Bibcode
Scarpa, R.; Falomo, R.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 523, id.A43
Fecha de publicación:
11
2010
Revista
Número de citas
30
Número de citas referidas
25
Descripción
Context. Stellar kinematics in the external regions of globular clusters
can be used to probe the validity of Newton's law in the low
acceleration regimes without the complication of non-baryonic dark
matter. Indeed, in contrast to the case of galaxies, in globular
clusters a systematic deviation of the velocity dispersion profile from
the expected Keplerian falloff would be indicative of a breakdown of
Newtonian dynamics rather than the existence of dark matter.
Aims: We perform a detailed analysis of the velocity dispersion in the
globular cluster ω Centauri to determine whether it decreases
monotonically with distance as expected within the framework of
Newtonian dynamics, or whether it converges toward a constant value as
recent works suggest. Methods: We combine measurements from two
previous studies to almost double the data available at large radii, to
better constrain the velocity dispersion profile in the low acceleration
regime. Results: We found the inner region of ω Centauri is
clearly rotating, while the rotational velocity tends to vanish, being
consistent with no rotation at all in the external regions. The cluster
velocity dispersion at large radii from the center is found to clearly
deviate from the Newtonian prediction. Conclusions: We conclude
that there are strong similarities between globular clusters and
elliptical galaxies, for in both classes of objects the velocity
dispersion tends to remain constant at large radii. In the case of
galaxies, this is ascribed to the existence of a massive halo of dark
matter, which is physically unlikely in the case of globular clusters.
This similarity, if confirmed, is best explained by a breakdown of
Newtonian dynamics below a critical acceleration.
Tables 2 and 3 are only available in electronic form at http://www.aanda.org
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