Gaia Data Release 1. Open cluster astrometry: performance, limitations, and future prospects

Context. The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry, the proper motion and parallax are calculated using Hipparcos and Tycho-2 positions in 1991.25 as prior information. Aim...

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Detalles Bibliográficos
Autores: van Leeuwen, F., Vallenari, A., Jordi i Nebot, Carme, Luri Carrascoso, Xavier, Castañeda Pons, Javier Bernardo, Fabricius, Claus, Masana Fresno, Eduard, Portell i de Mora, Jordi, Torra Roca, Jorge, Balaguer Núñez, María de los Dolores, Borrachero, Raúl, Carrasco Martínez, José Manuel, Clotet Altarriba, Marcial, Figueras Siñol, Francesca, Garralda Torre, Nora, González Vidal, Juan José, Julbe, Francesc, Molina Martínez, Daniel, Mor Crespo, Roger, Romero Gómez, Mercè, Soria Nieto, Sergio, Voss, Hölger, Weiler, Michael, Antoja, T. (Teresa), Gaia Collaboration
Tipo de recurso: artículo
Estado:Versión publicada
Fecha de publicación:2017
País:España
Institución:Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya)
Repositorio:Recercat. Dipósit de la Recerca de Catalunya
OAI Identifier:oai:recercat.cat:2445/127905
Acceso en línea:https://hdl.handle.net/2445/127905
Access Level:acceso abierto
Palabra clave:Astrometria
Paral·laxi
Galàxies
Cúmuls de galàxies
Astrometry
Parallax
Galaxies
Clusters of galaxies
Descripción
Sumario:Context. The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry, the proper motion and parallax are calculated using Hipparcos and Tycho-2 positions in 1991.25 as prior information. Aims. We investigate the scientific potential and limitations of the TGAS component by means of the astrometric data for open clusters. Methods. Mean cluster parallax and proper motion values are derived taking into account the error correlations within the astrometric solutions for individual stars, an estimate of the internal velocity dispersion in the cluster, and, where relevant, the e ects of the depth of the cluster along the line of sight. Internal consistency of the TGAS data is assessed. Results. Values given for standard uncertainties are still inaccurate and may lead to unrealistic unit-weight standard deviations of least squares solutions for cluster parameters. Reconstructed mean cluster parallax and proper motion values are generally in very good agreement with earlier Hipparcos-based determination, although the Gaia mean parallax for the Pleiades is a significant exception. We have no current explanation for that discrepancy. Most clusters are observed to extend to nearly 15 pc from the cluster centre, and it will be up to future Gaia releases to establish whether those potential cluster-member stars are still dynamically bound to the clusters. Conclusions. The Gaia DR1 provides the means to examine open clusters far beyond their more easily visible cores, and can provide membership assessments based on proper motions and parallaxes. A combined HR diagram shows the same features as observed before using the Hipparcos data, with clearly increased luminosities for older A and F dwarfs.

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