TY - JOUR
T1 - Foreground mismodeling and the point source explanation of the Fermi Galactic Center excess
AU - Buschmann, Malte
AU - Rodd, Nicholas L.
AU - Safdi, Benjamin R.
AU - Chang, Laura J.
AU - Mishra-Sharma, Siddharth
AU - Lisanti, Mariangela
AU - Macias, Oscar
N1 - Funding Information:
We thank P. Fox, D. Hooper, R. Leane, F. List, S. McDermott, S. Murgia, K. Perez, T. Slatyer, T. Tait, K. Van Tilburg, N. Weiner, C. Weniger, and Y. Zhong 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 supported by the NSF CAREER grant No. PHY-1554858, NSF grants No. PHY-1620727 and No. PHY-1915409, and the Simons Foundation. 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 Grant No. DESC0019225. O. M. acknowledges support by JSPS KAKENHI Grants No. JP17H04836, No. JP18H04340, No. JP18H04578 and by World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan. This work was performed in part at the Aspen Center for Physics, which is supported by National Science Foundation grant No. PHY-1607611. This work was supported through computational resources and services provided by Advanced Research Computing at the University of Michigan, Ann Arbor. This work made use of resources provided by the National Energy Research Scientific Computing Center, a U.S. Department of Energy Office of Science User Facility supported by Contract No. DE-AC02-05CH11231.
Publisher Copyright:
© 2020 American Physical Society.
PY - 2020/7/15
Y1 - 2020/7/15
N2 - The Fermi Large Area Telescope has observed an excess of ∼GeV energy gamma rays from the center of the Milky Way, which may arise from near-thermal dark matter annihilation. Firmly establishing the dark matter origin for this excess is however complicated by challenges in modeling diffuse cosmic-ray foregrounds as well as unresolved astrophysical sources, such as millisecond pulsars. Non-Poissonian template fitting (NPTF) is one statistical technique that has previously been used to show that at least some fraction of the GeV excess is likely due to a population of dim point sources. These results were recently called into question by Leane and Slatyer (2019), who showed that a synthetic dark matter annihilation signal injected on top of the real Fermi data is not recovered by the NPTF procedure. In this work, we perform a dedicated study of the Fermi data and explicitly show that the central result of Leane and Slatyer (2019) is likely driven by the fact that their choice of model for the Galactic foreground emission does not provide a sufficiently good description of the data. We repeat the NPTF analyses using a state-of-the-art model for diffuse gamma-ray emission in the Milky Way and introduce a novel statistical procedure, based on spherical-harmonic marginalization, to provide an improved description of the Galactic diffuse emission in a data-driven fashion. With these improvements, we find that the NPTF results continue to robustly favor the interpretation that the Galactic Center excess is due, in part, to unresolved astrophysical point sources across the analysis variations that we have explored.
AB - The Fermi Large Area Telescope has observed an excess of ∼GeV energy gamma rays from the center of the Milky Way, which may arise from near-thermal dark matter annihilation. Firmly establishing the dark matter origin for this excess is however complicated by challenges in modeling diffuse cosmic-ray foregrounds as well as unresolved astrophysical sources, such as millisecond pulsars. Non-Poissonian template fitting (NPTF) is one statistical technique that has previously been used to show that at least some fraction of the GeV excess is likely due to a population of dim point sources. These results were recently called into question by Leane and Slatyer (2019), who showed that a synthetic dark matter annihilation signal injected on top of the real Fermi data is not recovered by the NPTF procedure. In this work, we perform a dedicated study of the Fermi data and explicitly show that the central result of Leane and Slatyer (2019) is likely driven by the fact that their choice of model for the Galactic foreground emission does not provide a sufficiently good description of the data. We repeat the NPTF analyses using a state-of-the-art model for diffuse gamma-ray emission in the Milky Way and introduce a novel statistical procedure, based on spherical-harmonic marginalization, to provide an improved description of the Galactic diffuse emission in a data-driven fashion. With these improvements, we find that the NPTF results continue to robustly favor the interpretation that the Galactic Center excess is due, in part, to unresolved astrophysical point sources across the analysis variations that we have explored.
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U2 - 10.1103/PhysRevD.102.023023
DO - 10.1103/PhysRevD.102.023023
M3 - Article
AN - SCOPUS:85088649599
SN - 2470-0010
VL - 102
JO - Physical Review D
JF - Physical Review D
IS - 2
M1 - 023023
ER -