This work employs high-quality Hubble Space Telescope ( HST ) Advanced Camera for Surveys ( ACS ) F606W and F814W photometry to correct for the differential reddening affecting the colour-magnitude diagram ( CMD ) of the poorly-studied globular cluster ( GC ) Palomar 2 .
Differential reddening is taken into account by assuming that morphological differences among CMDs extracted across the field of view of Palomar 2 correspond essentially to shifts ( quantified in terms of \delta E ( B - V ) ) along the reddening vector due to a non-uniform dust distribution .
The average reddening difference over all partial CMDs is \overline { \mbox { $ \delta E ( B - V ) $ } } = 0.24 \pm 0.08 , with the highest reaching \mbox { $ \delta E ( B - V ) $ } = 0.52 .
The corrected CMD displays well-defined and relatively narrow evolutionary sequences , especially for the evolved stars , i.e .
the red-giant , horizontal and asymptotic giant branches ( RGB , HB and AGB , respectively ) .
The average width of the upper main sequence and RGB profiles of the corrected CMD corresponds to 56 % of the original one .
Parameters measured on this CMD show that Palomar 2 is \approx 13.25 Gyr old , has the mass M \sim 1.4 \times 10 ^ { 5 } \mbox { $M _ { \odot } $ } stored in stars , is affected by the foreground \mbox { $E ( B - V ) $ } \approx 0.93 , is located at \mbox { $d _ { \odot } $ } \approx 26 Kpc from the Sun , and is characterized by the global metallicity Z / Zo \approx 0.03 , which corresponds to the range -1.9 \leq \mbox { $ [ Fe / H ] $ } \leq - 1.6 ( for 0.0 \leq [ \alpha / Fe ] \leq + 0.4 ) , quite consistent with other outer halo GCs .
Additional parameters are the absolute magnitude M _ { V } \approx - 7.8 , and the core and half-light radii \mbox { r$ { } _ { C } $ } \approx 2.6 pc and R _ { HL } \approx 4.7 pc , respectively .