We have used the ACS camera on HST to obtain ( V,I ) photometry for 57,000 red-giant stars in the halo of the Leo elliptical NGC 3377 , an intermediate-luminosity elliptical .
We use this sample of stars to derive the metallicity distribution function ( MDF ) for its halo field stars , and comment on its chemical evolution history compared with both larger and smaller E galaxies .
Our ACS/WFC field spans a radial range extending from 4 to 18 kpc projected distance from the center of NGC 3377 and thus covers a significant portion of this galaxy ’ s halo .
We find that the MDF is broad , reaching a peak at log ( Z / Z _ { \odot } ) \simeq - 0.6 , but containing virtually no stars more metal-poor than log ( Z / Z _ { \odot } ) = -1.5 .
It may , in addition , have relatively few stars more metal-rich than log ( Z / Z _ { \odot } ) = -0.3 , although interpretation of the high-metallicity end of the MDF is limited by photometric completeness that affects the detection of the reddest , most metal-rich stars .
NGC 3377 appears to have an enrichment history intermediate between those of normal dwarf ellipticals and the much larger giants .
As yet , we find no clear evidence that the halo of NGC 3377 contains a significant population of “ young ” ( < 3 Gy ) stars .