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We investigate the properties of dark energy halos in models with a
nonminimal coupling in the dark sector. We show, using a quasistatic
approximation, that a coupling of the mass of dark matter particles to a
standard quintessence scalar field $\phi$ generally leads to the formation of
dark energy concentrations in and around compact dark matter objects. These are
associated with regions where scalar field gradients are large and the dark
energy equation of state parameter is close to $-1/3$. We find that the energy
and radius of a dark energy halo are approximately given by $E_{\rm halo} \sim
\boldsymbol{\beta}^2 \varphi \, m$ and $r_{\rm halo} \sim
\sqrt{\boldsymbol{\beta} \,\varphi ({R}/{H})}$, where $\varphi=Gm/(R c^2)$, $m$
and $R$ are, respectively, the mass and radius of the associated dark matter
object, $\boldsymbol{\beta} = -(8\pi G)^{-1/2} d \ln m/d \phi$ is the
nonminimal coupling strength parameter, $H$ is the Hubble parameter, $G$ is the
gravitational constant, and $c$ is the speed of light in vacuum. We further
show that current observational limits on $\boldsymbol{\beta}$ over a wide
redshift range lead to stringent constraints on $E_{\rm halo}/m$ and,
therefore, on the impact of dark energy halos on the value of the dark energy
equation of state parameter. We also briefly comment on potential backreaction
effects that may be associated with the breakdown of the quasistatic
approximation and determine the regions of parameter space where such a
breakdown might be expected to occur.