Indication of Gamma-Ray Emission from the Newly Discovered Dwarf Galaxy Reticulum II

Geringer-Sameth, Alex; Walker, Matthew G.; Koushiappas, Savvas M.; Koposov, S. E.; Belokurov, V.; Torrealba, G.; Evans, N. W.

doi:10.1103/physrevlett.115.081101

Cited by 160 publications

(230 citation statements)

References 63 publications

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“…It is interesting to note that such a favored parameter region is consistent with that to fit the GeV γ-ray excess in the Galactic center region [54,55], as well as the tentative γ-ray excesses in the directions of two dwarf galaxies [56,57].…”

supporting

confidence: 61%

“…The annihilation channel is assumed to be bb. Also shown are the Fermi-LAT exclusion limits from observations of dwarf spheroidal galaxies [52], and the best-fit parameters (with a re-scaling of the local density) through fitting to the Galactic center GeV excess [53].It is interesting to note that such a favored parameter region is consistent with that to fit the GeV γ-ray excess in the Galactic center region [54,55], as well as the tentative γ-ray excesses in the directions of two dwarf galaxies [56,57].3 Also we find that the favored DM mass is consistent with that inferred from a tentative γ-ray line-like signal with energies ∼ 43 GeV from a population of clusters of galaxies [58]. Such a consistency, if not solely due to coincidence, strongly supports the common DM origin of the antiproton "anomaly" and GeV γ-ray excesses.…”

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confidence: 65%

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Possible Dark Matter Annihilation Signal in the AMS-02 Antiproton Data

et al. 2017

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Using the latest AMS-02 cosmic ray antiproton flux data, we search for potential dark matter annihilation signal. The background parameters about the propagation, source injection, and solar modulation are not assumed a priori, but based on the results inferred from the recent B/C ratio and proton data measurements instead. The possible dark matter signal is incorporated into the model self-consistently under a Bayesian framework. Compared with the astrophysical background only hypothesis, we find that a dark matter signal is favored. The rest mass of the dark matter particles is ∼ 20 − 80 GeV and the velocity-averaged hadronic annihilation cross section is about (0.2 − 5) × 10 −26 cm 3 s −1 , in agreement with that needed to account for the Galactic center GeV excess and/or the weak GeV emission from dwarf spheroidal galaxies Reticulum 2 and Tucana III. Tight constraints on the dark matter annihilation models are also set in a wide mass region. PACS numbers: 95.35.+d,Introduction -The precise measurements of cosmic ray (CR) anti-particle spectra by space-borne instruments, such as PAMELA and AMS-02, provide very good sensitivity to probe the particle dark matter (DM) annihilation or decay in the Milky Way. The CR antiprotons, primarily come from the inelastic collisions between the CR protons (and Helium) and the interstellar medium (ISM), are effective to constrain the DM models [1][2][3]. Recent observations of the antiproton fluxes [4][5][6] are largely consistent with the expectation from the CR propagation model, leaving very limited room for the annihilation or decay of DM [2,[7][8][9][10].There are several sources of uncertainties in using antiprotons to constrain DM models. The largest uncertainty may come from the propagation parameters. Usually the secondary-to-primary ratio of CR nuclei, such as the Boronto-Carbon ratio (B/C), and the radioactive-to-stable isotope ratio of secondary nuclei, such as the Beryllium isotope ratio 10 Be/ 9 Be, are used to determine the propagation parameters [11,12]. Limited by the data quality, the constraints on the propagation parameters are loose [13,14]. Even the effect on the background antiproton flux due to uncertainties of propagation parameters is moderate, the flux from the DM component depends sensitively on propagation parameters [15]. Additional uncertainties include the injection spectrum of the CR nuclei, solar modulation, and hadronic interaction models [8]. Those uncertainties make the DM searches with antiprotons inconclusive [16,17].Given the new measurements of the proton, Helium, and B/C data by , improved constraints on the propagation and source injection parameters can be obtained through global Bayesian approaches [22][23][24][25]. With these data, we conduct a global study to determine the propagation, injection, and solar modulation parameters si- * The corresponding author: yuanq@pmo.ac.cn † The corresponding author: yzfan@pmo.ac.cn multaneously using the Markov Chain Monte Carlo (MCMC) method [26]. These "background" parameters and their like...

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supporting

confidence: 61%

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confidence: 65%

Possible Dark Matter Annihilation Signal in the AMS-02 Antiproton Data

et al. 2017

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“…Within the context of our spherically-symmetric and isotropic model for the dark matter phase space distribution, we quantify the astrophysical uncertainty in the J S -factors and show that the relative ordering of the most promising J S -factors can be interchanged relative to the standard velocity-independent J-factors. This result may have important implications for the interpretation of possible gamma-ray excesses from a dSph [37,38].…”

Section: Discussionmentioning

confidence: 81%

Sommerfeld-enhanced J -factors for dwarf spheroidal galaxies

2017

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For models in which dark matter annihilation is Sommerfeld-enhanced, the annihilation cross section increases at low relative velocities. Dwarf spheroidal galaxies (dSphs) have low characteristic dark matter particle velocities and are thus ideal candidates to study such models. In this paper we model the dark matter phase space of dSphs as isotropic and spherically-symmetric, and determine the J-factors for several of the most important targets for indirect dark matter searches. For Navarro-Frenk-White density profiles, we quantify the scatter in the J-factor arising from the astrophysical uncertainty in the dark matter potential. We show that, in Sommerfeld-enhanced models, the ordering of the most promising dSphs may be different relative to the standard case of velocity-independent cross sections. This result can have important implications for derived upper limits on the annihilation cross section, or on possible signals, from dSphs.

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“…However, such an attractive weak signal has not been confirmed by the latest Pass 8 data analysis of the dwarf galaxies [52]. A signal comparable with the Galactic GeV excess was claimed in a search for γ-ray emission from the direction of the newly discovered dwarf galaxy Reticulum 2 [56] while the Fermi-LAT collaboration did not confirm [57]. Nevertheless, as shown in Fig.8, the σv obtained in a few fits is still consistent with the current strictest limit reported in [52].…”

Section: Discussionmentioning

confidence: 99%

GeV excess in the Milky Way: The role of diffuse galactic gamma-ray emission templates

et al. 2015

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Several groups have analyzed the publicly-available Fermi-LAT data and reported a spatially extended γ−ray excess of around 1 − 3 GeV from the region surrounding the Galactic Center that might originate from annihilation of dark matter particles with a rest mass mχ ∼ 30 − 40 GeV. In this work we examine the role of the diffuse Galactic gamma ray emission (DGE) templates played in suppressing the GeV excess. For such a purpose, we adopt in total 128 background templates that have been generated by Ackermann et al. [1] in the study of the Fermi-LAT observations of the diffuse gamma ray emission considering the effects of cosmic rays and the interstellar medium. The possible GeV excess, assumed to follow the spatial distribution of the prompt gamma-rays produced in the annihilation of dark matter particles taking a generalized NFW profile with an inner slope α = 1.2, has been analyzed in some regions of interest. The introduction of such an additional component centered at the Galactic center is found to have improved the goodness of fit to the data significantly in all background template models regardless of whether the excess spectrum is fixed or not. Our results thus suggest that the presence of a statistically significant GeV excess in the inner Galaxy is robust thought its spectrum depends on the DGE model adopted in the analysis. The possible physical origin of the GeV excess component is discussed and in the dark matter model the annihilation cross section of such particles is evaluated.PACS numbers: 98.70. Rz, 95.35.+d

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Indication of Gamma-Ray Emission from the Newly Discovered Dwarf Galaxy Reticulum II

Cited by 160 publications

References 63 publications

Possible Dark Matter Annihilation Signal in the AMS-02 Antiproton Data

Possible Dark Matter Annihilation Signal in the AMS-02 Antiproton Data

Sommerfeld-enhanced J -factors for dwarf spheroidal galaxies

GeV excess in the Milky Way: The role of diffuse galactic gamma-ray emission templates

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