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The Spectral Index Distribution of Blazars: Prospects for GLAST

The Spectral Index Distribution of Blazars: Prospects for GLAST. Tonia Venters with Vasiliki Pavlidou The University of Chicago. Outline. Past Work Monte Carlo Studies Determining ISIDs from Maximum Likelihood Studies Investigating Spectral Index Hardening using Maximum Likelihood

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The Spectral Index Distribution of Blazars: Prospects for GLAST

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  1. The Spectral Index Distribution of Blazars: Prospects for GLAST Tonia Venters with Vasiliki Pavlidou The University of Chicago First GLAST Science Symposium February 5-8, 2007

  2. Outline • Past Work • Monte Carlo Studies • Determining ISIDs from Maximum Likelihood Studies • Investigating Spectral Index Hardening using Maximum Likelihood • Conclusions First GLAST Science Symposium February 5-8, 2007

  3. BL Lacs Past Work Stecker and Salamon (1996)  importance of the SID • importance of accounting for measurement error FSRQs Affect the blazar contribution to the EGRB  concavity of the spectrum First GLAST Science Symposium February 5-8, 2007

  4. Hints from Monte Carlo… FSRQs BL Lacs First GLAST Science Symposium February 5-8, 2007

  5. ---3EG Catalog —Mattox (2001) The Maximum Likelihood Approach First GLAST Science Symposium February 5-8, 2007

  6. The ISIDs—Maximum Likelihood in Action —BL Lacs ---FSRQs Separate populations? First GLAST Science Symposium February 5-8, 2007

  7. GLAST to the Rescue!!! • Simulate GLAST data using the number distributions in Dermer (2006) • Draw true spectral indices from EGRET ISIDs • Uncertainty determined from the number of detectable photons: • Draw measured spectral index from Gaussian with mean being the true spectral index and sigma the uncertainty —BL Lacs ---FSRQs First GLAST Science Symposium February 5-8, 2007

  8. Spectral Index Hardening? ---Quiescent —Flaring ---Quiescent —Flaring Real EGRET data Simulated EGRET data First GLAST Science Symposium February 5-8, 2007

  9. Spectral Index Hardening—The GLAST Answer First GLAST Science Symposium February 5-8, 2007

  10. Conclusions • Maximum Likelihood ISID of the blazar population is a Gaussian with mean = 2.29 and σ = 0.22concavity in the spectrum of the blazar contribution to the EGRB is relatively small. • Some indication that BL Lacs and FSRQs are spectrally distinct • No evidence for spectral index hardening GLAST will settle all issues!!!! First GLAST Science Symposium February 5-8, 2007

  11. References Dermer, C. D. 2006, ArXiv Astrophysics e-prints, arXiv:astro-ph/0605402 Mattox, J. F., Hartman, R. C., & Reimer, O., ApJS, 135, 155 Stecker, F. W. & Salamon, M. H. 1996, ApJ, 464, 600 Pavlidou, V. & Venters, T. M., 2007, EGRB paper, in preparation Venters, T. M., & Pavlidou, V., 2007, this talk, on astro-ph soon! First GLAST Science Symposium February 5-8, 2007

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