Galaxy infall kinematics as a test of modified gravity
Abstract
Infrared modifications of General Relativity (GR) can be revealed by comparing the mass of galaxy clusters estimated from weak lensing to that from infall kinematics. We measure the 2D galaxy velocity distribution in the cluster infall region by applying the galaxy infall kinematics (GIK) model developed by Zu & Weinberg to two suites of f(R) and Galileonmodified gravity simulations. Despite having distinct screening mechanisms, namely, the Chameleon and the Vainshtein effects, the f(R) and Galileon clusters exhibit very similar deviations in their GIK profiles from GR, with ∼100200 km s^{1} enhancement in the characteristic infall velocity at r = 5 h^{1} Mpc and 50100 km s^{1} broadening in the radial and tangential velocity dispersions across the entire infall region, for clusters with mass ∼10^{14} h^{1} M_{⊙} at z = 0.25. These deviations are detectable via the GIK reconstruction of the redshiftspace clustergalaxy crosscorrelation function, ξ ^{s}_{cg}(r_p,r_π ), which shows ∼12 h^{1} Mpc increase in the characteristic lineofsight distance r_{π, c} at r_{p} < 6 h^{1} Mpc from GR predictions. With overlapping deep imaging and large redshift surveys in the future, we expect that the GIK modelling of ξ ^{s}_{cg}, in combination with the stacked weak lensing measurements, will provide powerful diagnostics of modified gravity theories and the origin of cosmic acceleration.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 December 2014
 DOI:
 10.1093/mnras/stu1739
 arXiv:
 arXiv:1310.6768
 Bibcode:
 2014MNRAS.445.1885Z
 Keywords:

 galaxies: kinematics and dynamics;
 largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 14 pages, 10 figures, comments welcom