Assessing the Impact of Hydrogen Absorption on the Characteristics of the Galactic Center Excess

Abstract

We present a new reconstruction of the distribution of atomic hydrogen in the inner Galaxy that is based on explicit radiation-transport modelling of line and continuum emission and a gas-flow model in the barred Galaxy that provides distance resolution for lines of sight toward the Galactic Center. The main benefits of the new gas model are, a), the ability to reproduce the negative line signals seen with the H$I$4PI survey and, b), the accounting for gas that primarily manifests itself through absorption. We apply the new model of Galactic atomic hydrogen to an analysis of the diffuse gamma-ray emission from the inner Galaxy, for which an excess at a few GeV was reported that may be related to dark matter. We find with high significance an improved fit to the diffuse gamma-ray emission observed with the Fermi-LAT, if our new H$I$ model is used to estimate the cosmic-ray induced diffuse gamma-ray emission. The fit still requires a nuclear bulge at high significance. Once this is included there is no evidence for a dark-matter signal, be it cuspy or cored. But an additional so-called boxy bulge is still favoured by the data. This finding is robust under the variation of various parameters, for example the excitation temperature of atomic hydrogen, and a number of tests for systematic issues.

arXiv commentApJ in press, 19 pages

References in corpus (52)

• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• HI4PI: A full-sky HI survey based on EBHIS and GASS
• Fermi Large Area Telescope Fourth Source Catalog
• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• Dark Matter Annihilation in The Galactic Center As Seen by the Fermi Gamma Ray Space Telescope
• The Characterization of the Gamma-Ray Signal from the Central Milky Way: A Compelling Case for Annihilating Dark Matter
• The Fermi Galactic Center GeV Excess and Implications for Dark Matter
• Fermi-LAT Observations of High-Energy Gamma-Ray Emission Toward the Galactic Center
• GASS: The Parkes Galactic All-Sky Survey. I. Survey Description, Goals, and Initial Data Release
• Strong support for the millisecond pulsar origin of the Galactic center GeV excess
• The Spectrum and Morphology of the Fermi Bubbles
• Dark matter cores all the way down
• Evidence for Unresolved Gamma-Ray Point Sources in the Inner Galaxy
• Three-Dimensional Distribution of the ISM in the Milky Way Galaxy: II. The Molecular Gas Disk
• Gas Dynamics in the Milky Way: Second Pattern Speed and Large-Scale Morphology
• The Effelsberg-Bonn HI Survey: Milky Way gas. First data release
• GASS: The Parkes Galactic All-Sky Survey. Update: improved correction for instrumental effects and new data release
• A New Model For The Loop-I (The North Polar Spur) Region
• Galactic Bulge Preferred Over Dark Matter for the Galactic Center Gamma-Ray Excess
• Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centre
• High-Energy Gamma Rays from the Milky Way: Three-Dimensional Spatial Models for the Cosmic-Ray and Radiation Field Densities in the Interstellar Medium
• 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
• Dark Matter Strikes Back at the Galactic Center
• Dark Halos of M31 and the Milky Way
• The Effelsberg-Bonn HI Survey (EBHIS)
• 3D Distribution of Molecular Gas in the Barred Milky Way
• A Self-Absorption Census of Cold HI Clouds in the Canadian Galactic Plane Survey
• Strong Evidence that the Galactic Bulge is Shining in Gamma Rays
• A New 1.4GHz Radio Continuum Map of the Sky South of Declination +25 deg
• Strong constraints on thermal relic dark matter from Fermi-LAT observations of the Galactic Center
• Foreground Mismodeling and the Point Source Explanation of the Fermi Galactic Center Excess
• The Denoised, Deconvolved, and Decomposed Fermi $\gamma$-ray sky - An application of the D${}^3$PO algorithm
• The Three-Dimensional Spatial Distribution of Interstellar Gas in the Milky Way: Implications for Cosmic Rays and High-Energy Gamma-Ray Emissions
• The morphology of the Milky Way - I. Reconstructing CO maps from simulations in fixed potentials
• Magnetically Confined Interstellar Hot Plasma in the Nuclear Bulge of our Galaxy
• Spurious Point Source Signals in the Galactic Center Excess
• The Enigmatic Galactic Center Excess: Spurious Point Sources and Signal Mismodeling
• Characterizing the Nature of the Unresolved Point Sources in the Galactic Center
• On the Interpretation of the l-v Features in the Milky Way Galaxy
• A neural simulation-based inference approach for characterizing the Galactic Center $\gamma$-ray excess
• Dissecting the inner Galaxy with $\gamma$-ray pixel count statistics
• A radio continuum survey of the southern sky at 1420 MHz. Observations and data reduction
• Dim but not entirely dark: Extracting the Galactic Center Excess' source-count distribution with neural nets
• An Automated Method for the Detection and Extraction of HI Self-Absorption in High-Resolution 21cm Line Surveys
• Maximum Entropy Estimation of the Galactic Bulge Morphology via the VVV Red Clump
• Analysis of GeV-band gamma-ray emission from SNR RX J1713.7-3946
• Gaia-DR2 extended kinematical maps. Part III: Rotation curves analysis, dark matter, and Modified Newtonian dynamics tests
• Cherenkov Telescope Array sensitivity to the putative millisecond pulsar population responsible for the Galactic center excess
• Inverse Compton emission from millisecond pulsars in the Galactic bulge
• Bayesian inference of three-dimensional gas maps: I. Galactic CO
• Production of secondary particles in heavy nuclei interactions in supernova remnants

Cited by in corpus (8)

• A Search for Dark Matter Lines at the Galactic Center with 14 Years of Fermi Data
• A Phantom Menace: On the Morphology of the Galactic Center Excess
• 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
• The Andromeda Gamma-Ray Excess: Background Systematics of the Millisecond Pulsars and Dark Matter Interpretations
• The Cherenkov Telescope Array Will Test Whether Pulsars Generate the Galactic Center Gamma-Ray Excess
• Characterizing the Expected Behavior of Non-Poissonian Template Fitting
• Improved Modeling of the Discrete Component of the Galactic Interstellar Gamma-ray Emission and Implications for the Fermi-LAT Galactic Center Excess