Indirect Dark Matter Detection with Dwarf Galaxies Neelima Sehgal KIPAC-SLAC/Stanford SnowPAC, Utah 2010 Rouven Essig, NS, Louis Strigari, arxiv: 0902.4750, PRD 80, 023506 (2009) Rouven Essig, NS, Louis Strigari, Marla Geha, Josh Simon (to appear)
Indirect Dark Matter Detection Direct dark matter detection: dark matter interacts with nuclei; look for recoil signal of nuclei signal strength ρ Indirect dark matter detection: dark matter annihilates or decays producing standard model particles signal strength for annihilations ρ 2 (one reason this signal may be promising)
Dwarf Galaxies and Galactic Center are good targets Via Lactea II Simulation (only DM, no baryons) [Diemand et.al.] 800 kpc cube
Dwarf Galaxies and Galactic Center are good targets Via Lactea II Simulation (only DM, no baryons) [Diemand et.al.] visible Milky Way galaxy ~30 kpc some subhalos will form stars and become dwarf galaxies 800 kpc cube
Galactic center brightest, but difficult to disentangle DM signal Dwarfs at high galactic latitude are clean targets Galactic Center in Radio Fermi 1-year sky
Dwarf Galaxies: Advantages Large Signal relatively nearby (~20 kpc to few 100 kpc) DM dominated: high mass-to-light ratio (M/L~100-1000) Low background high galactic latitude small magnetic fields and little gas Also use stellar kinematics to determine dark matter distribution better than galactic center multiple dwarfs allow for confirmation of any signal
Known Nearby Dwarf Galaxies Classical Dwarfs (pre-2005) Ultra-faint Dwarfs (post-2005, SDSS) [Geha]
Existing Data Fermi observes all dwarfs [Geha]
Existing Data Fermi observes all dwarfs 66 kpc 38 kpc 80 kpc Blue: Observed by ACTs VERITAS, MAGIC HESS 24 kpc [Geha]
Existing Data Fermi observes all dwarfs 66 kpc 38 kpc 23 kpc 80 kpc Blue: Observed by ACTs VERITAS, MAGIC HESS 24 kpc IceCube data coming Segue 1: best target? [Geha] Least luminous galaxy known (M/L~1000) [Geha et.al.] (Observed by MAGIC and VERITAS and data is being analyzed )
Draco (discovered 1954) Segue 1 classical dwarf flux Segue 1 data on >200 stellar velocities Current analysis suggests ultra-faint dwarf (discovered 2006) determined from stellar velocities L Segue1 L Draco New stellar data is being analyzed (~65 stars) [Simon et. al.] However, this is preliminary and analysis is still ongoing!
Current Fermi & ACT limits [Essig, NS, Strigari, Geha, Simon] Σv cm 3 s 1 10 19 10 20 10 21 10 22 10 23 10 24 10 25 10 26 FERMI Excl. Segue 1 (preliminary) ΧΧ bb ACT Excl. Draco ACT Prosp. Segue 1 (preliminary) 10 2 10 3 10 4 Fermi data: 9 months of data [Farnier, RICAP 09] [Wang, CINC 09] m Χ GeV Σv cm 3 s 1 ACT data: VERITAS obs. of Draco [0810.1913] 10 19 10 20 10 21 10 22 10 23 10 24 10 25 10 26 ΧΧ W W ACT Excl. Draco ACT Prosp. Segue 1 (preliminary) FERMI Excl. Segue 1 (preliminary) 10 2 10 3 10 4 m Χ GeV Thermal WIMP cross-section: σv =3 10 26 cm 3 s 1
Current Fermi & ACT limits [Essig, NS, Strigari, Geha, Simon] Σv cm 3 s 1 10 19 10 20 10 21 10 22 10 23 10 24 10 25 10 26 FERMI Excl. Segue 1 (preliminary) ΧΧ bb ACT Excl. Draco ACT Prosp. Segue 1 (preliminary) 10 2 10 3 10 4 Fermi data: 9 months of data [Farnier, RICAP 09] [Wang, CINC 09] m Χ GeV Σv cm 3 s 1 ACT data: VERITAS obs. of Draco [0810.1913] 10 19 10 20 10 21 10 22 10 23 10 24 10 25 10 26 ΧΧ W W ACT Excl. Draco ACT Prosp. Segue 1 (preliminary) FERMI Excl. Segue 1 (preliminary) WINO LSP [Kane et.al.] 10 2 10 3 10 4 m Χ GeV Thermal WIMP cross-section: σv =3 10 26 cm 3 s 1
PAMELA e + Theory curve PAMELA Recent anomalies: e +, e - excess No excess FERMI HESS
Implications for DM annihilations DM mass > 1 TeV Annihilation only into charged leptons, NOT p Cross-section ~100-1000 times larger than during thermal freeze-out How can we test if anomalies are from DM? -
Gamma Rays guaranteed from Final State Radiation Distinctive spectrum [Beacom et.al.] [Birkedal et.al.] [Bringmann et.al] Neutrinos guaranteed if,
Σv cm 3 s 1 10 19 10 20 10 21 10 22 10 23 10 24 10 25 10 26 Current Fermi & ACT limits FERMI Excl. Segue 1 (preliminary) ΧΧ Μ Μ ACT Excl. Draco 10 2 10 3 10 4 m Χ GeV PAMELA and Fermi [Meade et. al.] [Essig, NS, Strigari, Geha, Simon] Fermi data: 9 months of data [Farnier, RICAP 09] [Wang, CINC 09] ACT data: VERITAS obs. of Draco [0810.1913] Fermi better at lower masses, ACTs at higher masses
Prospects for MAGIC & VERITAS from Segue 1 [Essig, NS, Strigari, Geha, Simon] Σv cm 3 s 1 10 19 10 20 10 21 10 22 10 23 10 24 10 25 10 26 ΧΧ Μ Μ FERMI Excl. ACT Excl. Draco Segue 1 ACT Prosp. Segue 1 (preliminary) (preliminary) PAMELA and Fermi [Meade et. al.] 10 2 10 3 10 4 m Χ GeV
IceCube Prospects for in ice: [Essig, NS, Strigari, Geha, Simon] (N=Nucleus) Σv cm 3 s 1 10 19 10 20 10 21 10 22 10 23 10 24 10 25 10 26 # of Signal Events ΧΧ Μ Μ Muon Signal Events in IceCube Segue 1 50 10 3 PAMELA and Fermi [Meade et. al.] 10 2 10 3 10 4 m Χ GeV Σv cm 3 s 1 10 19 10 20 10 21 10 22 10 23 10 24 10 25 10 26 ΧΧ Μ Μ IceCube Prosp. Segue 1 ACT Prosp. Segue 1 (preliminary) PAMELA and Fermi [Meade et. al.] 10 2 10 3 10 4 m Χ GeV [see also Sandick et.al.]
How obtain large DM annihilation cross-section? many ways... (e.g. Kane et.al., Ibe et.al.) Sommerfeld enhancement [e.g. Arkani-Hamed et.al; Pospelov, Ritz; Hisano et.al; March-Russell et.al; Cirelli et.al] new particle with m ~ 0.1-1 GeV Produces a long-range force large today small at freeze-out signal potentially enhanced at dwarf! ( saturates when )
Segue 1 can constrain Sommerfeld enhancement [Essig, NS, Strigari, Geha, Simon] Σv cm 3 s 1 10 19 10 20 10 21 10 22 10 23 10 24 10 25 10 26 ΧΧ ΦΦ e e e e ACT Prosp. Segue 1 Sommerfeld, m Φ 1 GeV, Α D 0.1 (preliminary) 10 2 10 3 10 4 m Χ GeV Will probe resonances Β Segue 1 Β Milky Way PAMELA and Fermi [Meade et. al.]
Segue 1 can constrain Sommerfeld enhancement [Essig, NS, Strigari, Geha, Simon] Σv cm 3 s 1 10 19 10 20 10 21 10 22 10 23 10 24 10 25 10 26 ΧΧ ΦΦ e e e e ACT Prosp. Segue 1 Sommerfeld, m Φ 0.1 GeV, Α D 0.1 10 2 10 3 10 4 m Χ GeV Intriguing prospects (preliminary) Β Segue 1 Β Milky Way PAMELA and Fermi [Meade et. al.]
Future in Optical [LSST homepage] LSST: 6-band, 8.4 meter telescope, will survey 20,000 sq deg in southern sky with 9.6 sq deg field-of-view, 2015 first light TMT: 30 meter telescope on Mauna Kea, 10 times collecting area of KECK, 10 times better spatial resolution than Hubble with adaptive optics, completed in 2018 [TMT homepage]
Future in Gamma-Ray CTA: Cherenkov Telescope Array, currently European effort, order of magnitude improvement in sensitivity over current ACTs, construction of prototype in ~2011 [AGIS homepage] AGIS: Advanced Gamma-ray Imaging System, currently U.S. effort, order of magnitude improvement in sensitivity over current ACTs, improved resolution, construction should begin by 2013 [ASPERA/G.Toma/A. Saftoiu]
Conclusion Dwarf galaxies are good targets for indirect dark matter detection; complimentary to Galactic Center New (preliminary) stellar data for Segue 1 suggests interesting constraints already; may be good target for Fermi and ACTs Interesting prospects for constraining Sommerfeld enhanced models with dwarfs Future optical telescopes will find more dwarfs and improve stellar kinematic measurements; future gamma-ray telescopes will improve sensitivity by order of magnitude