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S. J. U. Higdon, J. L. Higdon (Cornell University), B. J. Smith (East Tennessee State University)
The tidal plume in the ring galaxy system Arp 143 (NGC 2444/45) is one of the largest (14.5' or 240 kpc in projection; Ho=70 km s-1 Mpc-1) and consequently, one of the oldest known (~750 Myr). This makes it interesting from the standpoint of the formation and evolution of Tidal Dwarf Galaxies (TDGs). In addition, TDG's may represent instances of present day galaxy formation, and are thus highly relevant for the study of galaxy formation at early epochs.
We present high resolution VLA HI maps of Arp 143's gas plume, which reveal an unprecedented number (25) of condensations with sizes and HI masses characteristic of dwarf galaxies (D>1~kpc, MHI ~108 Mo). These data are complemented by deep WHT Prime Focus Mosaic Camera B, R, and H-alpha images to constrain the stellar masses and populations, and ongoing star formation activity in the HI clumps.
We compare the stellar and HI properties of these condensations to other TDG candidates, as well as bona fide dwarf galaxies. We also compare the distribution and mass function of the condensations in Arp 143's plume with models of TDG formation. The large age difference inferred between the HI plume (~750 Myr) and the ring in NGC 2445 (60 ± 15 Myr) require multiple interactions in the Arp 143 system.