Despite considerations of mass loss from stellar evolution suggesting otherwise , the content of gas in globular clusters seems poor and hence its measurement very elusive .
One way of constraining the presence of ionized gas in a globular cluster is through its dispersive effects on the radiation of the millisecond pulsars included in the cluster .
This effect led Freire et al .
in 2001 to the first detection of any kind of gas in a globular cluster in the case of 47 Tucanae .
By exploiting the results of 12 additional years of timing , as well as the observation of new millisecond pulsars in 47 Tucanae , we revisited this measurement : we first used the entire set of available timing parameters in order to measure the dynamical properties of the cluster and the three-dimensional position of the pulsars .
Then we applied and tested various gas distribution models : assuming a constant gas density , we confirmed the detection of ionized gas with a number density of n = 0.23 \pm 0.05 cm ^ { -3 } , larger than the previous determination ( at 2 \sigma uncertainty ) .
Models predicting a decreasing density or following the stellar distribution density are highly disfavoured .
We are also able to investigate the presence of an intermediate mass black hole in the centre of the cluster , showing that is not required by the available data , with an upper limit for the mass at \sim 4000 M _ { \odot } .