Astrophysics with 2 sr and 24/7 VHE Detectors

Brenda Dingus20 Oct 2005

Astrophysics with 2 sr and 24/7 VHE Detectors

Brenda Dingus for the Milagro and HAWC

collaborations


Milagro Gamma Ray Observatory @ 8600’ altitude near Los Alamos, NMAbdo9, R.Atkins,1,2 W. Benbow,3,4 D. Berley,5 E. Blaufuss5, D.G. Coyne,3 T. DeYoung,3,5

B.L. Dingus,6 D.E. Dorfan,3 R.W. Ellsworth,7 L. Fleysher,8 R.Fleysher8, M.M. Gonzalez,1,14 J.A. Goodman5, E. Hays5, C.M. Hoffman,6

C.P. Lansdell,5 J.T. Linnemann,9 J.E. McEnery,1,10 A.I. Mincer,8 M.F. Morales,3,11

P. Nemethy,8 D. Noyes,5 J.M. Ryan,12 F.W. Samuelson,6 P.M. Saz Parkinson,3 Shoup,13 G. Sinnis,6 A.J. Smith,5 G.W. Sullivan,5 D.A. Williams,3 X.W. Xu6

and G.B. Yodh13

1. Department of Physics, University of Wisconsin2. Current Address: Department of Physics, University of Utah3. Santa Cruz Institute for Particle Physics, University of California, Santa Cruz4. Current address: Max-Plank-Institute fur Kernphysik5. Deoartment of Physics, University of Maryland6. Los Alamos National Laboratory7. Department of Physics and Astronomy, George Mason University8. Department of Physics, New York University9. Department of Physics and Astronomy, Michigan State University10. Current address: NASA Goddard Space Flight Center11. Current address: Massachusetts Institute of Technology12. Department of Physics, University of New Hampshire13. Department of Physics and Astronomy, University of California, Irvine14. UNAM, Mexico City


Water Cherenkov Detectors

8 meters

e

80 meters

50 meters

• Detect Particles in Extensive Air Showers from Cherenkov light created in a covered pond containing filtered water.

• Reconstruct shower direction from the time different photodetectors are hit.

• Multi-kHz trigger rate mostly due to Extensive Air Showers created by cosmic rays

• Field of view is ~2 sr and the average duty factor is nearly 100%Milagro Cross Section Schematic


Milagro, miniHAWC, HAWC

Median Energy

Angular

Res.Time for 5

on CrabmCrab/day

@ 5mCrab/

month@ 5mCrab/year

@ 5

Milagro w/o outriggers

3 TeV 0.75o 1.1 years 21,000 3,800 1,200

Milagro 3 TeV 0.5o ½ year 13,000 2,500 700

miniHAWC 700 GeV 0.4o 2 days 1,700 300 70

HAWC 250 GeV 0.3o ½ hour 300 50 15

Design details about miniHAWC and HAWC are in other presentations. #s below depends on source spectrum and declination plus trigger cuts.

– Crab spectrum of dN/dE E-2.59 was assumed.– Background was normalized from Milagro observations.– Detector latitude is arbitrarily same as Milagro, so Crab transits at 15o


Pre-Outrigger – data since 2000• Optimized with MC simulations• Published detection of the Crab (ApJ 595, 803 (2003))• Sensitivity: ~4.7/yr on the Crab• 10.0 from 4.5yr

Sensitivity of Milagro to the Crab Nebula

Post-Outrigger – data since 2003• Good angular reconstruction on off-pond cores• Sensitivity: ~8/yr on the Crab

• 9.7 from 1.5yr


Predicted TeV AGNs

HAWC can monitor multiple AGN on daily to monthly timescales

1-year HAWC observation

Costamante & Ghisellini AGN (31 sources)

Kneiske, Hartmann, Mannheim 2005 IR model absorption model

+ known TeV sources

0

5

10

15

20

25

30

1day 1month 0.5 yr 1yr 2yr 4yr

HAWC Observation Time

# o

f C

&G

AG

N >

5 s

igm

a

StandardDeviations


GLAST AGNs

Dermer & Davis, 1999

• BL Lacs will be largest fraction of GLAST AGN.• Many will not be known at other wavelengths.• GLAST localization at flux threshold ~20’.• HAWC sensitivity extrapolated as E-2 down to

100 MeV is ~ GLAST flux threshold.• HAWC detection of GLAST sources would

constrain redshift, location, and variability as well as point to targets for air Cherenkov telescopes.


Energy Measurement

Average Energy vs Compactness

Milagro is sensitive to energy above the median detected energy of 3 TeV.

HAWC should have similar capabilities above it’s median energy of 250 GeV.


GRBs Rate of Satellite Triggers

is Low– SWIFT 2/week – GLAST GBM 4/week

but ~4o position error– GLAST LAT detection

(10 MeV) ~1/week with rapid positions ~1/month

HAWC fov ~1/6 of sky and duty factor ~100% so ~1 GRB/week is searched for VHE emission

HAWC will detect even high z GRBs IF VHE fluence is ~ keV fluence Lines are 5sensitivity to a known

location within 20o of zenith


High Energy Component in GRBsCombined EGRET-BATSE observation shows a new high energy component with hard spectrum and more fluence. (Gonzalez, 2003 Nature 424, 749)

The highest energy gamma-ray detected by EGRET from a GRB was ~20 GeV and was over an hour late. (Hurley, 1994 Nature 372, 652)

Milagrito’s > 650 GeV observation implies a new mechanism with greater fluence than synchrotron. (Atkins, 2003, Ap J 583 824)

GRB940217

GRB970417

GRB941017


VHE & GRBs

VHE Prompt emission constrains bulk Lorentz factors due to opacity in source

VHE early afterglow probes B field and electron energy densities

VHE lightcurve constrains quantum gravity

Razzaque, Meszaros & Zhang 2004

Zhang & Meszaros 2001

1min

1 hr

1 day

1month

HAWC Median Energy

HAWC Median Energy


Searching for VHE transients HAWC data can be searched for VHE transient within a few seconds Milagro search yields model dependent limit on VHE fluence from GRBs Model assumptions will be better constrained by SWIFT and GLAST

redshift T90 Eiso

(1) Assumptions:

(2) Predictions:

(3) Upper Limit on VHE Emission:


Other Transients

X-ray binaries– PSR1259-63 has low

duty cycle as observed by HESS for few months out of 3.4 year elliptical orbit

Microquasars– Variable at other

wavelengths


HESS Galactic Sources PWN, SNR, & UnID Most HESS detections

in the Galactic Plane are extended sources

Flux of HESS Sources is 2-20% of Crab Flux >300 GeV

Largest Source is Vela Jr with diameter of 2 degrees (F. Aharonian et al., Astron. Astrophys. 437 (2005) L7-L10)


EGRET Diffuse Model

Milagro excess in overlapping 5.9o bins in left fig. Milagro excess convolved with 0.75o psf in right fig.

Milagro Galactic Source

HEGRA detected TeV Source: TEV J2032_4130.

PSF


EGRET Unidentified Sources & Milagro Morphology

> 100 MeV/cm2s 1 3EG J2016+3657 (34.7 ± 5.7) x 10-8 2.092 3EG J2020+4017 (123. ± 6.7) x 10-8 2.08 3 3EG J2021+3716 (59.1 ± 6.2) x 10-8 1.864 3EG J2022+4317 (24.7 ± 5.2) x 10-8 2.315 3EG J2027+3429 (25.9 ± 4.7) x 10-8 2.286 3EG J2033+4118 (73.0 ± 6.7) x 10-8 1.967 3EG J2035+4441 (29.2 ± 5.5) x 10-8 2.08

1

2

3

4

5

6

7

3rd EGRET Catalog sources shown with 95% position error circle.

Flux of maximum point: 500mCrab(May be extended)


Molecular Clouds– GLAST predicted to

detect >100 molecular clouds (Torres, et al 2005)

– Measures ratio of CO to Molecular Hydrogen and samples cosmic ray spectrum outside solar neighborhood

LMC and SMC Starburst Galaxies Galaxy Clusters

VHE Emission from Cosmic Rays

Maddalena, 1986


Milagro’s Observation of the Galactic Plane (-2O<b<2O)

Consider Region l = 20O-100O

Weighted Map: 7.5

Exclude the Cygnus Region: l=20O-75O

Weighted Map: 5.8

Galactic longitude 20-75 excludes Cygnus region Galactic longitude 20-100 includes Cygnus region

=1.42 +/- .26


Integral Flux: Milagro & EGRET

E-2.51±0.05

R1 (Gal. Long. 40 to 100 deg) Based on 3ys of data, 4.5 Flux(>3.5 TeV)

= (6.8±1.5±2.2)x10-11 cm-2 sec-1 sr-1

Spectral Index to connect with EGRET = -2.61± 0.03±0.05

With outriggers we can measure the spectrum at TeV energies

2 more years of data needed for ±0.1 on spectral index at TeV energies

R2 (Gal. Long. 140 to 200 deg) Flux(>3.5 TeV)

< 4 x 10-11cm-2 sec-1 sr-1 (99% c.l.) Spectral index to connect with EGRET

< -2.66 (99% c.l.) Not yet a crisis but spectrum may be

softer in outer Galaxy Additional data will tellSubmitted to PRL



Summary

Water Cherenkov Technique has been proven to work and is discovering new VHE phenomena

Future Water Cherenkov Detectors can have the sensitivity to – Detect multiple sources daily – Survey the sky for pt sources >1% of the Crab flux

above 250 GeV in 2 years (5 )– Search 2 sr of the sky for short duration transients

with nearly 100% duty factor– Explore the morphology of extended sources such as

the Galactic plane and molecular clouds

Documents

Astrophysics with 2 sr and 24/7 VHE Detectors