2001/11/30 by N. Dalal, C. S. Kochanek
Physics and Astronomy · #astro-ph
paper · pdf · doi:10.1086/340303
published as Astrophys.J. 572 (2002) 25-33 · ApJ in press, 23 pages, 6 figures
arxiv created 2002/04/02 · arxiv updated 2009/12/01
We devise a method to measure the abundance of satellite halos in gravitational lens galaxies, and apply our method to a sample of 7 lens systems. After using Monte Carlo simulations to verify the method, we find that substructure comprises fraction f=0.02 (median, 0.006<f<0.07 at 90% confidence) of the mass of typical lens galaxies, in excellent agreement with predictions of CDM simulations. We estimate a characteristic critical radius for the satellites of 0.0001<b/arcsec<0.006 (90% confidence). For a satellite mass function of dn/dM Mx with x=-1.8 and Ml<M<Mh, the critical radius provides an estimate that the upper mass limit is 106Msun < Mh < 109Msun. Our measurement confirms a generic prediction of CDM models, and may obviate the need to invoke alternatives to CDM like warm dark matter or self-interacting dark matter.