Testing the equivalence principle for dark matter using tidal streams
Download
1 / 19

Testing the Equivalence Principle for Dark Matter Using Tidal Streams - PowerPoint PPT Presentation


  • 139 Views
  • Uploaded on

Testing the Equivalence Principle for Dark Matter Using Tidal Streams. Michael Kesden, CITA Collaborator: Marc Kamionkowski, Caltech COSMO ‘06 Tahoe City, CA Thursday, September 28, 2006. What is the Dark Matter?.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Testing the Equivalence Principle for Dark Matter Using Tidal Streams' - eydie


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Testing the equivalence principle for dark matter using tidal streams

Testing the Equivalence Principle for Dark Matter Using Tidal Streams

Michael Kesden, CITA

Collaborator: Marc Kamionkowski, Caltech

COSMO ‘06

Tahoe City, CA

Thursday, September 28, 2006


What is the dark matter
What is the Dark Matter? Tidal Streams

  • Galactic rotation curves, large-scale structure (LSS), galaxy clusters all indicate ΩDM 0.25

  • Extensions to the Standard Model offer many possible WIMPs (axions, neutralinos, etc.)

  • Detection of non-gravitational interactions could help identify DM. What interactions might be observable?


Long range dm interactions
Long-range DM interactions Tidal Streams

  • Perhaps DM interacts with DE

    • Log(/mPl4)  -120 « 1

    •  ~ m … Why now?

    • Maybe acceleration due to scalar field, just like inflation. Scalar field should couple generically.

  • String theory includes “dilatons”, light, neutral scalar fields that might interact with DM (Damour et al. 1990, Gubser & Peebles, 2004)


A 5th force for dark matter
A “5th Force” for Dark Matter? Tidal Streams

  • Long-range DM force interpreted as violation of the equivalence principle (EP), the universality of free fall between stars and DM

  • Laboratory tests place tight limits on fifth force in visible sector (Su et al., 1994); no such limits for DM

  • Modeled by Lint = g V = -g2/4r exp{-mr} (Frieman & Gradwohl, 1991)

  • Force suppressed by a factor 2  g2mPl2/4m2 compared to gravity; how might we detect such a force?


Cosmic tests for 5th force
Cosmic Tests for 5th Force Tidal Streams

  • LSS

    • Attractive DM force enhances structure for (r < m-1) (Gradwohl & Frieman, 1992)

    • 5th force leads to scale-independent bias (Amendola & Tocchini-Valentini, 2002)

  • CMB

    • Models where coupled DE traces DM constrained by WMAP (Amendola & Quercellini, 2003)

  • Clusters

    • Baryons preferentially lost during mergers

  • Is there new test with different systematics, greater sensitivity?


Tidal disruptions
Tidal Disruptions Tidal Streams

  • Galaxies form hierarchically; dwarf galaxies in Local Group continue to merge with Milky Way

  • Smaller galaxies tidally disrupted by larger hosts at distances R where:

    rsat > rtid ~ R(msat/2MR)1/3

  • Tidal disruption establishes energy scales:

  • Esat» Etid» Ebin disrupted stars retain similar orbits to satellite; trail/lead with gain/loss in energy


Tidal stream asymmetry
Tidal-stream Asymmetry Tidal Streams

  • Non-uniformity of Galactic gradient leads to natural asymmetry:

  • DM force displaces stars from bottom of satellite’s potential well, a new DM-induced asymmetry

  • DM asymmetry exceeds natural asymmetry when:


Sagittarius dwarf spheroidal
Sagittarius Dwarf Spheroidal Tidal Streams

  • Sgr dwarf is closest satellite at 24 kpc

  • Stellar stream observed by 2MASS using M-giants with known age, color-magnitude relation

  • Surface densities, radial velocities, distances well-measured for

    leading: -100º <  < -30º

    trailing: 25º <  < 90º

    (Law, Johnston, & Majewski, 2005)

  • Stellar densities also measured by SDSS (Belokurov et al., 2006)


Simulations
Simulations Tidal Streams

  • N-body simulation of satellite galaxy with:

    • M = 5  108 M, M/L = 40 M/L

    • Pericenter = 14 kpc, Apocenter = 59 kpc

  • Initial conditions generated by GALACTICS (Widrow & Dubinski, 2005)

  • Simulations evolved using GADGET-2 (Springel, 2005)




Satellite mass
Satellite Mass Tidal Streams


Satellite spin
Satellite Spin Tidal Streams


Satellite orbit
Satellite Orbit Tidal Streams


Galactic model
Galactic Model Tidal Streams



Mass to light ratio
Mass-to-Light Ratio Tidal Streams


Leading to trailing stream ratios
Leading-to-Trailing Stream Ratios Tidal Streams

  • Attractive force suppresses leading-to-trailing ratio

    CurveColor

    Standard black

    Satellite Mass magenta

    Satellite Spin red

    Circular Orbit top blue

    Planar orbit bottom blue

    Heavy disk cyan

    Two profiles green

    Lower M/L yellow


Conclusions
Conclusions Tidal Streams

  • We don’t know what the DM is. Theory suggests we consider the possibility of a long-range “fifth force”.

  • Tidally disrupting galaxies ideal test; core DM-dominated but not streams

  • Attractive DM-force sweeps core ahead. Disrupted stars preferentially gain energy; LTR suppressed.

  • Tidal streams are a messy probe of new physics, but the signature of a DM force is very distinctive, model-independent.

  • The Sgr tidal stream is well observed; new tidal streams have been discovered in last few months in SDSS. Future surveys like SIM or Gaia will find even more.

  • Like dropping stars and DM off Leaning Tower of Pisa!


ad