Return of the templates: Revisiting the Galactic Center excess with multimessenger observations

Journal Article · Fri May 20 00:00:00 EDT 2022 · Physical Review. D.

DOI:https://doi.org/10.1103/physrevd.105.103023· OSTI ID:1839550

Cholis, Ilias  ^[1]; Zhong, Yi-Ming  ^[2]; McDermott, Samuel D.  ^[3]; Surdutovich, Joseph P. ^[4]

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1. Oakland Univ., Rochester, MI (United States)
2. Univ. of Chicago, IL (United States). Kavli Inst. for Cosmological Physics (KICP)
3. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
4. Carleton College, Northfield, MN (United States)

The Galactic center excess (GCE) remains one of the most intriguing discoveries from the Fermi Large Area Telescope (LAT) observations. We revisit the characteristics of the GCE by first producing a new set of high-resolution galactic diffuse gamma-ray emission templates. This diffuse emission, which accounts for the bulk of the observed gamma rays, is ultimately due to cosmic-ray interactions with the interstellar medium. Using recent high-precision cosmic-ray observations, in addition to the continuing Fermi-LAT observations and observations from lower energy photons, we constrain the properties of the galactic diffuse emission. We describe a large set of diffuse gamma-ray emission templates which account for a very wide range of initial assumptions on the physical conditions in the inner galaxy. The broad properties of the GCE that we find in this work are qualitatively unchanged despite the introduction of this new set of templates, though its quantitative features appear mildly different than those obtained in previous analyses. In particular, we find a high-energy tail at higher significance than previously reported. Additionally, this tail is very prominent in the northern hemisphere, and less so in the southern hemisphere. This strongly affects one prominent interpretation of the excess: known millisecond pulsars are incapable of producing this high-energy emission, even in the relatively softer southern hemisphere, and are therefore disfavored as the sole explanation of the GCE. The annihilation of dark matter particles of mass 40$$^{ +10}_{-7}$$ GeV (95% CL) to b-quarks with a cross-section of $$\langle$$σ_Av$$\rangle$$ = 1.4$$^{+0.6}_{-0.3}$$ x 10^-26 cm³s^-1 provides a good fit to the excess especially in the relatively cleaner southern sky. Dark matter of the same mass range annihilating to $b$ quarks or heavier dark matter particles annihilating to heavier Standard Model bosons can combine with millisecond pulsars to provide a good fit to the southern hemisphere emission as well, as can a broken power-law spectrum which would be related to recent cosmic-ray burst activity. As part of this paper, we make publicly available all of our templates and the data covariance matrix we have generated to account for systematic uncertainties.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Oakland Univ., Rochester, MI (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP); National Aeronautics and Space Administration (NASA); National Science Foundation (NSF)
• Grant/Contract Number: AC02-07CH11359; NNX15AJ20H; 80NSSC20M0124; SC0022352; PHY-1607611
• OSTI ID: 1839550
• Alternate ID(s): OSTI ID: 1868973
• Report Number(s): FERMILAB-PUB-21-709-T; arXiv:2112.09706; oai:inspirehep.net:1994112; TRN: US2301084
• Journal Information: Physical Review. D., Vol. 105, Issue 10; ISSN 2470-0010
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
cosmic rays & astroparticles
gamma ray astronomy
particle astrophysics
particle dark matter
Dark Matter
gamma rays