EDP Sciences
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Volume 380, Number 2, December III 2001
Page(s) 418 - 424
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20011362

A&A 380, 418-424 (2001)
DOI: 10.1051/0004-6361:20011362

Did VV 29 collide with a dark Dark-Matter halo?

F. H. Briggs1, O. Möller1, J. L. Higdon1, 2, N. Trentham3 and E. Ramirez-Ruiz3

1  Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
2  Department of Astronomy, Cornell University, Ithaca, NY 14853, USA
3  Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK

(Received 27 August 2001 / Accepted 23 September 2001)

Westerbork Radio Synthesis Telescope observation of the galaxy $\rm VV 29=Arp 188=UGC 10214$ shows that there are at least three distinct dynamical components whose kinematics can be traced in 21 cm line emission. The system appears to be the result of a galaxy-galaxy interaction. We identify a sufficient number of dynamical elements containing baryons (stars and neutral gas) that there is no compelling reason to postulate the presence of an additional dark matter halo that is devoid of detectable baryons. The central galaxy VV 29a is massive ( $V_{\rm rot}\sim 330$ km s-1) and gas rich ( $M_{\rm HI}\sim 6 \times 10^{9} h^{-2} M_{\odot}$). The distinctive optical plume (VV 29b), which extends eastward from the main galaxy, is also gas rich ( $M_{\rm HI}\sim 3\times 10^{9} h^{-2} M_{\odot}$) and has a very low gradient in line of sight velocity (< 30 km s-1) over ${\sim}70 h^{-1}$ kpc. On the western side, there is an HI feature of $M_{\rm HI}\sim 4\times 10^{8} h^{-2} M_{\odot}$ that participates strongly in orbital motion about the host in the same sense of rotation as the VV 29a itself. A blue, less massive, gas-rich galaxy "VV 29c" ( $M_{\rm HI}\sim 9\times 10^{8} h^{-2} M_{\odot}$) appears clearly in the HI maps as an ~170 km s-1 wide spectral feature, seen in projection against or, more likely, behind the west side of the host disk. Its high recessional velocity is counter to the host rotation direction. The optical images of Trentham et al. (2001) show signs of this blue dwarf against the redder VV 29a disk. The companion galaxy CGCG 27-021 = MGC 09-26-54 (at projected distance ${\sim}115 h^{-1}$ kpc) is not detected in 21 cm line emission ( $M_{\rm HI}< 10^{9} h^{-2} M_{\odot}$).

Key words: galaxies: dynamics -- galaxies: evolution -- galaxies: interaction -- radio lines: galaxies

Offprint request: F. H. Briggs, fbriggs@astro.rug.nl

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© ESO 2001