1,721,003 research outputs found
The determination of a complete sample of open clusters to compare with star clusters in other galaxies
No full textUn segno per il primo meridiano d’Italia a Roma
No full textA sign for Italy's Prime Meridian
Italy's Prime Meridian, defined in 1871, is situated in a brick tower at the top of Monte Mario - Rome's highest hill. The Italian Government chose the site to be the point of passage for the Prime Meridian on September 20 1870 the same time the italian army had arrived back in Rome. This meridian remained in use for official italian land maps until 1995 when a new cartography based on the WGS84 reference system was adopted. For this reason Italy's Prime Meridian can be considered an historical geodetic monument. Studium Urbis began the first demarcation of the meridian in february 2007
with a plaque inside the Vatican Gardens. The Studium Urbis is currently continuing the ongoing project of the demarcation of the Italy's Prime Meridian in significant spots in Rome
The age distribution of galactic open clusters
No full textThe fifth edition of the Lynga 'Catalogue of open cluster data' (1987) is used to obtain a number-complete sample of galactic open clusters, which represents a suitable data base to deduce information on the evolution of the system of open clusters in our Galaxy. From the sample age distribution we have deduced: i) the present-day cluster formation rate; ii) the efficiency of cluster formation; iii) the destruction function; iv) an evaluation of cluster lifetimes
A new automatic identification technique for OB associations in unresolved galaxies.
No full textWe present a new automatic technique based on Principal Component Analysis and Cluster Analysis, with the aim of its application to the identification of those clumps in unresolved galaxies which likely represent regions of star formation. We test the method by applying it to the galaxy M 31, for which there are already several sets of identifications of OB associations based on multi-colour images of resolved stars. We use small-scale digital images of M 31 and compare the associations that we detect from these unresolved data with previously-published large-scale data, finding a rather good agreement. We obtain a strict agreement of our identification with the most compact associations of the original van den Bergh (1964) identification. We then apply the technique to CCD images of the more distant spiral galaxy NGC 2903 and identify 68 OB association candidates
Extension of the C Star Rotation Curve of the Milky Way to 24 kpc
No full textDemers and Battinelli published in 2007 the rotation curve of the Milky Way based on the radial velocity of carbon (C) stars outside the Solar circle. Since then we have established a new list of candidates for spectroscopy. The goal of this paper is to determine the rotation curve of the Galaxy, as far as possible from the Galactic center, using N-type C stars. The stars were selected from their dereddened 2MASS colors, then the spectra were obtained with the Dominion Astrophysical Observatory and Asiago 1.8 m telescopes. This publication adds radial velocities and Galactrocentric distances of 36 C stars, from which 20 are newly confirmed. The new results for stars up to 25 kpc from the Galactic center suggest that the rotation curve shows a slight decline beyond the Solar circle
Application of an objective method for the identification of young star grouping in spiral galaxies
No full textThe interpretation of the difference observed between the radial distribution of globular clusters and that of halo-bulge stars in elliptical galaxies is discussed in terms of evolution of their globular cluster systems. I present a short summary of the evidence that dynamical evolution of globular cluster systems is not only able to explain the flattening of their distribution toward the galactic center, but also it may have played an important role on the primordial activity of the parent galaxy
Spectroscopic observations of the young open cluster NGC 366
No full textIn this note we give the spectral classification for ten of the brightest stars in the field of the young open cluster NGC 366. This allows us to obtain a reliable estimate of the individual reddenings, the distance and age of the cluster. One of the stars shows an emission line spectrum, and is classified as Be. We confirm NGC 366 to be a very young cluster (age ~10^7^yr) and we obtain a slightly smaller distance compared to that given by Phelps & Janes (1994).In this note we give the spectral classification for ten of the brightest stars in the field of the young open cluster NGC 366. This allows us to obtain a reliable estimate of the individual reddenings, the distance and age of the cluster. One of the stars shows an emission line spectrum, and is classified as Be. We confirm NGC 366 to be a very young cluster (age ~10^7^yr) and we obtain a slightly smaller distance compared to that given by Phelps & Janes (1994)
Toward an Objective Identification Technique for OB Associations in Galaxies
No full textWe present a new semi-automatic, objective way to identify OB associations in unresolved galaxies
An identification technique for OB associations in unresolved galaxies
No full textA method is advanced that combines principal component analysis (PCA) and cluster analysis (CA) for selecting OB associations in unresolved fields using photometric data. The PCA and CA techniques are applied to fluxes and colors to derive an artificial image that allows the determination of possible locations of star-forming regions. The method is tested on data from NGC 2903, and the PCA/CA code allows the identification of outer-branch clumps and well defined knots in the galaxy
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