Sommerfeld-enhanced 
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-factors for dwarf spheroidal galaxies

Boddy, Kimberly K.; Kumar, Jason; Strigari, Louis E.

doi:10.1103/physrevd.95.123008

Cited by 53 publications

(55 citation statements)

References 68 publications

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“…Another well-motivated scenario is Sommerfeld-enhanced dark matter annihilation [29], in which case S(v) is large at small v. The effective J-factors for this scenario have been considered previously in the context of dwarf spheroidal galaxies (dSphs) [19][20][21]. Since the dark matter velocity dispersion at the GC is expected to be much larger than in known dSphs, the enhancement is correspondingly larger in dSphs.…”

Section: Resultsmentioning

confidence: 99%

“…This dependence can lead to a suppression or enhancement of the annihilation rate for low-velocity dark matter. In either case, using the standard J-factor is no longer suitable; instead, it is necessary to calculate an effective J-factor, which incorporates information from the full dark matter velocity distribution [17][18][19][20][21]. Since this velocity distribution has a nontrivial spatial dependence, any velocity dependence of the annihilation cross section leads to a departure from the expected angular distribution of the photon flux arising from dark matter annihilation near the GC.…”

Section: Introductionmentioning

confidence: 99%

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Effective J -factor of the Galactic Center for velocity-dependent dark matter annihilation

2018

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We present the effective J-factors for the Milky Way for scenarios in which dark matter annihilation is p-wave or d-wave suppressed. We find that the velocity suppression of dark matter annihilation can have a sizable effect on the morphology of a potential dark matter annihilation signal in the Galactic Center. The gamma-ray flux from the innermost region of the Galactic Center is in particular suppressed. We find that for dark matter density profiles with steep inner slopes, the morphology of the inner Galaxy gamma-ray emission in p-wave models can be made similar to the morphology in standard s-wave models. This similarity may suggest that model discrimination between s-wave and p-wave is challenging, for example, when fitting the Galactic Center excess. However, we show that it is difficult to simultaneously match s-and p-wave morphologies at both large and small angular scales. The J-factors we calculate may be implemented with astrophysical foreground models to self-consistently determine the morphology of the excess with velocity-suppressed dark matter annihilation.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effective J -factor of the Galactic Center for velocity-dependent dark matter annihilation

2018

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“…There is an extensive literature on determining J -factors of dSphs [37,40,[48][49][50][51][52][53][54][55][56][57][58][59]. Typically, studies constrain the dark matter distributions within dSphs by using their member stars as tracers of the gravitational poten- 3 6 We use the make3FGLxml.py script by T. Johnson, available at https://fermi.gsfc.nasa.gov/ssc/data/analysis/user/.…”

Section: J-factorsmentioning

confidence: 99%

A global analysis of dark matter signals from 27 dwarf spheroidal galaxies using 11 years of Fermi-LAT observations

Hoof

Geringer-Sameth

Trotta

2020

J. Cosmol. Astropart. Phys.

116

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We perform a search for a dark matter signal in Fermi-LAT gamma-ray data from 27 Milky Way dwarf spheroidal galaxies with spectroscopically measured J -factors. Our analysis properly includes uncertainties in J -factors and background normalisations and systematically compares results from a Bayesian and a frequentist perspective. We revisit the dwarf spheroidal galaxy Reticulum II, confirming that the purported gamma-ray excess seen in Pass 7 data is much weaker in Pass 8, independently of the statistical approach adopted. We introduce for the first time posterior predictive distributions to accurately quantify the probability of a dark matter detection from another dwarf galaxy given a tentative excess. A global analysis including all 27 dwarfs shows no indication for a signal in the τ + τ − and bb channels. We present new stringent Bayesian and frequentist upper limits on the velocity-averaged annihilation cross section as a function of the dark matter mass. The best-fit dark matter parameters associated with the Galactic Centre excess are excluded at more than 95% confidence level/posterior probability in the frequentist/Bayesian framework. However, from a Bayesian model comparison perspective, dark matter annihilation within the dwarfs is not strongly disfavoured compared to a background-only model. These results constitute the highest exposure analysis on the most complete sample of dwarfs to date.

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“…If saturation does not occur, or has not occurred for the velocities of interest for indirect detection, then the constraints we present in this work can still be used as estimates if the typical velocity of DM particles in the system of interest is known, but a detailed calculation would require inclusion of the full velocity dependence (as done for two-body annihilation in e.g. [31]).…”

Section: Implications For Cosmologymentioning

confidence: 99%

Enhanced n-body annihilation of dark matter and its indirect signatures

Namjoo

Slatyer

2019

J. High Energ. Phys.

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We examine the possible indirect signatures of dark matter annihilation processes with a non-standard scaling with the dark matter density, and in particular the case where more than two dark matter particles participate in the annihilation process. We point out that such processes can be strongly enhanced at low velocities without violating unitarity, similar to Sommerfeld enhancement in the standard case of two-body annihilation, potentially leading to visible signals in indirect searches. We study in detail the impact of such multibody annihilations on the ionization history of the universe and consequently the cosmic microwave background, and find that unlike in the two-body case, the dominant signal can naturally arise from the end of the cosmic dark ages, after the onset of structure formation. We examine the complementary constraints from the Galactic Center, Galactic halo, and galaxy clusters, and outline the circumstances under which each search would give rise to the strongest constraints. We also show that if there is a population of ultra-compact dense dark matter clumps present in the Milky Way with sufficiently steep density profile, then it might be possible to detect point sources illuminated by multi-body annihilation, even if there is no large low-velocity enhancement. Finally, we provide a case study of a model where 3-body annihilation dominates the freezeout process, and in particular the resonant regime where a large low-velocity enhancement is naturally generated. arXiv:1810.09455v1 [astro-ph.CO] 22 Oct 2018 m 2 Pl ρ r ∼ 1 m 2 Pl g * T 4 , whereρ r = (π 2 /30)g * T 4 is the radiation energy density (g * counts the number of relativistic degrees of freedom as usual), i.e. H ∼ g 1/2 * T 2 /m Pl . Thus the criterion for freezeout becomes (g * )

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Sommerfeld-enhanced J -factors for dwarf spheroidal galaxies

Cited by 53 publications

References 68 publications

Effective J -factor of the Galactic Center for velocity-dependent dark matter annihilation

Effective J -factor of the Galactic Center for velocity-dependent dark matter annihilation

A global analysis of dark matter signals from 27 dwarf spheroidal galaxies using 11 years of Fermi-LAT observations

Enhanced n-body annihilation of dark matter and its indirect signatures

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