactic Center Why are astronomers so fascinated by the Galactic Center? Why are astronomers so fascinated by the Galactic Center? Triggering event for the MAGIC observation campaign Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC The MAGIC GC observation campaign and results Observability of the GC from the MAGIC site Results Speculations 2 / 33
A MAGIC picture of our Galactic Center Why are astronomers so fascinated by the Galactic Center? Some of the most important reasons ... ◮ The GC hosts the by far closest Super Massive Black Hole (SMBH) to Earth ◮ Studying the GC might finally allow for testing new theories describing Gravity in a quantum-mechanical framework ◮ Spatial/angular resolution of sub Event Horizon scales of the GC BH in radio and optical are only few years away ◮ The DM concentrated at the GC , if annihilating/decaying should be the most luminous when observed from Earth ◮ Therefore the GC is one of the best candidates for indirect DM searches ◮ The GC is a very dense and active environment, from an astrophysical point of view ◮ It hosts star forming regions with plenty of molecular gas, heavy young stars, and many supernova remnants 3 / 33
A MAGIC picture of our Galactic Center Why are astronomers so fascinated by the Galactic Center? Putting the Galactic Center into context Milky Way galaxy: ◮ disk (30 kpc x 0.3 kpc): young stars, gas, molecular clouds, dust ◮ bar (4.5 kpc) and bulge (1.5 kpc): old stars low star formation ◮ Galactic Center (250 pc): dense molecular clouds high star formation rate image source: en.wikipedia.org 4 / 33
A MAGIC picture of our Galactic Center Why are astronomers so fascinated by the Galactic Center? GC region in 20cm, 1.1mm, IR ◮ VLA (20cm): H II regions that are illuminated by hot, massive stars, supernova remnants, and synchrotron emission ◮ Caltech Submillimeter Observatory (1.1mm): cold (20-30 K) dust associated with molecular gas ◮ Spitzer (IR): primarily emission from stars and from polycyclic aromatic hydrocarbons image source: http://images.nrao.edu 5 / 33
A MAGIC picture of our Galactic Center Why are astronomers so fascinated by the Galactic Center? Radio sources SgrA and SgrA* ◮ bright point-like radio source ◮ at the center of SgrA-West (Mini-Spiral) ◮ at the edge of SNR SgrA-East ◮ thought to be SMBH ◮ from stelar motions: ≈ 4 · 10 6 M ⊙ image source (left): N. E. Kassim, D. S. Briggs, T. J. W. Lazio, T. N. LaRosa, J. Imamura (NRL/RSD) image source (right): astro.ucla.edu 6 / 33
A MAGIC picture of our Galactic Center Why are astronomers so fascinated by the Galactic Center? The Galactic Center S-star cluster — stellar motion reveals the SMBH ◮ few 10 OB stars confined inside the central arc-sec around SgrA* ◮ star S2 periastron: 120 AU, period: 15.6 y refer to for example: Ghez, A. M., et al. The Astrophysical Journal 509.2 (1998): 678. 7 / 33
A MAGIC picture of our Galactic Center Triggering event for the MAGIC observation campaign Why are astronomers so fascinated by the Galactic Center? Triggering event for the MAGIC observation campaign Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC The MAGIC GC observation campaign and results Observability of the GC from the MAGIC site Results Speculations 8 / 33
A MAGIC picture of our Galactic Center Triggering event for the MAGIC observation campaign G2 gas cloud falling onto the Galactic Center ◮ Reports by ESO about a gas cloud of three times the Earth mass on its way to SgrA* (S. Gillessen et al. 2012) ◮ Pericenter passage 2013-2014, ≈ 2000 Schwarzschild radii (20 light hours) (S. Gillessen et al. 2013) ◮ Tidal disruption of the cloud has already begun 2011 ◮ Likely that part of the cloud will be subjected to accretion in the upcoming years ⇒ Monitoring campaigns triggered in nearly all wavelengths 9 / 33
A MAGIC picture of our Galactic Center Triggering event for the MAGIC observation campaign Possible scenarios Rough summary of possible observable accretion scenarios: ◮ Formation of a hot accretion disk ⇒ Production of thermal X-rays (X-ray satellites) ◮ Production of energetic electrons ⇒ Synchrotron radiation from Radio to X-ray from energetic electrons (Radio telescopes, X-ray satellites) ⇒ Bremsstrahlung and/or Inverse Compton scattering of high energy e − ( � ray satellite observatories, ground based � ray observatories) ◮ Acceleration of protons and heavy nuclei ⇒ � 0 production in interaction of hadronic cosmic rays ( � ray satellite observatories, ground based � ray observatories) 10 / 33
A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC Why are astronomers so fascinated by the Galactic Center? Triggering event for the MAGIC observation campaign Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC The MAGIC GC observation campaign and results Observability of the GC from the MAGIC site Results Speculations 11 / 33
A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC IACTs in context of other Instruments Cosmic microwave background, ~3 mm 1 EeV 1 PeV 1 TeV 1 GeV 1 MeV 1 keV -3 18 15 12 9 6 3 -6 -9 -12 -15 10 eV 10 eV 10 eV 10 eV 10 eV 10 eV 1 eV 10 eV 10 eV 10 eV 10 eV 10 eV 1 mm UV IR radio VHE HE X UHE γ-rays visible -18 10 -15 m 10 -12 m 10 -9 m 10 -6 m 10 -3 m 10 3 10 6 10 m 1 m m m 1 am 1 fm 1 pm 1 nm 1 m µ 1 mm 1 km 1 Mm 300 MHz 300 GHz 300 kHz satellites m 0 k 0 1 γ N 2 , O 2 , O 3 , O 50% of incident rockets radiation absorbed balloons H 2 O m k 0 4 EAS CO 2 radio telescopes optical m Cherenkov telescopes k 2 0 telescopes Earth surface fluorescence detectors particle detectors image credit: Robert Wagner 12 / 33
Cosmic Ray (p, Primary , Fe ...) A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC Extended air-showers EM (left) and hadronic (right) shower and Atmospheric MC simulations (center) Atmospheric Nucleus EM Shower e+ e- Nucleons, K , etc. Atmospheric Nucleus e+ EM Shower e- e+ Nucleons, e - e+ e- K , etc. e+ e- e+ e+ e- e - + EM Shower image credit: Robert Wagner / CORSIKA 13 / 33
A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC Imaging Air Cherenkov Telescopes γ Extensive Reconstructed Air Shower Source Position Cherenkov Light Cameras with PMT pixels Impact point Air Shower Images 14 / 33
A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC The MAGIC telescopes ◮ located on the Roque de los Muchachos (at 2200 m a.s.l.) on the Canary island La Palma ◮ Two 17m diameter parabolic single-mirror telescopes consisting of 239 1 m 2 mirror panels each ◮ Support structure from carbon fiber can rotate 180 ◦ in about 20 s image credit: Robert Wagner 15 / 33
A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC Images recorded by the cameras of the MAGIC telescopes ◮ The two cameras consist of 1039 photomultiplier pixels each (3 . 5 ◦ FoV) ◮ Events last only a few ns ◮ Di ff erent coincidence criteria (charge concentration in small region of camera in one and simultaneous such events in both telescopes) required for the events to be recorded ◮ Typical CR event rate 300 Hz ◮ Event classification o ffl ine via Random Forests CleanData CleanData CleanData Mean 2.341 Mean 2.546 Mean 3.781 RMS 4.346 RMS 2.107 RMS 3.707 60 18 34 56 17 32 52 16 30 48 14 28 44 13 26 40 12 23 36 11 21 32 10 19 29 9 17 25 8 15 21 7 13 17 5 11 13 4 8 9 3 6 5 2 4 1 1 2 0.60 ° 0.60 ° 0.60 ° -3 -0 -0 187mm 187mm 187mm L L L 16 / 33
A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC Short excursion: How are VHE � -rays produced? ◮ � -rays in the TeV regime are exclusively of non-thermal origin. ◮ They are always produced as a by-product of the acceleration of charged particles to VHE ◮ The favored acceleration scenarios are: Di ff usive shock acceleration and acceleration in rotating magnetic fields (Pulsars, BH plerions) charged u = β c strong shock-wave particle v ≈ c u 1 magnetic mirror u 2 u = β c θ θ u 4 v charged particle x u 5 17 / 33
A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC Short excursion: How are VHE � -rays produced? ◮ � -rays are then produced via: ◮ Leptonic: Bremsstrahlung, Curvature radiation, Inverse Compton scattering (IC) – mostly on synchrotron radiation produced by the same population (SSC) ◮ Hadronic: decay of � 0 form pp interaction 18 / 33
A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Why are astronomers so fascinated by the Galactic Center? Triggering event for the MAGIC observation campaign Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC The MAGIC GC observation campaign and results Observability of the GC from the MAGIC site Results Speculations 19 / 33
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