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

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

Corresponding author: F. H. Briggs, fbriggs@astro.rug.nl

Received: 27 August 2001
Accepted: 23 September 2001

Abstract

Westerbork Radio Synthesis Telescope observation of the galaxy 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 ( km s^-1) and gas rich (). The distinctive optical plume (VV 29b), which extends eastward from the main galaxy, is also gas rich () and has a very low gradient in line of sight velocity ( km s^-1) over kpc. On the western side, there is an HI feature of 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" () 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 kpc) is not detected in 21 cm line emission ().