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

Ultralight axionlike particles (ALPs) are compelling dark matter candidates because of their potential to resolve small-scale discrepancies between ΛCDM 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 φγ 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 × 10 − 22 eV ≤ m φ ≤ 4 . 7 × 10 − 20 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 GeV/cm 3 , this corresponds to g φγ < 1 . 18 × 10 12 GeV . These new limits represent an improvement over the previous strongest limits set using the same effect by a factor of ∼ 3 . 8.