Disentangling cosmic-ray and dark-matter inducedγ-rays in galaxy clusters

Abstract

Context. Galaxy clusters are among the best targets for indirect dark matter detection in γ-rays, despite the large astrophysical background expected from these objects. Detection is now within reach of current observatories (Fermi-LAT or Cerenkov telescopes); however, assessing the origin of this signal might be difficult. Aims. We investigate whether the behaviour of the number of objects per "flux" bin (log N − log F) and that of the stacked signal could be used as a signature of the dominant process at stake. Methods. We use the Clumpy code to integrate the signal from decaying or annihilating dark matter and from cosmic rays along the line of sight. We assume the standard Navarro-Frenk-White (NFW) profile for the dark matter density and rely on a parametrised emissivity for the cosmic-ray component. In this context, the consequences of stacking are explored using the MCXC meta-catalogue of galaxy clusters. Results. We find the value of the slope of the log N − log F power law (or the increase of the signal with the number of stacked objects) to be a clear diagnosis to disentangle decaying dark matter from cosmic-ray induced γ-rays. For dark matter annihilation, depending on the signal boost from the substructures, it is either similar to the cosmic-ray signal (no boost) or similar to the decay case (large boosts). The shift between the brightest object and its followers also depends on the signal origin. For annihilation, this shift and the stacked signal are poorly constrained because of the large uncertainty affecting the boost. We also underline that the angular dependence of the annihilation signal is not universal because of the substructure contribution.

γ-ray and ν Searches for Dark-Matter Subhalos in the Milky Way with a Baryonic Potential

“…CLUMPY v2.0 [5] was used for this purpose, to estimate the sensitivity of the CTA [1] and HAWC [27] γ-ray telescopes to galactic DM subhalos. Aside from galactic subhalo studies, CLUMPY has also been used by several teams to model DM annihilation or decay in γ-rays or ν in many targets: dwarf spheroidal galaxies [37][38][39][40][41][42][43][44][45][46], the galactic halo [47][48][49], the Smith HI cloud [50], nearby galaxies [51], galaxy clusters [52][53][54], and also for the extragalactic diffuse emission [55].…”

CLUMPY : Jeans analysis,γ-ray andνfluxes from dark matter (sub-)structures

“…This has now been extended to any level with a recursive implementation of Eq. (17). Part of this implementation requires to identify the radius at which the slope of the spatial distribution of the clumps equals −2, i.e., it can only be enabled with distributions whose outer slope is steeper than −2.…”

“…from a user list or for clumps drawn in the Galaxy). For more illustrations, see the population study performed with CLUMPY on clusters of galaxies in [15,16,17] and in CLUMPY runs. Note that the list of subhaloes is stored in ASCII files (extension .drawn).…”

“…CLUMPY has been used to calculate J-factor in DM haloes of dwarf spheroidal galaxies (dSphs) [11,12], DM-supported Hi clouds [13], and towards the Galactic centre to place limits on DM annihilation using the ANTARES neutrino telescope [14]. The code has been extended to provide additional outputs (sorting, population study) when applied on a sizeable sample of galaxy cluster haloes [15,16,17], or galactic subhaloes. The second CLUMPY release, presented in this paper, includes these additional outputs, but also provides a better description of several quantities related to DM haloes and their substructures, as well as more flexible and useful outputs.…”

Spherical Jeans analysis for dark matter indirect detection in dwarf spheroidal galaxies - impact of physical parameters and triaxiality

“…This tremendously speeds up the calculation with respect to the Baes & van Hese profile case, for which no shortcut was found in the literature. All the Jeans analyses presented here are performed with a new module of the CLUMPY 2 code (Charbonnier et al 2012), which was developed and used to calculate J and D factors Charbonnier et al 2011;Nezri et al 2012;Combet et al 2012;Maurin et al 2012). The new Jeans analysis module was validated by systematic cross-checks with the results (obtained with a different code and MCMC engine) of Charbonnier et al (2011); it will be made publicly available in the second release of CLUMPY (Bonnivard et al, in prep.…”