Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
Can we better constrain the nature of Dark Matter
with new observations?
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Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
Possible issues with Cold Dark Matter
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• Cusps in galaxy centers
• Numerous subhalos
• Prolate halos
Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
Gaia
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Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier 4
Astrometric satellite with 100x Gaia’s accuracy
PI: Céline Bohm (Durham)
Co-PI: Alberto Krone-Martins (Lisbon)
Gary Mamon (IAP), 11 Juillet 2016, Journée CNES de propositions de mission ESA M5
Astrometric mission: 30x Gaia’s accuracy
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Gaia post-launch Theia improvement Telescope Aperture 1.45 x 0.5 = 0.73 m 2 0.8 m → 0.40 m 2 0.55
Field of view 0.6 deg
Coverage Survey Pointed
Astrometry Global Differential
Exposure time per field 76 x 9 (CCD) x 4.4 sec 20 x 50 hr = 1000 hr 1200
Additional factors 2D vs 1D astrometry: 1.4, Gaia Stray light: 1.9, non-uniform sampling: 1.6
Proper motion accuracy
G=10 star 3.5 μas/yr 0.03 μas/yr 119
Proper motion accuracy
G=15 star 14 μas/yr 0.23 μas/yr 60
Proper motion accuracy
G=20 star 330 μas/yr 2.8 μas/yr 118
naïve global gain = (0.55 x 1200) 1/2 = 26 ➜ 110 after additional factors
Gary Mamon (IAP), 11 Juillet 2016, Journée CNES de propositions de mission ESA M5
Astrometric mission: 30x Gaia’s accuracy
6
Gaia post-launch Theia improvement Telescope Aperture 1.45 x 0.5 = 0.73 m 2 0.8 m → 0.40 m 2 0.55
Field of view 0.6 deg
Coverage Survey Pointed
Astrometry Global Differential
Exposure time per field 76 x 9 (CCD) x 4.4 sec 20 x 50 hr = 1000 hr 1200
Additional factors 2D vs 1D astrometry: 1.4, Gaia Stray light: 1.9, non-uniform sampling: 1.6
Proper motion accuracy
G=10 star 3.5 μas/yr 0.03 μas/yr 119
Proper motion accuracy
G=15 star 14 μas/yr 0.23 μas/yr 60
Proper motion accuracy
G=20 star 330 μas/yr 2.8 μas/yr 118
naïve global gain = (0.55 x 1200) 1/2 = 26 ➜ 110 after additional factors
Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
Precision vs. magnitude
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Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier 8
what
science?
Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
dwarf spheroidal galaxies:
numbers of stars for Draco
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M. Fairbairn
Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
numbers of stars per dSph
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Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
Dark Matter (DM) in mock dwarf Spheroidal galaxies without & with proper motions
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dSph = DM-dominated velocity dispersion:
σ v ≈ 10 km/s
Theia proper motions
→ ∆v = 3 km/s
Mass-orbit modeling (Jeans equation) of mock dSph galaxies → DM density profiles
Gaia Challenge: mocks from M. Walker; with J. Read & L. Watkins
10 2 10 1
r [kpc]
10 2 10 1 100 101 102
⇢[Msunpc3 ]
PM+LOS fit LOS only fit true
10 1 100
r [kpc]
10 2 10 1 100 101
⇢[Msunpc3 ]
PM+LOS fit LOS only fit true
10 1 100
r [kpc]
10 3 10 2 10 1 100
⇢[Msunpc3 ]
PM+LOS fit LOS only fit true
radius (kpc) D M ma ss de nsi ty (M
⦿pc
–3)
radius (kpc) radius (kpc)
D M ma ss de nsi ty (M
⦿pc
–3) D M ma ss de nsi ty (M
⦿pc
–3)
cuspy DM mocks
LOS only fit LOS+PM fit true
LOS only fit LOS+PM fit true
isotropic velocities
10 1 100
r [kpc]
10 2 10 1 100 101
⇢[Msunpc3 ]
PM+LOS fit LOS only fit true
D M ma ss de nsi ty (M
⦿pc
–3)
cored DM mocks
isotropic velocities
LOS only fit LOS+PM fit true
LOS only fit LOS+PM fit true
radius (kpc)
radial outer velocities
radial outer velocities
L. Watkins
L. Watkins
L. Watkins
L. Watkins If cores found in ~all dSphs:
case for interacting DM
calibration of DM annihilation x-section from γ-ray obs of dSph galaxies
Theia proper motions dramatically reduce bias & uncertainty on inner DM slope!
Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
Detecting subhalos in Milky Way
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Largest effect when subhalo passes through disk
in disk
Feldmann & Spolyar 15
still visible after 1st passage
Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
Detecting subhalos in Milky Way
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Gaia can detect log M = 8 subhalos (rare: closest at 3 kpc)
Theia (20 LOS in 2 yr) can unambiguously detect log M = 6.7 subhalos
→ avoid confusion with other perturbers
If no subhalos found: case for Warm Dark Matter
Gaia Gaia
time (Myr)
after disk crossing
before disk crossing
Theia
400h, 1σ
Theia
400h, 1σ
G a ia l imi t
A. Siebert & D. Spolyar
Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
tomography of halo substructure
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A. Siebert & D. Spolyar
Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
Detecting Ultra-Compact Minihalos in Milky Way
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by micro-lensing
fra ct io n o f D M in U C MH s
P. Scott, H. Clark & A. Erickcek
Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
Shape of outer Dark Matter halo of Milky Way using Hypervelocity stars
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10 µas/yr accuracy required Gnedin+05
standard DM halo
model oblate
spherical
prolate
> 20 Hyper-Velocity Stars known (v LOS > 500 km/s)
Brown+05,…,15
Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
Shape of outer Dark Matter halo of Milky Way using Hypervelocity stars
O. Gnedin & W. Brown
17Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
Habitable exo-Earths
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Gary Mamon (IAP), 11 Juillet 2016, Journée CNES de propositions de mission ESA M5
Strategy
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Gary Mamon (IAP), 11 October 2016, 4th Gaia Challenge, Stockholm, Theia: the new Astrometry Frontier
Targets
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