EDP Sciences
Free access
Volume 371, Number 2, May IV 2001
Page(s) 470 - 475
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20010394

A&A 371, 470-475 (2001)
DOI: 10.1051/0004-6361:20010394

Dark haloes in Karachentsev's sample of binary galaxies

P. Teerikorpi

Tuorla Observatory, University of Turku, 21500 Piikkiö, Finland

(Received 1 February 2001 / 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 M/L vs. $X_{\rm proj}$ 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 M/L from the emerging short-projection envelope in the M/L vs. $X_{\rm norm}$ diagram. This part of the diagram is little influenced by the incompleteness at large values of separation $X_{\rm proj}$, 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 M/L (conservatively) larger than about 25 (for H0 = 75 km s-1/Mpc), consistent with the simulation studies on Karachentsev's triplets by Chernin & Mikkola (1991) and on the binaries by Wiren et al. (1996), and other more recent studies of the triplets (Karachentsev 2000).

Key words: galaxies: general -- dark matter

© ESO 2001