3 years ago

# The HST large programme on $\omega$ Centauri -- III. Absolute proper motion.

A. P. Milone, J. Anderson, E. Moreno, L. L. Watkins, R. P. van der Marel, M. Libralato, L. R. Bedin, D. Apai, A. F. Marino, J. M. Rees, A. J. Burgasser, A. Bellini, B. Pichardo, J. G. Fernández-Trincado

In this paper we report a new estimate of the absolute proper motion (PM) of the globular cluster NGC 5139 ($\omega$ Cen) as part of the HST large program GO-14118+14662. We analyzed a field 17 arcmin South-West of the center of $\omega$ Cen and computed PMs with an epoch span of $\sim$15.1 years. We employed 45 background galaxies to link our relative PMs to an absolute reference-frame system. The absolute PM of the cluster in our field is: $(\mu_\alpha \cos\delta , \mu_\delta) = (-3.341 \pm 0.028 , -6.557 \pm 0.043)$ mas yr$^{-1}$. Upon correction for the effects of viewing perspective and the known cluster rotation, this implies that for the cluster center of mass $(\mu_\alpha \cos\delta , \mu_\delta) = (-3.238 \pm 0.028, -6.716 \pm 0.043)$ mas yr$^{-1}$. This measurement is direct and independent, has the highest random and systematic accuracy to date, and will provide an external verification for the upcoming Gaia Data Release 2. It also differs from most reported PMs for $\omega$ Cen in the literature by more than 5$\sigma$, but consistency checks compared to other recent catalogs yield excellent agreement. We computed the corresponding Galactocentric velocity, calculated the implied orbit of $\omega$ Cen in two different Galactic potentials, and compared these orbits to the orbits implied by one of the PM measurements available in the literature. We find a larger (by about 500 pc) perigalactic distance for $\omega$ Cen with our new PM measurement, suggesting a larger survival expectancy for the cluster in the Galaxy.

Publisher URL: http://arxiv.org/abs/1801.01502

DOI: arXiv:1801.01502v2

You might also like
Never Miss Important Research

Researcher is an app designed by academics, for academics. Create a personalised feed in two minutes.
Choose from over 15,000 academics journals covering ten research areas then let Researcher deliver you papers tailored to your interests each day.

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.