87 research outputs found

    A Quantitative Evaluation of the Galaxy Component of COSMOS and APM Catalogs

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    We have carried out an independent quantitative evaluation of the galaxy component of the "COSMOS/UKST Southern Sky Object Catalogue" (SSC) and the "APM/UKST J Catalogue" (APM). Using CCD observations our results corroborate the accuracy of the photometry of both catalogs, which have an overall dispersion of about 0.2 mag in the range 17 <= b_J <= 21.5. The SSC presents externally calibrated galaxy magnitudes that follow a linear relation, while the APM instrumental magnitudes of galaxies, only internally calibrated by the use of stellar profiles, require second-order corrections. The completeness of both catalogs in a general field falls rapidly fainter than b_J = 20.0, being slightly better for APM. The 90% completeness level of the SSC is reached between b_J = 19.5 and 20.0, while for APM this happens between b_J = 20.5 and 21.0. Both SSC and APM are found to be less complete in a galaxy cluster field. Galaxies misclassified as stars in the SSC receive an incorrect magnitude because the stellar ones take saturation into account besides using a different calibration curve. In both cases, the misclassified galaxies show a large diversity of colors that range from typical colors of early-types to those of blue star-forming galaxies. A possible explanation for this effect is that it results from the combination of low sampling resolutions with properties of the image classifier for objects with characteristic sizes close to the instrumental resolution. We find that the overall contamination by stars misclassified as galaxies is < 5% to b_J = 20.5, as originally estimated for both catalogs. Although our results come from small areas of the sky, they are extracted from two different plates and are based on the comparison with two independent datasets.Comment: 14 pages of text and tables, 8 figures; to be published in the Astronomical Journal; for a single postscript version file see ftp://danw.on.br/outgoing/caretta/caretta.p

    The Northern Sky Optical Cluster Survey II: An Objective Cluster Catalog for 5800 Square Degrees

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    We present a new, objectively defined catalog of candidate galaxy clusters based on the galaxy catalogs from the Digitized Second Palomar Observatory Sky Survey (DPOSS). This cluster catalog, derived from the best calibrated plates in the high latitude (|b|>30) Northern Galactic Cap region, covers 5,800 square degrees, and contains 8,155 candidate clusters. A simple adaptive kernel density mapping technique, combined with the SExtractor object detection algorithm, is used to detect galaxy overdensities, which we identify as clusters. Simulations of the background galaxy distribution and clusters of varying richnesses and redshifts allow us to optimize detection parameters, and measure the completeness and contamination rates for our catalog. Cluster richnesses and photometric redshifts are measured, using integrated colors and magnitudes for each cluster. An extensive spectroscopic survey is used to confirm the photometric results. This catalog, with well-characterized sample properties, provides a sound basis for future studies of cluster physics and large scale structure.Comment: 49 pages, 16 figures. Accepted to AJ; appearing in April. Version with full resolution figures, and full length tables available at http://dposs.caltech.edu:8080/NoSOCS.htm

    Observational Mass-to-Light Ratio of Galaxy Systems: from Poor Groups to Rich Clusters

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    We study the mass-to-light ratio of galaxy systems from poor groups to rich clusters, and present for the first time a large database for useful comparisons with theoretical predictions. We extend a previous work, where B_j band luminosities and optical virial masses were analyzed for a sample of 89 clusters. Here we also consider a sample of 52 more clusters, 36 poor clusters, 7 rich groups, and two catalogs, of about 500 groups each, recently identified in the Nearby Optical Galaxy sample by using two different algorithms. We obtain the blue luminosity and virial mass for all systems considered. We devote a large effort to establishing the homogeneity of the resulting values, as well as to considering comparable physical regions, i.e. those included within the virial radius. By analyzing a fiducial, combined sample of 294 systems we find that the mass increases faster than the luminosity: the linear fit gives M\propto L_B^{1.34 \pm 0.03}, with a tendency for a steeper increase in the low--mass range. In agreement with the previous work, our present results are superior owing to the much higher statistical significance and the wider dynamical range covered (about 10^{12}-10^{15} M_solar). We present a comparison between our results and the theoretical predictions on the relation between M/L_B and halo mass, obtained by combining cosmological numerical simulations and semianalytic modeling of galaxy formation.Comment: 25 pages, 12 eps figures, accepted for publication in Ap

    Decision Tree Classifiers for Star/Galaxy Separation

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    We study the star/galaxy classification efficiency of 13 different decision tree algorithms applied to photometric objects in the Sloan Digital Sky Survey Data Release Seven (SDSS DR7). Each algorithm is defined by a set of parameters which, when varied, produce different final classification trees. We extensively explore the parameter space of each algorithm, using the set of 884,126884,126 SDSS objects with spectroscopic data as the training set. The efficiency of star-galaxy separation is measured using the completeness function. We find that the Functional Tree algorithm (FT) yields the best results as measured by the mean completeness in two magnitude intervals: 14r2114\le r\le21 (85.285.2%) and r19r\ge19 (82.182.1%). We compare the performance of the tree generated with the optimal FT configuration to the classifications provided by the SDSS parametric classifier, 2DPHOT and Ball et al. (2006). We find that our FT classifier is comparable or better in completeness over the full magnitude range 15r2115\le r\le21, with much lower contamination than all but the Ball et al. classifier. At the faintest magnitudes (r>19r>19), our classifier is the only one able to maintain high completeness (>>80%) while still achieving low contamination (2.5\sim2.5%). Finally, we apply our FT classifier to separate stars from galaxies in the full set of 69,545,32669,545,326 SDSS photometric objects in the magnitude range 14r2114\le r\le21.Comment: Submitted to A

    Do clusters contain a large population of dwarf galaxies?

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    We analyze systematic effects in the determination of the galaxy luminosity function in clusters using a deep mock catalogue constructed from a numerical simulation of a hierarchical universe. The results indicate a strong tendency to derive a rising faint end (\alpha \lsim -1.5) in clusters selected in two dimensions, using a galaxy catalogue constructed with a universal flat luminosity function with α1.0\alpha \simeq -1.0. This is due to the projection effects inherent in catalogues of clusters constructed using 2 dimensional data. Many of the clusters found in 2d have no significant 3d counterparts, and most suffer from massive background contamination that cannot be corrected for by subtracting random offset fields. The luminosity function of high surface brightness galaxies in the field and within small groups follows a Schechter function with a fairly flat faint end slope, n(L)Lαn(L)\propto L^{\alpha} with α=0.9\alpha = -0.9 to -1.2. On the contrary, observational studies of clusters constructed using Abell, EDCC and APM catalogues are systematically found to have steeper luminosity functions with α=1.4\alpha = -1.4 to -2.0. This may be attributed to projection effects rather than a dominant population of high surface brightness dwarf galaxies (M\gsim M^*+2) in clusters. It should be straighforward to confirm our results by measuring redshifts of these faint cluster galaxies.Comment: 23 pages, 7 Postscript figures TeX, accepted for publication in the Astrophysical Journal, e-mail:[email protected] http://iate.oac.uncor.edu/cv.htm

    Antitumour 2-(4-aminophenyl)benzothiazoles generate DNA adducts in sensitive tumour cells in vitro and in vivo

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    2-(4-Aminophenyl)benzothiazoles represent a potent and highly selective class of antitumour agent. In vitro, sensitive carcinoma cells deplete 2-(4-aminophenyl)benzothiazoles from nutrient media; cytochrome P450 1A1 activity, critical for execution of antitumour activity, and protein expression are powerfully induced. 2-(4-Amino-3-methylphenyl)benzothiazole-derived covalent binding to cytochrome P450 1A1 is reduced by glutathione, suggesting 1A1-dependent production of a reactive electrophilic species. In vitro, 2-(4-aminophenyl)benzothiazole-generated DNA adducts form in sensitive tumour cells only. At concentrations >100 nM, adducts were detected in DNA of MCF-7 cells treated with 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F 203). 5F 203 (1 μM) led to the formation of one major and a number of minor adducts. However, treatment of cells with 10 μM 5F 203 resulted in the emergence of a new dominant adduct. Adducts accumulated steadily within DNA of MCF-7 cells exposed to 1 μM 5F 203 between 2 and 24 h. Concentrations of the lysylamide prodrug of 5F 203 (Phortress) ≥100 nM generated adducts in the DNA of sensitive MCF-7 and IGROV-1 ovarian cells. At 1 μM, one major Phortress-derived DNA adduct was detected in these two sensitive phenotypes; 10 μM Phortress led to the emergence of an additional major adduct detected in the DNA of MCF-7 cells. Inherently resistant MDA-MB-435 breast carcinoma cells incurred no DNA damage upon exposure to Phortress (⩽10 μM, 24 h). In vivo, DNA adducts accumulated within sensitive ovarian IGROV-1 and breast MCF-7 xenografts 24 h after treatment of mice with Phortress (20 mg kg−1). Moreover, Phortress-derived DNA adduct generation distinguished sensitive MCF-7 tumours from inherently resistant MDA-MB-435 xenografts implanted in opposite flanks of the same mouse

    Lista de gêneros de Hymenoptera (Insecta) do Espírito Santo, Brasil

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    The first checklist of genera of Hymenoptera from Espírito Santo state, Brazil is presented. A total of 973 genera of Hymenoptera is listed, of which 555 (57%) are recorded for the first time from this state. Ichneumonoidea and Chalcidoidea are the two superfamilies with the most genera, 241 and 203 respectively. Braconidae, with 141 genera, are the richest family.The first checklist of genera of Hymenoptera from Espírito Santo state, Brazil is presented. A total of 973 genera of Hymenoptera is listed, of which 555 (57%) are recorded for the first time from this state. Ichneumonoidea and Chalcidoidea are the two superfamilies with the most genera, 241 and 203 respectively. Braconidae, with 141 genera, are the richest family.Fil: Azevedo, Celso O.. Universidade Federal do Espírito Santo; BrasilFil: Molin, Ana Dal. Texas A&M University; Estados UnidosFil: Penteado-Dias, Angelica. Universidade Federal do São Carlos; BrasilFil: Macedo, Antonio C. C.. Secretaria do Meio Ambiente do Estado de São Paulo; BrasilFil: Rodriguez-V, Beatriz. Universidad Nacional Autónoma de México; MéxicoFil: Dias, Bianca Z. K.. Universidade Federal do Espírito Santo; BrasilFil: Waichert, Cecilia. State University of Utah; Estados UnidosFil: Aquino, Daniel Alejandro. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Entomología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Smith, David. Smithsonian Institution; Estados UnidosFil: Shimbori, Eduardo M.. Universidade Federal do São Carlos; BrasilFil: Noll, Fernando B.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Gibson, Gary. Agriculture and Agri-Food Canada; CanadáFil: Onody, Helena. Universidade Federal do São Carlos; BrasilFil: Carpenter, James M.. American Museum of Natural History; Estados UnidosFil: Lattke, John. Universidad Nacional de Loja; EcuadorFil: Ramos, Kelli dos S.. Universidade de Sao Paulo; BrasilFil: Williams, Kevin. Florida State Collection of Arthropods; Estados UnidosFil: Masner, Lubomir. Agriculture and Agri-Food Canada; CanadáFil: Kimsey, Lynn. University of California; Estados UnidosFil: Tavares, Marcelo T.. Universidade Federal do Espírito Santo; BrasilFil: Olmi, Massimo. Università degli Studi della Tuscia; ItaliaFil: Buffington, Matthew L.. United States Department of Agriculture; Estados UnidosFil: Ohl, Michael. Staatliches Museum fur Naturkunde Stuttgart; AlemaniaFil: Sharkey, Michael. University of Kentucky; Estados UnidosFil: Johnson, Norman F.. Ohio State University; Estados UnidosFil: Kawada, Ricardo. Universidade Federal do Espírito Santo; BrasilFil: Gonçalves, Rodrigo B.. Universidade Federal do Paraná; BrasilFil: Feitosa, Rodrigo. Universidade Federal do Paraná; BrasilFil: Heydon, Steven. University of California; Estados UnidosFil: Guerra, Tânia M.. Universidade Federal do Espírito Santo; BrasilFil: da Silva, Thiago S. R.. Universidade Federal do Espírito Santo; BrasilFil: Costa, Valmir. Instituto Biológico; Brasi
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