Journal Article

Chemically tagging the Hyades stream: does it partly originate from the Hyades cluster?*

L. Pompéia, T. Masseron, B. Famaey, S. Van Eck, A. Jorissen, I. Minchev, A. Siebert, C. Sneden, J. R. D. Lépine, C. Siopis, G. Gentile, T. Dermine, E. Pasquato, H. Van Winckel, C. Waelkens, G. Raskin, S. Prins, W. Pessemier, H. Hensberge, Y. Frémat, L. Dumortier and O. Bienaymé

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 415, issue 2, pages 1138-1154
Published in print August 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18685.x
Chemically tagging the Hyades stream: does it partly originate from the Hyades cluster?*

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The Hyades stream has long been thought to be a dispersed vestige of the Hyades cluster. However, recent analyses of the parallax distribution, of the mass function, and of the action-space distribution of stream stars have shown it to be rather composed of orbits trapped at a resonance of a density disturbance. This resonant scenario should leave a clearly different signature in the element abundances of stream stars than the dispersed cluster scenario, since the Hyades cluster is chemically homogeneous. Here, we study the metallicity as well as the element abundances of Li, Na, Mg, Fe, Zr, Ba, La, Ce, Nd and Eu for a random sample of stars belonging to the Hyades stream, and compare them with those of stars from the Hyades cluster. From this analysis: (i) we independently confirm that the Hyades stream cannot be solely composed of stars originating in the Hyades cluster; (ii) we show that some stars (namely 2/21) from the Hyades stream nevertheless have abundances compatible with an origin in the cluster; (iii) we emphasize that the use of Li as a chemical tag of the cluster origin of main-sequence stars is very efficient in the range 5500 K ≤ Teff≤ 6200 K, since the Li sequence in the Hyades cluster is very tight, while at the same time spanning a large abundance range; (iv) we show that, while this evaporated population has a metallicity excess of ∼0.2 dex with respect to the local thin-disc population, identical to that of the Hyades cluster, the remainder of the Hyades stream population has still a metallicity excess of ∼0.06–0.15 dex, consistent with an origin in the inner Galaxy and (v) we show that the Hyades stream can be interpreted as an inner 4:1 resonance of the spiral pattern: this then also reproduces an orbital family compatible with the Sirius stream, and places the origin of the Hyades stream up to 1 kpc inwards from the solar radius, which might explain the observed metallicity excess of the stream population.

Keywords: Galaxy: evolution; Galaxy: kinematics and dynamics; open clusters and associations: individual: Hyades

Journal Article.  9187 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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