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

Abstract

In order to study the internal dynamics of actual galaxy pairs, we need to derive 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. Our Isolated Galaxy Pair Catalog (IGPC) of 13114 pairs \cite{Nottale2018a} is used here for this research. The algorithms of statistical deprojection elaborated in \cite{Nottale2018b} are applied to these observational data. We derive the orbital velocity PDFs for the whole catalog and for several selected subsamples. The interdistance PDF is deprojected and compared to analytical profiles which are expected from semi-theoretical arguments. The PDF of deprojected pair orbital velocities is characterized by the existence of a main probability peak around $\approx 150$ km.s${}^{-1}$ for all subsamples of the IGPC as well as for the UGC pair catalog \cite{Chamaraux2016}. The interdistance PDFs of both the projected and deprojected data are described at large distances by the same power law with exponent $\approx -2$. The whole distributions, including their cores, are fairly fitted by King profiles. The mass deprojection yields a mass/luminosity ratio for the pairs of $M/L=(30\pm 5)$ in Solar units. The orbital velocity probability peak is observed at the same value, $\approx 150$ km/s, as the main exoplanet velocity peak, which points toward a possible universality of Keplerian structures, whatever the scale. The pair $M/L$ ratio is just 5 times the standard ratio for luminous matter, which does not require the existence of non-baryonic dark matter in these systems.

24 pages, 19 figures, submitted for publication

References in corpus (3)

• HyperLEDA. III. The catalogue of extragalactic distances
• Close galaxy pairs with accurate photometric redshifts
• A catalog of UGC isolated galaxy pairs with accurate radial velocities

Cited by in corpus (4)

• From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity
• On the Orbital Velocity of Isolated Galaxy Pairs: II Accurate MOND Predictions
• The intervelocity of galaxy pairs in $\Lambda$CDM -- The observed velocity peak at ~130 km/s is not unique to MOND
• On the Orbital Velocity of Isolated Galaxy Pairs: a test of gravity in the low acceleration regime