Searching for axion-like time-dependent cosmic birefringence with data from SPT-3G

Abstract

Ultralight axionlike particles (ALPs) are compelling dark matter candidates because of their potential to resolve small-scale discrepancies between $\hat{I}›$CDM predictions and cosmological observations. Axion-photon coupling induces a polarization rotation in linearly polarized photons traveling through an ALP field; thus, as the local ALP dark matter field oscillates in time, distant static polarized sources will appear to oscillate with a frequency proportional to the ALP mass. We use observations of the cosmic microwave background from SPT-3G, the current receiver on the South Pole Telescope, to set upper limits on the value of the axion-photon coupling constant $g_{\ddot{I}•{\hat{I}}^3}$ over the approximate mass range $10^{-22}-10^{-19}$ eV, corresponding to oscillation periods from 12 hours to 100 days. For periods between 1 and 100 days ($4.7\times 10^{-22}\text{ eV}\le m_{\ddot{I}}•\le 4.7\times 10^{-20}\text{ eV}$), where the limit is approximately constant, we set a median 95% C.L. upper limit on the amplitude of on-sky polarization rotation of 0.071 deg. Assuming that dark matter comprises a single ALP species with a local dark matter density of $0.3{\text{ GeV/cm}}^3$, this corresponds to $g_{\ddot{I}•{\hat{I}}^3}<1.18\times 10^{-12}{\text{ GeV}}^{-1}\times \left(\frac{m_{\ddot{I}}•}{1.0\times 10^{-21}\text{ eV}}\right)$. These new limits represent an improvement over the previous strongest limits set using the same effect by a factor of ~3.8.

16 pages, 5 figures. Accepted for publication in Physical Review D