The Galactic Center Excess Kevork N. Abazajian
WIMP Annihilation gamma rays in the Galactic Center? Model Data Abazajian & Kaplinghat 2012
Canonical Weakly-Interacting Massive-Particle (WIMP) Cold Dark Matter Production proceeds from thermal equilibrium to freeze-out of pairproduction/annihilation processes dn X dt +3Hn X = σ XX v ( n 2 X n 2 ) X,eq The pair-production process is directly related to the annihilation rate in the present universe XX $ ȲY The predicted annihilation rate s associated primary and secondary photons are comparable to the detectable limit in gamma-ray observations Predicted rate: σ XX v 3 10 26 cm 3 s 1
CDM structure: all of this should be annihilating today...
The Signal Projected in Galactic Coordinates Springel et al 2008
The Signal Projected in Galactic Coordinates Galactic Center Springel et al 2008
The Signal Projected in Galactic Coordinates Galactic Center Dwarf Galaxies Springel et al 2008
Let s just go ahead and look
Let s just go ahead and look
Let s just go ahead and look Evidence for an extended source consistent with a dark matter interpretation: Hooper & Goodenough, 2010 Hooper & Linden, 2011 Boyarsky et al. 2011
Let s just go ahead and look Evidence for an extended source consistent with a dark matter interpretation: Hooper & Goodenough, 2010 Abazajian & Kaplinghat 2012 Hooper & Linden, 2011 Boyarsky et al. 2011
Let s just go ahead and look Evidence for an extended source consistent with a dark matter interpretation: Hooper & Goodenough, 2010 Abazajian & Kaplinghat 2012 Hooper & Linden, 2011 Gordon & Macias (2013), Cirelli et al. (2013), Boyarsky et al. 2011 Abazajian et al. (2014), Daylan et al (2014), Calore et al. (2014), Abazajian et al (2015), Ackermann et al (2015)
Modeling the γ ray sources in the Galactic Center Fit all 17 significant point sources in the ROI iteratively, starting from the central sources, also varying the Galactic & Isotropic Diffuse Backgrounds Add central extended sources with several morphologies & spectra, repeating the step above for each case Abazajian & Kaplinghat 2012
WIMP Dark Matter in the Galactic Center?! m = 30 GeV NFW =1.2 Abazajian & Kaplinghat 2012
WIMP Dark Matter in the Galactic Center?! m = 30 GeV TS true =2 ln L = 824, 28.7, p =4 10 181 NFW =1.2 Abazajian & Kaplinghat 2012
GCE is Consistent with MSPs (Abazajian 1011.4275) 47 Tuc Omega Cen M 62 NGC 6388 Terzan 5 NGC 6440 M 28 NGC 6652 Requires the flux from the GC MSPs to be 200 times that in Omega Cen - reasonable stellar mass is 800 times Spectrum is consistent Γ=0.45 ± 0.21 and E c = 1.65 ± 0.2 GeV Requires a centrally concentrated density profile n~r -2.6, which is seen for the central density distribution of LMXBs in M31 Point source consistent with non-poisson statistics (Lee+ 2015; Bartels+ 2015)
GCE as MSPs: Spectral Comparison GCE-MSP Spectral Equivalence: Abazajian 2010
GCE as MSPs: Spectral Comparison GCE-MSP Spectral Equivalence: Abazajian 2010
GCE as MSPs: Spectral Comparison 2010 Gal. Center 2010 GCE: Hooper & Goodenough GCE-MSP Spectral Equivalence: Abazajian 2010
GCE as MSPs: Spectral Comparison 2010 Gal. Center Geminga Pulsar 2010 GCE: Hooper & Goodenough GCE-MSP Spectral Equivalence: Abazajian 2010
GCE as MSPs: Spectral Comparison 2010 Gal. Center Omega Cen Geminga Pulsar 2010 GCE: Hooper & Goodenough GCE-MSP Spectral Equivalence: Abazajian 2010
GCE as MSPs: Spectral Comparison 2010 Gal. Center Omega Cen NGC 6388 Geminga Pulsar 2010 GCE: Hooper & Goodenough GCE-MSP Spectral Equivalence: Abazajian 2010
GCE as MSPs: Spectral Comparison 2010 Gal. Center Omega Cen NGC 6388 M 28 Geminga Pulsar 2010 GCE: Hooper & Goodenough GCE-MSP Spectral Equivalence: Abazajian 2010
Effects of the Choice of GCE Spectral Form: Equivalent Match between MSP-like Spectrum and DM-like Spectrum 40.1 9.6 Abazajian et al. 1402.4090 Daylan et al. 1402.6703
End of GCE and start of Stellar Bulge Gamma-rays? GCE match with WISE IR X-map: Macias+ arxiv:1611.06644 Luminosity function consistency: Ploeg+ arxiv:1705.00806
Signal Parameters: forecasts for dwarf galaxy sensitivities in 2013
Signal Parameters: forecasts for dwarf galaxy sensitivities in 2013 Thermal Expected
Signal Parameters: forecasts for dwarf galaxy sensitivities in 2013 Thermal Expected
Signal Parameters: forecasts for dwarf galaxy sensitivities in 2013 Thermal Expected
Signal Parameters: forecasts for dwarf galaxy sensitivities in 2013 Thermal Expected
Dwarf Galaxies Searches Remain Dark Ackermann et al. 2015
Bright GCE, Dim Dwarfs: Tension? The inferred annihilation rate for the GCE is directly dependent on the DM profile of the Milky Way d de = h Avi 2 J (b, l) =J 0 xmax x min J J 0 1 4 m 2 dn de ρ 2 (r gal (b, l, x)) dx Sample of 9000 K-dwarf stars from the Sloan Digital Sky Survey (SDSS) by Zhang et al. The velocity distribution the local gravitational potential and, combined with stellar density constraints ρ = 0.28 ± 0.08 GeV cm 3 McKee et al. use star counts and find a significantly lower total stellar mass density than the dynamical stellar density profile measures. Combined with determinations of local total mass densities, they find a higher local dark matter density ρ = 0.49 ± 0.13 GeV cm 3. Pato et al. use measures of gas kinematics from neutral hydrogen terminal velocities and thickness, carbon monoxide terminal velocities, ionized hydrogen regions, and giant molecular clouds, as well as stellar and maser kinematics: ρ = 0.420+0.011 ± 0.025 GeV cm 3.
Bright GCE, Dim Dwarfs: Strong Tension! 5σ Dwarf limit (95%) Abazajian & Ryan Keeley arxiv:1510.06424
Bright GCE, Dim Dwarfs: Strong Tension! 5σ Dwarf limit (95%) Abazajian & Ryan Keeley (2016)
Dependence on Diffuse Emission Models and tension remains nob & noic noic Full Background dynamically excluded MW Abazajian & Ryan Keeley arxiv:1510.06424
Scaled probability: another view of strong Dwarf/GCE Tension Abazajian & Ryan Keeley (in preparation)
Discriminating Dark Matter: Self-Interacting Dark Matter A dark matter candidate that does not directly produce gamma rays in annihilation, but requires the conditions in the Galactic Center to light up. If the DM annihilates into hard leptons (electrons), they can upscatter the high density of stellar light in the GC (inverse Compton): χχ e + e - e ± + γ IR e ± + γ GeV Realizable in Self-Interacting Dark Matter (SIDM) [Kaplinghat, Linden, Yu arxiv:1501.03507] Abazajian & Ryan Keeley (in preparation)
Summary
Summary The γ-ray excess in the Galactic Center is a whopping signal (~13σ) that is in itself consistent with dark matter annihilation of ~40 GeV WIMPS to b-quarks or ~10 GeV to τ- leptons.
Summary The γ-ray excess in the Galactic Center is a whopping signal (~13σ) that is in itself consistent with dark matter annihilation of ~40 GeV WIMPS to b-quarks or ~10 GeV to τ- leptons. Since 2010, we have known of an astrophysical interpretation of the γ-ray excess in the GC: a standard population of millisecond pulsars. Spectrum, flux and morphology are consistent with MSPs, most closely following stellar X-bulge. Luminosity function is also consistent.
Summary The γ-ray excess in the Galactic Center is a whopping signal (~13σ) that is in itself consistent with dark matter annihilation of ~40 GeV WIMPS to b-quarks or ~10 GeV to τ- leptons. Since 2010, we have known of an astrophysical interpretation of the γ-ray excess in the GC: a standard population of millisecond pulsars. Spectrum, flux and morphology are consistent with MSPs, most closely following stellar X-bulge. Luminosity function is also consistent. DM interpretation in > 5σ tension with dwarf galaxies in most measures of local DM density [Abazajian & Keeley 2016, 2017]
Summary The γ-ray excess in the Galactic Center is a whopping signal (~13σ) that is in itself consistent with dark matter annihilation of ~40 GeV WIMPS to b-quarks or ~10 GeV to τ- leptons. Since 2010, we have known of an astrophysical interpretation of the γ-ray excess in the GC: a standard population of millisecond pulsars. Spectrum, flux and morphology are consistent with MSPs, most closely following stellar X-bulge. Luminosity function is also consistent. DM interpretation in > 5σ tension with dwarf galaxies in most measures of local DM density [Abazajian & Keeley 2016, 2017] DM models that discriminate between GC and dwarf galaxies can survive constraints, e.g. SIDM models. Abazajian & Keeley 2016, 2017 releasing tools to test your favorite model.