Investigating the Uniformity of the Excess Gamma rays towards the Galactic Center Region

Abstract

We perform a composite likelihood analysis of subdivided regions within the central $26^{\circ }\times 20^{\circ }$ of the Milky Way, with the aim of characterizing the spectrum of the gamma-ray galactic center excess in regions of varying galactocentric distance. Outside of the innermost few degrees, we find that the radial profile of the excess is background-model dependent and poorly constrained. The spectrum of the excess emission is observed to extend upwards of 10 GeV outside $\sim 5^{\circ }$ in radius, but cuts off steeply between 10--20 GeV only in the innermost few degrees. If interpreted as a real feature of the excess, this radial variation in the spectrum has important implications for both astrophysical and dark matter interpretations of the galactic center excess. Single-component dark matter annihilation models face challenges in reproducing this variation; on the other hand, a population of unresolved millisecond pulsars contributing both prompt and secondary inverse Compton emission may be able to explain the spectrum as well as its spatial dependency. We show that the expected differences in the photon-count distributions of a smooth dark matter annihilation signal and an unresolved point source population are an order of magnitude smaller than the fluctuations in residuals after fitting the data, which implies that mismodeling is an important systematic effect in point source analyses aimed at resolving the gamma-ray excess.

27 pages, 9 figures. Matches accepted version: references added, typo corrected in Sec. 4.2, some additional discussion added (results unchanged)

References in corpus (26)

• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• The spectrum of isotropic diffuse gamma-ray emission between 100 MeV and 820 GeV
• The Parkes multibeam pulsar survey: VI. Discovery and timing of 142 pulsars and a Galactic population analysis
• Background model systematics for the Fermi GeV excess
• The Spectrum and Morphology of the Fermi Bubbles
• A Tale of Tails: Dark Matter Interpretations of the Fermi GeV Excess in Light of Background Model Systematics
• Inverse Compton Origin of the Hard X-Ray and Soft Gamma-Ray Emission from the Galactic Ridge
• Possible Evidence For Dark Matter Annihilation In The Inner Milky Way From The Fermi Gamma Ray Space Telescope
• GeV excess in the Milky Way: The Role of Diffuse Galactic gamma ray Emission template
• Cosmic Ray Protons in the Inner Galaxy and the Galactic Center Gamma-Ray Excess
• WIMPs at the Galactic Center
• Galactic Center gamma-ray "excess" from an active past of the Galactic Centre?
• Millisecond pulsars and the Galactic Center gamma-ray excess: the importance of luminosity function and secondary emission
• A description of sources detected by INTEGRAL during the first 4 years of observations
• Updated cosmic-ray and radio constraints on light dark matter: Implications for the GeV gamma-ray excess at the Galactic center
• Millisecond pulsar interpretation of the Galactic center gamma-ray excess
• The High-Energy Tail of the Galactic Center Gamma-Ray Excess
• Galactic Center Excess in Gamma Rays from Annihilation of Self-Interacting Dark Matter
• Distinguishing Dark Matter from Unresolved Point Sources in the Inner Galaxy with Photon Statistics
• Testing the millisecond pulsar scenario of the Galactic center gamma-ray excess with very high energy gamma-rays
• Improved Cosmic-Ray Injection Models and the Galactic Center Gamma-Ray Excess
• Young Pulsars and the Galactic Center GeV Gamma-ray Excess
• Cosmic-ray positrons from millisecond pulsars
• Discovery of a New Galactic Center Excess Consistent with Upscattered Starlight
• A New Determination of the Spectra and Luminosity Function of Gamma-Ray Millisecond Pulsars
• The impact of propagation uncertainties on the potential Dark Matter contribution to the Fermi LAT mid-latitude gamma-ray data

Cited by in corpus (27)

• WIMP dark matter candidates and searches - current status and future prospects
• 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
• Dark Matter Strikes Back at the Galactic Center
• Dark Matter Interpretation of the Fermi-LAT Observation Toward the Galactic Center
• Strong Evidence that the Galactic Bulge is Shining in Gamma Rays
• Indirect Detection of Neutrino Portal Dark Matter
• The Return of the Templates: Revisiting the Galactic Center Excess with Multi-Messenger Observations
• The inert doublet model in the light of Fermi-LAT gamma-ray data: a global fit analysis
• Low Mass X-Ray Binaries in the Inner Galaxy: Implications for Millisecond Pulsars and the GeV Excess
• Model-independent analysis of the DAMPE excess
• Consistency Between the Luminosity Function of Resolved Millisecond Pulsars and the Galactic Center Excess
• Point Sources from Dissipative Dark Matter
• Analyzing the Gamma-ray Sky with Wavelets
• Saving the MSSM from the Galactic Center Excess
• Cherenkov Telescope Array sensitivity to the putative millisecond pulsar population responsible for the Galactic center excess
• Lepton-Flavor Violating Mediators
• Constraints on dark matter annihilation and decay from the large-scale structure of the nearby universe
• What the Milky Way's Dwarfs tell us about the Galactic Center extended excess
• Magnetic Monopoles and Dark Matter
• On Dark Matter Explanations of the Gamma-Ray Excesses from the Galactic Center and M31
• Millisecond Pulsars in Dense Star Clusters: Evolution, Scaling Relations, and the Galactic-Center Gamma-ray Excess
• Millisecond Pulsar Kicks Cause Difficulties in Explaining the Galactic Center Gamma-Ray Excess
• Applying Simulation-Based Inference to Spectral and Spatial Information from the Galactic Center Gamma-Ray Excess
• The Galactic Isotropic $\gamma$-ray Background and Implications for Dark Matter
• Implications of the Fermi-LAT Pass 8 Galactic Center Excess on Supersymmetric Dark Matter
• Dark matter properties implied by gamma ray interstellar emission models