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

F. van Leeuwen; A. Vallenari; C Jordi; L. Lindegren; U. Bastian; T. Prusti; JHJ de Brujne; Andrew G. Brown; C. Babusiaux; CAL Bailer-Jones; M. Biermann; D.W. Evans; L. Eyer; Jens Kirkeskov Knude; H.E.P. Lindstrøm

doi:10.1051/0004-6361/201730552

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

F. van Leeuwen, A. Vallenari, C Jordi, L. Lindegren, U. Bastian, T. Prusti, JHJ de Brujne, Andrew G. Brown, C. Babusiaux, CAL Bailer-Jones, M. Biermann, D.W. Evans, L. Eyer, Jens Kirkeskov Knude, H.E.P. Lindstrøm

Astrophysics and Planetary Science

54 Citations (Scopus)

Abstract

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 effects 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.

Original language	English
Article number	A19
Journal	Astronomy & Astrophysics
Volume	601
ISSN	0004-6361
DOIs	https://doi.org/10.1051/0004-6361/201730552
Publication status	Published - 1 May 2017

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van Leeuwen, F., Vallenari, A., Jordi, C., Lindegren, L., Bastian, U., Prusti, T., de Brujne, JHJ., Brown, A. G., Babusiaux, C., Bailer-Jones, CAL., Biermann, M., Evans, D. W., Eyer, L., Knude, J. K., & Lindstrøm, H. E. P. (2017). Gaia Data Release 1 Open cluster astrometry: performance, limitations, and future prospects. Astronomy & Astrophysics, 601, Article A19. https://doi.org/10.1051/0004-6361/201730552

van Leeuwen, F, Vallenari, A, Jordi, C, Lindegren, L, Bastian, U, Prusti, T, de Brujne, JHJ, Brown, AG, Babusiaux, C, Bailer-Jones, CAL, Biermann, M, Evans, DW, Eyer, L, Knude, JK & Lindstrøm, HEP 2017, 'Gaia Data Release 1 Open cluster astrometry: performance, limitations, and future prospects', Astronomy & Astrophysics, vol. 601, A19. https://doi.org/10.1051/0004-6361/201730552

@article{98cabbb2b528454ebbe249da3bd0d470,

title = "Gaia Data Release 1 Open cluster astrometry: performance, limitations, and future prospects",

abstract = "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 effects 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.",

author = "{van Leeuwen}, F. and A. Vallenari and C Jordi and L. Lindegren and U. Bastian and T. Prusti and {de Brujne}, JHJ and Brown, {Andrew G.} and C. Babusiaux and CAL Bailer-Jones and M. Biermann and D.W. Evans and L. Eyer and Knude, {Jens Kirkeskov} and H.E.P. Lindstr{\o}m",

year = "2017",

month = may,

day = "1",

doi = "10.1051/0004-6361/201730552",

language = "English",

volume = "601",

journal = "Astronomy & Astrophysics",

issn = "0004-6361",

publisher = "E D P Sciences",

}

TY - JOUR

T1 - Gaia Data Release 1 Open cluster astrometry

T2 - performance, limitations, and future prospects

AU - van Leeuwen, F.

AU - Vallenari, A.

AU - Jordi, C

AU - Lindegren, L.

AU - Bastian, U.

AU - Prusti, T.

AU - de Brujne, JHJ

AU - Brown, Andrew G.

AU - Babusiaux, C.

AU - Bailer-Jones, CAL

AU - Biermann, M.

AU - Evans, D.W.

AU - Eyer, L.

AU - Knude, Jens Kirkeskov

AU - Lindstrøm, H.E.P.

PY - 2017/5/1

Y1 - 2017/5/1

N2 - 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 effects 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.

AB - 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 effects 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.

U2 - 10.1051/0004-6361/201730552

DO - 10.1051/0004-6361/201730552

M3 - Journal article

SN - 0004-6361

VL - 601

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

M1 - A19

ER -

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

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