Gas and dark matter in the Sculptor group: NGC 55

Tobias Westmeier, B.S. Koribalski, R. Braun

    Research output: Contribution to journalArticlepeer-review

    27 Citations (Scopus)


    We present new, sensitive HI observations of the Sculptor group galaxy NGC 55 with the Australia Telescope Compact Array. We achieve a 5s HI column density sensitivity of 1019 cm-2 over a spectral channel width of 8 km s-1 for emission filling the 158×84 arcsec synthesized beam. Our observations reveal for the first time the full extent of the HI disc of NGC 55 at this sensitivity and at a moderately high spatial resolution of about 1 kpc. The HI disc of NGC 55 appears to be distorted on all scales. There is a strong east-west asymmetry in the column density distribution along the major axis, suggesting that the disc is under the influence of ram-pressure forces. We also find evidence of streaming motions of the gas along the bar of NGC 55. The fitting of tilted rings to the velocity field reveals a strong warping of the outer gas disc which could be the result of tidal interaction with either NGC 300 or a smaller satellite galaxy. Finally, we find a large numbe of distinct clumps and spurs across the entire disc, indicating that internal or external processes, such as satellite accretion or gas outflows, have stirred up the gas disc. We also detect several isolated HI clouds within about 20 kpc projected distance from NGC 55. Their dynamical properties and apparent concentration around NGC 55 suggest that most of the clouds are forming a circumgalactic population similar to the high-velocity clouds of the Milky Way and M31, although two of the clouds could be foreground objects and part of the Magellanic Stream. While it is difficult to determine the origin of these clouds, our data seem to favour either tidal stripping or gas outflows as the source of the gas. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
    Original languageEnglish
    Pages (from-to)3511-3525
    JournalMonthly Notices of the Royal Astronomical Society
    Issue number4
    Publication statusPublished - 2013


    Dive into the research topics of 'Gas and dark matter in the Sculptor group: NGC 55'. Together they form a unique fingerprint.

    Cite this