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Jonathan Irwin Simon Hodgkin Suzanne Aigrain Jerome Bouvier Leslie Hebb Estelle Moraux 《Monthly notices of the Royal Astronomical Society》2008,383(4):1588-1602
We report on the results of an I -band time-series photometric survey of NGC 2547 using the MPG/ESO 2.2-m telescope with Wide Field Imager, achieving better than 1 per cent photometric precision per data point over 14 ≲ I ≲ 18 . Candidate cluster members were selected from a V versus V − I colour–magnitude diagram over 12.5 < V < 24 (covering masses from 0.9 M⊙ down to below the brown dwarf limit), finding 800 candidates, of which we expect ∼330 to be real cluster members, taking into account contamination from the field (which is most severe at the extremes of our mass range). Searching for periodic variations in these gave 176 detections over the mass range 0.1 ≲ M /M⊙ ≲ 0.9 . The rotation period distributions were found to show a clear mass-dependent morphology, qualitatively intermediate between the distributions obtained from similar surveys in NGC 2362 and 2516, as would be expected from the age of this cluster. Models of the rotational evolution were investigated, finding that the evolution from NGC 2362 to 2547 was qualitatively reproduced (given the uncertainty in the age of NGC 2547) by solid body and core-envelope decoupled models from our earlier NGC 2516 study without need for significant modification. 相似文献
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Zhenglu Jiang 《Celestial Mechanics and Dynamical Astronomy》2009,103(1):31-47
In this paper we analyse the relations between a previously described oblate Jaffe model for an ellipsoidal galaxy and the
observed quantities for NGC 2974, and obtain the length and velocity scales for a relevant elliptical galaxy model. We then
derive the finite total mass of the model from these scales, and finally find a good fit of an isotropic oblate Jaffe model
by using the Gauss-Hermite fit parameters and the observed ellipticity of the galaxy NGC 2974. The model is also used to predict
the total luminous mass of NGC 2974, assuming that the influence of dark matter in this galaxy on the image, ellipticity and
Gauss-Hermite fit parameters of this galaxy is negligible within the central region, of radius 0.5R
e. 相似文献
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