Surface photometry of shell galaxies : NGC 2865, NGC 3923, and NGC 5018
Résumé
We present CCD surface photometry in four passbands of shells around three bright elliptical galaxies, NGC 2865, NGC 3923 and NGC 5018. Colors, profiles across the shells, and the precise geometry of the shells are determined. The observations all favor a merger process as the origin of the shells, and the colors are consistent with those of a recently accreted small galaxy. The characteristic thickness of the shells are of the order 10 % or less of their distance from the center of the galaxy.