Gamma-rays from Dark Matter

Annihilation in Milky Way Satellites

Louie Strigari UC Irvine, Center for Cosmology

Getting Prepared for GLAST

UCLA, 5.22.2007

Collaborators: James Bullock, Manoj Kaplinghat (UC Irvine), Savvas Koushiappas (LANL)

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Dark Matter in the Milky Way

Dark Matter Annihilation Flux = Particle Physics x

Astrophysics

Louie Strigari, UC Irvine GLAST, UCLA 5.22.2007

Relic abundance set by annihilation cross section

Dark Matter Annihilation Sites

Galactic center: astrophysical uncertainties, backgrounds [e.g. Bergstrom, Ullio, Buckley 1999; Hooper & Dingus 2004; Profumo 2005]

Dark substructures: [Calcaneo-Roldan & Moore 2000, Tasitsiomi & Olinto 2002; Stoehr et al. 2003; Koushiappas, Zentner, & Walker 2003; Pieri, Branchini, Hofmann 2005, Koushiappas 2006; Baltz, Taylor, Wai 2006, Diemand, Kuhlen, Madau 2006]

Luminous satellites: [Baltz et al. 2000; Tyler 2002; Evans, Ferrer, Sarkar 2003, Bergstrom & Hooper 2005, Pieri & Branchini 2004, Profumo & Kamionkowski 2006, Colafrancesco, Profumo, Ullio 2006, Strigari, Koushiappas, Kaplinghat, Bullock 2007]

Louie Strigari, UC Irvine GLAST, UCLA 5.22.2007

Orders of magnitude more dark matter substructures in numerical simulations than observed Milky Way Satellites: The ``Missing Satellites Problem’’

Possible that up to 3x more exist at these luminosities [e.g. willman et al 2004]

Census of Milky Way Satellites (Circa 2003)

Name Year DiscoveredLMC 1519SMC 1519Sculptor

1937Fornax 1938Leo II 1950Leo I 1950Ursa Minor 1954Draco 1954Carina 1977Sextans 1990Sagittarius 1994

Louie Strigari, UC Irvine GLAST, UCLA 5.22.2007

Walker et al ApJ 2006

Kinematics of Milky Way Satellites

Satellites are modeled with the jeans equation:

Louie Strigari, UC Irvine GLAST, UCLA 5.22.2007

Klypin, Kravtsov,

Bullock, Primack 01

Klypin, Kravtsov,

Bullock, Primack 01

Highest resolution simulations indicate that the inner slope is in the range 0.7-1.2 [Navarro et al. 2004, Diemand et al. 2005]

Scale as 1/r in the central regions. ‘NFW’ profile

break radius

outer radius

Density Profiles of CDM Halos

Louie Strigari, UC Irvine GLAST, UCLA 5.22.2007

Strigari et al. ApJ 2006

Fornax

Line-of-sight velocity dispersion

All dsphs fit by both cores and cusps, but focus on cusps for CDM

Louie Strigari, UC Irvine GLAST, UCLA 5.22.2007

Parameter Degeneracies

Louie Strigari, UC Irvine GLAST, UCLA 5.22.2007

Strigari, Koushiappas, Bullock, Kaplinghat PRD 2007

Masses of the luminous satellites

Strigari, Bullock, Kaplinghat, Diemand, Kuhlen, Madau 2007

Best-constrained parameter is the mass within

about 600 pc.

Louie Strigari, UC Irvine GLAST, UCLA 5.22.2007

Constraints on Astrophysical Parameters

Louie Strigari, UC Irvine GLAST, UCLA 5.22.2007

Strigari, Koushiappas, Bullock, Kaplinghat PRD 2007

Two order of magnitude boost?

Fluxes are ‘boosted’ with substructure

LS, Koushiappas, Bullock, Kaplinghat PRD 2007

Boost factor

Louie Strigari, UC Irvine GLAST, UCLA 5.22.2007

How will we know that we’ve detected dark matter?

Consider the ratio of fluxes from different dSphs

1) Fluxes must fall within the region determined by the CDM prior

2) Flux ratio is less sensitive to astrophysical processes

Louie Strigari, UC Irvine GLAST, UCLA 5.22.2007

Census of Milky Way Satellites (Circa 2007)

Name Year DiscoveredLMC 1519SMC 1519Sculptor

1937Fornax 1938Leo II 1950Leo I 1950Ursa Minor 1954Draco 1954Carina 1977Sextans 1990Sagittarius 1994Canis Major 2003Ursa Major I 2005Willman I

2005Ursa Major II 2006Bootes 2006Canes Venatici I 2006Canes Venatici II2006Coma 2006Leo IV 2006Hercules

2006Leo T 2007 Louie Strigari, UC Irvine KICP,

5.18.2007

Belukurov et al 2006

• New data sets strongly constrain mass and gamma-rays fluxes from luminous satellites

• How massive are the new, low-luminosity dwarfs? Will these be promising targets? Stay tuned…..

Concluding remarks

Louie Strigari, UC Irvine GLAST, UCLA 5.22.2007