u n c l a s s i f i e d high-energy astrophysics probing the extreme universe gus sinnis p-23

U N C L A S S I F I E D


High-Energy Astrophysics

Probing the Extreme Universe

Gus Sinnis

P-23



Outline

Milagro Tera-Volt Gamma-Ray Telescope• Physics Goals• The Milagro Detector• Recent results

Future Directions

Milagro at TA-57



The Milagro Collaboration

LANL• Sinnis (PI/co-spokesman), Dingus (TSM), Walker, Casanova, Spaulding (UGS)

U. Maryland• Goodman (PI/co-spokesman), Smith, Lansdell (at LANL), Vasilios (GRA), Noyes (GRA)

U.C. Irvine• Yodh, Shoup, Allen (GRA), Amarotto (UGS), Delay (tech at LANL)

U.C. Santa Cruz• Williams, Saz-Parkinson, Schneider (tech)

Michigan State University• Jim Linnemann, Aous Abdo (GRA), Iris Gebauer (GRA)

New York University• Nemethy, Mincer

George Mason University• Ellsworth



Milagro: A Tera-Volt Astrophysical Observatory

Physics Goals• Particle acceleration • Astrophysical shocks• Black hole environments• Neutron star environments• Gamma-ray bursts• Solar physics• Space weather

Open aperture/continuous observation • Monitoring of variable sources• Study large-scale structure of

sources• Discovery potential



Active Galactic Nuclei

~108 Msun black hole

Relativistic particle jets

1048 ergs/sec

TeV emission is along jet

Highly variable

Open questions• what is being accelerated?• how large is the bulk Lorentz factor

of shock?• B-field in shock?

Need multi-wavelength observations

• many objects• many flares• long-term monitoring



Water Cherenkov Technology

e T

ime

Top layer detects 50% of particles that enters the pond (,e+,e-)

Measure relative timing across pond (~1ns)

Reconstruct direction ~0.5o



Background Rejection in Milagro

Pro

ton

sG

am

ma

s

Reject 90% of proton background

Retain 50% of -ray signal



Galactic Plane in TeV Gamma Rays

Cosmic rays interacting with matter in Galaxy produce ’s that decay into rays

Gamma ray spectrum is sensitive to cosmic ray source models

• inverse Compton component• point sources

EGRET observations up to 20 GeV indicated an excess > 1 GeV

Higher energy observations have proven elusive despite 20 years of effort

Milagro has made the first detection of TeV gamma rays from the Galactic plane

S/B level ~3:10-4 – a very difficult analysis

Submitted to PRL

EGRET data



Galactic Plane in TeV Gamma Rays

Demonstrates the strength of Milagro in finding diffuse and extended sources• Due to good “inherent”

background rejection• ACTs get most of their rejection

from angular resolution• Large observation time• Large field of view

Our flux measurement is ~1/10 of previous upper limits

E-2.51±0.05



TeV Point-Source Survey of the Northern Hemisphere

Crab Nebula and active galaxy Mrk421 detected

9 regions of interest identified (>4) – 3 coincident with “roi’s” from Tibet array (Walker et al. ApJ)



Extended Source Survey

Two of the regions of interest are actually extended sources

~6 degree source in Cygnus arm of Galaxy

~3 degree source near the Crab Nebula

HESS telescope now performing follow-up observations



Solar Physics

Coronal mass ejections are an ideal laboratory to study particle acceleration in the cosmos

By monitoring the singles rates in all PMTs we are sensitive to “low”-energy particles (>10 GeV)

Milagro has detected 4 events from the Sun with >10 GeV particles



X7-Class flare Jan. 20, 2005

GOES proton data• >10 MeV• >50 MeV• >100 MeV

Milagro scaler data• > 10 GeV protons• ~1 min rise-time• ~5 min duration



Milagro Status and Future

Milagro is running in stable mode

We are discovering new source of TeV gamma rays• Galactic plane• Extended sources (not anticipated)

Online GRB analysis continuing• Tied into global alert network (GCN)

Several exciting solar events detected

NSF anticipates 2 more years of operations



Future Plans: miniHAWC

Reuse Milagro PMTs and electronics

Build pond at extreme altitude (Tibet – 4300m asl)

Incorporate new design• Optical isolation between PMTs• Larger PMT spacing• Deeper PMT depth (in top layer)

Increase collaboration• Added IHEP (Beijing), MSU, UNM, and Utah

$2-3M for complete detector

>15x sensitivity of Milagro• Crab Nebula in 2-3 days (now 1 year)• GRBs to redshift of >1 (now 0.4)



miniHAWC Sensitivity: Galactic Emission

Extrapolate from Milagro detection of Galactic plane

Use neutral H map to predict TeV intensity

Maps on left show 1-year of data from Milagro, miniHAWC and HAWC



Conclusion

Milagro has made several discoveries• TeV emission from the Galactic plane• 2 extended sources of TeV gamma rays

Milagro is a completely new technique and we are still learning. The best days lie ahead.

Design of next generation instrument in progress

For modest cost (~$2-3M) we can build an instrument >15x more sensitive than Milagro

Needed for monitoring of GLAST sources, ICECUBE sources, and discovery of new phenomena



HAWC Sensitivity: Active Galaxies

Assume theoretical model of 27 AGN

Account for IR absorption

Add in 5 known TeV sources



Forbush Decreases – The interplanetary field

3800

3600

3400

3200

3000

2800

10/18/03 10/23/03 10/28/03 11/2/03

UT

1.35

1.30

1.25

1.20 2003 October/November

Climax Milagro

1.5%

6%

3.2%/day

4.3%/day



The High Resolution Fly’s Eye

Studying the most energetic particles in the universe

• E=1018 eV to 1021 eV

Outstanding Issues• The shape of the spectrum (is there an

endpoint to the spectrum?)• The composition of these particles

(protons, gammas, Fe, ?)• Are there any anisotropies in their

arrival directions?

LANL’s role in HiRes• Post 9/11 Dugway closed to non-

cleared personnel• LANL “rescued” HiRes – operated

HiRes with Q-cleared personnel• 2004 Dugway allowed US citizen’s on

base – LANL no longer operates• LANL receives ~100k/year from NSF

for a postdoc (starting now)



The HiRes Detector

The fluorescence yield is proportional to the number of electrons

We directly measure the development of the extensive air shower and the energy of the primary particle



The Ultra-High-Energy Cosmic Ray Spectrum

Griesen, Zatsepin, and Kuzmin (GZK) predicted an endpoint to the UHECR spectrum at 1019.6 eV

• protons interacting with the 3K CMBR lose energy via pion production

AGASA measures a continuing spectrum

HiRes mono consistent with endpoint

HiRes stereo in progress



Anisotropy of Ultra-High Energy Cosmic Rays

Outstanding questions• Are there point sources of UHECRs?• Is there large-scale structure to the UHECR arrival directions?

Motivated by results from the AGASA array• Found event clusters (2 or more events from same direction)• Claimed strong evidence for neutral particles from the Galactic plane

LANL work• Hoffman working with Westerhoff (Columbia) developed maximum

likelihood analysis to search for point sources (paper accepted)• Sinnis searched for enhancement from Galactic plane (paper in

progress)



Point Source Search

Combining data from AGASA and HiRes > 4x1019 eV

Most likely “point source” position consists of 3 AGASA events and 1 HiRes event

Chance probability is 24% - no evidence for point sources of UHECRs



Galactic Plane Enhancement

AGASALong-standing claim of excess from Galaxy between 1018eV and 1018.4 eV – interpreted as neutral particles

HiRes4 years of stereo data No evidence of Galactic enhancement. 90% CL upper limit ~ to AGASA signal level



HiRes Status and Future

Operations will continue until ~March 2006

Stereo data analysis is our major effort

Spectrum – Utah and Nevis

Anisotropy – LANL and Columbia• Galactic plane• Point sources• Correlations with known objects

Expect 1-2 more years of analysis than effort shifting

u n c l a s s i f i e d high-energy astrophysics probing the extreme universe gus sinnis p-23

Documents

s s i f i e d milagro

s s i f i e d galactic

apj slide

o slide

ray signal slide

e measure relative timing

previous upper limits

longterm monitoring