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Population Studies of the Unidentified EGRET Sources In collaboration with A. V. Olinto, V. Pavlidou, C. Brown, and B. D. Fields. Jennifer Siegal-Gaskins KICP, University of Chicago Barcelona, July 7, 2006. Image Credit: EGRET Team/NASA/Honeywell Max Q Digital Group, Angela Cheyunski. - PowerPoint PPT Presentation
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Population Studies of the Population Studies of the Unidentified EGRET SourcesUnidentified EGRET SourcesIn collaboration with A. V. Olinto, V. Pavlidou, C. Brown, and B. D. FieldsIn collaboration with A. V. Olinto, V. Pavlidou, C. Brown, and B. D. Fields
Image Credit: EGRET Team/NASA/Honeywell Max Q Digital Group, Angela Cheyunski
Jennifer Siegal-GaskinsJennifer Siegal-GaskinsKICP, University of ChicagoKICP, University of Chicago
Barcelona, July 7, 2006Barcelona, July 7, 2006
The Source CatalogThe Source Catalog
http://home.uchicago.edu/~carolynb/unidentified_sources
271 sources in 3271 sources in 3rd rd
EGRET catalogEGRET catalog(Hartman et al. 1999)
121 sources 121 sources still unidentifiedstill unidentified
Updated listing of source identifications compiled Updated listing of source identifications compiled by Carolyn Brown (University of Chicago)by Carolyn Brown (University of Chicago)
EGRET’s Unidentified SourcesEGRET’s Unidentified Sources
blazarsblazars
pulsarspulsarssupernova remnantssupernova remnantsmicroquasarsmicroquasarsmolecular cloudsmolecular cloudspulsar wind nebulaepulsar wind nebulae
annihilating dark matter clumps?annihilating dark matter clumps?
Known Galactic sources
Known extragalactic sources
Exotic new possibilities?e.g. Bergström et al. (1999); Calcáneo-Roldán & Moore (2000); Tasitsiomi & Olinto (2002); Ullio et al. (2002); Blasi, Olinto, & Tyler (2003); Taylor & Silk (2003)
GoalsGoals Are the unidentified sources galactic?Are the unidentified sources galactic?
Do they include a new class of sources? Do they include a new class of sources?
Contribution to the Galactic and/or Contribution to the Galactic and/or extragalactic backgrounds due to unresolved extragalactic backgrounds due to unresolved sources?sources?
Predictions for GLASTPredictions for GLAST
A New ApproachA New Approach
Have M31 flux upper limit luminosity upper limit FM31(> 100 MeV) < 1.6 x 10-8 cm-2 s-1 (Blom et al. 1999) Expected diffuse emission due to CRs ≈ 1.0 x 10-8 cm-2 s-1 (Pavlidou & Fields
2001)
Have angular position (l,b) and fluxes of unidentified sources Need source distances to calculate total luminosity of Galactic population
Assume galaxies similar to the Assume galaxies similar to the Milky Way host comparable Milky Way host comparable populations of populations of γγ-ray sources -ray sources
Image Credit: Jason Ware
Use M31 luminosity to place limits Use M31 luminosity to place limits on the MW Galactic population!on the MW Galactic population!
Assigning DistancesAssigning Distances
1) For each source:1) For each source: integrate mass along line of sightintegrate mass along line of sight probability of distance probability of distance integrated integrated
massmass
2) Monte Carlo:2) Monte Carlo: assign a distance to each unidentified assign a distance to each unidentified
sourcesource calculate total luminosity for each calculate total luminosity for each
realizationrealization
3) Compare total luminosities to the M31 limit3) Compare total luminosities to the M31 limit
Assume unidentified source population follows MW mass Assume unidentified source population follows MW mass distribution…distribution…
Results: Halo ModelResults: Halo Model
Results: Disk and Bulge ModelResults: Disk and Bulge Model
GLASTGLAST
M31 detection M31 detection stronger stronger constraints on luminosity of constraints on luminosity of galactic populationgalactic population
M31 spectral info M31 spectral info test our test our assumption that M31 is similar assumption that M31 is similar to MW in gamma-ray emissionto MW in gamma-ray emission
More sources More sources better isotropy better isotropy teststests
Image Credit: General Dynamics C4 Systems Image Credit: General Dynamics C4 Systems
Future DirectionsFuture Directions How many unidentified sources can be in our halo? How many unidentified sources can be in our halo?
Repeat Monte Carlo for small numbers of randomly selected Repeat Monte Carlo for small numbers of randomly selected objectsobjects
Determine likely object classesDetermine likely object classes Use spectral indices and variability along with angular positionUse spectral indices and variability along with angular position
How many more blazars and pulsars will GLAST see?How many more blazars and pulsars will GLAST see? Extrapolate from known populations + our determined object Extrapolate from known populations + our determined object
classesclasses
Implications for Galactic and extragalactic backgroundsImplications for Galactic and extragalactic backgrounds Backgrounds will be reduced when GLAST resolves previously Backgrounds will be reduced when GLAST resolves previously
unresolved sourcesunresolved sources
ConclusionsConclusions Unidentified source populations:Unidentified source populations:
very few can be in halovery few can be in halo could be all disk/bulge sourcescould be all disk/bulge sources could be extragalacticcould be extragalactic
Further work will predict:Further work will predict: class of each source class of each source
(location + spectral info + variability)(location + spectral info + variability) how many new sources of each class GLAST will see how many new sources of each class GLAST will see
(extrapolating from known and expected populations)(extrapolating from known and expected populations)
GLAST will:GLAST will: test whether M31 is similar to the MWtest whether M31 is similar to the MW place stricter limits on the nature of the unidentified sourcesplace stricter limits on the nature of the unidentified sources better determine the G and EG backgroundsbetter determine the G and EG backgrounds
Disk/Bulge Sources – IsotropyDisk/Bulge Sources – Isotropy