The absolute motion of the peculiar cluster NGC6791

Abstract

We present improved values of the three components of the absolute space velocity of the open cluster NGC6791. One HST ACS/WFC field with two-epoch observations provides astrometric measurements of objects in a field containing the cluster center. Identification of 60 background galaxies with sharp nuclei allows us to determine an absolute reference point, and measure the absolute proper motion of the cluster. We find (mu_alpha cos(delta), mu_delta)_J2000.0 = (-0.57+/-0.13, -2.45+/-0.12)mas/yr, and adopt V_rad = -47.1+/-0.7km/s from the average of the published values. Assuming a Galactic potential, we calculate the Galactic orbit of the cluster for various assumed distances, and briefly discuss the implications on the nature and the origin of this peculiar cluster.

5 pages, 3 figures, 3 tables. Accepted for publication in A&A Letters, on October 18th 2006

References in corpus (2)

• Absolute motions of globular clusters. II. [HST astrometry and VLT radial velocities in NGC6397]
• CGCG 480-022: A distant lonesome merger?

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• The origin and orbit of the old, metal-rich, open cluster NGC 6791: Insights from kinematics
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