6 2009 Fermi Symposium, Washington, D.C., Nov. 2-5 Figure 4: Angular power spectrum of the EGB produced by dark matter annihilation as a function of the multipole l for E$_{γ,}$ 0 = 10 GeV. The line styles are as in Fig. 3 except for the dotted lines that show the predictions from Ando et al. [2007b] for a subhalo-dominant contribution with and without considering tidal destruction (lower and upper dotted lines), respectively. Figure 3: Upper panel: Mean annihilation intensity per comoving shell thickness, as a function of redshift for individual partial maps. The solid black line is for resolved halos and subhalos. The dashed black line is for main halos only, resolved and unresolved down to the cutoff mass using a boost factor b$_{h}$ = 60. The blue and red solid lines show the contribution of all components, resolved and unresolved halos and subhalos, boosted with the extreme values in the interval b sub = 2 − 60. All lines are for E$_{γ,}$ 0 = 10 GeV, except for the black dotted line which is for the ReHS component with E$_{γ,}$ 0 = 100 GeV. Lower panel: The same as the upper panel but for the accumulated intensity, I$_{γ,}$ 0 ( > 1 + z ). tures are relevant (red and black solid lines) behaves differently, however. In the range l ∈ [20 , 100], it be- comes slightly shallower, i.e. the signal is slightly more isotropic in this regime. Contrary to the strong cen- tral concentration of the matter in a halo, the number density profile of subhalos is considerably shallower than a NFW profile and produces a luminosity profile in projection which is essentially flat Springel et al. [2008]. This effect continues until l ∼ 200 where the power spectrum becomes dominated by the low-mass main halos. The dotted lines in Fig. 4 were taken from the an- alytical results of Ando et al. [2007b] and are shown here for comparison, see the las paragraphs of section 5.5 in Zavala et al. [2009] for a discussion on the dif- ferences between our results and those of Ando et al. [2007b]. halos. When only the main halo contribution to the EGB is considered (dashed black line), the normaliza- tion is lower because most of the γ -ray signal comes from low mass halos that are less clustered than more massive halos. The blue line in Fig. 4, corresponding to the full ex- trapolation including subhalos but with the minimal boost b$_{sub}$ = 2, has exactly the same power spectrum than the case with main halos only, at all scales. This is because the signal from main halos is dominant in this case, and subhalos have a negligible effect. In contrast, in the case where subhalos have a signifi- cant contribution mediated by b$_{sub}$ = 60 (red line), the normalization is larger at small scales because the signal is dominated by subhalos belonging to the most massive halos, and the latter are strongly clustered. An important result that we obtain from the anal- ysis of our results is that there are differences in the shape of the power spectra for different energies. We can exploit these differences and enhance the power at small or large angular scales by taking the ratio of sky maps at different energies. The upper panel of Fig. 5 shows the total sky maps for E$_{γ,}$$_{0}$ = 0 . 1 GeV and E$_{γ,}$$_{0}$ = 32 GeV in the left and right, respectively, smoothed with a Gaussian beam with a FWHM of 5 $^{◦}$. Both maps show only small anisotropies, with the As the angular scale decreases, l > 10, the power spectrum depends more and more on the internal structures of halos. For the cases where substructures are ignored or are negligible (dashed-black and blue lines), the slope becomes steeper, with a slope close to 2. The power spectrum for the cases where substruc- eConf C091122 3.5. Energy dependence