TY - JOUR
T1 - Characterizing the nature of the unresolved point sources in the Galactic Center
T2 - An assessment of systematic uncertainties
AU - Chang, Laura J.
AU - Mishra-Sharma, Siddharth
AU - Lisanti, Mariangela
AU - Buschmann, Malte
AU - Rodd, Nicholas L.
AU - Safdi, Benjamin R.
N1 - Funding Information:
We thank P. Fox, R. Leane, S. Murgia, K. Perez, T. Slatyer, T. Tait, K. Van Tilburg, and N. Weiner for useful conversations. L. J. C. is supported by a Paul & Daisy Soros Fellowship and an NSF Graduate Research Fellowship under Grant No. DGE-1656466. M. L. is supported by the DOE under Award No. DESC0007968 and the Cottrell Scholar Program through the Research Corporation for Science Advancement. S. M. is partially supported by the NSF CAREER Grant No. PHY-1554858 and NSF Grant No. PHY-1620727. N. L. R. is supported by the Miller Institute for Basic Research in Science at the University of California, Berkeley. M. B. and B. R. S. are supported by the DOE Early Career Award No. DESC0019225. This work was performed in part at the Aspen Center for Physics, which is supported by National Science Foundation Grant No. PHY-1607611. The work presented in this paper was performed on computational resources managed and supported by Princeton Research Computing, a consortium of groups including the Princeton Institute for Computational Science and Engineering and the Office of Information Technology’s High Performance Computing Center and Visualization Laboratory at Princeton University. This research made use of the healpy , ip ython , matplotlib , mpmath , n um p y , pandas , s ci p y , and corner software packages.
Publisher Copyright:
© 2020 American Physical Society.
PY - 2020/1/27
Y1 - 2020/1/27
N2 - The Galactic Center excess (GCE) of GeV gamma rays can be explained as a signal of annihilating dark matter or of emission from unresolved astrophysical sources, such as millisecond pulsars. Evidence for the latter is provided by a statistical procedure - referred to as non-Poissonian template fitting (NPTF) - that distinguishes the smooth distribution of photons expected for dark matter annihilation from a "clumpy" photon distribution expected for point sources. In this paper, we perform an extensive study of the NPTF on simulated data, exploring its ability to recover the flux and luminosity function of unresolved sources at the Galactic Center. When astrophysical background emission is perfectly modeled, we find that the NPTF successfully distinguishes between the dark matter and point source hypotheses when either component makes up the entirety of the GCE. When the GCE is a mixture of dark matter and point sources, the NPTF may fail to reconstruct the correct contribution of each component. These results are related to the fact that in the ultrafaint limit, a population of unresolved point sources is exactly degenerate with Poissonian emission. We further study the impact of mismodeling the Galactic diffuse backgrounds, finding that while a dark matter signal could be attributed to point sources in some outlying cases for the scenarios we consider, the significance of a true point source signal remains robust. Our work enables us to comment on a recent study by Leane and Slatyer (2019) that questions prior NPTF conclusions because the method does not recover an artificial dark matter signal injected on actual Fermi data. We demonstrate that the failure of the NPTF to extract an artificial dark matter signal can be natural when point sources are present in the data - with the effect further exacerbated by the presence of diffuse mismodeling - and does not on its own invalidate the conclusions of the NPTF analysis in the Inner Galaxy.
AB - The Galactic Center excess (GCE) of GeV gamma rays can be explained as a signal of annihilating dark matter or of emission from unresolved astrophysical sources, such as millisecond pulsars. Evidence for the latter is provided by a statistical procedure - referred to as non-Poissonian template fitting (NPTF) - that distinguishes the smooth distribution of photons expected for dark matter annihilation from a "clumpy" photon distribution expected for point sources. In this paper, we perform an extensive study of the NPTF on simulated data, exploring its ability to recover the flux and luminosity function of unresolved sources at the Galactic Center. When astrophysical background emission is perfectly modeled, we find that the NPTF successfully distinguishes between the dark matter and point source hypotheses when either component makes up the entirety of the GCE. When the GCE is a mixture of dark matter and point sources, the NPTF may fail to reconstruct the correct contribution of each component. These results are related to the fact that in the ultrafaint limit, a population of unresolved point sources is exactly degenerate with Poissonian emission. We further study the impact of mismodeling the Galactic diffuse backgrounds, finding that while a dark matter signal could be attributed to point sources in some outlying cases for the scenarios we consider, the significance of a true point source signal remains robust. Our work enables us to comment on a recent study by Leane and Slatyer (2019) that questions prior NPTF conclusions because the method does not recover an artificial dark matter signal injected on actual Fermi data. We demonstrate that the failure of the NPTF to extract an artificial dark matter signal can be natural when point sources are present in the data - with the effect further exacerbated by the presence of diffuse mismodeling - and does not on its own invalidate the conclusions of the NPTF analysis in the Inner Galaxy.
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U2 - 10.1103/PhysRevD.101.023014
DO - 10.1103/PhysRevD.101.023014
M3 - Article
AN - SCOPUS:85078669006
SN - 2470-0010
VL - 101
JO - Physical Review D
JF - Physical Review D
IS - 2
M1 - 023014
ER -