Formation of blue compact dwarf galaxies from merging and interacting gas-rich dwarfs

Abstract

Abstract We present the results of numerical simulations which show the formation of blue compact dwarf (BCD) galaxies from merging between very gas-rich dwarfs with extended H i gas discs. We show that dwarf–dwarf merging can trigger central starbursts and form massive compact cores dominated by young stellar populations. We also show that the pre-existing old stellar components in merger precursor dwarfs can become diffuse low surface brightness components after merging. The compact cores dominated by younger stellar populations and embedded in more diffusely distributed older ones can be morphologically classified as BCDs. Since new stars can be formed from gas transferred from the outer part of the extended gas discs of merger precursors, new stars can be very metal-poor ([Fe/H] < -1). Owing to very high gaseous pressure exceeding 105kB (where kB is the Boltzmann constant) during merging, compact star clusters can be formed in forming BCDs. The BCDs formed from merging can still have extended H i gas discs surrounding their blue compact cores. We discuss whether tidal interaction of gas-rich dwarfs without merging can also form BCDs.