We present improved constraints on an interacting vacuum model using updated astronomical observations including the first data release from Planck .
We consider a model with one dimensionless parameter , \alpha , describing the interaction between dark matter and vacuum energy ( with fixed equation of state w = -1 ) .
The background dynamics correspond to a generalised Chaplygin gas cosmology , but the perturbations have a zero sound speed .
The tension between the value of the Hubble constant , H _ { 0 } , determined by Planck data plus WMAP polarisation ( Planck+WP ) and that determined by the Hubble Space Telescope ( HST ) can be alleviated by energy transfer from dark matter to vacuum ( \alpha > 0 ) .
A positive \alpha increases the allowed values of H _ { 0 } due to parameter degeneracy within the model using only CMB data . Combining with additional datasets of including supernova type Ia ( SN Ia ) and baryon acoustic oscillation ( BAO ) , we can significantly tighten the bounds on \alpha .
Redshift-space distortions ( RSD ) , which constrain the linear growth of structure , provide the tightest constraints on vacuum interaction when combined with Planck+WP , and prefer energy transfer from vacuum to dark matter ( \alpha < 0 ) which suppresses the growth of structure .
Using the combined datasets of Planck+WP+Union2.1+BAO+RSD , we obtain the constraint on \alpha to be -0.083 < \alpha < -0.006 ( 95 % C.L .
) , allowing low H _ { 0 } consistent with the measurement from 6dF Galaxy survey .
This interacting vacuum model can alleviate the tension between RSD and Planck+WP in the \Lambda CDM model for \alpha < 0 , or between HST measurements of H _ { 0 } and Planck+WP for \alpha > 0 , but not both at the same time .