1,721,104 research outputs found
VST-GAME: Galaxy Assembly as a function of Mass and Environment with VST
Full text linkVST-GAME is a VST survey in four bands (u', g', r', i') to perform a unique wide field coverage (20x20 Mpc^2 at z=0.4) of 12 massive galaxy clusters, at 0.2<z<0.6 (z median ~0.4), and reaching the limiting magnitude of M*+6, (i.e. 10^9M⊙ at z=0.4). The main goal is to determine the relative importance of different cluster assembly processes in driving the evolution of galaxies as a function of mass and environment. These data will allow the investigation of galaxy populations examining the entire cluster infall regions, with the depth needed to reach stellar mass regimes where model predictions are in tension with the data. Moreover, the proposed area/filters/depth will also allow legacy science, e.g. searching for high-redshift galaxies and candidate AGN and QSOs. This survey is part of a concerted effort which includes NIR observations of VISTA Public Survey programme (G-CAV, P.I.: M. Nonino) and a massive spectroscopic campaign already in hand (e.g., CLASH-VLT, P.I.: P. Rosati) and ongoing. So VST-GAME data, together with the ancillary data already available, will result in a transformative self-consistent dataset, to test and drive the development of galaxy evolution models
Inside catalogs: a comparison of source extraction software
Full text linkhe scope of this article is to compare the catalog extraction performances obtained using the new combination of SExtractor with PSFEx against the more traditional and diffuse application of DAOPHOT with ALLSTAR; therefore, the paper may provide a guide for the selection of the most suitable catalog extraction software. Both software packages were tested on two kinds of simulated images, having a uniform spatial distribution of sources and an overdensity in the center, respectively. In both cases, SExtractor is able to generate a deeper catalog than DAOPHOT. Moreover, the use of neural networks for object classification plus the novel SPREAD_MODEL parameter push down to the limiting magnitude the possibility of star/galaxy separation. DAOPHOT and ALLSTAR provide an optimal solution for point-source photometry in stellar fields and very accurate and reliable PSF photometry, with robust star/galaxy separation. However, they are not useful for galaxy characterization and do not generate catalogs that are very complete for faint sources. On the other hand, SExtractor, along with the new capability to derive PSF photometry, turns out to be competitive and returns accurate photometry for galaxies also. We can report that the new version of SExtractor, used in conjunction with PSFEx, represents a very powerful software package for source extraction with performances comparable to those of DAOPHOT. Finally, by comparing the results obtained in the cases of a uniform and of an overdense spatial distribution of stars, we notice for both software packages a decline for the latter case in the quality of the results produced in terms of magnitudes and centroids
CLASH-VLT: A VIMOS Large Programme to Map the Dark Matter Mass Distribution in Galaxy Clusters and Probe Distant Lensed Galaxies
No full textThe CLASH-VLT VIMOS Large Programme builds on the CLASH Hubble Space Telescope multi-cycle treasury programme to carry out a comprehensive spectroscopic campaign on 13 massive galaxy clusters in the southern sky, at a median redshift of 0.4. Observations are 95% complete and provide spectroscopic identification for 500 to 1000 members per cluster, and over 200 background lensed galaxies at z 〈 7. When combined with a homogeneous set of multi-wavelength ancillary observations, this project will allow a determination of cluster mass density profiles with dynamical and lensing methods and a characterisation of the inner structure of cluster dark matter halos with unprecedented accuracy. The final spectroscopic CLASH-VLT dataset will contain ~ 30 000 spectra and redshifts, of which ~ 7000 are cluster members, providing a long-lasting legacy for studies of galaxy evolution in different environments
C3, a command-line catalog cross-match tool for large astrophysical catalogs
Full text linkModern Astrophysics is based on multi-wavelength data organized into large and heterogeneous catalogs. Hence, the need for efficient, reliable and scalable catalog cross-matching methods plays a crucial role in the era of the petabyte scale. Furthermore, multi-band data have often very different angular resolution, requiring the highest generality of cross-matching features, mainly in terms of region shape and resolution. In this work we present C 3 (Command-line Catalog Cross-match), a multi-platform application designed to efficiently cross-match massive catalogs. It is based on a multi-core parallel processing paradigm and conceived to be executed as a stand-alone command-line process or integrated within any generic data reduction/analysis pipeline, providing the maximum flexibility to the end-user, in terms of portability, parameter configuration, catalog formats, angular resolution, region shapes, coordinate units and cross-matching types. Using real data, extracted from public surveys, we discuss the cross-matching capabilities and computing time efficiency also through a direct comparison with some publicly available tools, chosen among the most used within the community, and representative of different interface paradigms. We verified that the C 3 tool has excellent capabilities to perform an efficient and reliable cross-matching between large data sets. Although the elliptical cross-match and the parametric handling of angular orientation and offset are known concepts in the astrophysical context, their availability in the presented command-line tool makes C 3 competitive in the context of public astronomical tools
Is there a dependence in metallicity evolution on galaxy structures?
Full text linkWe investigate the environmental dependence of the mass-metallicty (MZ) relation and its connection to galaxy stellar structures and morphologies. In our studies, we analyze galaxies in massive clusters at z ~ 0.4 from the CLASH (HST) and CLASH-VLT surveys and measure their gas metallicities, star-formation rates, stellar structures and morphologies. We establish the MZ relation for 90 cluster and 40 field galaxies finding a shift of ~ - 0.3 dex in comparison to the local trends seen in SDSS for the majority of galaxies with logM 1010 M ☉) lie below the main sequence which corresponds to the higher mass objects that reach solar abundances in the MZ diagram
A Command-line Cross-matching tool for modern astrophysical pipelines
Full text linkThe emerging need for efficient, reliable and scalable astronomical catalog cross-matching is becoming more pressing in the current data-driven science era, where the size of data has rapidly increased up to the Petabyte scale. C3 (Command-line Catalogue Cross-matching) is a multi-platform tool designed to efficiently cross-match massive catalogues from modern astronomical surveys, ensuring high-performance capabilities through the use of a multi-core parallel processing paradigm. The tool has been conceived to be executed as a stand-alone command-line process or integrated within any generic data reduction/analysis pipeline, providing the maximum flexibility to the end user, in terms of parameter configuration, coordinates and cross-matching types. In this work we present the architecture and the features of the tool. Moreover, since the modular design of the tool enables an easy customization to specific use cases and requirements, we present also an example of a customized C3 version designed and used in the FP7 project ViaLactea, dedicated to cross-correlate Hi-GAL clumps with multi-band compact sources...
SPECTROSCOPIC IDENTIFICATION OF HIGH REDSHIFT LENSED GALAXIES
Full text linkWe summarize an ongoing observational program, which combines HST imaging, VLT spectroscopy and exploits gravitational lensing of massive clusters, to identify faint lyman-α emitters (3.2 < z < 6.3)
Command-line Cross-matching Tool for Modern Astrophysical Pipelines
Full text linkThe emerging need for efficient, reliable and scalable astronomical catalog cross-matching is becoming more pressing in the current data-driven science era, where the size of data has rapidly increased up to the Petabyte scale. C3 (Command-line Catalogue Cross-matching) is a multi-platform tool designed to efficiently cross-match massive catalogues from modern astronomical surveys, ensuring high-performance capabilities through the use of a multi-core parallel processing paradigm. The tool has been conceived to be executed as a stand-alone command-line process or integrated within any generic data reduction/analysis pipeline, providing the maximum flexibility to the end user, in terms of parameter configuration, coordinates and cross-matching types. In this work we present the architecture and the features of the tool. Moreover, since the modular design of the tool enables an easy customization to specific use cases and requirements, we present also an example of a customized C3 version designed and used in the FP7 project ViaLactea, dedicated to cross-correlate Hi-GAL clumps with multi-band compact sources
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