Issue |
A&A
Volume 405, Number 1, July I 2003
|
|
---|---|---|
Page(s) | L15 - L18 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361:20030762 | |
Published online | 16 June 2003 |
Letter to the Editor
Using globular clusters to test gravity in the weak acceleration regime
European Southern Observatory, 3107 Alonso de Cordova, Santiago, Chile
Corresponding author: R. Scarpa, rscarpa@eso.org
Received:
21
March
2003
Accepted:
19
May
2003
We have carried out a study of the velocity dispersion of
the stars in the outskirts of the globular cluster ω Cen, finding
that the velocity dispersion remains constant at large radii rather
than decrease monotonically. The dispersion starts to be constant for
an acceleration of gravity of cm s-2. A similar result is obtained reanalyzing existing data for
the globular cluster M15 where the profile flattens out for
cm s-2. In both cases the
acceleration is comparable to that at which the effect of dark matter
becomes relevant in galaxies. Explanations for this result within
Newtonian dynamics exist (e.g. cluster evaporation, tidal effects,
presence of dark matter) but require ad hoc tuning of the relevant
parameters in order to make in both clusters the dispersion profile
flat starting exactly at the same acceleration. We suggest that this
result, together with a similar one for Palomar 13 and the anomalous
behavior of spacecrafts outside the solar system, may indicate a
breakdown of Newton's law in the weak acceleration regime. Although
not conclusive, these data prompt for the accurate determination of
the internal dynamics of as many GCs as possible.
Key words: gravity / globular cluster / star dynamics
© ESO, 2003
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.