Dwarf spheroidal J-factor likelihoods for generalized NFW profiles

Abstract

<jats:title>ABSTRACT</jats:title> <jats:p>Indirect detection strategies of particle dark matter (DM) in Dwarf spheroidal satellite galaxies (dSphs) typically entail searching for annihilation signals above the astrophysical background. To robustly compare model predictions with the observed fluxes of product particles, most analyses of astrophysical data – which are generally frequentist – rely on estimating the abundance of DM by calculating the so-called J factor. This quantity is usually inferred from the kinematic properties of the stellar population of a dSph using the Jeans equation, commonly by means of Bayesian techniques that entail the presence (and additional systematic uncertainty) of prior choice. Here, extending earlier work, we develop a scheme to derive the profile likelihood for J factors of dwarf spheroidals for models with five or more free parameters. We validate our method on a publicly available simulation suite, released by the Gaia Challenge, finding satisfactory statistical properties for bias and probability coverage. We present the profile likelihood function and maximum likelihood estimates for the J-factor of 10 dSphs. As an illustration, we apply these profile likelihoods to recently published analyses of γ-ray data with the Fermi Large Area Telescope to derive new, consistent upper limits on the DM annihilation cross-section. We do this for a subset of systems, generally referred to as classical dwarfs. The implications of these findings for DM searches are discussed, together with future improvements and extensions of this technique.</jats:p>

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

“…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/.…”

“…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.…”

A Next-Generation Liquid Xenon Observatory for Dark Matter and Neutrino Physics

“…The former is expected to be the brightest source in the sky because of the large dark matter overdensity, but it also has the brightest foregrounds and complex dynamics. The latter are the most extreme dark matter-dominated galaxies known to us, but have a much lower J-factor [1180,1181] compared to the Galactic center (around 10 17 − 10 19 GeV 2 cm −5 for dSphs and about 10 22 GeV 2 cm −5 for the Galactic centre, leading to a fainter potential signal.…”

Classification of gamma-ray targets for velocity-dependent and subhalo-boosted dark-matter annihilation

“…In the last decade, many studies have refined and improved the calculation of J-factors, in order to rank the best targets [14,[90][91][92][93][94][95][96][97][98][99]. Although these studies are overall in broad agreement, the assumptions made on the underlying ingredients (light and DM profiles, anisotropy distribution, triaxiality), methodology (e.g., using higher moments of the Jeans equation), and statistical analysis framework and priors used (data-driven approach, DM-simulation or mock-data based priors, etc.)…”