We present an analysis of the radial dependence of the stellar mass function in the diffuse outer-halo globular cluster Palomar 14 .
Using archival HST/WFPC2 data of the cluster ’ s central 39 pc ( corresponding to \sim 0.85 \times r _ { h } ) we find that the mass function in the mass range 0.55 \leq m / M _ { \odot } \leq 0.85 is well approximated by a power-law at all radii .
The mass function steepens with increasing radius , from a shallow power-law slope of 0.66 \pm 0.32 in the cluster ’ s centre to a slope of 1.61 \pm 0.33 beyond the core radius , showing that the cluster is mass-segregated .
This is seemingly in conflict with its long present-day half-mass relaxation time of \sim 20 Gyr , and with the recent finding by Beccari et al .
( 1 ) , who interpret the cluster ’ s non-concentrated population of blue straggler stars as evidence that dynamical segregation has not affected the cluster yet .
We discuss this apparent conflict and argue that the cluster must have either formed with primordial mass segregation , or that its relaxation time scale must have been much smaller in the past , i.e .
that the cluster must have undergone a significant expansion .