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Download Testing Warm Dark Matter Model with Dwarf Galaxies
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Dark Matter, Small-Scale Structure, and Dwarf Galaxies Louie Strigari Center for Cosmology and Particle Physics QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. New York University 10.19.2007 Main Collaborators: James Bullock, Manoj Kaplinghat (UC Irvine) Local Group circa 2003 Name Year Discovered LMC SMC Sculptor Fornax Leo II Leo I Ursa Minor Draco Carina Sextans Sagittarius 1519 1519 1937 1938 1950 1950 1954 1954 1977 1990 1994 •Possible that up to 3x more exist at these luminosities [e.g. willman et al 2004] •About a dozen satellites of M31 Louie Strigari, UC Irvine Local Group circa 2007 Name Year Discovered LMC SMC Sculptor Fornax Leo II Leo I Ursa Minor Draco Carina Sextans Sagittarius Ursa Major I Willman I Ursa Major II Bootes Canes Venatici I Canes Venatici II Coma Segue I Leo IV Hercules Leo T Bootes II Louie Strigari, UC Irvine 1519 1519 1937 1938 1950 1950 1954 1954 1977 1990 1994 2005 2005 2006 2006 2006 2006 2006 2006 2006 2006 2007 2007 ? Questions to be addressed • Is there a missing satellites problem is CDM? • What is the smallest dark matter system? • Can we ever distinguish between cores and cusps? • Viable alternatives to CDM? What are their phenomenological implications? Louie Strigari, UC Irvine CDM: Cosmological Consequences Zentner & Bullock 2003 Louie Strigari, UC Irvine CDM: Predictions including ``astrophysics” We are seeing: 1) Earliest Forming halos 2) Largest before capture 3) Most massive today 4) Some combination Bullock et al. 2001; Chiu, Gnedin, Ostriker 2001; Somerville 200; Stoehr et al. 2002; Hayashi et al. 2003; Kravtsov et al. 2004; Gnedin & Kravtsov 2006; Diemand et al. 2006 Louie Strigari, UC Irvine Kravtsov et al 2004 Maximum Circular Velocities? Walker et al. ApJL 2007 Louie Strigari, UC Irvine Characteristic Mass of Satellites Via Lactea Error projections: 200 LOS stars 0.6 kpc appropriate scale to characterize well-known MW satellites Louie Strigari, UC Irvine Mass Constraints: Take I The `Old’ Dwarfs Likelihoods are marginalized over 6-dimensional parameter space defining the dwarfs. Very new data: M0.6 ~ [2-7] x 106 Msun (Walker et al. 2007) Largest mass galaxies are least luminous and least extended Strigari, Bullock, Kaplinghat, Diemand, Kuhlen, Madau ApJ 2007 Louie Strigari, UC Irvine Implications: Take I Strigari, Bullock, Kaplinghat, Diemand, Kuhlen, Madau ApJ 2007 Precise Mass function rules out most massive z=0 hypothesis Louie Strigari, UC Irvine Belukurov et al 2006 Louie Strigari, UC Irvine Mass Constraints: Take II The Old and the New 300 pc is better scale to characterize the new and old MW satellites Mass within tidal radius of Willman 1 ~ 2x the estimate of Martin et al. 2007 Mass is independent of halo luminosity (Mateo 1998) Louie Strigari, UC Irvine Implications: Take II Masses are similar, but the CDM mass function is steep over the same range Louie Strigari, UC Irvine CDM: Cosmological Consequences cusp core Simon et al. 2005, Kuzio de Naray et al. 2006 Low mass dark matter halos are less `cuspy’ than predicted in CDM Louie Strigari, UC Irvine Dwarf kinematics (Circa 2005) Are survival of globular clusters in Fornax a sign of a kpc-sized core? Gilmore et al 2007 find no- dSph requires the existence of central cusps, and there is a characteristic dark matter core density Louie Strigari, UC Irvine Strigari et al. 2006 Velocity Anisotropy What can we learn from dwarfs? Truth = core Louie Strigari, UC Irvine Truth = cusp Proper Motions • Require accuracy on stellar transverse velocities of 5 km/s • At < 100 kpc, this corresponds to accuracy 10 micro-arcseconds/yr Louie Strigari, UC Irvine R Astronomy = “star naming” Astrometry = “star measuring” QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Reflex Motion of Sun from 100pc (axes 100 µas) SIM Positional Error Circle (4µas) Hipparcos Positional Error Circle (0.64 mas) Adapted from: http://planetquest.jpl.nasa.gov/SIM/sim_index.cfm SIM PlanetQuest (Space Interferometry Mission) Louie Strigari, UC Irvine HST Positional Error Circle (~1.5 mas) . Parallactic Displacement of Galactic Center Apparent Gravitational Displacement of a Distant Star due to Jupiter 1 degree away Previous Considerations • Wilkinson et al 2000 use a two-parameter model for the DM density profile • They determine that the inner slope is well-constrained Louie Strigari, UC Irvine Constraints with SIM Strigari, Bullock, Kaplinghat ApJL 2007 Inner slope is never well-constrained. However, log-slope at several hundred pc is constrained. This is sufficient to distinguish cores and cusps. Louie Strigari, UC Irvine Distinguishing Cores from Cusps Strigari, Bullock, Kaplinghat ApJL 2007 SIM key project would entail 1000 hrs of observing time and 200 stars from multiple dSphs Louie Strigari, UC Irvine Warm Dark Matter Abazajian 2006 QuickTime™ and a TIFF (U ncompressed) decompressor are needed to see this pi cture. Hogan & Dalcanton 2000 Seljak et al 2006, Viel et al 2006 find mwdm > 14 keV [Tremaine-Gunn Bound] m 4 3 3 Q 5 10 M sun pc (km /s) keV 4 Spergel & Steinhardt 2000, Ostriker and Steinhardt 2003, Bode, Ostriker, & Turok 2001, Cen 2000, Sanchez-Salcedo 2003 Louie Strigari, UC Irvine QCDM mcdm 3 / 2 3 3 7 10 M sun pc (km/s) 100GeV 14 Warm Dark Matter QuickTime™ and a TIFF (U ncompressed) decompressor are needed to see this picture. Ly-alpha + velocity dispersion imply small WDM cores -Strigari et al ApJ 2006 Louie Strigari, UC Irvine Dark Matter from Early Decays What if dark matter freezes-out, then decays to a `superweakly’ interacting particle? [Feng, Rajaraman, Takayama 2003] Large velocity at production: 0.1-1c Free-streaming scale: Q-1/3 Reduced Phase-Space Density 103 6 Q 10 m /m DM QuickTime™ and a TIFF (U ncompressed) decompressor are needed to see this pi cture. 3 3 z decay 3 3 M sun pc (km/s) 1000 See also Kang, Kawasaki, Steigman 1993; Starkman, Kaiser, Malaney 1994 Cembranos et al., Kaplinghat (2005) Is dark matter from decays just a oneparameter family of models? Louie Strigari, UC Irvine Dark Matter from Late Decays Mass splitting is a free parameter: what if they are of order GeV? (Universal Extra Dimensions) 1014 sec. Free-streaming scale now depends on the lifetime: (Meta-CDM) 1012 sec. Distinguishing between cold and `warm’ dark matter now requires separate investigation of dwarf galaxies and LSS Neutrino WDM Strigari, Kaplinghat, Bullock PRD 2006 Louie Strigari, UC Irvine The low energy gamma-ray background: Are WIMPs stable? G Cembranos, Feng, Strigari, PRL 2007 MeV gamma-ray background unexplained by astrophysical sources Louie Strigari, UC Irvine Dark matter, gamma-rays, 511 keV photons Cembranos & Strigari M ~ MeV ~ 1020/M(TeV) Teegarden & Watanabe Picciotto & Pospelov 2005, Hooper & Wang 2005, Kasuya & Kawasaki 2006, Finkbeiner & Weiner 2007, Pospelov & Ritz 2007 Louie Strigari, UC Irvine Indirect Dark Matter Detection Flux = Particle Physics x Astrophysics Strigari, Koushiappas, Bullock, Kaplinghat PRD 2007 Louie Strigari, UC Irvine Indirect Dark Matter Detection Boost factor Strigari et al. PRD 2007 Louie Strigari, UC Irvine The most dark matter dominated galaxies: Willman 1, Coma, Ursa Major II These galaxies may be visible in gamma-rays with GLAST Dark substructure `boosts’ the fluxes Louie Strigari, UC Irvine
