DDO 68: A Flea with Smaller Fleas that on Him Prey
Aloisi, Alessandra; Cignoni, Michele; Sacchi, Elena; Tosi, Monica; Annibali, Francesca; Paris, Diego; Bellazzini, Michele; Cusano, Felice; Nipoti, Carlo; Ciotti, Luca
Italy, United States
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.