A ~ 12 kpc H i extension and other H i asymmetries in the isolated galaxy CIG 340 (IC 2487)

T. C. Scott, C. Sengupta, L. Verdes Montenegro, A. Bosma, E. Athanassoula, J. Sulentic, D. Espada, M. S. Yun, MARIA DEL CARMEN ARGUDO FERNANDEZ

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7 Scopus citations


Context. H i kinematic asymmetries are common in late-type galaxies irrespective of environment, although the amplitudes are strikingly low in isolated galaxies. As part of our studies of the H i morphology and kinematics in isolated late-type galaxies we have chosen several very isolated galaxies from the AMIGA sample for H i mapping. We present here the results of H i mapping of CIG 340 (IC 2487) which was selected because its integrated H i spectrum has a very symmetric profile (Aflux = 1.03 ± 0.02). Aims. Optical images of the galaxy hinted at a warped disk in contrast to the symmetric integrated H i spectrum profile. Our aim is to determine the extent to which the optical asymmetry is reflected in the resolved H i morphology and kinematics. Methods. Resolved 21-cm H i line mapping has been carried out using the Giant Metrewave Radio Telescope (GMRT). The H! i morphology and kinematics from this mapping together with other multi-wavelength data have been used to study the relationship between the H i and stellar components of CIG 340. Results. GMRT observations reveal significant H i morphological asymmetries in CIG 340 despite it's overall symmetric optical form and highly symmetric H i spectrum. The most notable H i features are: 1) a warp in the H i disk (with an optical counterpart), 2) the H i north/south flux ratio = 1.32 is much larger than expected from the integrated H i spectrum profile, and 3) a ~ 45′′ (12 kpc) H i extension containing ~6% of the detected H i mass on the northern side of the disk. Conclusions. Overall, we conclude that in isolated galaxies a highly symmetric H i spectrum can mask significant H i morphological asymmetries which can be revealed by H i interferometric mapping. The northern H i extension appears to be the result of a recent perturbation (108 yr), possibly by a satellite which is now disrupted or projected within the disk. But, we cannot rule out that the H i extension and the other observed asymmetries are the result of a long lived dark matter halo asymmetry. This study provides an important step in our ongoing programme to determine the predominant source of H i asymmetries in isolated galaxies. For CIG 340 the isolation from major companions, symmetric H i spectrum, optical morphology and interaction timescales have allowed us to narrow the possible causes the H i asymmetries and identify tests to further constrain the source of the asymmetries.

Original languageEnglish
Article numberA56
JournalAstronomy and Astrophysics
StatePublished - Jul 2014
Externally publishedYes


  • Galaxies: individual: CIG 340 (IC 2487)
  • Galaxies: ISM
  • Radio lines: galaxies

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