Kavli Affiliate: George Efstathiou
| First 5 Authors: Calvin Preston, Keir K. Rogers, Alexandra Amon, George Efstathiou,
| Summary:
We investigate the degeneracy between the effects of ultra-light axion dark
matter and baryonic feedback in suppressing the matter power spectrum. We
forecast that galaxy shear data from the Rubin Observatory’s Legacy Survey of
Space and Time (LSST) could limit an axion of mass $m = 10^{-25},mathrm{eV}$
to be $lesssim 5%$ of the dark matter, stronger than any current bound, if
the interplay between axions and feedback is accurately modelled. Using a halo
model emulator to construct power spectra for mixed cold and axion dark matter
cosmologies, including baryonic effects, we find that galaxy shear is sensitive
to axions from $10^{-27},mathrm{eV}$ to $10^{-21},mathrm{eV}$, with the
capacity to set competitive bounds across much of this range. For axions with
$m sim 10^{-25},mathrm{eV}$, the scales at which axions and feedback impact
structure formation are similar, introducing a parameter degeneracy. We find
that, with an external feedback constraint, we can break the degeneracy and
constrain the axion transfer function, such that LSST could detect a
$10^{-25},mathrm{eV}$ axion comprising 10% of the dark matter at $sim 3
sigma$ significance. Direct reconstruction of the non-linear matter power
spectrum provides an alternative way of analysing weak lensing surveys, with
the advantage of identifying the scale-dependent features in the data that the
dark matter model imposes. We advocate for dedicated cosmological
hydrodynamical simulations with an axion dark matter component so that upcoming
galaxy and cosmic microwave background lensing surveys can disentangle the dark
matter-baryon transfer function.
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