Constraints on millicharged dark matter and axionlike particles from timing of radio waves

We derive constraints on millicharged dark matter and axionlike particles using pulsar timing and fast radio burst observations. For dark matter particles of charge $\epsilon e$, the constraint from time of arrival (TOA) of waves is $\epsilon /m_{\mathrm{milli}}\lesssim {10}^{-8}{\mathrm{eV}}^{-1}$, for masses $m_{\mathrm{milli}}\gtrsim {10}^{-6}\mathrm{eV}$. For axionlike particles, the polarization of the signals from pulsars yields a bound in the axial coupling $g/m_a\lesssim {10}^{-13}{\mathrm{GeV}}^{-1}/({10}^{-22}\mathrm{eV})$, for $m_a\lesssim {10}^{-19}\mathrm{eV}$. Both bounds scale as $(\rho /{\rho }_{\mathrm{dm}}{)}^{1/2}$ for fractions of the total dark matter energy density ${\rho }_{\mathrm{dm}}$. We make a precise study of these bounds using TOA from several pulsars, FRB 121102, and polarization measurements of PSR $\mathrm{J}0437-4715$. Our results rule out a new region of the parameter space for these dark matter models.

Figure 1

Constraint on millicharged DMa in the $\epsilon -m_{\text{milli}}$ space from pulsar (solid red line) and FRB 121102 (dashed red line) DM at 95% confidence level. Solid blue line indicates the bound from Red Giants [15]. We assume a homogeneous DMa density ${\rho }_{\mathrm{dm}}={\rho }_{\text{milli}}\approx 0.3\mathrm{GeV}/{\mathrm{cm}}^3$. The bound scales as ${\rho }_{\text{milli}}^{-1/2}$ for fractional components.

Figure 2

Constraints for ALP DMa in the plane $g-m_a$ at 95% C.L. The dash-dotted purple line indicates the lower bound set by polarization measurements using real data. The darker gray band indicates the region excluded by CAST experiment [31] and by supernova cooling [60], while the amaranth pink area indicates the region excluded by MOJAVE VLBA polarization observations of parsec-scale jets from active galaxies [46]. The vertical dashed line represents an estimation of the masses for which the ALP DMa candidate can constitute all the ${\rho }_{\mathrm{dm}}$ [57, 58, 59].