Two Emission Mechanisms in the Fermi Bubbles: A Possible Signal of Annihilating Dark Matter

By D. Hooper, T. Slatyer. 2013

287 citations recorded by the source corpus.

We study the variation of the spectrum of the Fermi Bubbles with Galactic latitude. Far from the Galactic plane (|b| > 30 degrees), the observed gamma-ray emission is nearly invariant with latitude, and is consistent with arising from inverse Compton scattering of the interstellar radiation field by cosmic-ray electrons with an approximately power-law spectrum. The same electrons in the presence of microgauss-scale magnetic fields can also generate the the observed microwave "haze". At lower latitudes (b < 20 degrees), in contrast, the spectrum of the emission correlated with the Bubbles possesses a pronounced spectral feature peaking at 1-4 GeV (in E^2 dN/dE) which cannot be generated by any realistic spectrum of electrons. Instead, we conclude that a second (non-inverse-Compton) emission mechanism must be responsible for the bulk of the low-energy, low-latitude emission. This second component is spectrally similar to the excess GeV emission previously reported from the Galactic Center (GC), and also appears spatially consistent with a luminosity per volume falling approximately as r^-2.4, where r is the distance from the GC. We argue that the spectral feature visible in the low-latitude Bubbles is the extended counterpart of the GC excess, now detected out to at least 2-3 kpc from the GC. The spectrum and angular distribution of the signal is consistent with that predicted from ~10 GeV dark matter particles annihilating to leptons, or from ~50 GeV dark matter particles annihilating to quarks, following a distribution similar to the canonical Navarro-Frenk-White (NFW) profile. We also consider millisecond pulsars as a possible astrophysical explanation for the signal, as observed millisecond pulsars possess a spectral cutoff at approximately the required energy. Any such scenario would require a large population of unresolved millisecond pulsars extending at least 2-3 kpc from the GC.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/cea5299e4dbb3a5460ed75c44412c8567181c580

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. E. Orlando
2. Christoph Weniger
3. I. Cholis
4. Anna Franckowiak
5. C. McCabe
6. F. Calore
7. Troy A. Porter
8. M. Dolan

In Nuclear and High Energy Physics

1. Anna Franckowiak
2. E. Orlando
3. Christoph Weniger
4. F. Calore
5. I. Cholis
6. C. McCabe
7. M. Dolan
8. Troy A. Porter

Citations in the corpus

• FERMI-LAT OBSERVATIONS OF HIGH-ENERGY γ-RAY EMISSION TOWARD THE GALACTIC CENTER (2015, background): “…of the data toward the region surrounding the GC have been made by various authors (Goodenough & Hooper 2009; Hooper & Goodenough 2011; Abazajian & Kaplinghat 2012; Hooper & Slatyer 2013; Gordon & Macı́as 2013; Huang et al. 2013; Abazajian et al. 2014; Daylan et al. 2014; Calore et al. 2015a).”
• Extended gamma-ray emission from Coy Dark Matter (2014, background): “A spectrally and morphologically similar excess has also been reported at more extended distances from the galactic plane [48, 49].”
• A tale of tails: Dark matter interpretations of the Fermi GeV excess in light of background model systematics (2014, methodology): “In most of the previous studies on the GeV excess [11,12,14,15,24] the contribution from the Galactic diffuse emission has been modeled by using the P6V11 model provided by the Fermi-LAT Collaboration.”
• The Fermi Galactic Center GeV Excess and Implications for Dark Matter (2017, methodology): “At latitudes b 10> ∣ ∣ the bubbles have an approximately uniform spectrum (e.g., Hooper & Slatyer 2013; Ackermann et al. 2014).”
• Dark nuclei. I. Cosmology and indirect detection (2014, background): “Having discussed the broad indirect detection features of dark nucleosynthesis, we will now show the utility of this process by entertaining the possibility that the gamma ray excess at the galactic center is due to DM [81–89], specifically considering an interpretation in terms of dark nucleosynthe”
• Dark matter and pulsar model constraints from Galactic Center Fermi-LAT gamma-ray observations (2013, methodology): “[53], the spectral and spatial properties typical of a population of MSPs would not be a good fit to the signal [45].”
• 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”
• Background model systematics for the Fermi GeV excess (2014, background): “8 × 10−26 cm3s−1, [62], which fall largely outside our 99% CL contour.”