Multi-messenger studies of point sources Multi-messenger studies of - - PowerPoint PPT Presentation

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

Cherenkov 2005 27-29 April 2005 Palaiseau, France

Elisa Bernardini

bernardi@ifh.de

Contents:

• The AMANDA/IceCube detection principles
• Search for High Energy neutrino point sources:
• 4 years time-averaged signals
• Transient (time-variable) signals
• Observations of the Blazar 1ES1959+ 650
• Towards an extension of multi-wavelength

campaigns to neutrino observatories?

http://icecube.wisc.edu

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The AMANDA Detection principles

Up Down ~ 109 events/ year ~ 103 events/ year A few events/ year

Neutrino candidates

are selected up-going muon tracks, with good angular resolution

Muons detected

from Cherenkov light in ice

Elisa Bernardini - Cherenkov 2005 - 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

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 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 : Φν

lim ≈ 0.6·10-8 cm-2s-1

= 2.25°-3.75° = 807 days

3329 ↑ observed 3438 ↑ expected atm. MC

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Search for clusters of events in the Northern sky

Source

• Nr. of ν

events (4 years) Expected backgr. (4 years) Flux Upper Limit

Φ90%(Eν> 10 GeV)

[10-8cm-2s-1] Markarian 421 6 5.58 0.68 1ES1959+ 650 5 3.71 0.38 SS433 2 4.50 0.21 Cygnus X-3 6 5.04 0.77 Cygnus X-1 4 5.21 0.40 Crab Nebula 10 5.36 1.25

Selected objects and full scan of the northern sky: No statistically significant effect observed … out of 33 Sources Systematic uncertainties under investigation

Crab Nebula: The

chance probability

• f such an excess

(or higher) given the number of trials is 64%

Sensitivity

Φν/Φγ~ 2

for 200 days of “high-state” and spectral results from HEGRA

Preliminary

5/ 12

Elisa Bernardini - Cherenkov 2005 - Palaiseu, Paris 6/ 12

IMAGE CREDIT: NASA/Honeywell Max Q Digital Group, Dana Berry

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

• 1. Look at known periods (active states)

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 1.63 1.59 1.37 1ES1959+ 650 ASM/RXTE 283 days 2 Cygnus X-3 Ryle Telesc. 114 days 2

Search for events in coincidence with known periods of enhanced electromagnetic emission:

• Periods and sources selected on the basis of the available multi-

wavelength information

• Wavelengths investigated are possible indicators for a correlated

neutrino emission (X-ray for Blazars and radio for Microquasars)

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Multi-wavelength information and theoretical knowledge of the time- correlation with the possible neutrino emission are meager: Search for neutrino flares without a-priori hypothesis on their time of

• ccurrence

• 2. Search for neutrino flares

Search for excesses in time-sliding windows: No statistical significant effect observed

Preliminary

= 2.25°-3.75° Source

• Nr. of ν

events (4 years) Expected backgr. (4 years) Period duration

• Nr. of

doublets Probability for highest multiplicity Markarian 421 6 5.58 40 days 1 1 1 1 Close to 1 1ES1959+ 650 5 3.71 40 days 0.34 3EG J1227+ 4302 6 4.37 40 days 0.43 QSO 0235+ 164 6 5.04 40 days 0.52 Cygnus X-3 6 5.04 20 days Close to 1 GRS 1915+ 105 6 4.76 20 days 0.32 GRO J0422+ 32 5 5.12 20 days Close to 1 = 40/20 days for Extragalactic/Galactic Objects

events time sliding window

… out of 12 Sources

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“A posteriori”: 3 (of 5) events in 66 days Period of major outburst measured at different wavelengths in 2002 (and an “orphan flare”) Error bars:

• ff-source

background per 40 days Yellow bars: width of sliding search window

Preliminary

Triangles: event times

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Red lines: AMANDA – 2.25o 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 “Orphan flare” (MJD 52429)

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Multi-messenger campaigns?

• 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

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Summary

• No statistically significant effect observed in the search for point sources of

neutrino with 4 years of AMANDA data

• Observations of the Blazar 1ES1959+ 650 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

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Neutrino Astrophysics : The new “Era” -- IceCube

Elisa Bernardini - Cherenkov 2005 - Palaiseu, Paris 13/ 12

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The IceCube Project

Design:

4800 Optical Modules 80 strings (@ 125 meters) Depth: ~ 1400-2400 m

Extensive Air Shower Array @ surface: I ceTop

Instrumented volume: 1 km3 Installation: 2005-2010, started!

A km3-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

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SS433:

Observational hints of hadronic acceleration from α-spectral lines Promising neutrino source candidate

galactic Analogy Quasar / Microquasar: extra-galactic

Search for ν flares: Method

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Search for excesses of events in sliding time windows of fixed size (∆t): Method: Compare observed and background events in ∆t.

In what follows is shown how to: 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
• 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.

• 2. Choose the window size:
• Detection probability not “too-low”
• Limited dependence on flare duration

Consideration from multi-wavelength

• bservations:
• Tflare(galactic) < Tflare(extragalactic)

(* * ) 40 d: Extragalactic / 20 d Galactic sources

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Neutrino-Production and Propagation

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
• Hadron spectrum at the source is expected to show a power-law

shape (Fermi acceleration) power law spectrum for neutrinos Flavor ratio (case 1 and 2):

νe : νµ : ντ ~ 1:2:< 10-5 @ the source νe : νµ : ντ ~ 1:1:1 @ the detector

Propagation Spectrum

γ γ ν µ π π γ ν ν ν µ π

µ µ

+ → + → + → + → + + + → + → + → +

+

.... p n p e p p

e

Production

Neutrinos from neutron decay emerge with much lower multiplicity and energy.

The AMANDA medium

Absorption

dust ice

Scattering

bubbles dust

Optical properties:

Data from calibration light sources deployed along the strings and from cosmic rays.

Absorption length @ 400 nm

• Eff. Scattering

length @ 400 nm

110 m 20 m

Noise Rate from Optical Modules < 1.5 kHz

A stable OMs sub-set

• perates as

“SuperNova Watch” AMANDA contributes to SNEWS

Effective scattering coefficient Absorption length On average:

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cos θ µAeff / km2

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)

19/ 12

PeV ντ cascade events: capability to separate vertex cascade and τ decay (“double bang” signature) above several PeV.

2 x 1019 eV event in AMANDA and IceCube:

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21/ 12

~ 300 Optical Modules built 2 Optical Modules per tank

27 January 2005 27 January 2005

First First I ceCube I ceCube string string (“string 21”) (“string 21”) successfully deployed successfully deployed

60 Optical Modules in Ice 60 Optical Modules in Ice

8 I ceTop tanks installed

HV board DOM main board Penetrator Mu-metal cage Optical Gel

http://veritas.sao.arizona.edu/VERITAS_whipple_science.html

Markarian 421

Spectral Energy Distribution

Hadronic Leptonic 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.

Neutrinos provide the only unambiguous way to discriminate scenarios. Proton Blazar models:

simultaneous ν production!

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23/ 12

First IceCube events

An almost vertical event: 12 I ceTop DOMs hit (out of 16) 30 I ceCube 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)

Data filtering and event reconstruction 00-03

Filtering/ Fit Event Selection P.Rate Down-going Likelihood (DL) reconstruction (* * )

7.14 billion events

L1 Hit & Optical Module selection Two fast first-guess reconstructions (* ): Direct-Walk JAMS ZenithDW> 70o 1 3.7% L2 Cross-talk hit-filter Up-going Likelihood (UL) reconstruction (* * ) ZenithJAMS> 80o 0.39% 0.39% L3 Topological parameters calculation Hits distributions along the tracks Single track angular resolution ZenithUL> 80o 0.11%

7.85 million muon tracks

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(* ) “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

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Source Total Nr. Events Total Backgr. Period duration

• Nr. of

doublets Probability for highest significance Markarian 421

6 5.58 40 days 1 1 1 1 1 1 Close to 1

1ES1959+ 650

5 3.71 40 days 0.34

3EG J1227+ 4302

6 4.37 40 days 0.43

QSO 0235+ 164

6 5.04 40 days 0.52

QSO 0528+ 134

4 4.98 40 days Close to 1

3EG J0450+ 1105

6 4.67 40 days 0.47

GRS 1915+ 105

6 4.76 20 days 0.32

Cygnus X-3

6 5.04 20 days Close to 1

Cygnus X-1

4 5.21 20 days Close to 1

GRO J0422+ 32

5 5.12 20 days Close to 1

3EG J1828+ 1928

3 3.32 20 days Close to 1

3EG J1928+ 1733

7 5.01 20 days 0.35

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Results from the multi- wavelength campaign (a) Whipple and HEGRA (b-c) X-ray (d-f) optical (g-h) radio ApJ 601, 151 (2004)

Unique observation

• f a high flux γ-rays

flare without

corresponding X-ray counterpart