Searching for axionlike 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 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 /cm³, this corresponds to g_(ϕγ) < 1.18 × 10⁻¹² GeV⁻¹ × ((m_ϕ)/(1.0 × 10⁻²¹ eV)). These new limits represent an improvement over the previous strongest limits set using the same effect by a factor of ∼ 3.8.

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