Constraining Unresolved Point Source Contributions to the GeV
Excess with Probabilistic Catalogues
Constraining Unresolved Point Source Contributions to the GeV
Excess with Probabilistic CataloguesStephen K N Portillowith Tansu
Daylan and Douglas P Finkbeiner3 August 2015, APS DPF Ann Arbor
GeV Excess
F. Calore, I. Cholis, and C. Weniger, JCAP 3, 38 (2015)T. Daylan
et al., arXiv:1402.6703 (2014)
Millisecond Pulsars (MSPs)Similar spectrum to GeV ExcessFormed
in stellar binaries where primary becomes pulsarFormation rates and
gamma-ray emission mechanisms are active research topicsT. Daylan
et al., arXiv: 1402.6703 (2014)Bill Saxton, NRAO
MSP InterpretationA central population of thousands of
MSPsMechanism distributing them to match Excess morphologyPossibly
harder spectrum than local MSPs to better match excess spectrumBut
no MSP has been detected in the Inner GalaxyUnclear how many should
already be detected:MSP luminosity functionFermi LAT
sensitivity
J. Petrovi, P. D. Serpico,and G. Zaharijas, JCAP 2, 23
(2015)Point Sources vs. Diffuse SourceUnresolved point source
emission looks different than diffuse emission, even without
sensitivity to detect individual sources
Unresolved point source emission overdisperses Poisson photon
statistics
S. K. Lee, M. Lisanti, and B. R.Safdi, JCAP 5, 53 (2015)Evidence
for Point SourcesLee et al. 2015 favour interpretation of entire
GeV Excess as unresolved point source emissionInferred luminosity
function peaks just below Fermi LAT detection thresholdHow else can
we distinguish unresolved point sources from diffuse emission?
S. K. Lee, et al., arXiv:1506.05124 (2015)Probabilistic
CataloguesSampling the Probabilistic CatalogueB. Brewer, L. B.
Prtay, and G. Csnyi, arXiv:0912.2380 (2009)B. Brewer,
arXiv:1411.3921(2014)First StepsStart with high latitude:Galactic
emission is weak so background is isotropic extragalactic
emissionActive galaxies are point sourcesCreate mock data set based
on Lee et al. 2015 high latitude resultUsable results for a 20x20
patch of sky in an hour with 8 threads
Video: Posterior Samples
ConclusionGeV Excess compelling DM annihilation
candidatePopulation of MSPs also plausible interpretationPoint
source emission can be distinguished from diffuse emission, even if
sources unresolvedLee et al. 2015 claim that GeV Excess prefers
point sources, and find their luminosity functionProbabilistic
catalogues may feasible to probe this possible point source
population in more detail
