The HAWC (High Altitude Water Cherenkov) Observatory

The HAWC Collaboration Instituto Nacional de Astrofísica Óptica y Electrónica (INAOE): Alberto Carramiñana, Eduardo Mendoza, Luis Carrasco, William Wall, Daniel Rosa, Guillermo Tenorio Tagle, Sergey Silich Universidad Nacional Autónoma de México (UNAM): Instituto de Astronomía: Octavio Valenzuela, V ladimir Avila-Reese, Marco Martos, Maria Magdalena Gonzalez, Sergio Mendoza, Dany Page, William Lee, Hector Hernández, Deborah Dultzin, Erika Benitez Instituto de Física: Arturo Menchaca, Rubén Alfaro, Varlen Grabski, Andres Sandoval, Ernesto Belmont. Arnulfo Matinez-Davalos Instituto de Ciencias Nucleares: Lukas Nellen, Gustavo Medina- Tanco, Juan Carlos D’Olivo Instituto de Geofísica: José Valdés Galicia, Alejandro Lara, Rogelio Caballero Benemérita Universidad Autónoma de Puebla:Humberto Salazar, Arturo Fernández, Caupatitzio Ramirez, Oscar Martínez, Eduardo Moreno, Lorenzo Diaz, Alfonso Rosado, Universidad Autónoma de Chiapas: Cesar Álvarez, Eli Santos Rodriguez, Omar Pedraza Universidad de Guadalajara: Eduardo de la Fuente Universidad Michoacana de San Nicolás de Hidalgo: Luis Villaseñor, Umberto Cotti, Ibrahim Torres, Juan Carlos Arteaga Velazquez Centrode Investigacion y de Estudios Avanzados: Arnulfo Zepeda Universidad de Guanajuato: David Delepine, Gerardo Moreno, Edgar Casimiro Linares, Marco Reyes, Luis Ureña, Mauro Napsuciale, Victor Migenes University of Maryland: Jordan Goodman, Andrew Smith, Greg Sullivan, Jim Braun, David Berley Los Alamos National Laboratory: Gus Sinnis, Brenda Dingus, John Pretz University of Wisconsin: Teresa Montaruli, Stefan Westerhoff, Segev Ben Zvi, Juanan Aguilar, Dan Wahl University of Utah: Dave Kieda, Wayne Springer Univ. of California, Irvine: Gaurang Yodh’ Michigan State University: Jim Linnemann, Kirsten Tollefson, Dan Edmunds George Mason University: Robert Ellsworth Colorado State University: Miguel Mustafa, Dave Warner University of New Hampshire: James Ryan Pennsylvania State University: Tyce DeYoung, Patrick Toale, Kathryne Sparks University of New Mexico: John Matthews, William Miller Michigan Technical University: Petra Hüntemeyer NASA/Goddard Space Flight Center: Julie McEnery, Elizabeth Hays, Vlasios Vasileiou Georgia Institute of Technology: Ignacio Taboada, Andreas Tepe HAWC Technical Staff: Michael Scheinder, Scott Delay Mexico USA

The HAWC Collaboration Instituto Nacional de Astrofísica Óptica y Electrónica (INAOE): Alberto Carramiñana, Eduardo Mendoza, Luis Carrasco, William Wall, Daniel Rosa, Guillermo Tenorio Tagle, Sergey Silich Universidad Nacional Autónoma de México (UNAM): Instituto de Astronomía: Octavio Valenzuela, V ladimir Avila-Reese, Marco Martos, Maria Magdalena Gonzalez, Sergio Mendoza, Dany Page, William Lee, Hector Hernández, Deborah Dultzin, Erika Benitez Instituto de Física: Arturo Menchaca, Rubén Alfaro, Varlen Grabski, Andres Sandoval, Ernesto Belmont. Arnulfo Matinez-Davalos Instituto de Ciencias Nucleares: Lukas Nellen, Gustavo Medina- Tanco, Juan Carlos D’Olivo Instituto de Geofísica: José Valdés Galicia, Alejandro Lara, Rogelio Caballero Benemérita Universidad Autónoma de Puebla:Humberto Salazar, Arturo Fernández, Caupatitzio Ramirez, Oscar Martínez, Eduardo Moreno, Lorenzo Diaz, Alfonso Rosado, Universidad Autónoma de Chiapas: Cesar Álvarez, Eli Santos Rodriguez, Omar Pedraza Universidad de Guadalajara: Eduardo de la Fuente Universidad Michoacana de San Nicolás de Hidalgo: Luis Villaseñor, Umberto Cotti, Ibrahim Torres, Juan Carlos Arteaga Velazquez Centrode Investigacion y de Estudios Avanzados: Arnulfo Zepeda Universidad de Guanajuato: David Delepine, Gerardo Moreno, Edgar Casimiro Linares, Marco Reyes, Luis Ureña, Mauro Napsuciale, Victor Migenes University of Maryland: Jordan Goodman, Andrew Smith, Greg Sullivan, Jim Braun, David Berley Los Alamos National Laboratory: Gus Sinnis, Brenda Dingus, John Pretz University of Wisconsin: Teresa Montaruli, Stefan Westerhoff, Dan Wahl University of Utah: Dave Kieda, Wayne Springer Univ. of California, Irvine: Gaurang Yodh Michigan State University: Jim Linnemann, Kirsten Tollefson, Dan Edmunds George Mason University: Robert Ellsworth University of New Hampshire: James Ryan Pennsylvania State University: Tyce DeYoung, Patrick Toale, Kathryne Sparks University of New Mexico: John Matthews, William Miller Michigan Technical University: Petra Hüntemeyer NASA/Goddard Space Flight Center: Julie McEnery, Elizabeth Hays, Vlasios Vasileiou Georgia Institute of Technology: Ignacio Taboada, Andreas Tepe HAWC Technical Staff: Michael Scheinder, Scott Delay USA Mexico

HAWC Science Objectives Discover the origin of cosmic rays by measuring gamma-ray spectra to 100 TeV Hadronic sources have unbroken spectra beyond 30-100 TeV Galactic diffuse gamma rays probe the distant cosmic ray flux Understand particle acceleration in astrophysical jets with wide field of view, high duty factor observations. Trigger Multi-Messenger/Multi-Wavelength Observations of Flaring Active Galactic Nuclei (including TeV orphan flares) Detect Short and Long Gamma-Ray Bursts Explore new physics via HAWC’s unbiased survey of ½ the sky. Increase understanding of TeV sources to search for new physics. Study the local TeV cosmic rays and their anisotropy. HAWC Collaboration April 2010

HAWC Science Gamma Astronomy with wide FoV and high duty cycle: Understand particle acceleration in AGN and GRB jets through the discovery of short and long GRBs at > 100 GeV energies and MWL Target of Opportunity programs on flares; Understand the sources of Galactic CRs through the observation of galactic sources including extended ones (SNRs in molecular clouds, superbubbles) Studies on EBL and diffuse gamma emissions. Hadronic Astronomy: find evidence of proton acceleration in Galactic CR sources (eg understanding Milagro regions with larger statistics) Exotic phenomena photon oscillations in axion-like particles through EBL studies; Lorentz invariance; Slow Monopoles and Q-balls.

Comparison of Gamma-Ray Detectors Low Energy Threshold EGRET/Fermi Space-based (Small Area) “Background Free” Large Duty Cycle/Large Aperture Sky Survey (< 10 GeV) AGN Physics Transients (GRBs) < 300 GeV High Sensitivity HESS, MAGIC, VERITAS Large Effective Area Excellent Background Rejection Low Duty Cycle/Small Aperture High Resolution Energy Spectra up to ~20 TeV Studies of known sources Surveys of limited regions of sky Large Aperture/High Duty Cycle Milagro, Tibet, ARGO, HAWC Moderate Area Excellent Background Rejection Large Duty Cycle/Large Aperture Unbiased Sky Survey Extended sources Transients (GRB’s) > 100 GeV High Energies up to 100 TeV

Milagro and HAWC Intro Milagro was a first generation wide-field gamma-ray telescope: Proposed in 1990 Operations began in 2001/04 Developed g/h separation Discovered: more than a dozen TeV sources diffuse TeV emission from the Galactic plane a surprising directional excess of cosmic rays Showed that most bright galactic GeV sources extend to the TeV Best instrument for hard spectrum and extended sources HAWC is the next logical step It will be 15x more sensitive than Milagro It can be running in 3 yrs (with Fermi) HAWC Collaboration April 2010

NSF Review Panel December 2007: HAWC Science Reviews PASAG - October 2009 HAWC is a moderate-priced initiative that will carry out excellent astrophysics using a novel technique; there is also the possibility of surprising results of relevance for particle physics. NSF Review Panel December 2007: “There is a strong case for HAWC as a wide field of view survey instrument at the TeV scale.” They concluded the project is well understood and technically ready with a strong collaboration.

Abdo et al. ApJL (accepted) Milagro Results 15 TeV associations out of 35 likely galactic sources in our field of view Abdo et al. ApJL (accepted) arXiv:0904.1018

GeV Pulsars Produce TeV PWN GeV Emission is pulsed & due to rotation axis misaligned with Magnetic Dipole of ~1012 G TeV Emission is produced by particles further accelerated in the shock interacting with the ambient medium. IMPLICATIONS TeV PWN are prevalent with GeV pulsars GeV emission has broad beam

Geminga (J0634.0+1745) Brightest GeV source of 34 searched is Geminga Old (300 kyr) PWN and nearby (250 pc) ~10 parsec extent is similar to HESS observations of more distant PWN 10 parsecs 68% PSF Milagro HAWC Milagro sees Geminga at 30% of the Crab at ~20 TeV while IACTs have a limit of ~1% of the Crab at >200 GeV

Geminga with HAWC Brightest GeV source of 34 searched is Geminga Old (300 kyr) PWN and nearby (250 pc) ~10 parsec extent is similar to HESS observations of more distant PWN 10 parsecs HAWC 68% PSF Milagro Milagro sees Geminga at 30% of the Crab at ~20 TeV while IACTs have a limit of ~1% of the Crab at >200 GeV

Milagro Spectrum of the Crab Milagro Results Milagro Spectrum of the Crab HESS Crab data/fit Energy reach from ~3TeV to >100 TeV Peak sensitivity for E-2 source at ~100 TeV Milagro 68% HAWC

Milagro Spectrum of the Crab w/HAWC Energy reach from ~3TeV to >100 TeV Peak sensitivity for E-2 source at ~100 TeV Milagro 68% HAWC HEGRA Crab data/fit

MGRO J2019+37/ 0FGL J2020.8+3649 Milagro Results In Milagro J2019+37 is 700 mCrab The flux in γ/s >200 GeV is 95mCrab HESS Crab fit: (Io =3.76x10-7,Γ=2.39, Ec=14.1 TeV) Milagro 68% HAWC This source is almost as bright as the Crab at Milagro’s energy

MGRO J2019+37/ 0FGL J2020.8+3649 In Milagro J2019+37 is 700 mCrab The flux in γ/s >200 GeV is 95mCrab HESS Crab fit: (Io =3.76x10-7,Γ=2.39, Ec=14.1 TeV) Milagro 68% HAWC

MGRO J1908+06 Milagro Results Ecut 14 40 (1σ) 56 (2σ) Milagro 68% HAWC A Milagro discovered source now seen by HESS and VERITAS Using HESS spectrum of -2.1 as input, Milagro requires a cut-off at <40(56) TeV (N.B. Milagro measures a larger flux, possibly because we are integrating over a larger area than HESS)

Milagro 3σ source detected at 20σ HAWC (3months) HAWC Simulation Milagro 3σ source detected at 20σ HAWC (3months)

Milagro 3σ source detected at 20σ HAWC (3months) HAWC Simulation Milagro 3σ source detected at 20σ HAWC (3months)

Milagro 3σ source detected at 20σ HAWC (3months) HAWC Simulation Milagro 3σ source detected at 20σ HAWC (3months)

Milagro Results Diffuse TeV Excess Whether or not there is a GeV excess, Milagro sees a TeV excess. This excess could be due to unresolved sources or hadronic cosmic rays hitting matter near their source. If the TeV excess has a flat spectrum, it is likely hadronic in origin and may not be detectable at GeV energies. With help from ACTs and Fermi we will do a source subtraction This will allow us to measure the spectrum and morphology of the excess This study could point to regions of the galaxy with a higher concentration of cosmic rays than near earth - pointing to sites of acceleration. Abdo et. al ApJ 2008

Active Galactic Nuclei Flares HAWC makes daily observations without weather, moon, or solar constraints. HAWC’s 5 σ sensitivity for Mrk 421 is (10,1,0.1) Crab in (3 min, 5 hrs, 1/3 yr) HAWC will notify multiwavelength observers in real time of flaring AGN Study correlations with x-rays, etc to determine emission mechanisms Discovery potential for orphan TeV flares producing neutrinos and UHECR X-ray flux Milagro flux Quadratic or Linear? Synchrotron Self Compton or External Compton? Crab Flux Milagro’s 9σ Mrk421 1 month

Distinguishing New Physics from Astrophysics Violation of Lorentz Invariance OR Energy Dependent Particle Acceleration HAWC will detect multiple flaring extragalactic sources (AGN and GRBs) to resolve redshift vs source mechanisms Cosmological Star Formation OR Spectral Cut- offs in the source HAWC will trigger multiwavelength observations of flaring AGN to obtain best measured and modeled TeV spectra Continuum Gamma-Ray Emission from Dark Matter Annihilation OR Astrophysical Source HAWC will search for time variability which would imply an astrophysical source

Cosmic Ray Observations Milagro Results Cosmic Ray Observations Heliotail Geminga Significance (σ’s) Milagro data show an unexpected anisotropy (PRL 101, 221101, 2008) No weighting or cutting. Map dominated by charged cosmic rays. 10o smoothing, looking for intermediate sized features. Two regions of excess 15.0σ and 12.7σ. Fractional excess of 6x10-4 (4x10-4) for region A(B).

Milagro Results 21 http://people.roma2.infn.it/~aldo/RICAP09_trasp_Web/Vernetto_ARGO_RICAP09ar.pdf

Cosmic Ray Anisotropy Data are not consistent with: Milagro Results Cosmic Ray Anisotropy Data are not consistent with: Mostly gamma-rays –> data looks hadronic with cosmic ray spectrum –> flatter, with ~10 TeV cutoff HAWC with better energy resolution and gamma- hadron rejection can: Measure the spectrum with much higher precision Measure the gamma-ray fraction Understanding this is important for Dark Matter Searches HAWC Collaboration April 2010

Geminga as a Local Cosmic Ray Source “If the observed cosmic ray excess does indeed arise from the Geminga SN explosion, the long–sought “smoking gun” connecting cosmic rays with supernovae would finally be at hand. - Salvati and Sacco (AA 09) The confirmed presence of a nearby, ancient source of high-energy electrons and positrons immediately suggests an explanation for the positron excess. -Yüksel, Kistler, Stanev arXiv:0810.2784 PAMELA’s positron excess Fit well given Milagro’s flux from Geminga HAWC Collaboration April 2010