http://arxiv.org/abs/2303.15513
The resonantly produced sterile neutrino ($N_1$) of the neutrino minimal standard model ($\nu$MSM) is a compelling dark matter candidate, especially in the reported possible detection of $N_1$ with mass $m_\mathrm{s}=7.1$~keV in X-ray decay. This particle will be accessible to the XRISM X-ray mission over the next 12 months. We revisit the physics behind $N_1$ and the uncertainty in its parameters. We compare predictions for the $m_\mathrm{s}=7.1$keV $N_1$ mixing angle, $\sin^{2}(2\theta)$, and half-mode mass, $M_\mathrm{hm}$, to existing X-ray observations and structure formation constraints. The strongest available constraints rule out $N_1$ as a dark matter candidate, and a more optimistic reading of the data prefers $\sin^{2}(2\theta)=5\times10^{-11}$ and $M_\mathrm{hm}=3.5\times10^{8}$$\mathrm{M}_{\odot}$. We highlight that the most promising upcoming opportunity for a detection is to find a line of velocity dispersion $\sim500$$\mathrm{kms^{-1}}$ in the Virgo cluster with XRISM, and then draw up a list of future objects of study to determine: (i) whether the line is from dark matter generally, and (ii) if from dark matter, whether that candidate is indeed $N_1$.
M. Lovell
Wed, 29 Mar 23
43/73
Comments: 13 pages, 7 figures. To be submitted to MNRAS. Contact: lovell@hi.is