7–11 Aug 2017
Columbus, Ohio, USA
US/Eastern timezone

Evidence Against a Dark Matter Explanation of the Galactic Center Excess

7 Aug 2017, 16:45
15m
Corinthian Room (The Athenaeum)

Corinthian Room

The Athenaeum

Oral Galactic sources (incl. transients) Galactic sources

Speaker

Oscar Macias (Virginia Tech)

Description

An anomalous, apparently diffuse, gamma-ray signal not readily attributable to known Galactic sources has been found in Fermi space telescope data covering the central ~10 degrees of the Galaxy. This "Galactic Center Gamma-Ray Excess" (GCE) signal has a spectral peak at ~2 GeV and reaches its maximum intensity at the Galactic Centre (GC) from where it falls off as a radial power law ~r^{-2.4}. Given its morphological and spectral characteristics, the GCE is ascribable to self-annihilation of dark matter particles governed by an Navarro-Frenk-White-like density profile. However, it could also be composed of many dim, unresolved point sources for which millisecond pulsars (MSPs) or pulsars would be natural candidates given their GeV-peaked spectra. Statistical evidence that many sub-threshold point sources contribute up to 100% of the GCE signal has recently been claimed. We have developed a novel analysis that exploits hydrodynamical modelling to better register the position of gamma-ray emitting gas in the Inner Galaxy. Our improved analysis reveals that the excess gamma-rays are spatially correlated with both the X-shaped stellar over-density in the Galactic bulge and the nuclear stellar bulge. Given these correlations, we argue that the excess is not a dark matter phenomenon but rather associated with the stellar population of the X-shaped bulge and the nuclear bulge.

Primary author

Oscar Macias (Virginia Tech)

Co-authors

Dr Gordon Chris (University of Canterbury) Dr Roland Crocker (Australian National University) Mr Brendan Coleman (University of Canterbury) Mr Dylan Paterson (University of Canterbury) Prof. Shunsaku Horiuchi (Virginia Tech) Prof. Martin Pohl (Potsdam University)

Presentation materials