1 / 15

Evidence for a Long-Range Dark Matter Self Interaction (“Fifth Force”)

Evidence for a Long-Range Dark Matter Self Interaction (“Fifth Force”). Glennys R. Farrar Center for Cosmology and Particle Physics New York University See GRF + Rachel Rosen astro-ph/0610298. Long Range Interaction of ~Gravitational Strength is Generic!.

mahala
Download Presentation

Evidence for a Long-Range Dark Matter Self Interaction (“Fifth Force”)

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. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Evidence for a Long-Range Dark Matter Self Interaction (“Fifth Force”) Glennys R. Farrar Center for Cosmology and Particle Physics New York University See GRF + Rachel Rosen astro-ph/0610298

  2. Long Range Interaction of ~Gravitational Strength is Generic! V(r ) =  VN (r ) exp(-r/r5) • String theory and most extensions of the SM contain fields, e.g., moduli, which are massless at every order of perturbation theory => very long range. •  ~ (MPl / vev)2and vev’s are naturally of order MGUT or MPl => gravitational strength coupling. • May be Yukawa with r 5 ~ m-1 or r 5 ~ a (GF+Peebles astro-ph/0307316) • May have more complicated dependence on distance, e.g., Chameleon models. => must test for fifth force on all scales.

  3. IE0657-56 “bullet cluster” Markevitch astro-ph/0511345 Z = 0.3 Mach 3.0 ± 0.4 vgas = 4740 ± 630 km/s (actually, - 550 km/s) Tclus = 14 keV (Tif quiescent ~ 10 keV)

  4. IE 0657-56 in 2004

  5. NEW -- IE 0657-56 in 2006Weak + Strong Lensing Surface Density (red)X-ray Brightness (white) From Bradac et al astro-ph/0608408 DM proof: Clowe et al, astro-ph/0608

  6. Lensing => • Main cluster: • M200 = 1.5 1015 Msun • V200 = 1740 km/s • Sub cluster: • M200 = 1.5 1014 Msun

  7. Furthermore… • Sub-cluster is moving in plane of sky (<~8o). • Sub-cluster is on its first pass; went almost directly through center of main cluster. • Gas bullet lags DM. (model-independent dis-proof of MOND-instead-of-DM) • DM sub-cluster velocity = 4740 +670- 550 km/s • If Keplerian, vplunging = 21/2 vcirc = 3360 km/s • How serious is this > 2  “discrepancy”?

  8. More careful modelingGRF + Rachel Rosen, astro-ph/0610298 • Consider various density profiles for main DM cluster. • Use Mass Accretion History of Wechsler et al (2002) • Use actual MAH of 12 most massive simulated clusters • Fix initial infall velocity to 300 km/s (600 km/s) => initial position and time are not independent. • Predicted final velocity is insensitive to starting time. • “Fiducial model” predicts v = 2950 km/sec • Observed: v = 4740 km/s; v-1 = 4190 km/s • “Conspiracy model” predicts v = 3435 km/sec

  9. Predictions with Gravity Alone

  10. Atypical Mass Accretion History? • Results with actual Mass Accretion History of 12 most massive halos in M. White simulation • Compare to Wechsler et al formula (red curve) • Most extreme case has 10% bigger velocity than given by mean MAH

  11. Other Uncertainties • Weak Lensing -- Mass along line-of-sight: Decreases predicted velocity • Interpretation of X-ray data --Trajectory not exactly in plane of sky: Increases observed velocity • Dynamical Calculation -- Trajectory not exactly through center of cluster: more dynamical friction => Decreases predicted velocity • Unseen Mass -- Add maximum consistent withRosat: Increases predicted velocity by ~10 km/s

  12. Hayashi and WhiteMNRAS 370, L38 (2006) and GRF+RAR update • HW: Parameterize distribution of vsubcl/v200 in Millenium Run. • HW: using old (and rounded) values of vsubcl and v200 find 1/500 chance of finding subcluster as fast as bullet. • FR: Same analysis but updating vsubcl and v200 => find probability = 0.8 10-7. • FR: With vsubcl = 4190 km/s, find probability = 10-3.

  13. Some Observational Benefits of a 5th ForceLarge scale, high precision simulations underway (GRF, V. Springel) • Helps reconcile 8 from WMAP (.75) and Large Scale Structure simulations (0.9-1.1) • Helps explain factor-10 discrepancy between LCDM simulations and number of superclusters observed in SDSS (Einasto et al, astro-ph/06…) • Helps explain insufficiency of observed DM substructures in galaxies • Reducesbaryonic fraction in clusters. • Helps empty voids; reduces late accretion • GRF-Peebles qualitative argument: voids emptier, less late accretion • Confirmed by Nusser, Gubser, Peebles simulation astro-ph/0412586: static case, rough statistics.

  14. Sagittarius Tidal Streams --evidence for or against 5th force? Majewski et al. ApJ 599:1082, 2003 (2MASS M-Stars, ages ≤ 2 Gyr • Law, Johnston, Majewski: • Precession of orbital plane: Oblate Halo • L.o.s. velocities: Prolate Halo • Kesden Kamionkowski: • Symmetric tails (?) constrain  to be small • GRF: • Prolate-oblate contradiction can be solved • by  > 0 -- GF, KJ, PJEP in progress Law, Johnston, Majewski ApJ 619:807, 2005

  15. Conclusions • Interpreting IE 0657-56 at face value as “5th” force: • r5 1 Mpc  ~ 0.2 - 1 • Consistent with present constraints (Gradwohl&Frieman, ApJ 398, 1992) • Improving IE 0657-56 measurements: • Improve lensing, measure redshifts of more arcs • Model gas deceleration; reduce error on gas bullet velocity • Need large statistics studies in other systems (edges of voids, velocity dispersion vs weak lensing, …) SDSS…. • Smaller r5 accessible via Tidal Tails of dwarf galaxies in Milky Way. Kesden&Kamionkowski 2006 • IfDM experiences a 5th force, loop corrections + EotWash => DM will be hard (impossible?) to see in direct detection expts

More Related