1 / 62

The Spectrum of Markarian 421 Above 100 GeV with STACEE

The Spectrum of Markarian 421 Above 100 GeV with STACEE. Jennifer Carson UCLA / Stanford Linear Accelerator Center February 2006. Space-based. 10 MeV. 100 MeV. 10 GeV. 100 GeV. 10 TeV. 1 GeV. 1 TeV. 1 MeV. Ground-based. Outline.

melvyn
Download Presentation

The Spectrum of Markarian 421 Above 100 GeV with STACEE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Spectrum of Markarian 421 Above 100 GeV with STACEE Jennifer Carson UCLA / Stanford Linear Accelerator Center February 2006 Space-based 10 MeV 100 MeV 10 GeV 100 GeV 10 TeV 1 GeV 1 TeV 1 MeV Ground-based

  2. Outline I. Science goal for -ray detections from active galaxies • Understanding particle acceleration II. Brief overview of VHE gamma-ray astronomy III. Ground-based detection techniques • Atmospheric Cherenkov technique • Imaging vs. wavefront sampling IV. STACEE V. Markarian 421 • First STACEE spectrum • Detection of high-energy peak? VI. Prospects for the future

  3. Blazars Radio-loud AGN viewed at small angles to the jet axis • bright core •  3% optical polarization • strong multi-wavelength variability

  4. Blazars Radio-loud AGN viewed at small angles to the jet axis 1 eV (IR) 1 keV (X-ray) 1 MeV 1 GeV • bright core •  3% optical polarization • strong multi-wavelength variability • Double-peaked SED: synchrotron emission + ? 10-3 eV (radio) ? Maraschi et al. 1994 synchrotron What physical processes produce the high-energy emission?

  5. Blazar High-Energy Emission Models Is the beam particle an e- or a proton?

  6. Blazar High-Energy Emission Models Is the beam particle an e- or a proton? Leptonic models: • Inverse-Compton scattering off accelerated electrons • Synchrotron self-Compton and/or • External radiation Compton

  7. Blazar High-Energy Emission Models Is the beam particle an e- or a proton? Leptonic models: • Inverse-Compton scattering off accelerated electrons • Synchrotron self-Compton and/or • External radiation Compton Hadronic models: • Accelerated protons • Gamma rays from pion decay or • Synchroton gamma-ray photons

  8. Blazar High-Energy Emission Models Is the beam particle an e- or a proton? Leptonic models: • Inverse-Compton scattering off accelerated electrons • Synchrotron self-Compton and/or • External radiation Compton Hadronic models: • Accelerated protons • Gamma rays from pion decay or • Synchroton gamma-ray photons Gamma-ray observations around 100 GeV can distinguish between models

  9. Compton Gamma Ray Observatory 10 MeV 100 MeV 10 GeV 100 GeV 10 TeV 1 GeV 1 TeV 1 MeV Energy Atm. Cherenkov Wavefront Sampling Atm. Cherenkov Wavefront Sampling Atm. Cherenkov Single Dish Imaging Air shower arrays Exploring the Gamma-ray Spectrum Past Present/Future Atm. Cherenkov Imaging Arrays GLAST

  10. e- e+ … e+ e- e+ e+ Atmospheric Cherenkov Technique g-ray q ~ 1.5o

  11. Single-dish Imaging Telescopes g-ray q ~ 1.5o Whipple 10-meter

  12. Wavefront Sampling Technique g-ray q ~ 1.5o

  13. Wavefront Sampling Technique g-ray q ~ 1.5o

  14. Compton Gamma Ray Observatory 10 MeV 100 MeV 10 GeV 100 GeV 10 TeV 1 GeV 1 TeV 1 MeV Energy Atm. Cherenkov Wavefront Sampling Atm. Cherenkov Wavefront Sampling Atm. Cherenkov Single Dish Imaging Air shower arrays Exploring the Gamma-ray Spectrum Past Present/Future Atm. Cherenkov Imaging Arrays GLAST Whipple 10-meter

  15. 10 MeV 100 MeV 10 GeV 100 GeV 10 TeV 1 GeV 1 TeV 1 MeV Energy Atm. Cherenkov Wavefront Sampling Atm. Cherenkov Wavefront Sampling Atm. Cherenkov Single Dish Imaging Air shower arrays Exploring the Gamma-ray Spectrum STACEE Atm. Cherenkov Imaging Arrays GLAST Whipple 10-meter CELESTE

  16. 10 MeV 100 MeV 10 GeV 100 GeV 10 TeV 1 GeV 1 TeV 1 MeV Energy Atm. Cherenkov Wavefront Sampling Atm. Cherenkov Wavefront Sampling Atm. Cherenkov Single Dish Imaging Air shower arrays Exploring the Gamma-ray Spectrum STACEE Present/Future Atm. Cherenkov Imaging Arrays GLAST

  17. 10 MeV 100 MeV 10 GeV 100 GeV 10 TeV 1 GeV 1 TeV 1 MeV Energy Atm. Cherenkov Wavefront Sampling Exploring the Gamma-ray Spectrum STACEE HESS Present/Future Atm. Cherenkov Imaging Arrays GLAST VERITAS

  18. The High-Energy Gamma Ray Sky 1995  3 sources Mrk421 Mrk501 Crab (2) (1) Pulsar Nebula AGN (0) (0) Other, UNID SNR R.A.Ong Aug 2005

  19. The High-Energy Gamma Ray Sky 2004  12 sources Mrk421 H1426 M87 Mrk501 1ES1959 RXJ 1713 Cas A GC TeV 2032 Crab 1ES 2344 PKS 2155 (7) (1) Pulsar Nebula AGN (2) (1,1) Other, UNID SNR R.A.Ong Aug 2005

  20. The High-Energy Gamma Ray Sky 2005  31 sources! + 8-15 add. sources in galactic plane. 1ES 1218 Mrk421 H1426 M87 Mrk501 PSR B1259 1ES 1101 1ES1959 SNR G0.9 RXJ 1713 RXJ 0852 Cas A LS 5039 GC Vela X TeV 2032 Crab 1ES 2344 HessJ1303 Cygnus Diffuse MSH 15-52 PKS 2155 H2356 PKS 2005 (11) (4+2) Pulsar Nebula AGN (3+4) (3,3+1) Other, UNID SNR R.A.Ong Aug 2005

  21. e- e+ … e+ e- e+ e+ Wavefront Sampling Detectors STACEE & CELESTE Cherenkov light intensity on ground  energy of gamma ray Cherenkov pulse arrival times at heliostats  direction of source

  22. National Solar Thermal Test Facility Albuquerque, NM 5 secondary mirrors & 64 PMTs 64 heliostats STACEE Solar Tower Atmospheric Cherenkov Effect Experiment

  23. National Solar Thermal Test Facility Albuquerque, NM 5 secondary mirrors & 64 PMTs 64 heliostats STACEE Solar Tower Atmospheric Cherenkov Effect Experiment • PMT rate @ 4 PEs: ~10 MHz • Two-level trigger system (24 ns window): - cluster: ~10 kHz - array: ~7 Hz • 1-GHz FADCs digitize each Cherenkov pulse

  24. Ethresh = 165 GeV STACEE Advantages / Disadvantages • 2-level trigger system  good hardware rejection of hadrons • GHz FADCs  pulse shape information • Large mirror area (6437m2)  low energy threshold

  25. Ethresh = 165 GeV STACEE Advantages / Disadvantages • 2-level trigger system  good hardware rejection of hadrons • GHz FADCs  pulse shape information • Large mirror area (6437m2)  low energy threshold But… • Limited off-line cosmic ray rejection  limited sensitivity: 1.4/hour on the Crab Nebula • Compare to Whipple sensitivity: 3/hour above 300 GeV

  26. STACEE Data Observing Strategy: Equal-time background observations for every source observation (1-hour “pairs”) Analysis: Cuts for data quality Correction for unequal NSB levels Cosmic ray background rejection Significance/flux determination

  27. 200 GeV gamma ray 500 GeV proton Energy Reconstruction Idea • Utilize two properties of gamma-ray showers: • Linear correlation: Cherenkov intensity and gamma-ray energy • Uniform intensity over shower area

  28. Energy Reconstruction Method New method to find energies of gamma rays from STACEE data: 1. Reconstruct Cherenkov light distribution on the ground from PMT charges 2. Reconstruct energy from spatial distribution of light Results: fractional errors < 10% energy resolution ~25-35%

  29. Markarian 421 • Nearby: z = 0.03 • First TeV extragalactic source detected (Punch et al. 1992) • Well-studied at all wavelengths except 50-300 GeV • Inverse-Compton scattering is favored • High-energy peak expected around 100 GeV • Only one previous spectral measurement at ~100 GeV (Piron et al. 2003) Blazejowski et al. 2005 STACEE Krawczynski et al. 2001 STACEE ? log (E2 dN/dE / erg cm-2 s-1) log (Energy/eV)

  30. Pairwise distribution of  STACEE Detection of Mkn 421 • Observed by STACEE January – May 2004 • 9.1 hours on-source + equal time in background observations • Non – Noff = 2843 gamma-ray events • 5.8 detection • 5.52  0.95 gamma rays per minute • Energy threshold ~198 GeV for  = 1.8 Eth = 198 GeV  = 1.8

  31. Rate (photons s-1 GeV-1) Spectral Analysis of Mkn 421 • Six energy bins between 130 GeV and 2 TeV • Find gamma-ray excess in each bin • Convert to differential flux with effective area curve Gamma-ray rate (photons s-1 GeV-1) Effective area (m2) Aeff(E) (m2) Energy (GeV) Energy (GeV)

  32. Spectral Analysis of Mkn 421 First STACEE spectrum  = 1.8  0.3stat

  33. Spectral Analysis of Mkn 421 First STACEE spectrum  = 1.8  0.3stat Flat SED

  34. January February March April TeV X-ray 2004 Multiwavelength Campaign PCA data courtesy of W. Cui, Blazejowski et al. 2005

  35. January February March April TeV X-ray 2004 Multiwavelength Campaign STACEE observations PCA data courtesy of W. Cui, Blazejowski et al. 2005 • STACEE coverage: 40% of MW nights • ~90% of STACEE data taken during MW nights • STACEE combines low and high flux states

  36. Multiwavelength Results Blazejowski et al. 2005

  37. Multiwavelength Results STACEE region Blazejowski et al. 2005

  38. STACEE + Whipple Results

  39. STACEE + Whipple Results

  40. Science Interpretation • • STACEE’s first energy bin is ~90 GeV below Whipple’s. • • STACEE result: •  is consistent with a flat or rising SED.  suggests that the high-energy peak is above ~200 GeV. • slghtly is inconsistent with most past IC modeling. • Combined STACEE/Whipple data suggest that the peak is around 200-500 GeV. • • SED peak reflects peak of electron energy distribution.

  41. Gamma-ray spectrum Compton Gamma Ray Observatory Air Cherenkov Wavefront Sampling Air Cherenkov Single Dish Imaging 10 MeV 100 MeV 10 GeV 100 GeV 10 TeV 1 GeV 1 TeV 1 MeV Energy Prospects for the Future • STACEE will operate for another year

  42. Air Cherenkov Wavefront Sampling Prospects for the Future • STACEE will operate for another year • Imaging arrays coming online, Ethreshold 150 GeV - HESS: 5 Crab detection in 30 seconds! - VERITAS: 2 (of 4) dishes completed Gamma-ray spectrum Air Cherenkov Imaging Arrays Compton Gamma Ray Observatory 10 MeV 100 MeV 10 GeV 100 GeV 10 TeV 1 GeV 1 TeV 1 MeV Energy

  43. TIBET MILAGRO MAGIC STACEE VERITAS TACTIC CANGAROO HESS VHE Experimental World TIBET ARGO-YBJ MILAGRO STACEE TACTIC PACT GRAPES

  44. Compton Gamma Ray Observatory Air Cherenkov Wavefront Sampling GLAST Prospects for the Future • STACEE will operate for another year • Imaging arrays coming online, Ethreshold 150 GeV - HESS: 5 Crab detection in 30 seconds! - VERITAS: 2 (of 4) dishes completed • GLAST launch in 2007! Gamma-ray spectrum Air Cherenkov Imaging Arrays 10 MeV 100 MeV 10 GeV 100 GeV 10 TeV 1 GeV 1 TeV 1 MeV Energy

  45. GLAST Large Area Telescope (LAT) Burst Monitor (GBM) GLAST • Two instruments:  LAT: 20 MeV – >300 GeV   GBM: 10 keV – 25 MeV • LAT energy resolution ~ 10% • LAT source localization < 0.5’

  46. EGRET Sources

  47. GLAST Potential

  48. Conclusions • Gamma-ray observations of AGN are key to understanding particle acceleration in the inner jets • Many new VHE gamma-ray detectors & detections • STACEE - “1st-generation” instrument sensitive to ~100 GeV gamma rays - Energy reconstruction is successful - 5.8 detection of Markarian 421 - Preliminary spectrum between 130 GeV and 2 TeV - Second spectrum of Mkn 421 at 100-300 GeV - High-energy peak is above ~200 GeV • Bright future for gamma-ray astronomy

  49. Cosmic Ray Background Rejection What we have: • Hardware hadron rejection (~103) • Off-source observations for subtraction • 2 from shower core reconstruction (‘templates’) • Timing information & 2 from wavefront fit • RMS on average # photons at a heliostat • Limited directional information - reconstruction precision ~0.2°, FOV ~0.6° Some initial success with the Crab nebula… • 5.4 hours on-source after data quality cuts • 3.0 before hadron rejection • Cut on core fit 2 + wavefront fit 2 + direction: 5.7!

  50. Field Brightness Correction Extra light in FOV from stars will increase trigger rate due to promotions of sub-threshold cosmic rays

More Related