Wide-Field Gamma-Ray Instruments:Milagro ResultsPlans for HAWC

Gus Sinnis

Los Alamos National Lab

TeVPA 2008 Beijing

Scientific Goals

Experimental Techniques

Recent Results

Future Plans

Modern Gamma-Ray Telescopes

Large Aperture/High Duty CycleMilagro, Tibet, ARGO

Large Area

Good Background Rejection

Good Angular Resolution

Large Duty Cycle/Large Aperture

Unbiased Sky Survey

Extended sources

Highest energies

Transients (GRB’s)

Low Energy ThresholdEGRET/FERMI

Space-based (Small Area)

“Background Free”

Good Angular Resolution

Large Duty Cycle/Large Aperture

Sky Survey 100 MeV - 10 GeV

AGN Physics

Transients (GRBs) < 100 GeV

High SensitivityHESS, MAGIC, VERITAS,

CANGAROO

Large Area

Excellent Background Rejection

Excellent Angular Resolution

Low Duty Cycle/Small Aperture

Surveys of limited regions of sky

High Resolution Energy Spectra

Source morphology

Science Goals of Ground-Based Observatories

• Cosmic-ray origins– High-energyW and high resolutionA spectra of Galactic sources– Galactic diffuse emissionW

– Discover Galactic cosmic-ray acceleratorsA

• Particle acceleration– Transient phenomena (AGN flares and GRBs)

• prompt emissionW & delayedA

• orphan flaresW, TeV duty factorsW, fastest phenomenaA

– Multi-wavelength (GLAST, x-ray, optical, radio) WA, multi-messengerA

– Source morphologyA

– PulsarsA

• Fundamental Physics– Lorentz invariance (GRBW, AGNA)– Dark matter detectorA (annihilation gammas from neutralinos)

• Discovery– Unbiased sky survey (2.6 sr) to 2% of Crab NebulaW

– Deep Galactic survey to 0.1% of CrabA W Wide field instrument

A Air Cherenkov Array

Abdo, Allen, Berley, DeYoung, Dingus, Ellsworth, Gonzalez, Goodman, Hoffman, Huentemeyer, Kolterman, Linnemann, McEnery, Mincer, Nemethy, Pretz, Ryan, Saz Parkinson, Shoup, Sinnis, Smith, Williams, Vasileiou, Yodh

The Milagro Collaboration

TeV gamma at 2600m asl

Water Cherenkov Technology

CASA-MIA

Milagro

• gammas• electrons

Provides fully active areaConverts ’s to electrons: electron ~ 6:1

60 m 80 m

Milagro Gamma-Ray Observatory• 2600m above sea level• 2 sr field-of-view• 95% duty factor

A. Abdo, B. Allen, D. Berley, T. DeYoung,B.L. Dingus, R.W. Ellsworth, M.M. Gonzalez, J.A. Goodman, C.M. Hoffman,P. Huentemeyer, B. Kolterman, J.T. Linnemann, J.E. McEnery, A.I. Mincer, P. Nemethy, J. Pretz, J.M. Ryan, P.M. Saz Parkinson, A. Shoup, G. Sinnis, A.J. Smith, D.A. Williams, V. Vasileiou, G.B. Yodh

8’ dia. x 3’ deep

• Angular resolution~0.5o

• 1700 Hz trigger rate

How Milagro Works

• Direction via timing (~1 ns)• Background rejection via muons• Energy via shower size

8 meters

e

80 meters

50 meters

time

time

position

ARGO

Background Rejection in Milagro

Bottom layer (6 mwe overburden) detects penetrating component of hadronic EAS

Reject 95% of backgroundRetain 50% of gammasRejection is highly energy dependent!

Proton MC Proton MC

Data Data MC MC

Boomerang PWN

Cygnus Region

Confirmed by HESS

Geminga

Milagro Wide Field View of Galaxy (10-50 TeV)

Sources are extendedCorrelated with EGRET GeV catalogHard spectra (-2.3 connects to EGRET)Clearly visible diffuse component

Tibet ASEGRET

Galactic Diffuse Emission

Cygnus Region with Matter Density Contours overlaying Milagro

Observation

component due to CR-matter interactions

Inverse Compton to e- (~CMB) interactions

Cygnus Region65o < l < 85o

GALPROP (Strong et al.)

EGRET data

Milagro

Milagro

EGRET data

GALPROP (Strong et al.)

30o < l < 65o

Large-Scale Cosmic-Ray Anisotropy

New analysis technique – forward backward asymmetry

Milagro results consistent with Tibet AS discovery

Modulation amplitude ~5x10-3 with deficit at RA=180o

Large-Scale Cosmic-Ray Anisotropy:Time Dependence

4/1/

2001

8/14

/200

2

5/10

/200

5

9/22

/200

6

12/2

7/20

03

Solar Max 2000-2001

Solar Min 2007/8

Amplitude of anisotropy has been increasing over past 6 years (solar max to solar min)

Error bars include systematic errors

Intermediate-Scale Cosmic-Ray Anisotropy at ~10 TeV

• Excesses are hadronic particles not gamma rays

• Anisotropy ~6x10-4 (~10% of the large-scale anisotropy)

• Larmor radius of 10 TeV proton in 1 G is .01pc

• Lifetime of 10 TeV neutron is 0.1 pc

• Explanations difficult: requires ordered B-field (Drury & Aharonian 2008)

BA

heliotailGeminga

Galactic Plane

HAWC: High Altitude Water Cherenkov

10-15x more sensitive than Milagro1 Crab in 5 hrs, 10 Crab in 3 minutes

Located at base of volcán Sierra Negra• latitude : 18º 59’• altitude : 4100mInside Parque Nacional Pico de Orizaba2 hours from Puebla (INAOE)

The HAWC Collaboration

Instituto Nacional de Astrofísica Óptica y ElectrónicaAlberto Carramiñana, L. Carasco, E. Mendoza,

S. Silich, G. T. TagleUniversidad Nacional Autónoma de México

R. Alfaro, E. Belmont, M. Carrillo, M. González, A. Lara,Lukas Nellin, D. Page, V. A. Reese, A. Sandoval,

G. Medina Tanco,O. Valenzuela, W. LeeBenemérita Universidad Autónoma de Puebla

C. Alvarez, A. Fernandez, O. Martinez, H. SalazarUniversidad Michoacana de San Nicolás de Hidalgo

L. VillasenorUniversidad de Guanajuato

David Delepine, Victor Migenes, Gerardo Moreno, Marco Reyes, Luis Ureña

UC IrvineG. Yodh

University of New HampshireJ. Ryan

Los Alamos National LaboratoryB. Dingus, J. Pretz, G. Sinnis

Uniersity of MarylandD. Berley, R. Ellsworth, J. Goodman, A.

Smith, G. Sullivan, V. VasileiouUniversity of New Mexico

J. MatthewsUniversity of Utah

D. Kieda, P. HuentemeyerPennsylvania State University

Ty DeYoungNASA Goddard

J. McEneryNaval Research Laboratory

A.AbdoU.C. Santa Cruz

M. Schneider

HAWC Design• ~1000 large tanks (~4m dia x ~4m height)

– 1 PMT/tank (looking up)

– Non-reflective interior

• 22,000 m2 enclosed area• 4100 m above sea level

150 m150 m15

0 m

150

m100 MeV photons shown

100 MeV 1/50 photons shown

HAWC Performance: Effective Area• At low energies (<1 TeV), HAWC has ~30x the effective area of Milagro

• larger dense sampling area (5x)• higher altitude• Larger muon detection area (10x)

HAWC w/reconstruction

HAWC w/Rejection

Milagro w/reconstruction

Milagro w/Rejection

HAWC Performance: Angular Resolution

• At similar energies, HAWC’s angular resolution is ~1.5x better than Milagro.• larger area• higher altitude• optical isolation

• Resolution defined as sigma of a 2-d Gaussian.

Resolution at 10 TeVA

ngul

ar R

eso

lutio

n (d

egre

es)

HAWC Background Rejection

Gam

mas

Pro

ton

s

Size of Milagro deep layer

Size of HAWC

• 10x better hadron rejection than Milagro above 10 TeV• larger muon detection area (10x)• optical isolation

• 2.5x higher gamma efficiency at lower energies (< 10 TeV)

HAWC Performance: Energy Resolution I

http://www.ast.leeds.ac.uk/~fs/photon-showers.html

Fixed first interaction elevation: 30km

HA

WC

ele

vatio

n 4.

1km

10 TeV

gamm

a-ray shower Longitudinal P

rofile

Distribution of height of Distribution of height of 11stst interaction interaction

Energy Resolution in an EAS is dominated by the fluctuations in the depth of first interaction

HAWC Performance: Energy Resolution II

• EAS arrays can measure shower size very well (<20% resolution)

• Shower fluctuations (depth of 1st interaction) dominate energy resolution of array.

• Because of increased altitude HAWC will have much better energy resolution than Milagro

Point Source Sensitivity

IACTs 50 hrs (~0.06 sr/yr)IACTs 50 hrs (~0.06 sr/yr)

1 yr1 yr

EAS 5 yrs (~2EAS 5 yrs (~2 sr) sr)

2000 km

2000 km22 sr

hr sr

hr

High-Energy Spectra with HAWC

HESS J1616-508

0.2 Crab @ 1 TeV

dN/dE -2.3

Highest energy ~20 TeV

Simulated HAWC data

1 year no cutoff

Simulated HAWC data

1 year 40 TeV cutoff

Transient Phenomena: AGN and GRB

PKS J2155-304 (z=0.117) 50PKS J2155-304 (z=0.117) 50xx quiescent (1 hr) dN/dE=kE quiescent (1 hr) dN/dE=kE-3.5-3.5

6 6 in HAWC in HAWC

10-1

210

-10

10-8

TeV AGN flares

GRB <1 MeV

GLAST and HAWC sensitivity for a source of spectrum dN/dE=KE-2

z=0 no E cutoffz=0.1 Eexp~700GeVz=0.3 Eexp~260GeVz=0.5 Eexp~170GeV

Gus SinnisAGIS Collaboration Meeting June 2008

Worldwide Dataset of TeV Observations of Mrk421

Transient Phenomena: AGN Flares

• HAWC will obtain TeV duty factors, search for orphan flares, & notify other observers in real time.

• All sources within ~2 sr would be observed every day for ~ 5 hrs.• HAWC sensitivity: 10 Crab in 3 min and 1 Crab in 5 hrs

3 min3 min

5 hr5 hr

Conclusions

• The role of wide-field instruments now established• Large sensitivity gain (>10x) is achievable• Strong Scientific Motivation

– Highest energies (>5-10 TeV)– Extended sources– Galactic diffuse emission– Unique TeV transient detector (GRBs and AGN flares)

• 4x Crab in 15 minutes

• HAWC Status– Fall 2007 Full proposal submitted to NSF and CONyCT

– July 2008 NSF funds $1M MRI grant for HAWC• Develop site infrastructure (roads, power, water, internet) • R&D for large tank

– US funding decision awaits Particle Astrophysics SAG (early 2009)

Thank You!

"Confirming an idea is always gratifying. But finding what you don't expect opens new vistas on the nature of reality. And that's what humans, including those of us who happen to be physicists, live for.”

-Brian Greene NYT 9/12/2008