Background model systematics for the Fermi GeV excess

By F. Calore, I. Cholis, Christoph Weniger. 2014

474 citations recorded by the source corpus.

The possible gamma-ray excess in the inner Galaxy and the Galactic center (GC) suggested by Fermi-LAT observations has triggered a large number of studies. It has been interpreted as a variety of different phenomena such as a signal from WIMP dark matter annihilation, gamma-ray emission from a population of millisecond pulsars, or emission from cosmic rays injected in a sequence of burst-like events or continuously at the GC. We present the first comprehensive study of model systematics coming from the Galactic diffuse emission in the inner part of our Galaxy and their impact on the inferred properties of the excess emission at Galactic latitudes 2° < |b| < 20° and 300 MeV to 500 GeV. We study both theoretical and empirical model systematics, which we deduce from a large range of Galactic diffuse emission models and a principal component analysis of residuals in numerous test regions along the Galactic plane. We show that the hypothesis of an extended spherical excess emission with a uniform energy spectrum is compatible with the Fermi-LAT data in our region of interest at 95% CL. Assuming that this excess is the extended counterpart of the one seen in the inner few degrees of the Galaxy, we derive a lower limit of 10.0° (95% CL) on its extension away from the GC. We show that, in light of the large correlated uncertainties that affect the subtraction of the Galactic diffuse emission in the relevant regions, the energy spectrum of the excess is equally compatible with both a simple broken power-law of break energy Ebreak = 2.1 ± 0.2 GeV, and with spectra predicted by the self-annihilation of dark matter, implying in the case of b̄b final states a dark matter mass of mχ=49+6.4−5.4 GeV.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/287676201186d0ee7db0d55f6b81ba3cad8b5d2b

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Citations in the corpus

SEARCHING FOR DARK MATTER ANNIHILATION IN RECENTLY DISCOVERED MILKY WAY SATELLITES WITH FERMI-LAT (2016, background): “The limits derived from LAT data coincident with confirmed and candidate dSphs do not yet conclusively confirm or refute a DM interpretation of the GCE (Gordon & Macias 2013; Daylan et al. 2016; Abazajian et al. 2014; Calore et al. 2015).”
DEVELOPMENT OF THE MODEL OF GALACTIC INTERSTELLAR EMISSION FOR STANDARD POINT-SOURCE ANALYSIS OF FERMI LARGE AREA TELESCOPE DATA (2016, background): “In this energy range, several studies have reported emission from the GC region in excess of the expectations from standard emission components (Vitale & Morselli 2009; Hooper & Linden 2011; Abazajian & Kaplinghat 2012; Calore et al. 2015).”
SEARCH FOR GAMMA-RAY EMISSION FROM DES DWARF SPHEROIDAL GALAXY CANDIDATES WITH FERMI-LAT DATA (2015, background): “The population of nearby DM-dominated dSphs represents an independent set of targets to test possible signals of DM annihilation in other regions such as the Galactic center (e.g., Gordon & Macias 2013; Abazajian et al 2014; Calore et al. 2015; Daylan et al. 2014).”
The Fermi Galactic Center GeV Excess and Implications for Dark Matter (2017, methodology): “…Goodenough & Hooper 2009; Vitale et al. 2009; Hooper & Goodenough 2011; Abazajian & Kaplinghat 2012; Gordon & Macías 2013; Hooper & Slatyer 2013; Calore et al. 2015; Zhou et al. 2015; Ajello et al. 2016; Daylan et al. 2016), while other groups refuted the existence of an excess after…”
A tale of tails: Dark matter interpretations of the Fermi GeV excess in light of background model systematics (2014, methodology): “[26] on possible DM interpretations of the Fermi GeV excess, and show that a much larger number of DM models is viable than what was claimed before.”
Gravitational probes of dark matter physics (2017, background): “Indirect detection searches for dark matter annihilation or decay in the Universe today can improve signal over background by targeting high-density regions — be it the Galactic Center [441, 442, 443, 444, 445, 446, 447, 448, 449, 450, 451, 452, 453, 454, 455, 456], satellite galaxies [457, 458, 459”
Sensitivity projections for dark matter searches with the Fermi large area telescope (2016, methodology): “[66]), undertake detailed fitting of the Galactic diffuse emission and point sources (e.”
A taste of dark matter: flavour constraints on pseudoscalar mediators (2014, unknown): “e the preferred DM mass for the dierent coupling structures, we generate the gamma rays from DM annihilation with Pythia 8.186 [144] and t to the spectral shape of the Galactic Centre excess data in [22,24], which is sensitive to the mass, but not the normalisation of the signal. We nd m ˜ = 43:5+5:”
FERMI-LAT OBSERVATIONS OF HIGH-ENERGY γ-RAY EMISSION TOWARD THE GALACTIC CENTER (2015, methodology): “…the same Galactocentric radial boundaries as the π0-decay templates, and allowing for spectral variations in the π0-decay templates from those predicted interior to the solar circle – that go beyond the modelling of the interstellar emission employed by other analyses (e.g., Calore et al. 2015b).”