IceCube Search for Galactic Neutrino Sources based on HAWC - - PowerPoint PPT Presentation

IceCube Search for Galactic Neutrino Sources based on HAWC Observations of the Milky Way

Ali Kheirandish

TAUP 2019, Toyama, Japan

2

Galactic Cosmic Ray Accelerators

ν

π±

[PDG 2018]

Galactic

Extragalactic

• The search for Galactic cosmic neutrino sources concentrates on the search

for “Pevatrons” which have the required energetics to produce cosmic rays up to the knee in the spectrum.

• “Pevatrons” will produce pionic 𝛿-rays whose spectrum extends to several

hundred TeV without cut-off.

• Supernova remnant meet these condition.
• TeV 𝛿-rays should be accompanied by TeV neutrinos, observable by IceCube.

3

Galactic Plane at High Energies

Galactic plane in 10 TeV gamma rays

Sources were identified in the initial map of Milagro that were the most significant sources after Crab. The idea was to look for supernova remnants in star forming regions.

Southern Hemisphere Sky

[Milagro]

Neutrino spectra for all sources

• Early predictions: IceCube should
• bserve sources after 5 years.

[Beacom+2007, Halzen+2008, Gonzalez-Garcia+2009]

[Halzen+2008]

HAWC VHE Survey of the Galaxy

[HAWC 2017]

4

Galactic

3 years, E > 0.3 TeV

HAWC VHE Survey of the Galaxy

[HAWC 2017]

4

Galactic

3 years, E > 0.3 TeV

Galactic plane at E>56 TeV

5

Joint IceCube-HAWC Search

✓HAWC targets the portion of sky IceCube is the most sensitive. ✓HAWC operates at very high energies related to IceCube. ✓HAWC can study sources with any extension.

• Using 2HWC Catalog, we perform
• Stacked Search for neutrino emission from identified sources
• Template analysis for neutrino emission from Galactic plane and special regions

HAWC-IceCube Synergy

Stacking Search Template Search

E2

ν Φνµ+¯ νµ [TeVcm−2s−1]

E2

ν Φνµ+¯ νµ [TeVcm−2s−1]

Eν[TeV]

Eν[TeV]

6

Stacking Search

• Stacked 20 sources from 2HWC

Catalog (excluding PWNe)

• Best fitted signal events: 15

→pre-trial p-value: 0.09

• 90% UL on neutrino flux:

1.5⨉10-13 TeV/cm2 s at 7 TeV

• Not constraining the hadronic

component!

Eν[TeV]

E2

ν Φνµ+¯ νµ [TeVcm−2s−1]

7

Template Search-Northern Plane

• Incorporating full morphology of

emission from HAWC

• Neutrinos weighted according to

their energy and 𝛿-ray flux with cut-off at 300 TeV

• Best fit signal events: 77

→pre-trial p-value: 0.06

• Constraining hadronic component

to < 80% of the total flux.

E2

ν Φνµ+¯ νµ [TeVcm−2s−1]

Eν[TeV]

Cygnus Region

• No Signal events!

→under-fluctuation.

• Compatible with other
• bservations and theoretical

studies of the 𝛿-ray emission.

• Hadronic component

constrained to < 60% of the total flux

MGRO J2031+041 MGRO J2019+037

• Star forming region with a high level of 𝛿-ray activity

and young stars

• Very high energy diffuse 𝛿-ray emission
• 𝛿-ray emission from the cocoon
• Uncertainties on resolved sources & their extensions

E2

ν Φνµ+¯ νµ [TeVcm−2s−1]

Eν[TeV]

8

9

MGRO J1908+06

• Region containing previously identified

sources with spectra consistent with PeVatron scenarios

• Located at the best place (near horizon) for

IceCube

• Nature of 𝛿-ray emission not well understood
• Best fit signal events: 12

→pre-trial p-value=0.14

• Upper limit is 1.3 times the

total flux, assuming all 𝛿- rays are hadronic! Not constraining!

E2

ν Φνµ+¯ νµ [TeVcm−2s−1]

Eν[TeV]

2HWC J1857+027

• Region containing previously identified sources

with spectra consistent with PeVatron scenarios

• Located at the best place for IceCube
• 𝛿-ray emission nature not well understood
• The most significant result!
• Best fit signal events: 36

→pre-trial p-value=0.02

• Upper limit is 3 times the

total flux, assuming all 𝛿- rays are hadronic! Not constraining!

E2

ν Φνµ+¯ νµ [TeVcm−2s−1]

Eν[TeV]

10

11

Summary

• Galactic cosmic ray accelerators are guaranteed to contribute to the

total observed high-energy cosmic neutrino flux.

• The contribution of Galactic sources to the IceCube neutrino flux is

limited to less than 15%.

• The upper limits from searching for high-energy neutrinos from major

𝛿-ray emitters in the Milky Way constrain but do not exclude hadronic components.

• Continuous observation of IceCube and new techniques for

identification of neutrinos with high purity will help finding Galactic neutrino sources.

• Advancements in ground base 𝛿-ray telescopes and future instruments

will improve our understanding of the spectra and morphologies and will help identifying potential sources of high-energy neutrinos in the Milky Way.

Thanks!

Back up Slides

14

High-Energy Cosmic Neutrino Flux

0.01 0.1 1 10 102 103 104 105 106 107 108 109 E [TeV] 10−9 10−8 10−7 10−6 10−5 10−4 10−3 E2φν+¯

ν [GeV cm−2 s−1 sr−1] IC HESE Auger E−2 ANITA E−2 IC E−2 IC νµ + ¯ νµ

• atmo. νe + ¯

νe (before HESE veto)

• atmo. νµ + ¯

νµ (before HESE veto)

neutrino fluxes and upper limits (per flavor)

Ahlers & Halzen, 2018

φ ∝ E−2.92

High-Energy Starting Events

7 years Observation ➛ 8𝜏

80 events (all flavor)

φ ∝ E−2.19

Up-going Muon Tracks

8 years Observation ➛ 6.7𝜏 ~ 500 astrophysical neutrinos

• Observation confirmed in

independent channels.

• Hardening of the spectrum at high

energies.

• Low-energy excess hinting at

spectral features.

• fluxes are compatible in the

common energy range

16

HE Cosmic Neutrinos & Multimessenger Interface

10 100 103 104 105 106 107 108 109 1010 1011 energy E [GeV] 10−9 10−8 10−7 10−6 E2φ [GeV cm−2 s−1 sr−1] B A C

high-energy neutrinos (IceCube)

HESE (7yr)

(Fermi) background isotropic γ-ray ultra-high energy cosmic rays (Auger)

νµ + ¯ νµ (8yr) cosmogenic ν + ¯ ν proton (E−2) γ-rays from π0 decay calorimetric limit π± / π0 production GZK mechanism

[Ahlers & Halzen, 2018]

Similar energy in the Universe in 𝛿-rays, neutrinos and cosmic rays

[Ahlers 2015, Murase+ 2014, Kowalski 2014]

17

Arrival Direction of Highest Energy Neutrinos

18

Point Source Searches

Stacking Search

• r.a.

declination

10−1 100 101 102 103 E [TeV] 10−9 10−8 10−7 E2dΦ/dEdΩ [GeV cm−2 s−1 sr−1]

5 PeV CR cutoff 5 P e V C R c u t

• ff

KRAγ model Combined UL KRAγ5 Combined UL KRAγ50 ANTARES UL KRAγ5 IceCube UL KRAγ50 IceCube starting events IceCube up-going νµ KRAγ model Combined UL KRAγ5 Combined UL KRAγ50 ANTARES UL KRAγ5 IceCube UL KRAγ50 IceCube starting events IceCube up-going νµ

19

Diffuse Galactic Neutrino Flux

IceCube+ANTARES 2018

• Search for the correlation of neutrinos with the template map of emission from

Galactic plane.

• Spatial distribution from gamma-ray data.
• Neutrino flux constrained at the level of ~15% of the total flux.
• Models have large uncertainty on the flux above 10 TeV

Fermi − LAT π0 Template

Energy cutoff Sensitivity [ΦKRAγ ] Fitted flux p-value UL at 90% CL Combined ANTARES IceCube [ΦKRAγ ] [%] [ΦKRAγ ] 5 PeV 0.81 1.21 1.14 0.47 29 1.19 50 PeV 0.57 0.94 0.82 0.37 26 0.90

20

MGRO J1908+06

• 103

104 105 109 108 107 106 EΓGeV EΓ

2 dNΓdEΓs1 m2 TeV

MGRO J190806 ΑΓ2

HAWC HESS VERITAS ARGOYBJ 2012 Milagro ApJL

[Halzen, AK, Niro, 2017]

• One of the primary candidates identified in

Milagro survey.

• Observation of the sources in IACT
• experiments. Tension in extension and

spectrum reported.

• Classified as an unidentified source. Gamma

ray emission nature not well understood

• Prospects for observation is highly

entangled with the extension of the source.

• Based on HESS’s observation, should

be seen in ~10 years.

5 10 15 20 108 107 106 105 104 103 102 101 1 tyr pvalue MGRO J190806 ΑΓ2 3Σ 5Σ

Ecut = 800 TeV Ecut = 30 TeV

20

MGRO J1908+06

• 103

104 105 109 108 107 106 EΓGeV EΓ

2 dNΓdEΓs1 m2 TeV

MGRO J190806 ΑΓ2

HAWC HESS VERITAS ARGOYBJ 2012 Milagro ApJL

[Halzen, AK, Niro, 2017]

• One of the primary candidates identified in

Milagro survey.

• Observation of the sources in IACT
• experiments. Tension in extension and

spectrum reported.

• Classified as an unidentified source. Gamma

ray emission nature not well understood

• Prospects for observation is highly

entangled with the extension of the source.

• Based on HESS’s observation, should

be seen in ~10 years.

5 10 15 20 108 107 106 105 104 103 102 101 1 tyr pvalue MGRO J190806 ΑΓ2 3Σ 5Σ

Ecut = 800 TeV Ecut = 30 TeV

IceCube 8 yr search

pre trial p-value: 0.008

HAWC > 50 TeV disfavoring low-energy cut-off

HAWC @ TeVPA 2017