Gamma-ray Astronomy - Easy Conferences · Gamma-ray Astronomy. Christian Stegmann EINN, Cyprus ......
Transcript of Gamma-ray Astronomy - Easy Conferences · Gamma-ray Astronomy. Christian Stegmann EINN, Cyprus ......
Gamma-ray Astronomy.
Christian Stegmann EINN, Cyprus November, 2nd 2015
The end of the electromagnetic spectrum
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Gamma rays – Messengers from the High Energy Universe
> Production § protons: pion-decay: π0 → γγ
§ electrons: Inverse Compton Scattering: e± γ → e± γ
γ-ray band
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Why would anybody be interested in research that does not concern cosmology, inflation, dark energy
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Why would anybody be interested in research that does not concern cosmology, inflation, dark energy and electromagnetic interaction with nucleons and nuclei?
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My answer
> 100 years after discovery of cosmic rays we still don’t fully understand how cosmic accelerators work
> Cosmic accelerators seem extremely efficient § in their energy conversion § in their speed of acceleration
> Cosmic rays probe some of the most extreme environments in the Universe
> Cosmic rays do influence galaxy evolution
> Need to understand cosmic-ray astrophysics before claiming new physics. e.g.
§ electrons/positrons from dark matter
§ effects of quantum gravity
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Displaying Cosmic Particle Accelerators
This talk
Radio Optical X-ray Gamma-ray
E2 d
N/d
E
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Displaying Cosmic Particle Accelerators
Stellar type
Supernova shell
Pulsars
Pulsar Wind Nebulae
Complex type
Y-ray binaries
Microquasars
ms-PSR
GRBs
Molecular clouds
Collective type
Star forming region
Starburst galaxies
Diffuse Galactic emission Isotropic extragalactic emission
Black-hole type
Galactic centre
AGNs (HBL, FSRQ, …)
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Experimental techniques
Satellites (Fermi-LAT)
Air Cherenkov Systems (MAGIC, VERITAS, H.E.S.S.)
Water Cherenkov Systems (HAWC)
MeV GeV TeV PeV
Cherenkov light Particle shower
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How to measure gamma-rays from the ground?
Photon
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How to measure gamma-rays from the ground?
Photon
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How to measure gamma-rays from the ground?
Photon
Camera image
Intensity à Energy
Orientation à Direction
Shape à Primary particle
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1989: The first VHE gamma-ray source
Whipple
VLT, optical
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How to measure gamma-rays from the ground?
Photon
Single telescope event
3 telescope image in common camera plane
Intensity à Energy
Orientation à Direction
Shape à Primary particle
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Gamma-ray astronomy – 3rd generation experiments
VERITAS, USA
H.E.S.S., Namibia
MAGIC, La Palma
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Number of sources
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Data quality
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Data quality today
> Morphologies § spacial
§ energy-dependent
> Periodicities/Variability § from ms to years
> Energy-coverage § over several decades
> Source position § on the arc-second level
RX J1713-3946
H.E.S.S.
0.2-0.8 TeV 0.8-2.5 TeV > 2.5 TeV
Vela pulsar
HESS J1825-137
LS 5039
RX J1713-3946
H.E.S.S.
Galactic center
H.E.S.S.
H.E.S.S.
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SURVEYS
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H.E.S.S. Galactic Plane Scan
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H.E.S.S. galactic plane survey
> Source extraction with automatic pipeline
> Likelihood fit of emission by multiple Gaussian components plus diffuse background, Overlapping emission components combined
> 66 VHE sources + 11 complex sources (e.g. shell SNR) excluded from pipeline
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The Galactic Plane in Gamma-rays
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Identifications
Mostly sources with multiple associations
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Current Galactic VHE sources (with distance estimates)
Current Instruments
2% Crab Sensitivity
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SUPERNOVA REMNANTS
RX J1713.7-3946
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Examples of Supernova Remnants
Gamma rays
X rays
Vela Jr RX J1713.7-3946 SN 1006 RCW 86
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RX J1713.7-3946: Details of gamma-ray emission
> High precision morphology
> Comparison of TeV and X-ray morphology
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RX J1713.7-3946: Energy Spectrum
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Evolution of Supernova Remnants?
( from S. Funk)
No Pevatron yet! Cas A (SN IIb)
RX J1713.7 (SN II/Ib ?)
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THE GALACTIC CENTER
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High Precision Measurement of the Galactic Center
> Full dataset: 2004 – 2012 (220 hours)
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Cosmic-ray Density Distribution
> Correlation with molecular clouds à pp interaction target mass (M)
> Gamma-ray luminosity (L) in several regions à CR density ~L/M
> CR radial distribution § Homogeneous à impulsive injection
of CRs and diffusive propagation
§ 1/r2 à Wind-driven propagation
§ 1/r à continuous injection and diffusive propagation
> Central accelerator located within 10 pc and injecting CRs continuously for > 1kyrs
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Diffuse Emission and Injection Spectra
> Diffuse gamma-ray spectrum § E-2.3 up to 50 TeV w/o cutoff
> Assume central source of protons § Solve transport equation of protons
§ fit to HESS data
> Proton injection spectrum: § E-2.2 power law from GeV to few PeV
§ Cut-off 0.6 PeV at 90% CL 2.9 PeV at 68% CL
> A cosmic PeVatron!
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The extra-galactic sky seen with H.E.S.S.
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VHE gamma rays from high-redshift AGN
PKS 1441+25 (z=0.939)
MAGIC: ATel 7416 (2015)
VERITAS: ATel 7433 (2015)
S3 218+35 (z=0.944): Gravitationally lensed blazar
MAGIC: ATel 6349 (2014)
B0218+357 (z=0.684) (z=0.944)
1010 yr +10 days
1010 yr
(z=0)
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VHE gamma rays from high-redshift AGN
PKS 1441+25 (z=0.939)
MAGIC: ATel 7416 (2015)
VERITAS: ATel 7433 (2015)
S3 218+35 (z=0.944): Gravitationally lensed blazar
MAGIC: ATel 6349 (2014)
MAGIC
Fermi
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VHE gamma rays from high-redshift AGN
B0218+357 (z=0.684) (z=0.944)
1010 yr +10 days
1010 yr
(z=0)
De Angelis et al. arXiv:0707.2695,0707.4312
Sanchez-Conde et al., arXiv:0905.3270
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Many more science…
> Imaging of cosmic particle acceleration sites > Physics of pulsars and pulsar winds > Binary systems > …
> Properties of AGN > Probing the extragalactic background light > …
> Limits on dark matter and new physics > …
> We just see the tip of the iceberg
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How to do better?
> More events § more photons = better spectra, images,
fainter sources
àlarger collection area for gamma-rays
> Better events § more precise measurements of
atmospheric cascades and hence primary gammas
àimproved angular resolution
àimproved background rejection power
àMore telescopes!
Simulation: Superimposed images from 8 cameras
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The ideal array W. Hofmann
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The affordable compromise W. Hofmann
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The affordable compromise
Low energy section Energy threshold of some 10 GeV
Medium energy section mCrab sensitivity in the 100 GeV – 10 TeV domain
High energy section 10 km2 area at multi-TeV energies
W. Hofmann
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CTA: A Worldwide Consortium
29 Countries 178 Institutes 1187 Members
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Site selection
+30
-30 South: negotiations started with ESO/Chile and Namibia; Conclusion likely not before end of 2015
North: negotiations started with Mexico and Spain Conclusion likely not before end of 2015
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Current Galactic VHE sources (with distance estimates)
Current Instruments
mCrab Sensitivity
CTA
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CTA – the Cherenkov Telescope Array
> A huge improvement in all aspects of performance § A factor ~10 in sensitivity, much wider energy coverage, much better resolution, field-
of-view, full sky, …
> A user facility / proposal-driven observatory § With two sites with a total of >100 telescopes
> A 29 nation ~€200M investment project § Including everyone from H.E.S.S., MAGIC and VERITAS
The future of ground based gamma-ray astronomy with Air Cherenkov Telescopes
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Our local neighbourhood
Christian Stegmann . H.E.S.S. Highlights . IPA 2014 . 18.8.2014
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Nearby Sources
ELECTRONS & POSITRONS
Source: AMS
Linear scale!
A. Kounine, AMS Days, CERN
Secondary positrons Additional
charge-symmetric component
electron plus positron
EXPLANATIONS: DARK MATTER / PULSARS / SNR / PROPAGATION / …
Explaining muon magnetic moment and AMS-02 positron excess in a gauged horizontal symmetric model Wino dark matter in light of the AMS-02 2015 data Revisiting multicomponent dark matter with new AMS-02 data Dark Matter with multi-annihilation channels and AMS-02 positron excess and antiproton Dark matter for excess of AMS-02 positrons and antiprotons Implications for dark matter annihilation from the AMS-02 $bar{p}/p$ ratio AMS-02 Antiprotons from Annihilating or Decaying Dark Matter Explaining AMS-02 positron excess and muon anomalous magnetic moment in dark left-right gauge model Confronting recent AMS-02 positron fraction and Fermi-LAT Extragalactic Gamma-Ray Background measurements with gravitino dark matter Leptophilic Dark Matter and AMS-02 Cosmic-ray Positron Flux Mass of Decaying Wino from AMS-02 2014 AMS-02, Strongly Self-Interacting Dark Matter, and QUD
“AMS” & “Dark Matter” 139 papers “AMS” & “Pulsar” 23 papers “AMS” & “Supernova” 20 papers “AMS” & “Propagation” 38 papers
DARK MATTER ANNIHILATION
Need leptophilic DM Need large boost factors of O(102-103) for annihilation rate Tension with Planck limits (Slatyer, arXiv:1506.03811, 03812)
Cirelli et al. arXiv:0809.2409 (2013 update) also Cholis & Hooper, 1304.1840 and may more
ALTERNATIVE FITS TO POSITRON FRACTION
Pulsars
Secondaries from SNR
Propagation & distribution of sources
§ All describe the data § None needs “new physics” § All use a few free (but
plausible) parameters / assumptions (just like the DM explanation)
Feng & Zhang arXiv:1504.03312
Cowsik et al., arXiv:1305.1242
Mertsch & Sarkar, arXiv:1402.0866,
ANTIPROTON / PROTON RATIO
A. Kounine, AMS Days, CERN
linear scale!
(pre-AMS) Anti- protons
SECONDARY ANTIPROTON PRODUCTION
Kappl et al. arXiv:1506.04145
Updated antiproton production cross sections based on data
log scale!
Similar result: Giesen et al. arXiv:1504.04276
➜ No need to invoke DM contribution
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Experimental techniques
MeV GeV TeV PeV
Fermi-LAT MAGIC
VERITAS
H.E.S.S.
HAWC
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Experimental techniques
MeV GeV TeV PeV
Fermi-LAT MAGIC
VERITAS
H.E.S.S.
HAWC
Fermi LAT IACTs HAWC Effective area 1 m2 105 m2 105 m2
Field of view 20% of the sky 3o – 5o 15% of the sky Energy res. 10% 10% 100% – 20% Angular res. 6o – 0.3o 0.1o 1o – 0.2o
Duty cycle Full year 1400 h/year Full year
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Large Size Telescopes LST
> Structure § 23 m diameter (389 m2)
§ 28 m focal length
§ 1.5 m mirror facets
> Camera § 4.5o field of view
§ 0.1o PMT pixels
§ Camera ∅ over 2 m
> Carbon-fiber structure for 20 s positioning
> 4 LSTs on South site
> 4 LSTs on North site
> Prototype = 1st telescope
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Medium Size Telescopes MST
> Structure § 12m diameter (100 m2)
§ 16 m focal length
§ 1.2 m mirror facets
> Camera § 8o field of view
§ ~2000 x 0.18o PMT pixels
> 25 MSTs on South site
> 15 MSTs on North site
> Prototype operational
MST prototype in Berlin
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Medium Size Telescopes (MST) with dual mirror
> Structure § 9.7 m primary
§ 5.4 m secondary
§ 40 m2 eff. coll. area
§ PSF better than 4.5’ across 8o fov
> Camera § 8o field of view
§ 11328 x 0.07o SiPMT pixels
> Extend South array by adding 24 SCTs
➜ increased γ-ray collection area and γ-ray angular resolution
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Small Size Telescopes
> 70 SSTs for South site
> Different designs under consideration
> Single mirror design § SST-1M
> Dual mirror design § ASTRI
§ GATE
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SST Prototypes
SST-1m
ASTRI
GATE
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Sensitivity
LST
MST
SST
background and systematics limited
background limited
rate (=area) limited
nFn (erg/cm2s)
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Science drivers for CTA
> Theme 1: Cosmic Particle Acceleration § How and where are particles accelerated?
§ How do they propagate?
§ What is their impact on the environment?
> Theme 2: Probing Extreme Environments § Processes close to neutron stars and black holes?
§ Processes in relativistic jets, winds and explosions?
§ Exploring cosmic voids
> Theme 3: Physics Frontiers – beyond the SM § What is the nature of Dark Matter? How it is distributed?
§ Is the speed of light a constant for high energy particles?
§ Do axion-like particles exist?
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Key Science Questions and Key Science Projects
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Survey Sensitivity
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Angular Resolution
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Transients with CTA
Hinton & Funk arXiv:1205.0832
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Gamma Ray Bursts (E>30 GeV)
from Gamma-Ray Burst Science in the Era of Cherenkov Telescope Array (Astroparticle Physics special issue article) Susumu Inoue et al., arXiv:1301.3014
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Schedule
Pre-Construction Phase
2014-2015
Pre-Production Phase
2016-2017
Production Phase 2018-2020 (?)
7/2016 First telescopes on site (earliest)
Deploy ~10% of tels. Mass deployment
Pre-Construction Phase 2014-2015
7/2014 CTAO GmbH founded
4/2014 Site
narrowing South
8/2015 Site decision South
6/2015 Critical Design Review
Site decision
North
3/2015 Site
narrowing North
Founding Agree- ment
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Galactic Plane Surveys
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H.E.S.S. Galactic Plane Surveys
> 2673 hours of high-quality data, taken in the years 2004 to 2013. § Longitude l = 250 to 65 degrees, latitude |b| < 3.5 degrees
§ Sensitivity for the detection of point-like sources is at the level of 2% Crab or better
1% Crab
2% Crab
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H.E.S.S. Galactic Plane Scan
> 2673 hours of high-quality data, taken in the years 2004 to 2013. § Longitude l = 250 to 65 degrees, latitude |b| < 3.5 degrees
§ Sensitivity for the detection of point-like sources is at the level of 2% Crab or better
1% Crab
2% Crab
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Morphology Model
> Source extraction with automatic pipeline
> Likelihood fit of emission by multiple Gaussian components plus diffuse background, Overlapping emission components combined
> HGPS catalog 77 = 64 + 13 complex sources (e.g. shell SNR) excluded from pipeline
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Associations
> Systematic association of HGPS sources with nearby PSR, SNR, PWN, GeV sources (3FGL and 1FHL)
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Gaussian Band Large-Scale Emission Model
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H.E.S.S. Galactic Scan
Blue lines: H.E.S.S. horizons for 1% and 10% Crab Dots: H.E.S.S. Galactic sources
Red: PWNe Yellow: SNRs Black: other sources
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Time Variability: IC 310
> The closest blazar (z=0.019) § Previously thought to be a (large viewing angle) radio galaxy, new: VLBI jet
> Extreme variability seen with MAGIC § Despite larger jet viewing angle ~15°
MAGIC
Science 346 (6213)
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Historically bright flares of LS I +61 303 in 2014
> VERITAS monitoring of the binary system LS I +61 303
> Peak flux above 25% Crab
> Contemporaneous light curves from Swift-XRT (0.3-10 keV) and Fermi-LAT (0.3-300 GeV) do not show evidence for similarly high emission