High-energy tail of the Galactic Center gamma-ray excess

Linden, Tim; Rodd, Nicholas L.; Safdi, Benjamin R.; Slatyer, Tracy R.

doi:10.1103/physrevd.94.103013

Cited by 75 publications

(84 citation statements)

References 80 publications

(215 reference statements)

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“…On the other hand, refitting sources individually above 10 GeV reduces the flux attributed to the excess for all PS lists. This is consistent with the analysis of Linden et al (2016), who find hat the GC excess above ∼ 10 GeV can be explained by a contribution of point sources.…”

Section: Refitting Point Sources Near the Galactic Centersupporting

confidence: 93%

The Fermi Galactic Center GeV Excess and Implications for Dark Matter

Ackermann¹,

Ajello²,

Albert³

et al. 2017

ApJ

371

497

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The region around the Galactic center (GC) is now well established to be brighter at energies of a few GeV than expected from conventional models of diffuse gamma-ray emission and catalogs of known gamma-ray sources. We study the GeV excess using 6.5 years of data from the Fermi Large Area Telescope. We characterize the uncertainty of the GC excess spectrum and morphology due to uncertainties in cosmic-ray source distributions and propagation, uncertainties in the distribution of interstellar gas in the Milky Way, and uncertainties due to a potential contribution from the Fermi bubbles. We also evaluate uncertainties in the excess properties due to resolved point sources of gamma rays. The Galactic center is of particular interest as it would be expected to have the brightest signal from annihilation of weakly interacting massive dark matter particles. However, control regions along the Galactic plane, where a dark-matter signal is not expected, show excesses of similar amplitude relative to the local background. Based on the magnitude of the systematic uncertainties, we conservatively report upper limits for the annihilation cross section as function of particle mass and annihilation channel.

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Section: Refitting Point Sources Near the Galactic Centersupporting

confidence: 93%

The Fermi Galactic Center GeV Excess and Implications for Dark Matter

Ackermann¹,

Ajello²,

Albert³

et al. 2017

ApJ

371

497

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show abstract

“…Especially at gamma-ray energies, the properties of this sky region might encode possible discoveries (e.g. Abazajian et al 2014;Calore et al 2015;Carlson et al 2016;Linden et al 2016;Ajello et al 2016;Ackermann et al 2017). Therefore, any effort in modeling the emission in this region is important.…”

Section: Gamma Rays From the Galactic Centrementioning

confidence: 99%

Imprints of cosmic rays in multifrequency observations of the interstellar emission

Orlando

2017

Monthly Notices of the Royal Astronomical Society

102

147

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Ever since the discovery of Cosmic Rays (CRs), significant advancements have been made in modeling their propagation in the Galaxy and in the Heliosphere. However, propagation models suffer from degeneracy of many parameters. To complicate the picture the precision of recent data have started challenging existing models.To tackle these issues we use available multifrequency observations of the interstellar emission from radio to gamma rays, together with direct CR measurements, to study local interstellar spectra (LIS) and propagation models. As a result, the electron LIS is characterized without any assumption on solar modulation, and favorite propagation models are put forward. More precisely, our analysis leads to the following main conclusions: (1) the electron injection spectrum needs at least a break below a few GeV; (2) even though consistent with direct CR measurements, propagation models producing a LIS with large all-electron density from a few hundreds of MeV to a few GeV are disfavored by both radio and gamma-ray observations; (3) the usual assumption that direct CR measurements, after accounting for solar modulation, are representative of the proton LIS in our ∼1 kpc region is challenged by the observed local gamma-ray HI emissivity. We provide the resulting proton LIS, all-electron LIS, and propagation parameters, based on synchrotron, gamma-ray, and direct CR data. A plain diffusion model and a tentative diffusive-reacceleration model are put forward. The various models are investigated in the inner-Galaxy region in X-rays and gamma rays. Predictions of the interstellar emission for future gamma-ray instruments (e-ASTROGAM and AMEGO) are derived.

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“…The residual signal map 8 is obtained through a similar analysis strategy as that used in Ref. [40]. The region of interest in this analysis is 1 • < |b| < 15 • and |l| < 15 • , as the diffuse background templates are optimized to this Figure 11.…”

Section: Fermi Datamentioning

confidence: 99%

“…We utilize standard template fitting methods (as in [40] for example) to determine the contribution of the following templates: a uniform isotropic template, a diffuse background model by Fermi's diffuse model p6v11, a bubbles template map and an NFW template for the DM contribution. The residual map is a HEALPix map with nside=256, obtained after subtraction of the non-DM contributions with a coefficient of their best fit.…”

Section: Fermi Datamentioning

confidence: 99%

“…An anomalous emission line at ∼3.5 keV has been found in a stacked analysis of 73 galaxy clusters [29] and in other regions [30][31][32][33]. Analysis of data from the Fermi Gamma-Ray Telescope (hereafter Fermi) [34] has shown an unexplained spherically symmetric excess of O(GeV) gamma rays at the center of the Galaxy [7,[35][36][37][38][39][40]. Studying expected properties could help discriminate DM against astrophysical backgrounds.…”

Section: Introductionmentioning

confidence: 99%

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Spherical cows in dark matter indirect detection

Bernal

Necib

Slatyer

2016

J. Cosmol. Astropart. Phys.

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Abstract. Dark matter (DM) halos have long been known to be triaxial, but in studies of possible annihilation and decay signals they are often treated as approximately spherical. In this work, we examine the asymmetry of potential indirect detection signals of DM annihilation and decay, exploiting the large statistics of the hydrodynamic simulation Illustris. We carefully investigate the effects of the baryons on the sphericity of annihilation and decay signals for both the case where the observer is at 8.5 kpc from the center of the halo (exemplified in the case of Milky Way-like halos), and for an observer situated well outside the halo. In the case of Galactic signals, we find that both annihilation and decay signals are expected to be quite symmetric, with axis ratios very different from 1 occurring rarely. In the case of extragalactic signals, while decay signals are still preferentially spherical, the axis ratio for annihilation signals has a much flatter distribution, with elongated profiles appearing frequently. Many of these elongated profiles are due to large subhalos and/or recent mergers. Comparing to gamma-ray emission from the Milky Way and X-ray maps of clusters, we find that the gamma-ray background appears less spherical/more elongated than the expected DM signal from the large majority of halos, and the Galactic gamma ray excess appears very spherical, while the X-ray data would be difficult to distinguish from a DM signal by elongation/sphericity measurements alone.

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High-energy tail of the Galactic Center gamma-ray excess

Cited by 75 publications

References 80 publications

The Fermi Galactic Center GeV Excess and Implications for Dark Matter

The Fermi Galactic Center GeV Excess and Implications for Dark Matter

Imprints of cosmic rays in multifrequency observations of the interstellar emission

Spherical cows in dark matter indirect detection

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