We present a photometric investigation on HB, RGB, and MSTO stars in omega Cen=NGC 5139. The center of the cluster was covered with a mosaic of F435W, F625W, and F658N band data collected with HST ...ACS. The outer reaches were covered with a mosaic of U-, B-, V-, and I-band data collected with the 2.2 m ESO/MPI telescope. The final catalog includes -1.7 million stars. We identified more than 3200 likely HB stars, the largest sample ever collected in a globular cluster. We found that the HB morphology changes with the radial distance from the cluster center. The relative number of extreme HB stars decreases from similar to 30% to similar to 21% when moving from the center toward the outer reaches of the cluster, while the fraction of less hot HB stars increases from similar to 62% to similar to 72%. The comparison between theory and observations indicates that the empirical star counts of HB stars are on average larger (30%-40%) than predicted by canonical evolutionary models. Moreover, the rate of HB stars is similar to 43% larger than the MSTO rate. We also compared theory and observations by assuming a mix of stellar populations made with 70% of canonical He ( gamma = 0.23) stars and 30% of He-enhanced ( gamma = 0.33, 0.42) stars. We found that the observed RG/MSTO ratio agrees with the predicted lifetimes of He-mixed stellar populations. The discrepancy between theory and observations decreases by a factor of 2 when compared with rates predicted by canonical He content models, but still 15%-25% ( gamma = 0.42) and 15%-20% ( gamma = 0.33) higher than observed. Furthermore, the ratios between HB and MSTO star counts are similar to 24% ( gamma = 0.42) and 30% ( gamma = 0.33) larger than predicted lifetime ratios.
Stellar evolution model databases, spanning a wide ranges of masses and initial chemical compositions, are nowadays a major tool to study Galactic and extragalactic stellar populations. We describe ...here the current status of the widely used BaSTI (A Bag of Stellar Tracks and Isochrones) database. We focus in particular on the efforts devoted to port BaSTI to a VO-compliant environment, the BaSTI Web portal that enables users to retrieve data tables and run a range of web tools to facilitate the theoretical analysis of observations, and planned future developments within the framework of the Italian Virtual Observatory project.
The Cherenkov Telescope Array (CTA) - an array of several tens of Cherenkov telescopes - is the next generation of ground-based instrument in the field of very high energy gamma-ray astronomy. The ...CTA observatory is expected to produce a main data stream for permanent storage of the order of 1-to-5 GB/s for about 1000 hours of observation per year, thus producing a total data volume of the order of several PB per year. The CPU time needed to calibrate and process one hour of data taking will be of the order of some thousands CPU hours with current technology. The high data rate of CTA, together with the large computing power requirements for Monte Carlo (MC) simulations, need dedicated computing resources. Massive MC simulations are needed to study the physics of cosmic-ray atmospheric showers as well as telescope response and performance for different detectors and layout configurations. Given these large storage and computing requirements, the Grid approach is well suited, and a vast number of MC simulations are already running on the European Grid Infrastructure (EGI). In order to optimize resource usage and to handle all production and future analysis activities in a coherent way, a high-level framework with advanced functionalities is desirable. For this purpose we have preliminarly evaluated the DIRAC framework for distributed computing and tested it for the CTA workload and data management systems. In this paper we present a possible implementation of a Distributed Computing Infrastructure (DCI) Computing Model for CTA as well as the benchmark test results of DIRAC.
Context. Future weak lensing surveys, such as the Euclid mission, will attempt to measure the shapes of billions of galaxies in order to derive cosmological information. These surveys will attain ...very low levels of statistical error, and systematic errors must be extremely well controlled. In particular, the point spread function (PSF) must be estimated using stars in the field, and recovered with high accuracy. Aims. The aims of this paper are twofold. Firstly, we took steps toward a nonparametric method to address the issue of recovering the PSF field, namely that of finding the correct PSF at the position of any galaxy in the field, applicable to Euclid . Our approach relies solely on the data, as opposed to parametric methods that make use of our knowledge of the instrument. Secondly, we studied the impact of imperfect PSF models on the shape measurement of galaxies themselves, and whether common assumptions about this impact hold true in an Euclid scenario. Methods. We extended the recently proposed resolved components analysis approach, which performs super-resolution on a field of under-sampled observations of a spatially varying, image-valued function. We added a spatial interpolation component to the method, making it a true 2-dimensional PSF model. We compared our approach to PSFEx , then quantified the impact of PSF recovery errors on galaxy shape measurements through image simulations. Results. Our approach yields an improvement over PSFEx in terms of the PSF model and on observed galaxy shape errors, though it is at present far from reaching the required Euclid accuracy. We also find that the usual formalism used for the propagation of PSF model errors to weak lensing quantities no longer holds in the case of an Euclid -like PSF. In particular, different shape measurement approaches can react differently to the same PSF modeling errors.
The present paper describes the construction, the installation and the operation of the Optical Imager Galileo (OIG), a scientific instrument dedicated to the 'imaging' in the visible. OIG was the ...first instrument installed on the focal plane of the Telescopio Nazionale Galileo (TNG) and it has been extensively used for the functional verification of several parts of the telescope (as an example the optical quality, the rejection of spurious light, the active optics and the tracking), in the same way also several parts of the TNG informatics system (instrument commanding, telemetry and data archiving) have been verified making extensive use of OIG. This paper provides also a frame of work for a further development of the imaging dedicated instrumentation inside TNG. OIG, coupled with the first near-IR camera (ARNICA), has been the 'workhorse instrument' during the first period of telescope experimental and scientific scheduling.
Workflow and science gateway technologies have been adopted by scientific communities as a valuable tool to carry out complex experiments. They offer the possibility to perform computations for data ...analysis and simulations, whereas hiding details of the complex infrastructures underneath. There are many workflow management systems covering a large variety of generic services coordinating execution of workflows. In this paper we describe our experiences in creating workflows oriented science gateways based on gUSE/WS-PGRADE technology and in particular we discuss the efforts devoted to develop a VO-compliant web environment.
Stellar evolution model databases, spanning a wide ranges of masses and initial chemical compositions, are nowadays a major tool to study Galactic and extragalactic stellar populations. The Bag of ...Stellar Tracks and Isochrones (BaSTI) database is a VO-compliant theoretical astrophysical catalogue that collects fundamental datasets involving stars formation and evolution. The creation of this database implies a large number of stellar evolutionary computations that are extremely demanding in term of computing power. Here we discuss the efforts devoted to create and update the database using Distributed Computing Infrastructures and a Science Gateway and its future developments within the framework of the Italian Virtual Observatory project.
The commissioning phase Bortoletto, F; Benetti, S; Bonanno, G ...
arXiv.org,
02/2023
Paper, Journal Article
Odprti dostop
In May 1997 a consistent part of the services and structures committed to the industry had already been released to the commissioning group. The telescope itself was, with the exception of the ...Nasmyth derotators, motors and all the optics groups, basically ready in its mechanical parts to accept the integration of all services and control equipment. Also the verification of the cabling (interlocks, data-nets, power and controls) already mounted was started in the same period. Starting from June 1998 (telescope first-light date) the telescope went gradually in use, several nights per week, in order to test and tune the tracking and pointing system, the optics and the first derotator system (Nasmyth A station). At the end of the commissioning period and with the first scientific instruments mounted (April 1999) also the first routinely observations started. In this moment the telescope is doing astronomy 80% of time and the complete first-light instrumentation is mounted.
INAF Trieste Astronomical Observatory (OATs) has a long tradition in information technology applied to Astronomical and Astrophysical use cases, particularly for what regards computing for data ...reduction, analysis and simulations; data and archives management; space missions data processing; design and software development for ground-based instruments. The ensemble of these activities, in the last years, pushed the need to acquire new computing resources and technologies and to deep competences in theirs management. In this paper we describe INAF-OATs computing centre technological stuff, our involvement in different EU Projects both in the path of building of EOSC, the European Open Science Cloud; in the design and prototyping of new Exascale supercomputers in Europe and the main research activities carried on using our computing centre.
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