Program: GN-2005B-Q-26

In the framework of our spectroscopic study of the emission-line populations of the galaxies in the Local Group, we propose to make a spectroscopic study of the PNe population in the dwarf spheroidal galaxy NGC 147, one of the companions of the Andromeda galaxy. From these spectra we aim at deriving their chemical abundances, which will be used to determine the chemical abundance at the time their stellar progenitors were born, by considering elements that are not processed during the stellar lifetime. This information, combined with the chemical abundances from the oldest Pop II (Han et al. 1997), will allow us to determine more accurately the chemical evolution of this peculiar galaxy --which is dust and gas free, and probably stopped its star formation several Gyr ago-- and to compare it with the chemical evolution history of its sister galaxy, NGC 185, which apparently had a different evolution.