Observation of the Crab Nebula with the MAGIC
Observation of the Crab Nebula with the MAGIC Telescope M. López-Moya Univ. Complutense de Madrid, on behalf of the MAGIC Collaboration 1
Outline n Introduction n Analysis n Data Set n First Results XXXXth Rencontres de Moriond 2
Crab Nebula: the standard candle (I) n Remnant of a supernova explosion, occurred in 1054. n Pulsar injecting relativistic electrons into the nebula. n Emission predominantly by nonthermal processes, covering a huge energy range (radio to Te. V). n First Te. V source (Whipple Telescope, 1989). n Very strong and stable at Te. V → our standard candle XXXXth Rencontres de Moriond 3
Crab Nebula: the standard candle (II) SSC model fits the observed spectrum. n Inverse Compton peak expected below 100 Ge. V. n n MAGIC should see the IC-peak. XXXXth Rencontres de Moriond Synchrotron. E mission Inverse-Compton Emission 4
The MAGIC Telescope n Located at 2220 m at La Palma (Canary islands) n Threshold: 30 Ge. V n Characteristics: n 17 m diameter dish n Active mirror control n 577 pixels, 3. 5 deg FOV camera n Optical signal transport n Fast pulse sampling: 300 MHz XXXXth Rencontres de Moriond 5
Imaging Cherenkov Technique (I) -like XXXXth Rencontres de Moriond hadron-like -arc 6
Imaging Cherenkov Technique (II) Alpha XXXXth Rencontres de Moriond 7
Background reduction (I) n Down to ~150 Ge. V, the traditional techniques based on simple image parameter cuts, still work well. E>180 Ge. V XXXXth Rencontres de Moriond 8
Background reduction (II) n At lower energies the traditional techniques start to be not so effective. XXXXth Rencontres de Moriond 9
Background reduction (III) n A new approach has been used for the gamma/hadron separation: Random Forest n n n 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”. XXXXth Rencontres de Moriond 10
Background reduction (IV) Hadrons All Energies E>200 Ge. V Gammas n For each energy bin we cut in different Hadronness and Alpha XXXXth Rencontres de Moriond 11
Energy Estimation n Basic principle: Energy light content of the shower (SIZE). n We use a Taylor expansion on the more relevant image parameters: n Coefficients obtained by minimizing: Resolution ~30% n Bias at very low energies, since very low size events are rejected (by trigger and analysis cuts). n XXXXth Rencontres de Moriond 12
Energy Estimation XXXXth Rencontres de Moriond 13
Energy Estimation n Basic principle: Energy light content of the shower (SIZE). n We use a Taylor expansion on the more relevant image parameters: n Coefficients obtained by minimizing: Resolution ~30% n Bias at very low energies, since very low size events are discarded (by trigger and analysis cuts). n n Currently applying new methods, like Random Forest energy estimation, giving similar results. XXXXth Rencontres de Moriond 14
Data Set n First data set after full mirror installation: Sept. 2004 n Background rate ~200 Hz date Zd. [ 0] Nº events [· 103] Tobs [min] ON 13, 14, 22 14 -30 1222 110 OFF 18, 21 11 -30 885 70 XXXXth Rencontres de Moriond 15
Collection Area & Expected Rates XXXXth Rencontres de Moriond 16
Alpha plots vs. Energy ON OFF XXXXth Rencontres de Moriond 17
Spectrum XXXXth Rencontres de Moriond 18
Conclusions MAGIC already operational and taking its first data since 2004. n Crab Nebula spectrum measured by MAGIC consistent with previous experiments, and compatible with SSC emission model. n First signals obtained well below 100 Ge. V with a Cherenkov telescope. n Analysis still can improve to push down more the analysis threshold. n XXXXth Rencontres de Moriond 19
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