Open AccessModified Newtonian dynamics in the Milky Way
Author(s) -
Famaey Benoit,
Binney James
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.09474.x
Subject(s) - physics , milky way , modified newtonian dynamics , gravitational microlensing , dark matter , galaxy , galaxy rotation curve , cosmology , newtonian potential , astrophysics , baryon , cold dark matter , galaxy formation and evolution , gravitation , classical mechanics
Both microlensing surveys and radio‐frequency observations of gas flow imply that the inner Milky Way is completely dominated by baryons, contrary to the predictions of standard cold dark matter (CDM) cosmology. We investigate the predictions of the modified Newtonian dynamics (MOND) formula for the Galaxy given the measured baryon distribution. Satisfactory fits to the observationally determined terminal‐velocity curve are obtained for different choices of MOND's interpolating function μ( x ). However, with simple analytical forms of μ( x ), the local circular speed v c ( R 0 ) can be as large as 220 km s −1 only for values of the parameter a 0 that are excluded by observations of NGC 3198. Only a numerically specified interpolating function can produce v c ( R 0 ) = 220 km s −1 , which is therefore an upper limit in MOND, while the asymptotic velocity is predicted to be v c (∞) = 170 ± 5 km s −1 . The data are probably not consistent with the functional form of μ( x ) that has been explored as a toy model in the framework of Bekenstein's covariant theory of gravity.