Detection of the Keplerian decline in the Milky Way rotation curve

Abstract

Our position inside the Galactic disc has previously prevented us from establishing an accurate rotation curve (RC). The advent of Gaia and its third data release (Gaia DR3) made it possible to specify the RC up to twice the optical radius. We aim to establish a new RC of the Galaxy from the Gaia DR3 by drastically reducing systematic uncertainties. Our goal is to provide a new estimate of the mass of the Galaxy. We compared different estimates, established a robust assessment of the systematic uncertainties, and addressed differences in methodologies, particularly regarding distance estimates. We find a sharply decreasing RC for the Milky Way; the decrease in velocity between 19.5 and 26.5 kpc is approximately 30 km s−1. We identify, for the first time, a Keplerian decline of the RC, starting at ∼19 kpc and ending at ∼26.5 kpc from the Galaxy centre, while a flat RC is rejected with a significance of 3σ. The total mass is revised downwards to 2.06−0.13+0.24 × 1011 M⊙, which is in agreement with the absence of a significant mass increase at radii larger than 19 kpc. We evaluated the upper limit on the total mass by considering the upper values of velocity measurements, which leads to a strict, unsurpassable limit of 5.4 × 1011 M⊙.

The Mass of the Center of the Milky Way Revalued from the Fastest Orbits around the Center and the Circular Velocity Curve of the Milky Way

“…The Figure 1 is a new predicted galactic circular velocity curve by returning to the Newtonian theory of gravity. The observations in [4][5][6][7][8][9][10][11][12][13][14][15] could be complete evidence for it. We emphasize, the observation of the fastest orbits [4][5][6] around the center of the Milky Way is very significant for understanding the mass of the center.…”

“…[4][5][6] And, the ultrafast galaxy bar was observed. [12][13][14][15] Therefore, the mass of the center of the Milky Way could be accurately known from the circular velocity curve of the Milky Way [7][8][9][10][11].…”

“…Here, it is emphasized that the conclusions of current observations were misled by the wrong Poisson equation (or the Poincaré's equation). It is clear, the galactic rotation curve and that the center of the Milky Way is 4 × 10 6 𝑀𝑀 ⨀ only is a conclusion of the Poisson equation and it is clearly contradicted with the new observations in [4][5][6][7][8][9][10][11][12][13][14][15]. Therefore, new understanding and more accurate and precision measurement are needed to have a more accurate mass for the center of the Milky Way.…”

“…From the velocity of the orbit of the Sun around the center of the Milky Way, it could be concluded that the mass of the center of the Milky Way need be 𝑀𝑀 𝑐𝑐𝑝𝑝𝑐𝑐𝑐𝑐𝑝𝑝𝑝𝑝 ~2 × 10 11 𝑀𝑀 ⨀ . In consideration of the circular velocity curve of the Milky Way [7][8][9][10][11], we intend to believe that the mass of the center of the Milky Way should be 𝑀𝑀 𝑐𝑐𝑝𝑝𝑐𝑐𝑐𝑐𝑝𝑝𝑝𝑝 ~10 11 𝑀𝑀 ⨀ . Here, it is emphasized that the conclusions of current observations were misled by the wrong Poisson equation (or the Poincaré's equation).…”

“…From V = �𝐺𝐺𝑀𝑀 𝑅𝑅 ⁄ , the complete figure for the circular velocity curve of the Milky Way for 𝑅𝑅 = 0~30𝑘𝑘𝑘𝑘𝑘𝑘 could be shown with the Figure 1. [4][5][6] and the circular velocity curve of the Milky Way [7][8][9][10][11]. And, the ultrafast galaxy bar [12][13][14][15] could be the evidence for the velocities in R ≤ 6.5kpc.…”