Observation of the Crab Nebula with the MAGIC Telescope

1. Observation of the Crab Nebula with the MAGIC Telescope M. López-Moya Univ. Complutense de Madrid, on behalf of the MAGIC Collaboration

2. Outline • Introduction • Analysis • Data Set • First Results

3. Remnant of a supernova explosion, occurred in 1054. Pulsar injecting relativistic electrons into the nebula. Emission predominantly by non-thermal processes, covering a huge energy range (radio to TeV). First TeV source (Whipple Telescope, 1989). Very strong and stable at TeV → our standard candle Crab Nebula: the standard candle (I)

4. SSC model fits the observed spectrum. Inverse Compton peak expected below 100 GeV. Crab Nebula: the standard candle (II) SynchrotronEmission Inverse-Compton Emission • MAGIC should see the IC-peak.

5. The MAGIC Telescope • Located at 2220m at La Palma (Canary islands) • 577 pixels, 3.5 deg FOV camera • Threshold: 30 GeV • Characteristics: • 17 m diameter dish • Active mirror control • Optical signal transport • Fast pulse sampling: 300MHz

6. -arc -like hadron-like Imaging Cherenkov Technique (I)

7. Imaging Cherenkov Technique (II) Alpha

8. E>180 GeV Background reduction (I) • Down to ~150 GeV, the traditional techniques based on simple image parameter cuts, still work well.

9. Background reduction (II) • At lower energies the traditional techniques start to be not so effective.

10. Background reduction (III) • A new approach has been used for the gamma/hadron separation: Random Forest • Train in the parameters: SIZE, DISTANCE, LENGTH, WIDTH, CONC, ASYM (no ALPHA used). • No a priori parameterization needed. • For each shower we get its “hadronness”.

11. Hadrons Gammas Background reduction (IV) • For each energy bin we cut in different Hadronness and Alpha All Energies E>200 GeV

12. We use a Taylor expansion on the more relevant image parameters: • Coefficients obtained by minimizing: • Resolution ~30% • Bias at very low energies, since very low size events are rejected (by trigger and analysis cuts). Energy Estimation • Basic principle: Energy  light content of the shower (SIZE).

13. Energy Estimation

14. Energy Estimation • Basic principle: Energy  light content of the shower (SIZE). • We use a Taylor expansion on the more relevant image parameters: • Coefficients obtained by minimizing: • Resolution ~30% • Bias at very low energies, since very low size events are discarded (by trigger and analysis cuts). • Currently applying new methods, like Random Forest energy estimation, giving similar results.

15. Data Set • First data set after full mirror installation: Sept. 2004 • Background rate ~200 Hz

16. Collection Area & Expected Rates

17. Alpha plots vs. Energy ON OFF

18. Spectrum

19. Conclusions • MAGIC already operational and taking its first data since 2004. • Crab Nebula spectrum measured by MAGIC consistent with previous experiments, and compatible with SSC emission model. • First signals obtained well below 100 GeV with a Cherenkov telescope. • Analysis still can improve to push down more the analysis threshold.