Keplerian rotation of our Galaxy?

TL;DR

This paper investigates the rotation curve of our Galaxy, suggesting that observed flat or Keplerian curves may result from assumptions of circular orbits, and proposes that elliptical orbits could explain these observations.

Contribution

It challenges the common interpretation of flat rotation curves by demonstrating that elliptical orbits can mimic Keplerian or flat profiles in galactic rotation data.

Findings

Verification of Keplerian rotation curve using old open clusters.

Elliptical orbits can produce flat or Keplerian rotation curves when analyzed with circular orbit assumptions.

Potential misinterpretation of galactic rotation curves due to orbit shape assumptions.

Abstract

It is common to attribute a flat rotation curve to our Galaxy. However Galazutdinov et al. (2015) in a recent paper have obtained a Keplerian rotation curve for interstellar clouds in outer parts of the Galaxy. They have calculated the distances from equivalent widths of interstellar CaII lines. The radial velocity was also measured on the interstellar CaII absorption line. We verify the result by Galazutdinov et al. (2015) basing on observations of old open clusters. We propose, that the observations of flat and Keplerian rotation curves may be caused by the assumption of circular orbits. The application of formulas derived with the assumption of circular orbits to elliptical ones may mimics the flat rotation curve. The interstellar clouds with cross-sections larger than stars may have almost circular orbits, and the derived rotation curve will be Keplerian.