Evaluation of pulse detection of the Geostationary Lightning Mapper (GLM)

En aquest estudi s'evalua la sensibilitat del sistema GLM (Geostationary Lightning Mapper) davant els fotòmetres de MMIA (Modular Multispectral Imaging Array), en concret el fotòmetre 3 captant llum a 777.4nm de longitud d'ona. Per a fer-ho, les dades de GLM i MMIA son extrets dels fitxers amb informació preprocessada per LCFA (Lightning Cluster Filter Algorithm) -dades classificades per temps, geolocalització, intensitat de la detecció i amb un número identificatiu- per a posteriorment ser tractats mitjançant la classificació de les seves senyals en deteccions donades per la xarxa de detecció de rajos Linet a Colombia, sincronització de senyals i comparació de pics de senyal.En este estudio se evalúa la sensibilidad del sistema GLM (Geostationary Lightning Mapper) frente a la de los fotómetros de MMIA (Modular Multispectral Imaging Array), en concreto el fotómetro 3 captando la luz en 777.4 nm de longitud de onda. Para ello, tanto los datos de GLM como de MMIA son extraídos de los ficheros con información preprocesada por LCFA (Lightning Cluster Filter Algorithm) -datos clasificados por tiempo, geolocalización, intensidad de la detección y con un número identificativo- para posteriormente ser tratados mediante la clasificación sus señales en detecciones dadas por la red de detección de rayos Linet en Colombia, sincronización de señales y comparación de picos de señal.This study evaluates the sensitivity of the Geostationary Lightning Mapper (GLM) versus the Modular Multispectral Imaging Array (MMIA)'s photometer 3, both operating at the oxygen band at 777.4nm of wavelength. To do so, both GLM's and MMIA's data is extracted from pre-processed data files by a Lightning Cluster Filter Algorithm (LCFA) -data classified by time, geolocalization, detection intensity and with an ID number- to be treated by classification of their signals according to Linet Lightning Mapper Array (LMA) detections in Colombia, signal synchronization and peak comparison

The Double Cluster G185 in M31

We have identified a small globular cluster in M31 located approximately 4 arcseconds northwest of the M31 globular cluster G185. While several multiple globular clusters have been observed in the Magellanic Clouds none have been found in the Galaxy or in M31. We estimate the probability of such a chance line-of-sight alignment occuring near the nucleus of M31 to be 0.09 +/- 0.03 and find no obvious indication of any tidal deformation in either cluster, as would be expected if the clusters were interacting. Two-dimensional modelling suggests G185 has a King (1966) [AJ, 71, 64] concentration of c = 1.11 +/- 0.08 while the companion has c = 0.67 +/- 0.17 and is physically smaller than G185. Both objects have integrated dereddened colors similar to those of Galactic globular clusters.Comment: 22 pages, ~1Mb postscript file http://www.astro.ubc.ca/~holland/bib.html/ ftp://nukta.astro.ubc.ca/pub/holland/G185_preprint.ps.

{BOAO Photometric Survey of Galactic Open Clusters. II. Physical Parameters of 12 Open Clusters

We have initiated a long-term project, the BOAO photometric survey of open clusters, to enlarge our understanding of galactic structure using UBVI CCD photometry of open clusters which have been little studied before. This is the second paper of the project in which we present the photometry of 12 open clusters. We have determined the cluster parameters by fitting the Padova isochrones to the color-magnitude diagrams of the clusters. All the clusters except for Be 0 and NGC 1348 are found to be intermediate-age to old (0.2 - 4.0 Gyrs) open clusters with a mean metallicity of [Fe/H] = 0.0.Comment: 11 page

Persistent Topology of Syntax

We study the persistent homology of the data set of syntactic parameters of the world languages. We show that, while homology generators behave erratically over the whole data set, non-trivial persistent homology appears when one restricts to specific language families. Different families exhibit different persistent homology. We focus on the cases of the Indo-European and the Niger-Congo families, for which we compare persistent homology over different cluster filtering values. We investigate the possible significance, in historical linguistic terms, of the presence of persistent generators of the first homology. In particular, we show that the persistent first homology generator we find in the Indo-European family is not due (as one might guess) to the Anglo-Norman bridge in the Indo-European phylogenetic network, but is related to the position of Ancient Greek and the Hellenic branch within the network.Comment: 15 pages, 25 jpg figure

High Angular Resolution JHK Imaging of the Centers of the Metal-Poor Globular Clusters NGC5272 (M3), NGC6205 (M13), NGC6287, and NGC6341 (M92)

The Canada-France-Hawaii Telescope (CFHT) Adaptive Optics Bonnette (AOB) has been used to obtain high angular resolution JHK images of the centers of the metal-poor globular clusters NGC5272 (M3), NGC6205 (M13), NGC6287, and NGC6341 (M92). The color-magnitude diagrams (CMDs) derived from these data include the upper main sequence and most of the red giant branch (RGB), and the cluster sequences agree with published photometric measurements of bright stars in these clusters. The photometric accuracy is limited by PSF variations, which introduce systematic errors of a few hundredths of a magnitude near the AO reference star. The clusters are paired according to metallicity, and the near-infrared CMDs and luminosity functions are used to investigate the relative ages within each pair. The near-infrared CMDs provide the tightest constraints on the relative ages of the classical second parameter pair NGC5272 and NGC6205, and indicate that these clusters have ages that differ by no more than +/- 1 Gyr. These results thus support the notion that age is not the second parameter. We tentatively conclude that NGC6287 and NGC6341 have ages that differ by no more than +/- 2 Gyr. However, the near-infrared spectral energy distributions of stars in NGC6287 appear to differ from those of stars in outer halo clusters, bringing into question the validity of this age estimate.Comment: 22 pages, 17 figures. To be published in the Astronomical Journa

The thickening of the thin disk in the third Galactic quadrant

In the third Galactic quadrant (180 < l < 270) of the Milky Way, the Galactic thin disk exhibits a significant warp ---shown both by gas and young stars--- bending down a few kpc below the formal Galactic plane (b=0). This warp shows its maximum at 240, in the direction of the Canis Major constellation. In a series of papers we have traced the detailed structure of this region using open star clusters, putting particular emphasis on the spiral structure of the outer disk. We noticed a conspicuous accumulation of young star clusters within 2-3 kpc from the Sun and close to b=0, that we interpreted as the continuation of the Local (Orion) arm towards the outer disk. While most clusters (and young stars in their background) follow closely the warp of the disk, our decade-old survey of the spiral structure of this region led us to identify three clusters, Haffner~18(1 and 2) and Haffner~19, which remain very close to b=0 and lie at distances (4.5, 8.0, and 6.4 kpc) where most of the material is already significantly warped. Here we report on a search for clusters that share the same properties as Haffner~18 and 19, and investigate the possible reasons for such an unexpected occurrence. We present UBVRI photometry of 5~young clusters, namely NGC~2345, NGC~2374, Trumpler~9, Haffner~20, and Haffner~21, which also lie close to the formal Galactic plane. With the exception of Haffner~20, in the background of these clusters we detected young stars that appear close to b=0, and are located at distances up to 8 kpc from the Sun, thus deviating significantly from the warp. These populations define a structure that distributes over almost the entire third Galactic quadrant. We discuss this structure in the context of a possible thin disk flaring, in full similarity with the Galactic thick disk.Comment: 53 pages, 12 eps figures, in press in the Astronomical Journa

VLT and NTT Observations of Two EIS Cluster Candidates. Detection of the Early-Type Galaxies Sequence at z~1

Optical data from the ESO VLT-UT1 Science Verification observations are combined with near-infrared data from SOFI at the NTT to obtain optical-infrared color-magnitude diagrams for the objects in the fields of two EIS cluster candidates. In both cases, evidence is found for a well-defined sequence of red galaxies that appear to be significantly more clustered than the background population. These results suggest that the two systems are real physical associations. The (R-Ks), (I-Ks) and (J-Ks) colors of the red sequences are used, in conjunction with similar data for spectroscopically confirmed clusters, to obtain redshift estimates of z ~ 0.9 and z ~ 1.0 for these two systems. These results make these EIS cluster candidates prime targets for follow-up spectroscopic observations to confirm their reality and to measure more accurately their redshift.Comment: 6 pages, 5 figures, to appear in Astronomy & Astrophysics (Special Letters Edition on "First Science with the VLT"