The Enigmatic Galactic Center Excess: Spurious Point Sources and Signal Mismodeling

Abstract

The Galactic Center GeV excess (GCE) has garnered great interest as a possible signal of either dark matter annihilation or some novel astrophysical phenomenon, such as a new population of gamma-ray emitting pulsars. In a companion paper, we showed that in a $10^{\circ }$ radius region of interest (ROI) surrounding the Galactic Center, apparent evidence for GCE point sources (PSs) from non-Poissonian template fitting (NPTF) is actually an artifact of unmodeled north-south asymmetry of the GCE. In this work, we develop a simplified analytic description of how signal mismodeling can drive an apparent preference for a PS population, and demonstrate how the behavior pointed out in the companion paper also appears in simpler simulated datasets that contain no PS signals at all. We explore the generality of this behavior in the real gamma-ray data, and discuss the implications for past and future studies using NPTF techniques. While the drop in PS preference once north-south asymmetry is included is not ubiquitous in larger ROIs, we show that any overly-rigid signal model is expected to yield a spurious PS signal that can appear very convincing: as well as apparent significance comparable to what one would expect from a true PS population, the signal can exhibit stability against a range of variations in the analysis, and a source count function that is very consistent with previous apparent NPTF-based detections of a GCE PS population. This contrasts with previously-studied forms of systematic mismodeling which are unlikely to mimic a PS population in the same way. In the light of this observation, and its explicit realization in the region where the GCE is brightest, we argue that a dominantly smooth origin for the GCE is not in tension with existing NPTF analyses.

47 pages, 14 figures, published in PRD. See also companion PRL paper arXiv:2002.12370

References in corpus (13)

• Background model systematics for the Fermi GeV excess
• 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
• Millisecond pulsars and the Galactic Center gamma-ray excess: the importance of luminosity function and secondary emission
• Diffuse gamma-ray emission from galactic pulsars
• Spurious Point Source Signals in the Galactic Center Excess
• A New Mask for An Old Suspect: Testing the Sensitivity of the Galactic Center Excess to the Point Source Mask
• Distinguishing Dark Matter from Unresolved Point Sources in the Inner Galaxy with Photon Statistics
• Source population synthesis and the Galactic diffuse gamma-ray emission
• Testing the millisecond pulsar scenario of the Galactic center gamma-ray excess with very high energy gamma-rays
• Young Pulsars and the Galactic Center GeV Gamma-ray Excess
• A New Determination of the Spectra and Luminosity Function of Gamma-Ray Millisecond Pulsars
• Modelling the light curves of Fermi LAT millisecond pulsars

Cited by in corpus (36)

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• The Return of the Templates: Revisiting the Galactic Center Excess with Multi-Messenger Observations
• Spurious Point Source Signals in the Galactic Center Excess
• The GCE in a New Light: Disentangling the $\gamma$-ray Sky with Bayesian Graph Convolutional Neural Networks
• Millisecond Pulsars from Accretion Induced Collapse as the Origin of the Galactic Centre Gamma-ray Excess Signal
• A neural simulation-based inference approach for characterizing the Galactic Center $\gamma$-ray excess
• Dissecting the inner Galaxy with $\gamma$-ray pixel count statistics
• Les Houches Lectures on Indirect Detection of Dark Matter
• Evidence of TeV Halos Around Millisecond Pulsars
• Dim but not entirely dark: Extracting the Galactic Center Excess' source-count distribution with neural nets
• Luminosity functions consistent with a pulsar-dominated Galactic Center Excess
• Dark Matter Candidates and Searches
• Cosmic-ray antiprotons in the AMS-02 era: A sensitive probe of dark matter
• Cherenkov Telescope Array sensitivity to the putative millisecond pulsar population responsible for the Galactic center excess
• Robust inference of the Galactic centre gamma-ray excess spatial properties
• A Compound Poisson Generator approach to Point-Source Inference in Astrophysics
• Probing the pulsar explanation of the Galactic-Center GeV excess using continuous gravitational-wave searches
• Mind the gap: The discrepancy between simulation and reality drives interpretations of the Galactic Center Excess
• A Closer Look at CP-Violating Higgs Portal Dark Matter as a Candidate for the GCE
• Harnessing the Population Statistics of Subhalos to Search for Annihilating Dark Matter
• Multi-Component Imaging of the Fermi Gamma-ray Sky in the Spatio-spectral Domain
• Towards resolving the Galactic center GeV excess with millisecond-pulsar-like sources using machine learning
• "Non-Local" Effects from Boosted Dark Matter in Indirect Detection
• Indirect Detection of Dark Matter in the Galaxy
• Constraining Dark Matter Microphysics with the Annihilation Signal from Subhalos
• Extracting the gamma-ray source-count distribution below the Fermi-LAT detection limit with deep learning
• The Cherenkov Telescope Array Will Test Whether Pulsars Generate the Galactic Center Gamma-Ray Excess
• The effect of kick velocities on the spatial distribution of millisecond pulsars and implications for the Galactic center excess
• Interpretation of the Galactic gamma-ray excess with the dark matter indicated by ${}^8$Be and ${}^4$He anomalous transitions
• Improved Modeling of the Discrete Component of the Galactic Interstellar Gamma-ray Emission and Implications for the Fermi-LAT Galactic Center Excess
• Characterizing the Expected Behavior of Non-Poissonian Template Fitting
• On the Gravitational Wave Counterpart to a Gamma-ray Galactic Center Signal from Millisecond Pulsars
• On the Energy Distribution of the Galactic Center Excess' Sources
• Millisecond Pulsars in Globular Clusters and Implications for the Galactic Center Gamma-Ray Excess
• Assessing the Impact of Hydrogen Absorption on the Characteristics of the Galactic Center Excess