Constraining dark matter properties with SPI

Abstract

Using the high‐resolution spectrometer SPI on board the International Gamma‐Ray Astrophysics Laboratory (INTEGRAL), we search for a spectral line produced by a dark matter (DM) particle with a mass in the range 40 keV < MDM < 14 MeV, decaying in the DM halo of the Milky Way. To distinguish the DM decay line from numerous instrumental lines found in the SPI background spectrum, we study the dependence of the intensity of the line signal on the offset of the SPI pointing from the direction toward the Galactic Centre. After a critical analysis of the uncertainties of the DM density profile in the inner Galaxy, we find that the intensity of the DM decay line should decrease by at least a factor of 3 when the offset from the Galactic Centre increases from 0° to 180°. We find that such a pronounced variation of the line flux across the sky is not observed for any line, detected with a significance higher than 3σ in the SPI background spectrum. Possible DM decay origin is not ruled out only for the unidentified spectral lines, having low (∼3σ) significance or coinciding in position with the instrumental ones. In the energy interval from 20 keV to 7 MeV, we derive restrictions on the DM decay line flux, implied by the (non‐)detection of the DM decay line. For a particular DM candidate, the sterile neutrino of mass MDM, we derive a bound on the mixing angle.

Constraining light dark matter with diffuse X-ray and gamma-ray observations

“…The available data cover a photon energy range from 10's of GeV down to a few keV, providing the possibility of exploring a much broader range of DM candidates than WIMPs. Indeed, some of these data have already been utilized to constrain LDM, see, e.g., [33][34][35][36][37][38][39][40][41][42][43][44]. Sterile neutrinos with a mass ∼ O(1 − 10 keV) are a particularly popular candidate and their constraints have been explored in, e.g., [36, 38-40, 45-51, 51-57].…”

X-ray photons from late-decaying majoron dark matter

“…Figure 3. Upper limit on the decay rate from NGC3227 (red), the Milky Way halo observed with a prototype cryogenic spectrometer (salmon) [27], XMM observations of the Milky Way (sand) [35], Chandra observations of the Bullet Cluster [30] and M31 [36,37] (orange), HEAO-1 observations of the diffuse x-ray background (aquamarine) [25,26], INTEGRAL SPI line search in the Milky Way halo (blue) [38,39]. Filled regions are excluded.…”

Cold ultrarelativistic pulsar winds as potential sources of galactic gamma-ray lines above 100 GeV

“…Recent reports of a possible narrow line-like feature in the spectrum of gamma-ray emission at 130 GeV from the Galactic center region, and, presumably, from some other parts of the Galactic plane (Bringmann et al 2012;Weniger 2012;Tempel et al 2012;Boyarsky et al 2012;Su & Finkbeiner 2012), have received a prompt and enthusiastic reaction from the astrophysics and particle physics communities. Despite the marginal statistical significance of the reported signals and some outstanding questions and inconsistencies, the implications of these results are hotly debated, basically in the context of dark matter (DM).…”