Cosmological bounds on dark-matter-neutrino interactions

We investigate the cosmological effects of a neutrino interaction with cold dark-matter. We postulate a neutrino that interacts with a “neutrino-interacting dark-matter” (NIDM) particle with an elastic-scattering cross section that either decreases with temperature as $T^2$ or remains constant with temperature. The neutrino-dark-matter interaction results in a neutrino-dark-matter fluid with pressure, and this pressure results in diffusion-damped oscillations in the matter power spectrum, analogous to the acoustic oscillations in the baryon-photon fluid. We discuss the bounds from the Sloan Digital Sky Survey on the NIDM opacity (ratio of cross section to NIDM-particle mass) and compare with the constraint from observation of neutrinos from supernova 1987A. If only a fraction of the dark matter interacts with neutrinos, then NIDM oscillations may affect current cosmological constraints from measurements of galaxy clustering. We discuss how detection of NIDM oscillations would suggest a particle-antiparticle asymmetry in the dark-matter sector.

Figure 1

Dark-matter perturbations of $k=1.04h{\mathrm{Mpc}}^{-1}$; the opacity $Q_2$ is in the unit of ${\mathrm{cm}}^2{\mathrm{MeV}}^{-1}$. Damped oscillations are clearly seen for $Q_2={10}^{-39}{\mathrm{cm}}^2{\mathrm{MeV}}^{-1}$.

Figure 2

Several matter power spectra with different opacities $Q_2$ (top panel) and $Q_0$ (bottom panel) between dark matter and neutrinos; $Q_2$ and $Q_0$ are in units of ${\mathrm{cm}}^2{\mathrm{MeV}}^{-1}$.

Figure 3

Angular power spectra with and without dark-matter-neutrino coupling. A small enhancement ($\sim 10\%$) of the height of the peaks on small scales is observed.

Figure 4

Matter power spectra for $\mathrm{cold}+\mathrm{interacting}$ dark matter with $Q_2={10}^{-38}{\mathrm{cm}}^2{\mathrm{MeV}}^{-1}$ (top panel) and $Q_2={10}^{-37}{\mathrm{cm}}^2{\mathrm{MeV}}^{-1}$ (bottom panel).

Figure 5

Constraints on the $Q_2$ vs ${\Omega }_{\mathrm{NIDM}}$ plane from SDSS $P(k)$ measurements. An overall matter density of ${\Omega }_m=0.27$ is assumed with ${\Omega }_b=0.04$.

Figure 6

Degeneracy for the baryon acoustic peak in the galaxy correlation function. Three models are plotted: (1) a standard CDM model with a baryon density that reproduces the baryon peak (dotted line), (2) a standard CDM model with a low baryon density (dashed line), and (3) a NIDM model with a low baryon density (solid line). While a CDM model with a low baryon density fails to describe the peak, a NIDM model with a low baryon density describes the peak adequately. The data are taken from the LRG analysis of Eisenstein et al. 2005.