Multi-messenger studies of point sources using AMANDA/IceCube data and strategies

Transcription

1 Multi-messenger studies of point sources using AMANDA/IceCube data and strategies Cherenkov April 2005 Palaiseau, France Contents: The AMANDA/IceCube detection principles Search for High Energy neutrino point sources: 4 yearstime-averaged signals Transient (time-variable) signals Observations of the Blazar 1ES Towards an extension of multi-wavelength campaigns to neutrino observatories? Elisa Bernardini bernardi@ifh.de

2 The AMANDA Detection principles Neutrino candidates are selected up-going muon tracks, with good angular resolution Muons detected from Cherenkov light in ice ~109 events/ year A few events/ year Up Down ~103 events/ year 2/12

3 Elisa Bernardini - Cherenkov Palaiseu, Paris 3/12 Search for a neutrino signal from point sources: 4 years time-averaged Blind-Analysis : Event selection and analysis procedures are optimized on events with randomized right ascension and/or time Background estimated from the data (off-source) On-Source Off-Source

4 Search for clusters of events in the Northern sky The data sample: 3369 neutrino candidates Event selection optimized for both dn/de ~ E -2 and E -3 spectra = = 807 days 3329 observed 3438 expected atm. MC Point Sources search: Search for excesses of events compared to the background from: A set of selected candidate sources The full Northern Sky Declination averaged sensitivity, integrated in energy (E>10 GeV), dn/de ~ E -2 : Φ ν lim cm -2 s -1 4/12

5 Search for clusters of events in the Northern sky 5/12 Selected objects and full scan of the northern sky: No statistically significant effect observed Preliminary Sensitivity Φ ν /Φ γ ~2 for 200 days of high-state and spectral results from HEGRA Crab Nebula: The chance probability of such an excess (or higher) given the number of trials is 64% Source Nr. of ν events (4 years) Expected backgr. (4 years) Flux Upper Limit Φ 90% (E ν >10 GeV) [10-8 cm -2 s -1 ] Markarian ES SS Cygnus X Cygnus X Crab Nebula out of33 Sources Systematic uncertainties under investigation

6 IMAGE CREDIT: NASA/Honeywell Max Q Digital Group, Dana Berry Elisa Bernardini - Cherenkov Palaiseu, Paris 6/12 Search for a neutrino signal from point sources: transient phenomena Enhance the detection chance by using the time information : Search for transient signals, still compatible with the 4 years-averaged flux upper limits

7 1. Look at known periods (active states) Search for events in coincidence with known periods of enhanced electromagnetic emission: Periods and sources selected on the basis of the available multiwavelength information Wavelengths investigated are possible indicators for a correlated neutrino emission (X-ray for Blazars and radio for Microquasars) Source EM light curve source Livetime in periods of high activity Nr. of ν events in high state Expected backgr. in high state Markarian 421 ASM/RXTE 141 days ES ASM/RXTE 283 days 2 Cygnus X-3 Ryle Telesc. 114 days Multi-wavelength information and theoretical knowledge of the timecorrelation with the possible neutrino emission are meager: Search for neutrino flares without a-priori hypothesis on their time of occurrence 7/12

8 2. Search for neutrino flares Preliminary Search for excesses in time-sliding windows: No statistical significant effect observed sliding window = = 40/20 days for Extragalactic/Galactic Objects Source Nr. of ν events (4 years) Expected backgr. (4 years) Period duration Nr. of doublets Markarian days 0 events Probability for highest multiplicity Close to 1 1ES days EG J days QSO days Cygnus X days 0 Close to 1 GRS days GRO J days 0 Close to 1 time out of12 Sources 8/12

9 9/12 Preliminary Yellow bars: width of sliding search window Triangles: event times Error bars: off-source background per 40 days A posteriori : 3 (of 5) events in 66 days Period of major outburst measured at different wavelengths in 2002 (and an orphan flare )

10 10/12 Orphan flare (MJD 52429) Red lines: AMANDA 2.25 o search bin Probability of a random coincidence with the orphan flare or the enhanced γ-ray activity undefined: a-posteriori hypothesis relative to the test

11 Multi-messenger campaigns? 11/12 Overlap of interests between the high energy electromagnetic measurements and neutrino observations: BL-Lac hadronic/mixed versus leptonic models: neutrino detection would discriminate scenarios combined efforts may increase discovery potential X-ray/γ-ray time correlation: what is the frequency of orphan flares (bias from X-ray triggered γ-ray observations?) Does the orphan-phenomenology represent a class of cosmic accelerators or is it rather unique? Data taking coordination: Long-term monitoring of the electromagnetic emission of this source and similar (light curves and spectral information) Target of opportunity triggered by AMANDA/IceCube on-line event filtering? Data analysis coordination: Identify common interests and guidelines for possible information exchange policy

12 Summary 12/12 No statistically significant effect observed in the search for point sources of neutrino with 4 years of AMANDA data Observations of the Blazar 1ES in coincidence with the orphan flare : no conclusive answers possible whether the observed events can be ascribed to the source or are accidental future observations could shed light on the nature of the source emission (electromagnetic/hadronic) The results from the point source analysis motivate new search strategies in AMANDA and IceCube A collaboration between the multi-wavelength community and neutrino observatories could be of mutual benefit A few viable scenarios have been mentioned: Data taking coordination Data analysis coordination

13 Neutrino Astrophysics : The new Era -- IceCube Elisa Bernardini - Cherenkov Palaiseu, Paris 13/12

14 The IceCube Project A km 3 -size detector at the South Pole: Goals: Sensitivity to look for neutrinos from AGNs, GRBs Study the knee region of the cosmic ray spectrum AMANDA as Pilot project Extensive technological development (e.g. digital readout) Optimized for energies > TeV Design: 4800 Optical Modules 80 strings (@ 125 meters) Depth: ~ m Extensive Air Shower surface: IceTop Instrumented volume: 1 km 3 Installation: , started! 14/12

15 Analogy Quasar / Microquasar: SS433: Observational hints of hadronic acceleration from α-spectral lines Promising neutrino source candidate extra-galactic galactic 15/12

16 Search for ν flares: Method Search for excesses of events in sliding time windows of fixed size ( t): Method: Compare observed and background events in t. In whatfollowsisshownhowto: 1. Select the data sample: use the 4 years data sample (807 days) 2. Select the search window size (time duration): 40 d/ 20 d (**) Depend on signal strength, spectrum and duration (unknown!) Constraints from steady point sources search results: Upper limit: Flares of duration t >100 days are almost excluxed Lower limit: Sensitivity ratio flares 10-day / 4-years: ~ 3 Photon flux ratio flare/no-flare state: O(10) from multi-wavelength observations 2. Choose the window size: Detection probability not too-low Limited dependence on flare duration Consideration from multi-wavelength observations: T flare (galactic) < T flare (extragalactic) 1. Choose the data sample: Standard sample (3329 events): livetime ~ 800 days (0.04 = 32 d) Flare sample (~ 8000 events): different signal energy spectra are shown. (**) 40 d: Extragalactic / 20 d Galactic sources 16/12

17 Neutrino-Production and Propagation 17/12 Most models: Neutrinos produced in hadron-hadron (pp) and hadron-photon (pγ) interactions followed by meson decay, with different energy yields. 1.A 2.A p p + + p γ π + n + µ + ν π... e µ + ν µ + ν e + ν µ + 0 Neutrinos from neutron decay emerge with much lower multiplicity + and π energy. p γ + γ Production Spectrum Hadron spectrum at the source is expected to show a power-law shape (Fermi acceleration) powerlawspectrumforneutrinos ν e : ν µ : ν τ ν e : ν µ : ν τ Flavor ratio (case 1 and 2): ~ the source ~ the detector Propagation

18 18/12 Scattering The AMANDA medium Optical properties: Data from calibration light sources deployed along the strings and from cosmic rays. Effective scattering coefficient Absorption Absorption length bubbles ice dust dust On average: Absorption 400 nm Eff. Scattering 400 nm 110 m 20 m Noise Rate from Optical Modules < 1.5 khz A stable OMs sub-set operates as SuperNova Watch AMANDA contributes to SNEWS

19 µa eff / km 2 19/12 cos θ Effective Area vs. zenith angle after rejection of background from downgoing atmospheric Muons. Angular resolution (point source analysis), but using standard AMANDA reconstruction and selection procedures (improvement from full Waveform information)

20 20/12 2 x ev event in AMANDA and IceCube: PeV ν τ cascade events: capability to separate vertex cascade and τ decay ( double bang signature) above several PeV.

21 21/12 Penetrator ~300 Optical Modules built Optical Gel 8 IceTop tanks installed HV board DOM main board Mu-metal cage 27 January 2005 First IceCube string ( string 21 ) successfully deployed 60 Optical Modules in Ice 2 Optical Modules per tank

22 A reference example: Blazars (Active Galactic Nuclei) Emission: Low energy (from radio up to UV / X-ray): non-coherent synchrotron radiation. High energy (up to TeV) under debate: leptonic versus hadronic models. 22/12 Neutrinos provide the only unambiguous way to discriminate scenarios. Proton Blazar models: simultaneous ν production! Hadronic Markarian 421 Spectral Energy Distribution Leptonic

23 First IceCube events An almost vertical event: 12 IceTop DOMs hit (out of 16) 30 IceCube DOMs hit (out of 36) powered at the time Direction reconstruction of the shower from IceTop hits Direction reconstruction including IceCube: different slope due to light delay (scattering) 23/12

24 L1 L2 L3 Data filtering and event reconstruction Filtering/Fit Event Selection P.Rate 7.14 billion events Hit & Optical Module selection 1 Two fast first-guess reconstructions (*): Direct-Walk Zenith DW >70 o 3.7% JAMS Zenith JAMS >80 o 0.39% Cross-talk hit-filter 0.39% Up-going Likelihood (UL) reconstruction (**) Zenith UL >80 o 0.11% Topological parameters calculation Hits distributions along the tracks Single track angular resolution Down-going Likelihood (DL) reconstruction (**) 7.85 million muon tracks (*) Moderate CPU-time consumptive ~ 10-3 s/events for a 2.5 GHz CPU (**) Intensively CPU-time consumptive, up to ~ 1 s/events, First guess results as seeds, 32 iterations for up-going, 64 for down-going hypothesis 24/12

25 Source Total Nr. Events Total Backgr. Period duration Nr. of doublets Markarian days 0 Probability for highest significance Close to 1 1ES days EG J days EG J days QSO days QSO days 0 Close to 1 Cygnus X days 0 Close to 1 Cygnus X days 0 Close to 1 GRS days GRO J days 0 Close to 1 3EG J days 0 Close to 1 3EG J days /12

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27 Unique observation of a high flux γ-rays flare without corresponding X-ray counterpart Results from the multiwavelength campaign (a) Whipple and HEGRA (b-c) X-ray (d-f) optical (g-h) radio ApJ 601, 151 (2004) 27/12