EDP Sciences
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Volume 372, Number 2, June III 2001
Page(s) L29 - L32
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20010435

A&A 372, L29-L32 (2001)
DOI: 10.1051/0004-6361:20010435

A molecular tidal tail in the Medusa minor merger

S. Aalto1, S. Hüttemeister2 and A. G. Polatidis1

1  Onsala Rymdobservatorium, Chalmers Tekniska Högskola, 43992 Onsala, Sweden
2  Astronomisches Institut der Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany

(Received 6 March 2001 / Accepted 23 March 2001)

We have detected CO 1-0 emission along the tidal tail of the NGC 4194 (the Medusa) merger. It is the first CO detection in the optical tail of a minor merger. Emission is detected both in the centre of the tail and at its tip. The molecular mass in the 33'' Onsala 20 m beam is estimated to be $\ga 8.5\times 10^7$ $M_{\odot}$ which is at least 4% of the total molecular mass measured so far in this system. We suggest that the emission is a molecular tidal tail which is part of the extended structure of the main body, and that the molecular gas was thrown out by the collision instead of having formed in situ from condensing atomic material. We find it unlikely that the emission is associated with a tidal dwarf galaxy (even if the future formation of such an object is possible), but high resolution HI, CO and optical observations are necessary to resolve the issue. The Medusa is very likely the result of an elliptical+spiral collison and our detection supports the notion that molecular gas in minor mergers can be found at great distances from the merger centre.

Key words: galaxies: evolution -- galaxies: individual (NGC 4194) -- galaxies: ISM -- galaxies: interacting -- radio lines: galaxies -- radio lines: ISM

Offprint request: S. Aalto, susanne@oso.chalmers.se

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