Cosmology with Ground-Based Cherenkov Telescopes Wei Cui (Purdue University)

Outline Indirect Dark Matter Search Signatures of annihilation of DM particles in astronomical settings Observing plan Extragalactic Background Light Absorption of gamma rays from bright distant sources

Dark Matter Search Triangle Three complementary approaches Produce neutralino in laboratory Directly detect DM WIMP in specialty detectors in (underground) labs Indirect detection of astrophysical gamma rays from DM annihilation

The Sky at Different Wavelengths Visible Light Microwave

TeV Sources Blazar:14 FR I:1 PWN:6 SNR:5 MG:2 Be Bin.:1 Unid.:15 Cui 2006

Gamma-Ray Signals

Annihilation Line?

Very Energetic Radiation Imaging Telescope Array System (VERITAS) 85 m 109 m 85 m 35 m T1 T4 T2 T3

Recent Development – Galactic Center HESS observations of galactic center (HESS J ) from 2003/4 find bulk of emission must have non-dark-matter origin (Aharonian et al.,Phys. Rev. Lett. 97, (2006). Spectrum appears to have simple power law dependence in contrast to expectation for gamma rays produced by neutralino annihilation Galactic Center may be difficult place to search for Dark Matter Aharonian et al. PRL 97, (2006)

Potential Targets Dwarf Galaxies – large mass to light ratio Globular Clusters – dense core gives rise to DM cusp? Galaxy Clusters DM dominated known density profile Possible DM cusp in cluster center Nearby Galactic Nuclei – possible cuspy DM near center

Results with Whipple

Observing Plan with Basecamp Observations 2006 M15(GC): 10 hours, September, B weather, 2 telescopes Targets 2007 – Survey several sources Spring, 2007 Ursa Minor(DG) – 24 hours * Draco(DG) – 21 hours * M87(RG) – 50 hours * ; comes for free as part of non-blazar proposal Fall, 2007 M15(GC) – allocation to be determined; hoping for 30 hrs. in Oct Targets 2008 – Plan also will be guided by GLAST results! Sextans(DG) – Jan, 2008? M13(GC) – Apr, 2008? Coma (CL)? Follow up on minihaloes should GLAST be fortunate enough to find evidence early on GC ≡ Globular Cluster, DG ≡ Dwarf Galaxy, CL ≡ Galaxy Cluster, RG ≡ radio galaxy *  Primary Target

Cosmic Background Ressel & Turner, K CMBR Cosmic X-ray Optical/IR Radio 10 GeV – 1 TeV Use TeV beams from, e.g., blazars, to probe the IR background

Tentative Evidence Krennrich et al Absorption features?

Universe more transparent to TeV gamma rays? lower limits from galaxy counts measure- ments upper limits Reference shape HESS limits X X Hoffman 2005

Intrinsic vs Extrinsic Data Theory IR de-absorbed spectrum Mrk 421 Blazejowski et al Courtesy of Alex Konopelko

Blazar Key Science Project 115 hrs/Year Total, Three Components: (a)40 hrs/year: Multiwavelength Campaign for >2 Crab Flares  Sample Temporal Evolution of Flux and Spectra. (b)40 hrs/year: Intensive Observations of 4 Sources in 2 Years Object RA(J2000) Dec(J2000) z Class 1ES HBL 1ES HBL BL HBL H HBL [1ES ] HBL (c) 35 hrs/year: Explore Other Blazar Classes Object RA(J2000) Dec(J2000) z Class 1ES HBL 1ES HBL BL Lacertae IBL B HSFRQ 1ES HSFRQ 1ES HBL BL HBL W Comae IBL 3C 66A ? IBL Mrk HSFRQ WGA J

Smithsonian Astrophysical Observatory * Smithsonian Astrophysical Observatory * Adler Planetarium Adler Planetarium Purdue University * Purdue University * Barnard College, NY Barnard College, NY Iowa State University * Iowa State University * DePauw University, IN DePauw University, IN Washington University, St. Louis * Washington University, St. Louis * Grinnell College, IA Grinnell College, IA University of Chicago * University of Chicago * University of California, Santa Cruz University of California, Santa Cruz University of Utah * University of Massachussetts University of Massachussetts University of California, Los Angeles * University of California, Los Angeles * Cork Institute of Technology Cork Institute of Technology McGill University, Montreal * McGill University, Montreal * Galway-Mayo Institute of Technology Galway-Mayo Institute of Technology National University of Ireland, Dublin * National University of Ireland, Dublin * National University of Ireland, Galway National University of Ireland, Galway University of Leeds * University of Leeds * Argonne National Lab Argonne National Lab Associate Members Associate Members Project office: Whipple observatory SAO VERITAS Collaboration ~65 members in more than 20 institutions Funding from NSF/DOE/Smithsonian/PPARC/SFI/NSERC