A Phantom Menace: On the Morphology of the Galactic Center Excess

Abstract

The characteristics of the Galactic Center Excess (GCE) emission observed in gamma-ray energies -- especially the morphology of the GCE -- remain a hotly debated subject. The manner in which the dominant diffuse gamma-ray background is modeled has been claimed to have a determining effect on the preferred morphology. In this work, we compare two distinct approaches to the galactic diffuse gamma-ray emission background: the first approach models this emission through templates calculated from a sequence of well-defined astrophysical assumptions, while the second approach divides surrogates for the background gamma-ray emission into cylindrical galactocentric rings with free independent normalizations. At the latitudes that we focus on, we find that the former approach works better, and that the overall best fit is obtained for an astrophysically motivated fit when the GCE follows the morphology expected of dark matter annihilation. Quantitatively, the improvement compared to the best ring-based fits is roughly 6500 in the chi^2 and roughly 4000 in the log of the Bayesian evidence.

arXiv comment10 pages (including the appendix), code available at https://github.com/samueldmcdermott/gcepy

References in corpus (37)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• The NumPy array: a structure for efficient numerical computation
• A Universal Density Profile from Hierarchical Clustering
• The Structure of Cold Dark Matter Halos
• MCMC using Hamiltonian dynamics
• MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics
• dynesty: A Dynamic Nested Sampling Package for Estimating Bayesian Posteriors and Evidences
• Propagation of cosmic-ray nucleons in the Galaxy
• The spectrum of isotropic diffuse gamma-ray emission between 100 MeV and 820 GeV
• Dark Matter Annihilation in The Galactic Center As Seen by the Fermi Gamma Ray Space Telescope
• On The Origin Of The Gamma Rays From The Galactic Center
• The Characterization of the Gamma-Ray Signal from the Central Milky Way: A Compelling Case for Annihilating Dark Matter
• The Nuclear Bulge of the Galaxy. III. Large-Scale Physical Characteristics of Stars and Interstellar Matter
• Background model systematics for the Fermi GeV excess
• Dark Matter and Pulsar Model Constraints from Galactic Center Fermi-LAT Gamma Ray Observations
• Development of the Model of Galactic Interstellar Emission for Standard Point-Source Analysis of Fermi Large Area Telescope Data
• Fermi-LAT Observations of High-Energy Gamma-Ray Emission Toward the Galactic Center
• Astrophysical and Dark Matter Interpretations of Extended Gamma-Ray Emission from the Galactic Center
• The Spectrum and Morphology of the Fermi Bubbles
• Universal structure of dark matter haloes over a mass range of 20 orders of magnitude
• Bar-driven dark halo evolution: a resolution of the cusp--core controversy
• The Consistency of Fermi-LAT Observations of the Galactic Center with a Millisecond Pulsar Population in the Central Stellar Cluster
• GeV excess in the Milky Way: The Role of Diffuse Galactic gamma ray Emission template
• Galactic Bulge Preferred Over Dark Matter for the Galactic Center Gamma-Ray Excess
• The characteristics of the Galactic center excess measured with 11 years of Fermi-LAT data
• The Fermi-LAT GeV Excess Traces Stellar Mass in the Galactic Bulge
• Strong Evidence that the Galactic Bulge is Shining in Gamma Rays
• The Bar-Halo Interaction - II. Secular evolution and the religion of N-body simulations
• Strong constraints on thermal relic dark matter from Fermi-LAT observations of the Galactic Center
• The Return of the Templates: Revisiting the Galactic Center Excess with Multi-Messenger Observations
• The High-Energy Tail of the Galactic Center Gamma-Ray Excess
• An Off-center Density Peak in the Milky Way's Dark Matter Halo?
• A New Mask for An Old Suspect: Testing the Sensitivity of the Galactic Center Excess to the Point Source Mask
• The Mass of the Milky Way from the H3 Survey
• SkyFACT: High-dimensional modeling of gamma-ray emission with adaptive templates and penalized likelihoods
• Dissecting the inner Galaxy with $\gamma$-ray pixel count statistics
• Assessing the Impact of Hydrogen Absorption on the Characteristics of the Galactic Center Excess

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• Towards resolving the Galactic center GeV excess with millisecond-pulsar-like sources using machine learning
• Applying Simulation-Based Inference to Spectral and Spatial Information from the Galactic Center Gamma-Ray Excess
• Observations of the Fermi bubbles and the Galactic center excess with the DArk Matter Particle Explorer
• On the Energy Distribution of the Galactic Center Excess' Sources
• Millisecond Pulsars in Globular Clusters and Implications for the Galactic Center Gamma-Ray Excess
• VERITAS Limits on Dark Matter Annihilation in the Galactic Center Halo
• High Energy Emission from the Galactic Center