Recent results from the Milagro TeV gamma-ray observatory Pablo Saz Parkinson Santa Cruz Institute for Particle Physics University of California, Santa Cruz La Thuile, 18 March 2005

Pablo Saz Parkinson, Recontres de Moriond Outline Introduction: The Milagro Gamma-ray Observatory (astro-ph/0110513) Recent Results VHE emission from the Galactic Plane (astro-ph/0502303) Other extended Sources (astro-ph/0503244) Gamma Ray Bursts (astro-ph/0503270) Future (astro-ph/0403096) Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

Current Milagro Collaboration List A. Abdo7, B. Allen1, D. Berley2, E. Blaufuss2, S. Cassanova4, D.G. Coyne3, T. DeYoung2, B.L. Dingus4, D.E. Dorfan3, R.W. Ellsworth5, M.M. Gonzalez6, J.A. Goodman2, E. Hays2, C.P. Lansdell2, J.T. Linnemann7, J.E. McEnery8, A.I. Mincer9, P. Nemethy9, D. Noyes2, J.M. Ryan10, P. Saz Parkinson3, A. Shoup1, G. Sinnis4, A.J. Smith2, G.W. Sullivan2, V. Vasileiou2, G. Walker4, D.A. Williams3, G.B. Yodh1 Department of Physics and Astronomy, University of California, Irvine. Department of Physics, University of Maryland. Santa Cruz Institute for Particle Physics, University of California, Santa Cruz. Group P-23, Los Alamos National Laboratory. Department of Physics and Astronomy, George Mason University. Department of Physics, University of Wisconsin. Department of Physics and Astronomy, Michigan State University. NASA Goddard Space Flight Center. Department of Physics, New York University. Department of Physics, University of New Hampshire. Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

The Milagro TeV observatory 2630 m above sea level in the Jemez Mountains, Los Alamos, New Mexico Operational since 2000 (with outriggers since 2003) Duty cycle greater than 90% ~ 2sr field of view Angular resolution of 0.75 degrees (0.45 with outriggers) Energy: ~ 100 GeV – 100 TeV (median ~ 2.5 TeV) 8” PMTs with “baffles” 2.8 x 2.8 m spacing Top Layer: 450 PMTs, 1.5 m deep Bottom Layer: 273 PMTs, 6.5 m deep Outriggers: 175 black plastic tanks each with a PMT, spread over 40,000 m2 Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

Pablo Saz Parkinson, Recontres de Moriond Galactic Plane EGRET All-sky survey above 100 MeV EGRET diffuse GeV flux (in black) Milagro exposure (in red) Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

g-rays from Galactic Plane significance (s) 4.5 s excess for the “Milagro inner galaxy” ~ 4.7 x 10-5 of CR flux First detection of the Galactic plane at TeV energies. Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

Profile and Energy Spectrum Consistent with extrapolation from EGRET Any rapidly rising component to explain >1 GeV excess cannot continue to 1 TeV Previous upper limits in this energy range well above extrapolation Submitted to PRL astro-ph/0502303 Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

Milagro All Sky Survey December 2000 to November 2003 Raw Significance (standard deviations) 3EG J0520+2556? RA=79.90, Dec=26.80 4.9 s Mrk 421 Crab Astrophysical Journal 608, 680 (2004) Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

Extended source search Apply standard event selection Vary source bin size from 2.1o (optimal for point sources) to 5.9o in steps of 0.2o Data set June 2000 to May 2004 1269 days live time Two sources appear with high significance: 3EG J0520+2556 and Cygnus Region Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

3EG J0520+2556? Preliminary RA = 79.8o±0.4o±0.15o J0520+2556 DEC = 26.0o±0.4o±0.10o Consistent with EGRET location For Gaussian source profile s = 0.8o±0.4o 5.9s excess for 2.9o bin size. Probability of excess anywhere in sky at any bin size 7 x 10-3 Flux ~0.85 x Crab Compatible with Whipple limit given source extent Accumulation of excess consistent with steady source J0520+2556 Crab Smoothed with 0.75o Gaussian Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

Pablo Saz Parkinson, Recontres de Moriond Cygnus Region Preliminary 5.5s excess for 5.9o bin size (2% chance for whole sky at any bin size) RA ~ 308o, Dec ~ 42o, consistent with steady source Consistent with diffuse emission from region of high density matter Brightest GeV EGRET source in the northern sky Galactic plane emission still significant with this region excluded Flux ~2 x Crab Nebula flux significance (s) Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

Pablo Saz Parkinson, Recontres de Moriond Milagro GRB Search Evidence for TeV emission from GRB 970417a seen by Milagrito 37 satellite detected GRBs have been within 45 degrees of zenith at Milagro from 2000 to 2005 Fewer than Milagrito because of BATSE’s demise No high energy emission is detected from any of the bursts Analysis of the most recent bursts still preliminary Constraints on TeV emission are most interesting for GRB with known redshift 5 have measured redshift z = 0.45, 0.859,1.01, 2.03, 2.04 Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

GRB 010921 First afterglow detected from HETE-localised burst Spectrum of the host galaxy measured by Palomar —> z = 0.45 Closest burst to fall in Milagro field of view Zenith angle of 10 degrees at Milagro astro-ph/0503270 HETE spectrum Milagro 99% c.l. upper limits Stecker & de Jager 1998 Primack et al. 2004 Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

Search for VHE GRB emission Swift launched in November 2004 It will detect ~100 bursts/year Already 2 Swift bursts in Milagro field of view. Analysis is ongoing. Redshift determination should be possible for most Swift bursts We expect ~15-20 GRBs per year in Milagro FOV with redshift information Larger sample by factor of ~4 Flux (even if limit) will be meaningful on each burst Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

Pablo Saz Parkinson, Recontres de Moriond Summary and Future Milagro has been operational since 2000 Operating with “outriggers” since 2003 Crab and Mkn 421 detected Galactic Plane observed at VHE for first time Two diffuse source candidates reported Ongoing search for Gamma-ray burst emission for the next two years of Swift mission Proposing move to higher altitude (~4500 m) site with O(10) increase in sensitivity Longer term — HAWC (astro-ph/0403096) Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

EXTRA SLIDES EXTRA SLIDES Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

Bkg Rejection – “Compactness” Data Proton (MC) Gammas (MC) Compactness PMTs > 2 PE Maximum PE C = using just bottom layer PMTs C > 2.5 removes 90% of the protons and keeps 50% of the gammas Astrophysical Journal 595, 803–811 (2003) Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

Most significant locations Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

Pablo Saz Parkinson, Recontres de Moriond Milagro Outriggers 175 black plastic tanks deployed over 20,000 m2 Each lined with Tyvek and filled with filtered water A single 8” PMT in each Operating since 2003 Pablo Saz Parkinson, Recontres de Moriond 12 January 2019

Pablo Saz Parkinson, Recontres de Moriond EGRET source Pablo Saz Parkinson, Recontres de Moriond 12 January 2019