Unusual displacement of HI due to tidal interaction in Arp 181

TL;DR

This study reveals that most HI gas in the interacting galaxy pair Arp 181 has been displaced far beyond their optical disks due to tidal interactions, with significant implications for understanding galaxy evolution and dwarf galaxy formation.

Contribution

First detailed HI 21 cm line observations of Arp 181 showing extensive HI displacement and tidal features, highlighting the role of interactions in gas redistribution and dwarf galaxy formation.

Findings

90% of HI displaced beyond optical disks

HI bridge indicates tidal interaction

Enhanced star formation in associated dwarf galaxy

Abstract

We present results from GMRT HI 21 cm line observations of the interacting galaxy pair Arp 181 (NGC 3212 and NGC 3215) at z =0.032. We find almost all of the detected HI (90%) displaced well beyond the optical disks of the pair with the highest density HI located ~70 kpc west of the pair. An HI bridge extending between the optical pair and the bulk of the HI together with their HI deficiencies provide strong evidence that the interaction between the pair has removed most of their HI to the current projected position. HI to the west of the pair has two approximately equal intensity peaks. The HI intensity maximum furthest to the west coincides with a small spiral companion SDSS J102726.32+794911.9 which shows enhanced mid-infrared (Spitzer), UV (GALEX) and H alpha emission indicating intense star forming activity. The HI intensity maximum close to the Arp 181 pair, coincides with a diffuse optical cloud detected in UV (GALEX) at the end of the stellar and HI tidal tails originating at NGC 3212 and, previously proposed to be a tidal dwarf galaxy in formation. Future sensitive HI surveys by telescopes like ASKAP should prove to be powerful tools for identifying tidal dwarfs at moderate to large redshifts to explore in detail the evolution of dwarf galaxies in the Universe.