Gamma-rays, neutrinos and AGILE Fabrizio Lucarelli (ASI-SSDC & INAF-OAR)
Outlook 2 Overview of neutrino astronomy Main IceCube results Cosmic neutrino source candidates AGILE search for γ-ray counterparts to the IceCube HESE events Summary and conclusions
ν-astronomy: main detection channel Looking for upward-going muons as signature of ν µ interactions (E ν =1 TeV è Θ νµ 1 ) Detector: 3D PMT array placed at depth (>2 km) in water or ice. Natural shield against sunlight and atmospheric CRs. Cherenkov light from µ ν µ 42 Sea bottom µ The reconstruction is based on local coincidences compatible with the Cherenkov light front ν µ CC weak interaction (ν µ (ν µ )+ N ==> µ - (µ + ) + X) Energy threshold ~ 10 GeV 3
Other detection channels 4 Charged-current ν e N events Charged-current ν à τ e.m. shower ν µ hadronic shower ν e Contained events: better energy res. but worse angular res. (~10º) Visible by pile-up of events near 100 TeV
The ANTARES Detector 5 2500m 900 PMTs 12 lines 25 storeys / line 3 PMTs / storey V. Bertin - CPPM - ARENA'08 @ Roma 70 m 450 m Interlink cables 40 km to shore Junction Box
6 Lucarelli F. 15th AGILE Workshop
Typical IceCube events 7 ~10-100 cosmic muon neutrinos expected per year
High-Energy Starting Event (HESE) 8 Require that event: do not start in veto region have at least 6000 p.e. (~30 TeV) deposited energy Bert (~1 PeV) All-sky, all ν-flavors Mostly shower-like events Shape (energy and zenith distribution) of signal and background is different...
Main IceCube results
ICECUBE HESE ν-signal (all-sky) First evidence of a diffuse flux of astrophysical neutrinos provided by ICECUBE using 3 and 4 years of data (2010-2014). In total, 54 high-energy starting events (HESE) with interaction inside the detector: mostly shower-like events from ν e and ν τ with ang. resolution of ~10 deg. IceCube Coll. (ICRC 2015) 10 Aartsen et al., Science 2013 Confirmed using a 8-year data sample (ICRC 2017)
ICECUBE ν µ -signal (northern-sky) Evidence of a diffuse flux of astrophysical origin also in upwardgoing muons produced by ν µ (2010-2012 data). In total 21 ν µ events with E>100 TeV with higher angular resolution (<1 deg). Confirmed also using 8 year data sample. IceCube Coll. (ICRC 2017) Aartsen et al., Phys. Rev. Lett. 115 2015 90 o absorption > 90% 11 198 189 360 o 442 466 193 178 184 709 400 1693 191 393 394 158 185 156 206 * 880 713 190 Northern Hemisphere Southern Hemisphere 179 0 o -90 o Galactic Plane Equatorial * event appears in both samples All-sky 7 years search using upward an downward going muons: no significant point-like source found.
Evidence for 2-source population? 12 IceCube Coll. (ICRC 2017) HESE events: soft spectrum (Γ ~ -2.9) Upward through-going muons: harder spectrum (Γ ~ 2.2)
Cosmic neutrino source candidates
Cosmic rays γ-rays neutrinos Lucarelli F. 15 th AGILE Workshop 14 Cosmic beam dump Black holes neutron stars matter / radiation fields π ±,π 0 γ,ν µ,e
Blazar AGNs main source candidates 15 Blazar jet ideal sites of CRs acceleration Photomeson production against intense radiation fields. Gammas and neutrinos from neutral and charged meson decay p + γ è Δ + è p + π 0 è p + γ γ p + γ è Δ + è n + π + è n + µ + ν Recently works (Resconi et al. 2017) provide hints that HBL subclass of blazars may be the sources of some of the IceCube HESE neutrinos as well as of UHECRs seen by Auger/TA. Sources of target radiation: Photons from the accretion disk IR photons from a dust torus Non-thermal photons inside the jet (SSC models)
Blazars contribution to the diffuse ν-flux 16 Based on the cumulative γ-ray emission from Fermi blazars, it results that blazars can contribute up to a maximum of 30% of the total IceCube 10 TeV -2 PeV observed flux. Aartsen et al. 2017
Other possible candidates 17 Star forming galaxies (SFGs): can explained at most 10% of the IceCube diffuse flux. Gamma-ray bursts (GRBs): any spatial and temporal correlation with single IceCube neutrinos has been seen yet (<1% contribution to the diffuse ν-flux). Radio-galaxies Galactic sources What else? Hidden blazars? 50% of (low luminosity) blazars might be not identified. E.M. hidden sources? γ-rays absorbed or degraded down to lower energies. Compact sources: AGN cores, white dwarf mergers,
AGILE search for γ-ray counterparts to the IceCube HESE events
ICECUBE ALERT SYSTEM 19 Sources of cosmic neutrinos may be identified by rapid follow-up observations by electromagnetic ground and space-based observatories. Since April 2016, ICECUBE alerts the astronomical community through the GCN network whenever a clear detection of a cosmic neutrinos occurs. Only HESE track-like events with good angular resolution (~<1º) are published through the network. Expected ν-energies: HESE events: 100 TeV - 1 PeV; EHE events: several hundreds of TeV (can start outside the fiducial volume) Expected occurrence rate: ~4-5/yr
Updated HESE/EHE event list 20 ICECUBE Event ID T0 (yy/mm/dd hh:mm:ss) Category 67093193 16/04/27 05:52:32.00 HESE 6888376 16/07/31 01:55:04.00 HESE/EHE 26552458 16/08/06 12:21:33.00 EHE 58537957 16/08/14 21:45:54.00 HESE 38561326 16/11/03 09:07:31.12 HESE 80127519 16/12/10 20:06:40.31 EHE 65274589 17/03/12 13:49:39.83 HESE 80305071 17/03/21 07:32:20.69 EHE 32674593 17/05/06 12:36:55.80 HESE 50579430 17/09/22 20:54:30.43 EHE 56068624 17/10/15 01:34:30.06 HESE 17569642 17/11/06 18:39:39.21 EHE
HESE/EHE sky distribution 21 Galactic coordinates
AGILE QL detections of IceCube events 22 Galactic coordinates 3 AGILE detections from the automatic Quick Look system (running over 2-day maps) consistent with time/ position of 3 IC events.
AGILE QL detections of IceCube events 23 IC-160731 (HESE/EHE) Galactic coordinates QL detections estimated in spinning over 2-days GRID maps.
AGILE QL detections of IceCube events 24 IC-160731 (HESE/EHE) Galactic coordinates IC-170922 (EHE) QL detections estimated in spinning over 2-days GRID maps.
AGILE QL detections of IceCube events 25 IC-160731 (HESE/EHE) IC-170321 (EHE) Galactic coordinates IC-170922 (EHE) QL detections estimated in spinning over 2-days GRID maps.
IC-160731/AGL J1418+0008 transient 26 PRELIMINARY Lucarelli et al., ApJ 846 (2017) Post-trial significance ~4σ Very brief episode (1 1.5 days). 4.9σ peak significance on the 24-hour integration T0-1.8; T0-0.8. Not seen by Fermi due to a very poor source visibility during this period. (T0 1.8; T0 0.8) days
IC-160731/AGL J1418+0008 transient 27 PRELIMINARY Lucarelli et al., ApJ 846 (2017) Post-trial significance ~4σ Very brief episode (1 1.5 days). 4.9σ peak significance on the 24-hour integration T0-1.8; T0-0.8. Not seen by Fermi due to a very poor source visibility during this period. (T0 1.8; T0 0.8) days AGL J1418+008 possible gamma-ray precursor of the IC-160731 event?
No clear e.m. counterpart 28 Search around ICECUBE-160731/AGL J1418 using ASDC SkyExplorer tool SSDC SEDBuilder Tool RASS detection FIRST detection (~2mJy) 1RXS J141658-00144: possible HBL blazar candidate è ICECUBE-160731 emitter candidate?
Targeted SWIFT data on 1RXS J141658 29 5 ks ToO observation performed ~6 months later than T0. No X-ray emission on the 1RXS J141658 position è HBL nature of this AGN candidate not confirmed. 5 un-catalogued X-rays sources detected during the ToO.
IC-170922 MWL detections 30 EHE IceCube event announced on Sept. 22, 2017. R.A., Decl. (J2000): (77.43, 5.72) deg. HE γ-rays observed both by AGILE and Fermi-LAT consistent with the IceCube error box (ATel s #10791 and #10801). Also VHE γ-rays observed by MAGIC a few days after the neutrino event T0 (ATel #10817). The blazar TXS 0506+056 (also known as a 3FGL and 3FHL source) located inside the IceCube error region è Main candidate as the IC-170922 neutrino emitter?
AGILE observation of IC-170922 31 AGILE detection over 2-days maps appeared again near T0 from the automatic QL detection systems. Lucarelli et al., in preparation AGILE 18-21 Sept. 2017 (21:00 UTC) PRELIMINARY
TXS 0506+056: broad-band SED 32 Fermi-LAT archival data (1FGL,2FGL, ) TXS 0506+056 classified as IBL/HBL object 32
Post-trial probabilities 33 An AGILE False Alarm Rate (FAR) for detections above 4σ on single 2-day integration maps has been estimated using the whole database of QL detections in spinning (Lucarelli et al., in prep.): è AGILE FAR ~ 5-8 x 10^-9 Hz (preliminary) Using this value, a false alarm probability can be calculated per each event as: è P 1 = FAR * Δt ~= 5 x 10^-9 Hz * 86400 s ~= 4.3E-04 (~3.3σ) Including also the spatial coincidence, the chance probability to observe an AGILE QL detection in spatial and (almost) temporal coincidence with an IC event will be lower (~4σ).
Summary: neutrino sources 34 IceCube has observed a non-terrestrial neutrino flux in the ~15 TeV to ~8 PeV energy range. The sources of these neutrinos are not known yet. Flux is consistent with isotropy. Evidence for a two-source population? Are the sources opaque? How many sources are there? How far away? On 22 Sept. 2017, first MWL detection of HE γ-rays and VHE γ-rays from a position consistent with a EHE neutrino event. The BL Lac TXS 0506+056, inside the IC-170922 error box, might be the possible neutrino emitter candidate.
Summary: AGILE and neutrinos AGILE also fully involved in the MWL follow-up of ICECUBE events published through the GCN network. In total, three AGILE automatic (and blind) QL detections spatially and almost temporal coincident with three IceCube EHE events: IC-160731, IC-170922 and IC-170321. For the IC-160731 HESE event, AGILE detected a possible short gamma-ray precursor, peaked about 1.5 days before the neutrino event T0. No clear e.m. counterpart found. Post-trial probabilities of the other two QL detections are under evaluation: preliminary calculation show a posttrial significance of each event >~3σ (joint probability of the three single events >>3σ). More IceCube events and MWL follow-up are needed. 35
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