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Luigi R. Bedin † Santi Cassisi Fiorella Castelli Giampaolo Piotto Jay Anderson Maurizio Salaris Yazan Momany Adriano Pietrinferni 《Monthly notices of the Royal Astronomical Society》2005,357(3):1038-1048
We propose a zero-point photometric calibration of the data from the Advanced Camera for Surveys (ACS) Wide Field Channel (WFC) on board the Hubble Space Telescope , based on a spectrum of Vega and the most up-to-date in-flight transmission curves of the camera. This calibration is accurate at the level of a few hundredths of a magnitude. The main purpose of this effort is to transform the entire set of evolutionary models into a simple observational photometric system for ACS/WFC data, and to make them available to the astronomical community. We provide the zero-points for the most used ACS/WFC bands, and give basic recipes for calibrating both the observed data and the models. We also present the colour–magnitude diagram from ACS data of five Galactic globular clusters, spanning the metallicity range −2.2 <[Fe/H] < −0.04 , and we provide fiducial points representing their sequences from several magnitudes below the turn-off to the red giant branch tip. The observed sequences are compared with the models in the newly defined photometric system. 相似文献
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G. Baume † G. Carraro ‡ Y. Momany § 《Monthly notices of the Royal Astronomical Society》2009,398(1):221-232
We present optical ( UBVI C ) observations of a rich and complex field in the Galactic plane towards l ∼ 305° and b ∼ 0° . Our analysis reveals a significantly high interstellar absorption ( A V ∼ 10) and an abnormal extinction law in this line of sight. Availing a considerable number of colour combinations, the photometric diagrams allow us to derive new estimates of the fundamental parameters of the two open clusters Danks 1 and Danks 2. Due to the derived abnormal reddening law in this line of sight, both clusters appear much closer (to the Sun) than previously thought. Additionally, we present the optical colours and magnitudes of the WR 48a star, and its main parameters were estimated. The properties of the two embedded clusters, DBS2003 130 and 131, are also addressed. We identify a number of young stellar objects which are probable members of these clusters. This new material is then used to revisit the spiral structure in this sector of the Galaxy showing evidence of populations associated with the inner Galaxy Scutum-Crux arm. 相似文献
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In this paper, we analyse very short arcs of minor bodies of the Solar System detected on Hubble Space Telescope (HST) Wide Field Channel ACS images. In particular, we address how to constrain the Keplerian orbital elements for minor body detections, illustrating the method for two objects. One of the minor bodies left 13 successive trails, making it the most well-sampled object yet identified in the HST archive. Most interestingly, we also address the problem of ephemeris prediction and show that in the particular case of HST very short arcs the confinement window for subsequent recovery is significantly reduced to a narrow linear region, that would facilitate successive observations. 相似文献
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We derive fundamental parameters of the embedded cluster DBSB 48 in the southern nebula Hoffleit 18 and the very young open cluster Trumpler 14, by means of deep JHKs infrared photometry. We build colour–magnitude and colour–colour diagrams to derive reddening and age, based on main sequence and pre-main sequence distributions. Radial stellar density profiles are used to study cluster structure and guide photometric diagram extractions. Field-star decontamination is applied to uncover the intrinsic cluster sequences in the diagrams. Ages are inferred from K-excess fractions. A prominent pre-main sequence population is present in DBSB 48, and the K-excess fraction fK = 55 ± 6% gives an age of 1.1 ± 0.5 Myr. A mean reddening of AKs=0.9±0.03 was found, corresponding to AV = 8.2 ± 0.3. The cluster CMD is consistent with the far kinematic distance of 5 kpc for Hoffleit 18. For Trumpler 14 we derived similar parameters as in previous studies in the optical, in particular an age of 1.7 ± 0.7 Myr. The fraction of stars with infrared excess in Trumpler 14 is fK = 28 ± 4%. Despite the young ages, both clusters are described by a King profile with core radii Rcore = 0.46 ± 0.05 pc and Rcore = 0.35 ± 0.04 pc, respectively, for DBSB 48 and Trumpler 14. Such cores are smaller than those of typical open clusters. Small cores are probably related to the cluster formation and/or parent molecular cloud fragmentation. In DBSB 48, the magnitude extent of the upper main sequence is ΔKs ≈ 2 mag, while in Trumpler 14 it is ΔKs ≈ 5 mag, consistent with the estimated ages. 相似文献
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