Astrophysical Constraints on Dark Matter Candidate

1
Astrophysical Constraints on Dark Matter Candidate
Gamma-Ray Group Science Discussion Seminer, March
31, 2004
by
Yasushi Ikebe
- CDM halo profile models - Comparison with
observations - Emerging theory on self
interacting dark matter (SIDM)
2
King model
Self gravitating system of collisionless
particles with lowered isothermal distribution
function
Michie 1963, MNRAS, 125, 127 Michie,
Bödenheimer 1963, MNRAS, 126, 269 King 1966, AJ,
71, 64
Density
Density
R/Rc
gives good approximation out to 3 rc
r r01(r/rc)2-1.5
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King model worked find with X-ray clusters
Isothermal b-model
Cooling Flow
ROSAT PSPC/ Centaurus cluster
Einstein IPC Jones Forman 1984, ApJ, 276, 38
Allen Fabian 1994, MNRAS, 269, 409
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ASCA observations show
- No Cooling Flow
- Mass profile has larger central mass
concentration than King profile, being
consistent with NFW model
Ikebe et al. 1999, ApJ, 525, 58
King profile
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NFW model
Hoeft, Muecket, Gottloeber 2004, ApJ, 602, 169
Nararro, Frenk, White, 1995, MNRAS, 275, 720
1996,
ApJ, 462, 563
Universal density profile
r rcrit dc (r/rs)-1 (1r/rs)-2
Velocity dispersion profile
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Another universal profile
Fukushige Makino, 1997, ApJ, 477, L9
Steeper than r-1
Moore et al. 1998, ApJ, 499, L5
Ghigna et al. 2000, ApJ, 544, 616
r rcrit dc (r/rs)-1.5 1(r/rs)-1.5-1
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More N-body Simulations
Jing Suto, 2000, ApJ, 529, L69
Central exponent - 1.1 -1.5
Power et al. 2003, MNRAS, 338, 14
No asymptotic slope is derived -1.2 at 0.5 of
virial radius
CDM predicts the slope of -1 -1.5
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Contradiction to CDM model 1
rotation curves of dwarf spiral galaxies
Moore et al. 1999, MNRAS, 310, 1147
Moore model
Circular velocity
Burkert 1995, ApJ, 447, L25
Mass
r r0 (1r/r0)-1 1(r/r0)2-1
NFW model
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Contradiction to CDM model 2 substructure
abundance
Moore et al. 1999, ApJ, 524, L19
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Self-Interacting Dark Matter (SIDM)
Non-zero cross section, sDM -gt collisions scatter
particles out of the center e.g. Spergel
Steinhardt 2000, Phys Rev. Lett.,84,3760 Davé et
al. 2001, ApJ, 547, 574
Yoshida et al. 2000, ApJ, 544, L87
Density
Number of subhalos
Collision count
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Constraints on sDM
1. From DM density profile
Rotation curve of dwarf galaxies e.g.
Firmani et al. 2001, MNRAS, 321, 713
Gravitational lenses Miralda-Escude,
2002, ApJ, 564, 60 Wyithe et al. 2001,
ApJ, 555, 504 Meneghetti et al. 2001,
MNRAS, 325, 435
X-ray observations Arabadjis, Bautz,
Garmire, 2002, ApJ, 572, 66 Ikebe
Böhringer, 2003, ApJ, submitted
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X-ray Mass estimate
Method 1
X-ray observation
Method 2
Modeling the total mass profile
R 0

?
GmmpM kBTgR2
T0 Tg
ng n0 exp - dR
Fit to data
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Abell 1795
XMM/EPIC
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Constraints on sDM
2. sDM cannot be too large
Constraints from the growth of supermassive black
holes The larger the cross-section is, the
larger the accreation rate is. (Ostriker 2000,
Phys. Rev. Lett. 84, 5258 Hennawi Ostriker
2002, ApJ, 572, 41)
Survival of galactic subhalos Heat transfer from
cluster DM evaporate galactic subhalos. (Gnedin
Ostriker, 2001, ApJ, 561, 61)
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If DM particles really have self-interacting
cross-section,
WIMPs axions
Candidates for SIDM
Mirror matter Mohapatra, Nussinov,
Teplitz, 2002, Phys. Rev. D, 66, 063002
Q-Ball Kusenko Steinhardt, 2001, Phys. Rev.
Lett. 87, 141301
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But don't worry. They might be wrong.
1. Revisit to the density profile measurement
from the rotation curves
Van den Bosch et al. 2000, ApJ, 119, 1579 van den
Bosch, Swaters 2001, MNRAS, 325, 1017
The current data may not be sufficient to put any
meaningful constraints on the dark matter density
profiles, due to - beam smearing, -
uncertain stellar mass-to-light ratio, -
unknown inclination angle, - degeneragy of the
fitting parameters, etc. The dark matter density
profile in dwarf galaxies are consistent with
CDM halo models with cuspy core
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But don't worry. They might be wrong.
2. Revision on the satellites' mass estimate
Stoehr et al. 2002, MNRAS, 335, L84 Hayashi et
al. 2003, ApJ, 584, 541
Hayashi et al.
N(gtVmax)
Result by Moore et al. 1999 derived with an
isothermal assumption
Vmax/V200