DDO 68: A FLEA WITH SMALLER FLEAS THAT ON HIM PREY

Abstract

We present new photometry of the dwarf irregular galaxy DDO 68, one of the most metal-poor and least massive dwarfs, located in the Lynx-Cancer Void. The images were acquired with the Large Binocular Telescope in the g and r passbands and show unequivocally that DDO 68 has previously unknown stellar streams related to the accretion of at least two smaller companions: a flea with smaller fleas biting it , to put it in Jonathan Swift’s words (from Jonathan Swift’s On Poetry: a Rhapsody : So, naturalists observe, a flea/has smaller fleas that on him prey/and these have smaller still to bite em/and so proceed ad infinitum). Our data provide direct observational evidence of multiple galaxy merging occurring at very low galactic mass scales. We present the results of an N -body simulation of the interaction of three dwarf galaxies that reproduce well the main morphological features of DDO 68.