Ratio of the cross–power spectrum ﹩P_{hm}( k) ﹩ of halos with background dark matter to the matter power spectrum ﹩P_{mm}( k) ﹩ vs. the wavelength in the linear regime. The top left and right panels are for the youngest 20% and oldest 20% of halos respectively, where the age is defined as the formation redshift ﹩z_{f}﹩. The bottom left and right panels show the results for the 20% of halos that have the highest and lowest concentrations, respectively. The mass of the halos, in units of the characteristic mass, is given in the panels.