Do counter rotating galaxies have dark matter? Have counter rotating dark matter galaxies been observed?
Counter rotating galaxies, you may already know, are galaxies where some stars or arms rotate in one direction and other stars or arms rotate in an opposite direction, possibly due to the merger of two or more galaxies.
 A: As you probably know, the presence of dark matter in galaxies can be assumed true due to the analysis of the velocity curves. In 1970, Freeman determined the velocity profiles of galaxies using the 21 cm line and he found that for NGC300 and M33 there should have been much more gravitational mass outside the last bright point. In the same year, Rubin and Ford (1970) determined the velocity profile for M31: the profile was flat until 24kpc, which is much greater than the last photometric radius.
The physical predicted model of a rotation curve of a galaxy must decrease smoothly following a keplerian model after the last luminous radius. As you can see, most studied galaxies show that their velocity curves are flat outside of their last visible point. The most accepted idea to solve this discrepancy between real and the predicted models is the hypothesis of the presence of dark matter in the galaxy halo. Another important parameter to estimate the presence of dark matter is the mass/luminosity ratio. For our Galaxy it has an approximate value of $~50 M_{\odot}/L_{\odot}$ (Binney and Tremaine 2008). This means that there should be mass that is not visible, maybe condensated in dark matter, brown dwarfs or other non luminous bodies.
In order to answer your question, counter rotating galaxies may have similar velocity curves and they can have the presence of gravitational but not luminous mass in there halo. As you can see in this small paper on the counter rotating Sa NGC3539 galaxy, https://ned.ipac.caltech.edu/level5/March14/Corsini/Corsini2.html, there is a plot at the end, which perfectly shows the velocity profile: it stays flat outside of the last radius instead of decreasing as predicted. This can be explained assuming that the halo is filled with dark matter.
