Implications of the Milky Way Declining Rotation Curve

2024/09/25 by Moffat, J. W., Sharron, H., Toth, V. T.
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc)

paper · doi:10.48550/arxiv.2409.17371

Abstract

Almost all spiral galaxies have been observed to have flattening rotation curves. The new Gaia DR3 released data shows a Milky Way sharply Keplerian declining rotation curve, starting at ∼ 16 kpc and ending at 26.5 kpc. The data reduces the total Milky Way mass by an order of magnitude, M=2.06× 10¹¹M_\odot, compared to the standard required dark matter halo mass, (2-5)×10¹²M_\odot. Newtonian and modified gravity (MOG) fits are applied to the Gaia DR3 rotation curve data. The fit obtained using MOG has a total mass of M∼1.3× 10¹¹M_\odot, while the Newtonian fit predicts a mass of M∼2× 10¹¹M_\odot. These are in excess of the estimated visible baryon mass of the Milky Way, M_b∼ (0.6-1.0)× 10¹¹M_\odot. It is possible that if the cicumgalactic (CGM) plasma-gas continues to be confirmed experimentally, then the additional baryon mass required to account for the estimated total Milky Way mass could be attributed to the CGM hot plasma-gas halo.

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