4 2009 Fermi Symposium, Washington, D.C., Nov. 2-5  0  0.2  0.4  0.6  0.8  1  1.2  1.4  1.6  1.8  0.01  0.1  1 dN/d(log 10  z) Redshift z U03(q) U03(q, $_{1}$) H05(q) H05(q, $_{1}$) EGRET blazars  0  0.1  0.2  0.3  0.4  0.5  0.6  0.7  0.8  43  44  45  46  47  48  49  50 dN/d(log 10  L ) log$_{10}$ (L  [erg s$^{-1}$]) U03(q) U03(q, $_{1}$) H05(q) H05(q, $_{1}$) EGRET blazars FIG. 2: Redshift and gamma-ray luminosity ( νL$_{ν}$ at 100 MeV) distributions of EGRET blazars. The histogram is the binned EGRET data, with one sigma Poisson errors. The four model curves are the best-fits for the GLF models of U03( q ), H05( q ), U( q, γ 1 ), and H05( q, γ 1 ), as indicated in the figure. Bottom panels: the same as the top panels, but for cumulative distributions. 10 -4 10 -3 10 -2 10 -1 10 -2 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 E 2  dN/dE   [MeV 2  cm -2  s -1  MeV -1  sr -1 ] Photon Energy [MeV] Blazar: U03 (q, $_{1}$) Non-blazar ( =3.5): ITU08 Non-blazar ( =3.8): ITU08 Blazar Non-blazar ( =3.5) Blazar Non-blazar ( =3.8) EGRET (S98) EGRET (S04a) EGRET (S98+S08) Fermi Recently, based on observations of Swift/BAT- selected blazars at 15–55 keV, Ref. [29] suggested that MeV blazars contribute significantly to the MeV background. However, this conclusion is based on an extrapolation of blazar SEDs from 55 keV to the MeV band, and some fine tuning may be required in the MeV blazar SED to reproduce the EGRB spec- trum that connects smoothly with the CXB. More- over, the spectral break in the EGRB around 10 MeV implies that such MeV blazars are a distinct popula- tion from those contributing to the EGRB above 10 MeV. Therefore, it seems more natural that the dom- inant contribution to the MeV background is coming from non-blazar AGNs as proposed by [28]. Further observational studies are desired to reveal the true ori- gin of the MeV background. FIG. 3: The EGRB spectrum from non-blazar AGNs and blazars for the GLF model of U03( q, γ 1 ). The model curves for the blazar component (absorbed+cascade), non-blazar AGN component, and the sum of the two are shown. Note that two models are plotted for the non-blazar component with different values of Γ. The observed data of HEAO- 1 [42], Swift /BAT [41], SMM [43], COMPTEL [44] and EGRET [3, 4] are shown. We also plot an alternative ver- sion of the EGRET data denoted as “S98+S08” which is the original EGRET results [3] modified with the correc- tion factors of Ref. [45]. The Fermi EGRB data is also shown [5]. V. PREDICTIONS FOR THE FERMI MISSION A. Expected Number of Blazars and Non-blazar AGNs B. Non-blazar AGNs and Blazars The left panel of Figure 4 shows the cumulative dis- tribution of > 100 MeV photon flux of blazars, non- blazar AGNs, and the total of the two. The GLF predicts that about 750 and 1200 blazars should be detected by Fermi where we assumed the Fermi sensi- tivity to be F lim = 3 × 10 $_{−}$9 and 1 × 10 $_{−}$9 photons cm $_{−}$2 s $_{−}$1 above 100 MeV. These sensitivities correspond to ∼ 1 and ∼ 5 years survey sensitivities. As can be seen in Fig. 3, the spectrum of the cos- mic MeV background connects smoothly with that of the cosmic X-ray background (CXB), while the spec- tral index of the EGRB changes abruptly around ∼ 10 MeV. This indicates that the sources of the EGRB below 10 MeV is the same population as that of the CXB (i.e. non-blazar AGNs), and the sources of the EGRB above 10 MeV is a different population (i.e. blazars). The model of Ref. [11], and the PLE and LDDE models [6] predicted ∼ 10000, 5000, and 3000 blazars for the 1-year sensitivity limit, respectively. It is re- markable that the GLF models in this work predict significantly smaller numbers of blazars than most of previous studies. About 4–50 non-blazar AGNs would be detected eConf C091122