The Milky Way, Coming into Focus: Precision Astrometry Probes its Evolution, and its Dark Matter

Gardner, Susan; McDermott, Samuel D.; Yanny, Brian

doi:10.48550/arxiv.2106.13284

Cited by 1 publication

(1 citation statement)

References 368 publications

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“…Recent measurements suggest that the galactocentric distance is closer to 8.3 kpc [150], but we retain the choice of 8.5 kpc as this is the assumption used in GALPROP [93] to produce the galactic diffuse emission maps. Changing the galactocentric distance to its updated smaller value would result in both the GCE and the diffuse templates increasing in brightness by ∼ 5%, which is smaller than the uncertainty on the local dark matter density [151]. This change would also be absorbed when fitting to the gamma-ray observations, as all templates have free normalizations.…”

Section: Emission From the Gcementioning

confidence: 99%

The Return of the Templates: Revisiting the Galactic Center Excess with Multi-Messenger Observations

Cholis,

Zhong,

McDermott

et al. 2021

Preprint

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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 gammaray 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. 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 σAv = 1.4 +0.6 −0.3 × 10 −26 cm 3 s −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.

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Section: Emission From the Gcementioning

confidence: 99%