Dynamical streams in the solar neighbourhood

Details Dynamical streams in the solar neighbourhood Dynamical streams in the solar neighbourhood

2004-11-18

arxiv.org/abs/astro-ph/0411540v1

Astronomy and Astrophysics

Astrophysics

5 pages, 1 figure, to appear in The Three Dimensional Universe with GAIA, eds M. Perryman & C. Turon

Scientific paper

The true nature of the Hyades and Sirius superclusters is still an open question. In this contribution, we confront Eggen's hypothesis that they are cluster remnants with the results of a kinematic analysis of more than 6000 K and M giants in the solar neighbourhood. This analysis includes new radial velocity data from a large survey performed with the Coravel spectrometer, complemented by Hipparcos parallaxes and Tycho-2 proper motions (Famaey et al. 2004). A maximum-likelihood method, based on a bayesian approach, has been applied to the data, in order to make full use of all the available data (including less precise parallaxes) and to derive the properties of the different kinematic subgroups. Two such subgroups can be identified with the Hyades and Sirius superclusters. Stars belonging to them span a very wide range of age, which is difficult to account for in Eggen's scenario. These groups are thus most probably "dynamical streams" related to the dynamical perturbation by spiral waves rather than to cluster remnants. In this scenario, the Hyades and Ursa Major clusters just happen to be in the Hyades and Sirius streams, which are purely dynamical features that have nothing to do with the remnants of more massive primordial clusters. This mechanism could be the key to understanding the presence of an old metal-rich population, and of many exoplanetary systems in our neighbourhood. Moreover, a strong spiral pattern seems to be needed in order to yield such prominent streams. Since spiral structure is usually baryonic, this would leave very little room for dark matter. This may be an indication that the era of the dark-matter paradigm explaining the dynamics of the Galaxy may come to an end, and is being superseded by modified gravity.

Affiliated with

Also associated with

No associations

Rating

Dynamical streams in the solar neighbourhood does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Dynamical streams in the solar neighbourhood, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dynamical streams in the solar neighbourhood will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-257195