H I  asymmetry in the isolated galaxy CIG 85 (UGC 1547)

¹ Instituto de Astrofísica de Andalucía (IAA/CSIC), Glorieta de la Astronomia s/n, 18080 Granada, Spain
e-mail: sengupta@iaa.es
² Calar-Alto Observatory, Centro Astronómico Hispano Alemán, C/Jesús Durbán Remón, 2-2 04004 Almeria, Spain
³ Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
⁴ Dept. de Física Teórica y del Cosmos, Facultad de Ciencias, Universidad de Granada, Spain
⁵ University of Wisconsin – Stevens Point, Department of Physics and Astronomy, 2001 Fourth Avenue, Stevens Point, WI 54481-1957, USA
⁶ National Astronomical Observatory of Japan (NAOJ), 2-21-1 Osawa, Mitaka, 181-8588 Tokyo, Japan
⁷ Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003, USA

Received: 4 July 2012
Accepted: 23 August 2012

Abstract

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.