Dark haloes in Karachentsev's sample of binary galaxies
Tuorla Observatory, University of Turku, 21500 Piikkiö, Finland
Accepted: 9 March 2001
Karachentsev's sample of 585 compact binary galaxies is inspected in order to see a signature of extended massive dark haloes around the component galaxies. Our approach utilizes the good velocity-separation resolution provided by this sample containing many close pairs, in order to see directly the expected trends in the vs. Xproj plane. A developed version of Turner's normalization, attempting to take into acount different sizes of binary orbits (increasing with luminosity), makes it possible to see "directly" a meaningful lower limit of from the emerging short-projection envelope in the vs. Xnorm diagram. This part of the diagram is little influenced by the incompleteness at large values of separation Xproj, which usually leads to too small values of mass-to-luminosity ratios. We conclude that these binaries give relatively direct evidence for the existence of massive dark haloes, with (conservatively) larger than about 25 (for km s-1/Mpc), consistent with the simulation studies on Karachentsev's triplets by Chernin & Mikkola ([CITE]) and on the binaries by Wiren et al. ([CITE]), and other more recent studies of the triplets (Karachentsev [CITE]).
Key words: galaxies: general / dark matter
© ESO, 2001