Naoko Kurahashi Neilson, Drexel University 1
Neutrino Astronomy with IceCube at the Earth's South Pole
Naoko Kurahashi Neilson (Drexel University)
Yale NPA Seminar, Jan 26th, 2017
Naoko Kurahashi Neilson, Drexel University 2
How it started....Highest energy particles observed
GeV
109eV
TeV
1012eV
PeV
1015eV
EeV
1018eV
Charged particles
Neutral particles γ ray
nucleihuman-made
(LHC)
Naoko Kurahashi Neilson, Drexel University 3
Naoko Kurahashi Neilson, Drexel University 4
GeV
109eV
TeV
1012eV
PeV
1015eV
EeV
1018eV
Charged particles
Neutral particles
nuclei
neutrino!
● How are neutral particles created at such high energies? The same way by us?● Can neutrinos be created the same way γ-rays are?● What are the connections between these high energy observations?● What are the most likely sources of these observed neutrinos?
γ ray
human-made(LHC)
How it started....Highest energy particles observed
High-Energy Astronomy
Producing γ rays
Inverse Compton
e-
e-
Leptonic Processes Hadronic Processes
Bremsstrahlung, etc
P + P or P + γ creates π0
π0
creates π+/- too!
Produces ν too
Naoko Kurahashi Neilson, Drexel University 10
See deeper into sources
Learn how gamma-rays are created
Learn where cosmic-rays are coming from
Neutrino Astronomy – The Dream
Naoko Kurahashi Neilson, Drexel University 11
Neutrino Astronomy – The Reality
Issue 1: cross section Issue 2: backgrounds
Galactic disk ~1023cm
Cross section from Gandhi et al., Phys. Rev. D 58 (1998) 093009
Atmosphere thickness 1x106cm
Earth radius 6x108cm
Observable universe ~1028cm
Naoko Kurahashi Neilson, Drexel University 12Completed in Dec 2010!
Naoko Kurahashi Neilson, Drexel University 13
~250 people for ~40 institutions
Naoko Kurahashi Neilson, Drexel University 14
Two Ways to Probe Neutrino Astrophysics
Goal: Resolve each spectral component in energy
Requirements: - Good energy proxy variable- Good purity in data over statistical power (need to understand all components)- Accurate estimate of energy proxy error range- Prior knowledge of characteristics of components helpful
Goal: Resolve sources (clusterings) in space
Requirements: - Good angular resolution- Good statistical power over purity (background is spatially uniform)- Accurate estimate of angular error range- Prior knowledge of potential source locations helpful
Diffuse Analyses Point Source Analyses
EarthIceCube
IceCube backgrounds are atmospheric shower components
0
● Most charged π/K decay to μ rather than e● ν produced in the same interaction, but lower cross
section● Most common bkg: μ > νμ > νe (Southern Hemisphere)
● νμ > νe (Northern Hemisphere)
● At higher energy, π/K lifetime is longer → more interact rather than decay
● μ, ν spectra softer than primary CR's
● At higher energies, charmed mesons produced● Shorter lifetime, decay products are harder spectra than
π/K decay → “prompt” flux
Naoko Kurahashi Neilson, Drexel University 16
Diffuse Analysis 1IceCube's discovery analysis in 2013
μ Veto
μ
νμ
Could be an atmospheric muon from a CR shower
Most likely a neutrino
Science 342, 1242856 (2013)
2010-2012 (2 years of data) ● Flux assuming E-2: ~1.2 x 10-8 E-2 [/GeV/cm2/s/sr]● Best fit spectral index: -2.2
Events with interaction vertices contained inside the IceCube detector
μ Veto
μ
νμ
More likely to be neutrino events
Could be an atmospheric muon or could be a muon caused by neutrinos
Most likely a neutrino
The higher the energy, the better this works!
Tagging atmospheric neutrinos
The accompanying muon trips the veto! → “Self-veto”
Naoko Kurahashi Neilson, Drexel University 19
Diffuse Analysis 1IceCube's discovery analysis in 2013
μ Veto
μ
νμ
Could be an atmospheric muon from a CR shower
Most likely a neutrino
Science 342, 1242856 (2013)
2010-2012 (2 years of data) ● Flux assuming E-2: ~1.2 x 10-8 E-2 [/GeV/cm2/s/sr]● Best fit spectral index: -2.2
Naoko Kurahashi Neilson, Drexel University 20
Diffuse Analysis 1IceCube's discovery analysis in 2013
μ Veto
μ
νμ
Could be an atmospheric muon from a CR shower
Most likely a neutrino
arXiv:1510.05223
2010-2014 (4 years of data) ● Flux assuming E-2: ~1.0 x 10-8 E-2 [/GeV/cm2/s/sr]● Best fit spectral index: -2.6
Naoko Kurahashi Neilson, Drexel University 21
Diffuse Analysis 2Updated veto to the discovery analysis
● Flux Level:~2.2 (E/100GeV)-2.5 10-8 [/GeV/cm2/s/sr] ● Spectral index: -2.5
IceCube Collaboration (2015) Phys. Rev. D. 91
* This was for 2010-2012 data. Update to this analysis in the pipeline
Naoko Kurahashi Neilson, Drexel University 22
Diffuse Analysis 3A different approach: Only look below the horizon to
avoid atmospheric muon background
2009-2010 2010-2011 2011-2012 2011-2015
arXiv:1607.08006
● Flux Level:~ 0.9 (E/100TeV)-2.13 10-18 [/GeV/cm2/s/sr] ● Spectral index: -2.1
Naoko Kurahashi Neilson, Drexel University 23
Diffuse Analyses Conclusion
● The universe emits high energy neutrinos
● Characterization in progress, but the whole picture is unclear for now
Assumptions:- one flux for whole sky- one spectral index- same flux for each flavor
Some tensions imply.....Break in the spectrum?
- difference in energy probed imply hardening- but then no Glashow events?- break and cutoff?
Spatially different flux?
90% confidence interval comparison
arXiv:1607.08006
Naoko Kurahashi Neilson, Drexel University 24
Two Ways to Probe Neutrino Astrophysics
Goal: Resolve each spectral component in energy
Requirements: - Good energy proxy variable- Good purity in data over statistical power (need to understand all components)- Accurate estimate of energy proxy error range- Prior knowledge of characteristics of components helpful
Goal: Resolve sources (clusterings) in space
Requirements: - Good angular resolution- Good statistical power over purity (background is spatially uniform)- Accurate estimate of angular error range- Prior knowledge of potential source locations helpful
Diffuse Analyses Point Source Analyses
Through-going tracks:Collect all good quality tracks
“2008” year Old Data (40-strings detector)~37,000 events
Equatorial coordinates
Likelihood Search for a Source- Test Statistic (TS) Calculation -
Maximize the likelihood L assuming a source at point x with energy spectrum E-γ
Probability density that event i comes form a
source with spectrum γ
Probability density that event i comes form a known background energy spectrum
Total # of events# of events from sourceVaried to maximize L
Probability densitythat event i comes from a source at position x
Probability density that event i is from backgrounds
expected at position x
Naoko Kurahashi Neilson, Drexel University 28
Point Source Analysis 1Search for cluster: all-sky and around known sources
All-sky search
Time-integrated unbinned search of hot spots in 7 years of data(4-year version Astrophys.J. 796:109,2014)
BL LacPKS 0537-441PKS 2155-304PKS 0235+1641ES 0229+200W ComaeMrk 421Mrk 501H 1426+4283C66A1ES 2344+5141ES 1959+650S5 0716+71PKS 2005-489PKS 0426-380PKS 0548-322H 2356-3091ES 1101-2321ES 0347-121
FSRQPKS 1454-354PKS 1622-297QSO 1730-130PKS 1406-076QSO 2022-0773C2793C 273PKS 1502+106PKS 0528+1343C 454.34C 38.41PKS 0454-234PKS 0727-11
GCSgr A*
NIMGRO J1908+06 HESS J1507-622 HESS J1503-582HESS J1741-302HESS J1834-087
PWNGemingaCrab NebulaMGRO J2019+37 HESS J1356-645PSR B1259-63HESS J1303-631MSH 15-52HESS J1023-575HESS J1616-508HESS J1632-478Vela XHESS J1837-0
SFRCyg OB2
SNRIC443Cas ATYCHOCen AM873C 123.0Cyg ANGC 1275M82RCW 86RX J0852.0-4622RX J1713.7-3946W28
SeyfertESO 139-G12
XB/mqso SS433HESS J0632+057 Cyg X-1Cyg X-3LSI 30Cir X-1GX 339-4S 5039
clusterHESS J1614-51
Naoko Kurahashi Neilson, Drexel University 29
Point Source Analysis 2Stack the sources
Quasi-diffuse search (~10% of the sky at our angular resolution)
IceCube Collab., arXiv:1410.1749 (2014)
2010-2013 data
Stacking of 127 nearby bright starburst galaxies• Within z < 0.03• FFIR(60 micron) > 4 Jy• Fradio(1.4 GHz) > 20 mJy
Waxman, TeVPA ‘13
Stacking of 862 Fermi 2LAC Blazars
Astrophys.J. 796:10 (,2014)
Naoko Kurahashi Neilson, Drexel University 30
Point Source Analyses conclusion
● No TeV sources in neutrinos (yet)
● Statistically insignificant overfluctuations come and go, but will any stick?
● MeV neutrinos still lead in number of sources (0 vs 2)
super-kamiokande
kamiokande
The Sun Supernova 1987A
*No direction, just timing
Naoko Kurahashi Neilson, Drexel University 31
Putting diffuse and point source together
arXiv:1502.03104All-sky source flux limit
Astrophysical DiffuseFlux
Naoko Kurahashi Neilson, Drexel University 32
Limits in terms of % of diffuse flux
Upper limit in diffuse flux
notes
Blazars ~ 17% 862 from Fermi 2nd AGN cat.Spectral index = -2.5
Nearby Starburst Galaxies ~ 8% 127 nearbySpectral index = -2
Galactic Sources
Young SNR ~ 5% 30 with no PWN or MCSpectral index = -2
Young PWN ~ 3% 10 with no MCSpectral index = -2
Galactic Plane ~14% Fermi Diffuse γ Spatial templateSpectral index = -2.5 to -2.7
GRBs ~1% 506 bursts observed Spectral index = -2 to -2.7
Astrophys.J. 796:10 (,2014), ApJ, 805, L5 (2015)
Naoko Kurahashi Neilson, Drexel University 33
Is it time to consider....
– New (more correct? more exotic?) models of emission?
– New sources? Optical or x-ray counterparts?
– “Dark” sources? Does this require new methods?
Naoko Kurahashi Neilson, Drexel University 34
Multi-Messenger Astronomy withNon-EM partners
Ultra-high Energy Cosmic Rays Gravity Waves
Correlation study with highest energy events from Auger and TANo correlation beyond 3.3σ
JCAP 1601 (2016) 01, 037
LIGO gravity signal and neutrino events within +/-500s
Naoko Kurahashi Neilson, Drexel University 35
How can we increase our chances of discovering sources sooner?
Factor of 10 doesn't seem like much until you realize how old you are in 10 years vs 100 years!
Naoko Kurahashi Neilson, Drexel University 36
IceCube's Realtime Efforts
Naoko Kurahashi Neilson, Drexel University 37
Example: HESE-160427A , on April 27 2016
Naoko Kurahashi Neilson, Drexel University 38
Historical Perspective: Gamma-ray AstronomyDiffuse signal → first source → catalog!
SAS-2
Diffuse celestial radiation
GSFC nasa.gov
COS-B Discreet sources
1970's
1980's
NOW
GSFC nasa.gov
Fermi 5-year data
Naoko Kurahashi Neilson, Drexel University 39
Historical Perspective: X-ray AstronomyDiffuse signal → first source → catalog
“The Cosmic Century” M. S. Longair
Diffuse emission and Scorpius X-1 1960's
(Sun detected in x-rays 1940's)
xte.mit.edu
APOD 8/19/2000 ROSAT
Naoko Kurahashi Neilson, Drexel University 40
IceCube Gen2 – The next generation facility for neutrino physics and astronomy at the South Pole
arXiv:1412.5106
Naoko Kurahashi Neilson, Drexel University 41
Getting there sooner
Naoko Kurahashi Neilson, Drexel University 42
Conclusions
● High-energy Neutrino Astronomy is becoming a reality
● Both diffuse and point source analyses are providing new information, but together they are giving us more insight
● We keep learning lessons, and have plans to get us to discovery sooner
Naoko Kurahashi Neilson, Drexel University 43
Backups
Naoko Kurahashi Neilson, Drexel University 44
More IceCube Jargon
40-strings (IC-40), 376 days livetime, ~50% complete59-strings (IC-59), 348 days livetime, ~50% complete79-strings (IC-79), 333 days livetime, almost complete86-strings (IC-86), 329 days livetime, complete
Naoko Kurahashi Neilson, Drexel University 45
A pitch for optical/x-ray/gamma-ray to followups on IceCube observations
● IceCube is updating fast alert systems (GCN/ATEL) to be sent when a “significant” neutrino is seen
● The (current) best case is ~0.5 degree error circle → not great for follow-up observations
It's a lot to ask other telescopes to observe for a long time in a large area, for most likely, nothing
● But lets not forget, the upshot is huge here! Your telescopes can discover the first non-photon source in the sky!
Naoko Kurahashi Neilson, Drexel University 46
Topologies of different event types
Through-going Track Shower
Charge Current Electron/Tau NeutrinosAll Neutral Current NeutrinosCharge Current Muon Neutrinos
Starting Track
Naoko Kurahashi Neilson, Drexel University 47
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