Chandreyee Sengupta

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.

Context. We present the results from the Giant Metrewave Radio Telescope (GMRT) interferometric H i and 20 cm radio continuum observations of CIG 85, an isolated asymmetric galaxy from the AMIGA (Analysis of the Interstellar Medium of Isolated GAlaxies – http://amiga.iaa.es) sample.Aims. Despite being an isolated galaxy, CIG 85 showed an appreciable optical and Hi spectral asymmetry and therefore was an excellent candidate for resolved Hi studies to understand the reasons giving rise to asymmetries in isolated galaxies.Methods. The galaxy was imaged in H i and 20 cm radio continuum using the GMRT. For a detailed discussion of the results we also made use of multi-wavelength data from archival SDSS, GALEX and Hα imaging.Results. We find the H i in CIG 85 to have a clumpy, asymmetric distribution which in the NW part is correlated with optical tail like features, but the H i velocity field displays a relatively regular rotation pattern. Evaluating all the observational evidence, we come to a conclusion that CIG 85 is most likely a case of a disturbed spiral galaxy which now appears to have the morphology of an irregular galaxy. Although it is currently isolated from major companions, the observational evidence is consistent with H i asymmetries, a highly disturbed optical disk and recent increase in star formation having been caused by a minor merger, remnants of which are now projected in front of the optical disk. If this is correct, the companion will be fully accreted by CIG 85 in the near future.

We present the results from the Giant Metrewave Radio Telescope (GMRT) interferometric HI and 20 cm radio continuum observations of CIG 85, an isolated asymmetric galaxy from the AMIGA (Analysis of the Interstellar Medium of Isolated GAlaxies) sample. Despite being an isolated galaxy, CIG 85 showed an appreciable optical and HI spectral asymmetry and therefore was an excellent candidate for resolved HI studies to understand the reasons giving rise to asymmetries in isolated galaxies. The galaxy was imaged in HI and 20 cm radio continuum using the GMRT. For a detailed discussion of the results we also made use of multi-wavelength data from archival SDSS, GALEX and Halpha imaging. We find the HI in CIG 85 to have a clumpy, asymmetric distribution which in the NW part is correlated with optical tail like features, but the HI velocity field displays a relatively regular rotation pattern. Evaluating all the observational evidence, we come to a conclusion that CIG 85 is most likely a case of a disturbed spiral galaxy which now appears to have the morphology of an irregular galaxy. Although it is currently isolated from major companions, the observational evidence is consistent with HI asymmetries, a highly disturbed optical disk and recent increase in star formation having been caused by a minor merger, remnants of which are now projected in front of the optical disk. If this is correct, the companion will be fully accreted by CIG 85 in the near future.