We present new broad-band optical and near-infrared CCD imaging together with deep optical intermediate-resolution spectroscopy of Mkn 1087 and its surrounding objects .
We analyze the morphology and colors of the stellar populations of the brightest objects , some of them star-formation areas , as well as the kinematics , physical conditions and chemical composition of the ionized gas associated with them .
Mkn 1087 does not host an Active Galactic Nucleus , but it could be a Luminous Compact Blue Galaxy .
Although it was classified as a suspected Wolf-Rayet galaxy , we do not detect the spectral features of these sort of massive stars .
Mkn 1087 shows morphological and kinematical features that can be explained assuming that it is in interaction with two nearby galaxies : the bright KPG 103a and a dwarf ( M _ { B } \sim - 18 ) star-forming companion .
We argue that this dwarf companion is not a tidal object but an external galaxy because of its low metallicity [ 12+log ( O/H ) = 8.24 ] with respect to the one derived for Mkn 1087 [ 12+log ( O/H ) = 8.57 ] and its kinematics .
Some of the non-stellar objects surrounding Mkn 1087 are connected by bridges of matter with the main body , host star-formation events and show similar abundances despite their different angular distances .
These facts , together their kinematics , suggest that they are tidal dwarf galaxies formed from material stripped from Mkn 1087 .
A bright star-forming region at the south of Mkn 1087 ( knot # 7 ) does not show indications of being a tidal galaxy or the product of a merging process as suggested in previous works .
We argue that Mkn 1087 and its surroundings should be considered a group of galaxies .