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: 14FR I: 1PWN: 6SNR: 5MG: 2Be Bin.: 1Unid.: 15

Cui 2006

Gamma-Ray Signals

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Annihilation Line?

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Very Energetic Radiation Imaging Telescope Array System (VERITAS)

85 m

109 m

85 m35 m

T1

T4

T2

T3

Recent Development – Galactic Center

HESS observations of galactic center (HESS J1745-290) from 2003/4 find bulk of emission must have non-dark-matter origin (Aharonian et al.,Phys. Rev. Lett. 97, 221102 (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 97,221102 (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 VERITAS @ Basecamp

Observations 2006M15(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, 2007M15(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, 1989

2.7 K

CMBR

Cosmic X-ray

Optical/IRRadio

10 GeV – 1 TeV

Use TeV beams from, e.g., blazars, to probe the

IR background

Tentative Evidence

Krennrich et al. 2001

Absorption features?

Universe more transparent to TeV gamma rays?

lower limitsfrom galaxy

counts

measure-ments

upperlimits

Reference shape

HESS limits

XX

Hoffman 2005

Intrinsic vs Extrinsic

Data

Theory

IR de-absorbed spectrum

Mrk 421

Blazejowski et al. 2004

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 1218+304 12 21 21.9 +30 10 37 0.182 HBL

1ES 2344+514 23 47 04.8 +51 42 18 0.044 HBL

BL 1101-232 11 03 37.6 -23 29 30 0.186 HBL

H 1426+428 14 28 32.7 +42 40 20 0.129 HBL

[1ES 1959+650] 19 59 59.9 +65 08 55 0.048 HBL

(c) 35 hrs/year: Explore Other Blazar ClassesObject RA(J2000) Dec(J2000) z Class

1ES 0120+340 01 23 08.9 +34 20 50 0.272 HBL

1ES 0806+524 08 09 49.2 +52 18 58 0.138 HBL

BL Lacertae 22 02 43.3 +42 16 40 0.069 IBL

B2 0321+33 03 24 41.2 +34 10 45 0.062 HSFRQ

1ES 1627+40.2 16 29 01.3 +40 08 00 0.271 HSFRQ

  1ES 0033+595 00 35 52.6 +59 50 05 0.086 HBL

BL 0647+250 06 50 46.6 +25 03 00 0.203 HBL

W Comae 12 21 31.7 +28 13 58 0.102 IBL

3C 66A 02 22 39.6 +43 02 07 0.444? IBL

Mrk 1218 08 38 11.0 +24 53 43 0.028 HSFRQ WGA J0838+2453.

Smithsonian Astrophysical Observatory *Smithsonian Astrophysical Observatory * Adler PlanetariumAdler Planetarium Purdue University *Purdue University * Barnard College, NYBarnard College, NY Iowa State University *Iowa State University * DePauw University, INDePauw University, IN Washington University, St. Louis *Washington University, St. Louis * Grinnell College, IAGrinnell College, IA University of Chicago *University of Chicago * University of California, Santa CruzUniversity of California, Santa Cruz

University of Utah *University of Utah * University of MassachussettsUniversity of Massachussetts University of California, Los Angeles *University of California, Los Angeles * Cork Institute of TechnologyCork Institute of Technology McGill University, Montreal *McGill University, Montreal * Galway-Mayo Institute of TechnologyGalway-Mayo Institute of Technology National University of Ireland, Dublin *National University of Ireland, Dublin * National University of Ireland, GalwayNational University of Ireland, Galway University of Leeds *University of Leeds * Argonne National LabArgonne National LabAssociate Members Associate Members

Project office: Whipple observatory SAO Project office: Whipple observatory SAO

VERITAS Collaboration VERITAS Collaboration ~65 members in more than 20 institutions~65 members in more than 20 institutions

Funding from Funding from NSF/DOE/Smithsonian/PPARC/SFI/NSERCNSF/DOE/Smithsonian/PPARC/SFI/NSERC