The Spectral Index Distribution of EGRET Blazars [electronic resource] : Prospects for GLAST
- Washington, D.C. : United States. Dept. of Energy, 2011.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
- Physical Description:
- 11 pages : digital, PDF file
- Additional Creators:
- SLAC National Accelerator Laboratory
United States. Department of Energy
United States. Department of Energy. Office of Scientific and Technical Information
- The intrinsic distribution of spectral indices in GeV energies of gamma-ray-loud blazars is a critical input in determining the spectral shape of the unresolved blazar contribution to the diffuse extragalactic gamma-ray background, as well as an important test of blazar emission theories. We present a maximum-likelihood method of determining the intrinsic spectral index distribution (ISID) of a population of γ-ray emitters which accounts for error in measurement of individual spectral indices, and we apply it to EGRET blazars. We find that the most likely Gaussian ISID for EGRET blazars has a mean of 2.27 and a standard deviation of 0.20. We additionally find some indication that FSRQs and BL Lacs may have different ISIDs (with BL Lacs being harder). We also test for spectral index hardening associated with blazar variability for which we find no evidence. Finally, we produce simulated GLAST spectral index datasets and perform the same analyses. With improved statistics due to the much larger number of resolvable blazars, GLAST data will help us determine the ISIDs with much improved accuracy. Should any difference exist between the ISIDs of BL Lacs and FSRQs or between the ISIDs of blazars in the quiescent and flaring states, GLAST data will be adequate to separate these ISIDs at a significance better than 3σ.
- Published through SciTech Connect.
Prepared for 1st GLAST Symposium, Stanford, Palo Alto, 5-8 Feb 2007.
Pavlidou, Vasiliki; Venters, Tonia M.
- Funding Information:
View MARC record | catkey: 13820567