Sky Model for DC2: Extragalactic & Miscellaneous Sources

1. Gamma-ray Large Area Space Telescope Sky Model for DC2: Extragalactic & Miscellaneous Sources

2. Credits • Advice from Diego Torres on galaxies and galaxy clusters. • Paolo Giommi and Jim Chiang for AGN populations (luminosity/redshift distributions) • Gino Tosti for blazar lightcurves. • Nicola Omodei for GRB simulation code • Luis Reyes for implementing EBL attenuation models. • Valerie Connaughton – GBM simulations

3. Extragalactic Gamma-ray sources • Galaxy Clusters • Galaxies • Active Galactic Nuclei • Gamma-Ray Bursts • Hard transient (PBH) • Extragalactic background light

4. Galaxy clusters • Motivated by Reimer etc al. (2003, ApJ, 588, 155) • Fluxes are chosen to be near the EGRET limits • Modeled as point sources with power law index of -2.1. • The redshifts are small, and assumed to be zero in the DC2 simulation. • Coma, flux = 3.177e-08 cm-2 s-1 • Oph, flux = 1.383e-08 cm-2 s-1 • Perseus, flux = 3.177e-08 cm-2 s-1 • Virgo, flux = 3.972e-08 cm-2 s-1

5. Galaxies • LMC - extended source using spatial model developed by Sreekumar (Private communication). Flux was 1.42e-7 cm^-2 s^-1 • SMC - from Pavlidou and Fields 2001, ApJ, 558, 63 • M31 – with EGRET upper limit (1.0e-8, Pavlidou and Fields 2001) • M82 – Using most optimistic prediction from Blom et al. 1999, ApJ, 516, 744, spectral shape is from fig 1 of that paper. • NGC 253 – Using the most optimistic prediction from Blom et al 1999.

6. AGN • AGN – 104 high confidence blazar identifications of 3EG sources from 2003 and 2004 papers by Soward-Emmerd, Romani etc al and high confidence 3EG blazars from the 3rd catalog. • 1005 AGN generated using package developed by Paolo Giommi (see Jim Chiang’s talk for details on redshift and flux distributions). • All 104 EGRET blazars and the brightest 100 Giommi blazars were defined as variable sources, the remaining 905 Giommi blazars were steady sources. • ~20 of the Giommi blazars were moved to locations and assigned the redshift of known AGN. • B3 1428+422 (z=4.72) was 42’ away from 1ES 1426+428.

7. AGN • 204 blazars were assigned lightcurves (see Gino Tosti’s talk for details). • Each blazar was fit as a broken power-law • There were two classes • Highly variable, low break energy assigned to FSRQ’s and LBL • Less variable, higher break energy assigned to HBLs. • The break energy, and gamma-gamma2 (the difference between the two power-law indices) did not vary with time for a given blazar.

8. AGN • Some examples 0210-5055, Ebreak = 181 MeV Mrk 421, Ebreak = 1047 MeV

9. Gamma-Ray Bursts • 132 GRB simulated over 4 pi • 64 triggered the GBM, the remainder did not trigger due to: • Earth occultation • SAA passages • Threshold cut of 6e-8 erg cm-2. • Small bug in GRB simulation software which caused input files for GBM simulation to not be produced for some bursts (~5 GRB). • GBM statistical uncertainty • Inversely proportional to the maximum intensity of the burst as measured on a 0.25 sec timescale in the 2 brightest detectors and cosine corrected. It was a Gaussian distribution. • GBM systematic uncertainty • 2 degree (1 sigma) assumed to be independent of statistical error/brightness and distributed as a Gaussian.

10. Gamma-Ray Bursts • GRB080125657 – an intriguing burst! • Theta = 132 deg (i.e. below the LAT horizon) • 104 photons triggered and passed OBF (but OBF filtered out all but the lowest energy events). • 70 events had a fit track – but the reconstructed directions were essentially random.

11. GRB afterglows • Two basic types • ~Power-law decay (soft) • Broken power-law, gamma=-1.9 and gamma2=-2.7 • Ebreak sweeps from 5 GeV down to 1 GeV as the afterglow ages. • Bright steady, hard component (hard) • Broken power-law, gamma=-1.1 and gamma2=-2.0, Ebreak=1000. • Afterglows were generated for 9 GRB using one or both of the above models (but with varying flux and duration normalizations).

12. GRB Afterglows • GRB080101283 – hard; duration = 5 mins • GRB080104514 - soft + hard; duration = 5 hrs, 5 mins • GRB080105885 – hard; duration = 400s • GRB080107334 - soft; duration = 5 hrs • GRB080118175 – soft; duration = 5 hrs • GRB080127553 – soft; duration = 5 hrs • GRB080131904 – hard; duration = 5 mins • GRB080213493 – soft; duration = 5 hrs • GRB080217126 – soft; duration = 5 hrs • Fluxes were fairly low – these would be hard to find!

13. PBH • A short very hard transient event. • Flux increases exponentially, spectra gets harder and cutoff moves to higher energies as a function of time. • This was designated GRB080106074 by Nukri Komin and David Band (from their blind searches)

14. EBL Model • Kneiske High UV

15. Extragalactic diffuse • Modeled as a power-law with -2.1 spectrum (Sreekumar 1998). • Cillis and Hartman (2005, ApJ, 621, 291) source subtracted map has average 5.1e-5 cm-2 s-1 sr-2 (>100MeV). The flux normalisation for the DC2 extragalactic diffuse was obtained by subtracting the galactic diffuse and sum of the 997 DC2 blazars below 5e-8 cm-2 s-1 (approx flux detection limit of EGRET).

16. Residual background Energy distribution of residual background events (classA/GoodEvent3) The excess at large energies (>10 GeV) would have been greatly lessened if we had implemented Bill’s ACD ribbon cuts (c.f. performance plots shown by Bill at the kickoff meeting.

17. Accounting of sources

18. Delving more deeply • In the DC2 sky there were 1719 discrete, persistent sources, 134 transient sources, 6 diffuse source (4 dark matter components, galactic diffuse and extragalactic diffuse). • We have collected information about the DC2 sky model onhttp://www-glast.slac.stanford.edu/software/DataChallenges/DC2/SkyModel/simulated_data.html • The DC2 data servers which serve root files, will now return data which contains the MC information (see the merittuple documentation for details). • The MC variable you probably care most about is McSourceId. This tells you which source produced the event. • The DC2 FT1 fits data have been reprocessed to add an additional variable: MC_SRC_ID (this is the same as McSourceId). • You can download an all-sky fits file containing this variable from the website above. • The GSSC data server will be updated sometime next week.

19. Webpages RA sorted table of DC2 sources FT1 data including MC_SRC_ID Tables of DC2 sources by source class

20. Webpages Pulsars

21. Webpages Variable blazars

22. Webpages Gamma-ray bursts

23. Conclusions • What has been presented in these talks is an overview of the DC2 sky. • We encourage everyone to visit the website and compare the details of their analysis against the DC2 truth. • Have fun!