Simulating the Dark Matter Decay Signal from the Perseus Galaxy Cluster
Abstract
The nearby Perseus galaxy cluster is a key target for indirect detection searches for decaying dark matter. We use the C-EAGLE simulations of galaxy clusters to predict the flux, width, and shape of a dark matter decay line, paying particular attention to the unexplained 3.55 keV line detected in the spectra of some galaxies and clusters, and the upcoming XRISM X-ray observatory mission. We show that the line width in C-EAGLE clusters similar to Perseus is typically [600-800] {km} {{{s}}}-1, and therefore narrower than the amplitude of the velocity dispersion of galaxies in the cluster. Halos that are significantly disturbed can, however, exhibit galaxy velocity dispersions higher than 1000 {km} {{{s}}}-1, and in this case will show a large difference between the line profiles of on- and off-center observations. We show that the line profile is likely to be slightly asymmetric, but still well approximated by a Gaussian at the 10% level, and that the halo asymmetry can lead to fluxes that vary by a factor of two. In summary, we predict that, if the previously reported 3.55 keV line detections do originate from dark matter decay, the XRISM mission will detect a line with a roughly Gaussian profile at a rest-frame energy of 3.55 keV, with a width >600 {km} {{{s}}}-1 and flux approximately in the range [4{--}9]× {10}-8 {counts} {{{s}}}-1 {cm}}-2.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2019
- DOI:
- 10.3847/2041-8213/ab13ac
- arXiv:
- arXiv:1903.11608
- Bibcode:
- 2019ApJ...875L..24L
- Keywords:
-
- dark matter;
- galaxies: clusters: general;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 6 pages and 3 figures, plus 5 pages and 6 figures in supplemental material. Accepted for publication in ApJL