Nucleation of dwarf galaxies in the Virgo cluster

Many dwarf galaxies are observed to be nucleated. But some dwarf galaxies, primarily those that are located beyond the core radius of clusters of gala xies, do not appear to be nucleated. We revisit the scenario that the forma tion of dwarf galaxies' nuclei is due to the orbital decay of globular clus ters within them and suggest that the observed dichotomy and spatial depend ence of dwarf galaxy morphology is due to the nature and the relative stren gth of the extragalactic tidal perturbation. Through a series of numerical simulations, Ne show that in dwarf galaxies with a relatively weak external tidal perturbation dynamical friction can lead to significant orbital deca ys of globular clusters and the formation of compact nuclei within a Hubble timescale. Similar tendencies also occur in those dwarf galaxies near the center of clusters of galaxies where the extragalactic tidal perturbation t ends to preserve the integrity of dwarf galaxies. Based on these numerical simulations, we show that the observed central structures of four nucleated dwarf galaxies in the Virgo Cluster are well modeled by superimposing a sm all number of globular clusters onto the background stellar distribution. W e also deduce a hat mass-weighted velocity-dispersion distribution that is consistent with some recent observations and suggest that the cores of nucl eated dwarfs may be slightly off center within similar to1 Gyr after each g lobular cluster merger event. In the outskirts of clusters of galaxies exte rnal tidal perturbation tends to disrupt dwarf galaxies and prevent the sed imentation of the globular clusters within them. We speculate that the resi dual nucleated dwarf galaxies near the central regions of the Virgo Cluster of galaxies may be the first entities to have congregated and remained the re. Such a scenario is consistent with the cold dark matter hypothesis for galaxy formation.