Dwarf spheroidal J-factors without priors: A likelihood-based analysis for indirect dark matter searches

Chiappo, Andrea; Cohen‐Tanugi, J.; Conrad, J.; Strigari, Louis E.; Anderson, B.; Sánchez‐Conde, Miguel A.

doi:10.1093/mnras/stw3079

Cited by 25 publications

(31 citation statements)

References 42 publications

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“…This will be particularly true as new dSphs continue to be discovered by the Dark Energy Survey [40], and even further into the future by the Large Synoptic Survey Telescope. Accounting for velocity-dependent cross sections will also be a future requirement of numerical methods that scan the theoretical parameter space given large spectroscopic data sets [41,42].…”

Section: Discussionmentioning

confidence: 99%

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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Section: Discussionmentioning

confidence: 99%

Sommerfeld-enhanced J -factors for dwarf spheroidal galaxies

2017

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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%

“…This re-interpretation poses a conceptual difficulty as discussed in Ref. [29,Sec. IX.C] and recent progress has been made in creating a frequentist likelihood function for the spectroscopic observations [56,58,59]. However, at the present time it is not possible to treat the majority of dSphs in the frequentist framework.…”

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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“…Complementing the above Bayesian methods, Ref. [80] recently introduced a frequentist-based method for parameter estimation using the likelihood functions. The frequentist approach has a couple of important motivations.…”

Section: Discussionmentioning

confidence: 99%

Dark matter in dwarf spheroidal galaxies and indirect detection: a review

Strigari

2018

Rep. Prog. Phys.

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Indirect dark matter searches targeting dwarf spheroidal galaxies (dSphs) have matured rapidly during the past decade. This has been because of the substantial increase in kinematic data sets from the dSphs, the new dSphs that have been discovered, and the operation of the Fermi-LAT and many ground-based gamma-ray experiments. Here we review the analysis methods that have been used to determine the dSph dark matter distributions, in particular the 'J-factors', comparing and contrasting them, and detailing the underlying systematics that still affect the analysis. We discuss prospects for improving measurements of dark matter distributions, and how these interplay with future indirect dark matter searches.

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Dwarf spheroidal J-factors without priors: A likelihood-based analysis for indirect dark matter searches

Cited by 25 publications

References 42 publications

Sommerfeld-enhanced J -factors for dwarf spheroidal galaxies

Sommerfeld-enhanced J -factors for dwarf spheroidal galaxies

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

Dark matter in dwarf spheroidal galaxies and indirect detection: a review

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