2025/10/28 by XRISM Collaboration, Audard, Marc, Awaki, Hisamitsu +150
#FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #High Energy Physics - Experiment (hep-ex)
paper · doi:10.48550/arxiv.2510.24560
We stack 3.75 Megaseconds of early XRISM Resolve observations of ten galaxy clusters to search for unidentified spectral lines in the E= 2.5-15 keV band (rest frame), including the E=3.5 keV line reported in earlier, low spectral resolution studies of cluster samples. Such an emission line may originate from the decay of the sterile neutrino, a warm dark matter (DM) candidate. No unidentified lines are detected in our stacked cluster spectrum, with the 3σ upper limit on the m\rm s∼ 7.1 keV DM particle decay rate (which corresponds to a E=3.55 keV emission line) of Γ∼ 1.0 × 10-27 s-1. This upper limit is 3-4 times lower than the one derived by Hitomi Collaboration et al. (2017) from the Perseus observation, but still 5 times higher than the XMM-Newton detection reported by Bulbul et al. (2014) in the stacked cluster sample. XRISM Resolve, with its high spectral resolution but a small field of view, may reach the sensitivity needed to test the XMM-Newton cluster sample detection by combining several years worth of future cluster observations.