Shengqi Yang, Fangzhou Jiang, Andrew Benson, Yi-Ming Zhong, Charlie Mace

| Summary:

[[{“value”:”One necessary step for probing the nature of self-interacting dark matter
(SIDM) particles with astrophysical observations is to pin down any possible
velocity dependence in the SIDM cross section. Major challenges for achieving
this goal include eliminating, or mitigating, the impact of the baryonic
components and tidal effects within the dark matter halos of interest — the
effects of these processes can be highly degenerate with those of dark matter
self-interactions at small scales. In this work we select 9 isolated galaxies
and brightest cluster galaxies (BCGs) with baryonic components small enough
such that the baryonic gravitational potentials do not significantly influence
the halo gravothermal evolution processes. We then constrain the parameters of
a cross section model $sigma(v)=sigma_0/(1+v^2/omega^2)^2$ with the measured
rotation curves and stellar kinematics through the gravothermal fluid formalism
and isothermal method. We are able to constrain a best-fit double power-law
result with the gravothermal fluid formalism
$log(sigma_0/[mathrm{cm^2/g}])=2.6/[(log(omega/[mathrm{km/s}])/1.9)^{0.85}+(log(omega/[mathrm{km/s}])/1.9)^{5.5}]-1.1$
with $log(omega/[mathrm{km/s}])leq3.7$ and a scatter of 0.5 dex at a 68%
confidence level. The constraint given by the isothermal model is
$log(sigma_0/[mathrm{cm^2/g}])=3.9/[(log(omega/[mathrm{km/s}])/1.6)^{0.29}+(log(omega/[mathrm{km/s}])/1.6)^{5.1}]-0.34$
with $1.4leqlog(omega/[mathrm{km/s}])leq3.5$ and a scatter of 0.34 dex at
68% confidence level. Cross sections constrained by the two methods are
consistent at $2sigma$ confidence level, but the isothermal method prefers
cross sections greater than the gravothermal approach constraints by a factor
of $sim4$.”}]] 

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