Growth of galactic bulges by mergers. II. Low-density satellites

Context. Satellite accretion events have been invoked for mimicking the internal secular evolutionary processes of bulge growth. However, N-body simulations of satellite accretions have paid littl e attention to the evolution of bulge photometric parameters, to the processes driving this evolution, and to the consistency of this evolution wit h observations. Aims. We want to investigate whether satellite accretions indeed drive the growth of bulges, and whether they are consistent with global scaling relations of bulges and discs. Methods. We perform N-body models of the accretion of satellites onto disc galaxi es. A Tully-Fisher (M∝ V � TF rot ) scaling between primary and satellite ensures that density ratios, critical to the outc ome of the accretion, are realistic. We carry out a full struc tural, kinematic and dynamical analysis of the evolution of the bulge mass, bulge central concentration, and bulge-to-disc scaling relations.