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In order to study the internal dynamics of actual galaxy pairs, we need toderive the probability distribution function (PDF) of true 3D (orbital)intervelocities and interdistances between pair members from their observed(projected) values, and of the pair masses from Kepler's third law. OurIsolated Galaxy Pair Catalog (IGPC) of 13114 pairs \cite{Nottale2018a} is usedhere for this research. The algorithms of statistical deprojection elaboratedin \cite{Nottale2018b} are applied to these observational data. We derive theorbital velocity PDFs for the whole catalog and for several selectedsubsamples. The interdistance PDF is deprojected and compared to analyticalprofiles which are expected from semi-theoretical arguments. The PDF ofdeprojected pair orbital velocities is characterized by the existence of a mainprobability peak around $\approx 150$ km.s$^{-1}$ for all subsamples of theIGPC as well as for the UGC pair catalog \cite{Chamaraux2016}. Theinterdistance PDFs of both the projected and deprojected data are described atlarge distances by the same power law with exponent $\approx -2$. The wholedistributions, including their cores, are fairly fitted by King profiles. Themass deprojection yields a mass/luminosity ratio for the pairs of $M/L=(30 \pm5)$ in Solar units. The orbital velocity probability peak is observed at thesame value, $\approx 150$ km/s, as the main exoplanet velocity peak, whichpoints toward a possible universality of Keplerian structures, whatever thescale. The pair $M/L$ ratio is just 5 times the standard ratio for luminousmatter, which does not require the existence of non-baryonic dark matter inthese systems.

Statistical deprojection of intervelocities, interdistances and masses in the Isolated Galaxy Pair Catalog