Kavli Affiliate: Kiyoshi Masui
| First 5 Authors: Wenxiu Yang, Yitian Sun, Yougang Wang, Katelin Schutz, Yichao Li
| Summary:
Axions are one of the leading dark matter candidates. If we are embedded in a
Milky Way dark matter halo comprised of axions, their stimulated decay would
enable us to observe a counterimage (“axion gegenschein") with a frequency
equal to half the axion mass in the opposite direction of a bright radio
source. This spectral line emission will be broadened to $Delta nu/nu sim
sigma_d/c sim 10^{-3}$ due to the velocity dispersion of dark matter,
$sigma_d$. In this pilot study, we perform the first search for the expected
axion gegenschein image of Vela supernova remnant (SNR) with 26.4 hours of
effective ON-OFF data from the Five-hundred-meter Aperture Spherical radio
Telescope (FAST) L-band (1.0 – 1.5~GHz) 19-beam receiver. Our null detection
limits the axion-photon coupling strength to be $g_{agammagamma} lesssim 2
times 10^{-10} mathrm{GeV}^{-1}$ in the mass ranges of $8.7,mumathrm{eV}
leq m_a leq 9.44,mumathrm{eV}$ and $10.85,mumathrm{eV} leq m_a leq
12.01,mumathrm{eV} $. These results provide a stronger constraint on
$g_{agammagamma}$ in this axion mass range than the current limits obtained
by the direct search of axion decay signal from galaxy clusters which uses FAST
observations, but is a factor of $sim 3$ times weaker than the current CAST
limit.Based on our observation strategy, data processing methods, and results,
the expected sensitivity will reach $sim 10^{-11}mathrm{GeV}^{-1}$ with $sim
2000$ hours of observation in the future.
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