Configurable/adaptive digital FIR filter

En este trabajo de obtención de grado se describe el proceso de diseño y posterior implementación en silicio de un filtro digital de respuesta finita adaptativo que, a la vez, puede ser un filtro configurable.ITESO, A. C

Histopathological lesions and bacteriological isolation in apparently healthy gamitanas (Colossoma macropomum)

El objetivo del presente estudio fue determinar lesiones histopatológicas y aislar agentes infecciosos en órganos y tejidos de gamitanas (Colossoma macropomum) aparentemente sanas. Se colectaron 40 especímenes juveniles en una piscigranja de la zona de Ucayali, Perú. Se tomaron muestras de hígado, bazo, riñón, estómago, branquias y músculo para análisis histopatológico y de los cinco primeros para análisis bacteriológico. En el hígado se encontró degeneración hidrópica (39/40), en el riñón se observó degeneración hidrópica y necrosis tubular (40/40), con incremento de centros melanomacrófagos en la periferia de los túbulos, en el estómago se observó degeneración hialina en las células de la mucosa (25/40), y en las branquias se observó infiltración de células inflamatorias en filamento branquial (40/40), hiperplasia del epitelio interlaminar (40/40) e hiperplasia del filamento branquial (18/40). No se encontraron lesiones en bazo. Se encontraron parásitos mixosporidios en branquias (2/40), riñón (40/40) y músculo (12/40) y parásitos monogeneos en branquias (6/40). Se aislaron, en baja frecuencia, bacterias potencialmente patógenas (Aeromonas hydrophila y Edwardsiella tarda) en branquias y órganos internos, pero sin relación con las lesiones histopatológicas.The aim of this study was to determine histopathological lesions and bacterial isolates in organs and tissues of clinically healthy gamitanas (Colossoma macropomum). Forty juveniles were collected from a fish farm in the region of Ucayali, Perú. Samples were collected from kidney, liver, spleen, stomach, gills and muscle for histopathological and bacteriological analysis. In the liver was found hydropic degeneration (39/40), in kidney, hydropic degeneration and tubular necrosis (40/40) with an increase of melanomacrophage centres in the periphery of the tubules, in stomach, hyaline degeneration (25/40), and in gills, infiltration of inflammatory cells in branchial filament (40/40), interlamellar epithelium hyperplasia (40/40) and hyperplasia in branchial filament (18/40). No lesions were found in the spleen. Myxosporean parasites were found in gills (2/40), kidney (40/40) and muscle (12/40), and monogenean parasites in gills (6/40). Bacteria were isolated in low frequency, including potentially pathogenic bacteria (Aeromonas hydrophila and Edwardsiella tarda) in gills and organs, but without association with the histopathological findings

Ultra Long Period Cepheids: a primary standard candle out to the Hubble flow

The cosmological distance ladder crucially depends on classical Cepheids (with P=3-80 days), which are primary distance indicators up to 33 Mpc. Within this volume, very few SNe Ia have been calibrated through classical Cepheids, with uncertainty related to the non-linearity and the metallicity dependence of their period-luminosity (PL) relation. Although a general consensus on these effects is still not achieved, classical Cepheids remain the most used primary distance indicators. A possible extension of these standard candles to further distances would be important. In this context, a very promising new tool is represented by the ultra-long period (ULP) Cepheids (P \geq 80 days), recently identified in star-forming galaxies. Only a small number of ULP Cepheids have been discovered so far. Here we present and analyse the properties of an updated sample of 37 ULP Cepheids observed in galaxies within a very large metallicity range of 12+log(O/H) from ~7.2 to 9.2 dex. We find that their location in the colour(V-I)-magnitude diagram as well as their Wesenheit (V-I) index-period (WP) relation suggests that they are the counterparts at high luminosity of the shorter-period (P \leq 80 days) classical Cepheids. However, a complete pulsation and evolutionary theoretical scenario is needed to properly interpret the true nature of these objects. We do not confirm the flattening in the studied WP relation suggested by Bird et al. (2009). Using the whole sample, we find that ULP Cepheids lie around a relation similar to that of the LMC, although with a large spread (~0.4 mag).Comment: 8 pages, 4 figures, accepted for publication in Astrophysics & Space Scienc

Using classical Cepheids to study the far side of the Milky Way disk: I. Spectroscopic classification and the metallicity gradient

The structure, kinematics, and chemical composition of the far side of the Milky Way disk, beyond the bulge, are still to be revealed. Classical Cepheids (CCs) are young and luminous standard candles. We aim to use a well-characterized sample of these variable stars to study the present time properties of the far side of the Galactic disk. A sample of 45 Cepheid variable star candidates were selected from near infrared time series photometry obtained by the VVV survey. We characterized this sample using high quality near infrared spectra obtained with VLT/X-Shooter, deriving radial velocities and iron abundances for all the sample Cepheids. This allowed us to separate the CCs, which are metal rich and with kinematics consistent with the disk rotation, from type II Cepheids (T2Cs), which are more metal poor and with different kinematics. We estimated individual distances and extinctions using VVV photometry and period-luminosity relations, reporting the characterization of 30 CCs located on the far side of the Galactic disk, plus 8 T2Cs mainly located in the bulge region, of which 10 CCs and 4 T2Cs are new discoveries. This is the first sizeable sample of CCs in this distant region of our Galaxy that has been spectroscopically confirmed. We use their positions, kinematics, and metallicities to confirm that the general properties of the far disk are similar to those of the well-studied disk on the solar side of the Galaxy. In addition, we derive for the first time the radial metallicity gradient on the disk's far side. Considering all the CCs with $R_{\mathrm{GC}} < 17\,\rm{kpc}$, we measure a gradient with a slope of $-0.062 \, \mathrm{dex\, kpc^{-1}}$ and an intercept of $+0.59 \, \rm{dex}$, which is in agreement with previous determinations based on CCs on the near side of the disk.Comment: 16 pages, 10 figures, accepted for publication in Astronomy & Astrophysic

A colour-excess extinction map of the southern Galactic disc from the VVV and GLIMPSE surveys

An improved high-resolution and deep A Ks foreground dust extinction map is presented for the Galactic disc area within 295◦ ≾ l ≾ 350◦, −1.0◦ ≾ b ≾ +1.0◦. At some longitudes the map reaches up to |b| ~ 2.25◦, for a total of ~148 deg 2. The map was constructed via the Rayleigh–Jeans colour excess (RJCE) technique based on deep near-infrared (NIR) and mid-infrared (MIR) photometry. The new extinction map features a maximum bin size of 1 arcmin, and relies on NIR observations from the Two Micron All-Sky Survey (2MASS) and new data from ESO’s Vista Variables in the Vía Láctea (VVV) survey, in concert with MIR observations from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire. The VVV photometry penetrates ~4 mag fainter than 2MASS, and provides enhanced sampling of the underlying stellar populations in this heavily obscured region. Consequently, the new results supersede existing RJCE maps tied solely to brighter photometry, revealing a systematic underestimation of extinction in prior work that was based on shallower data. The new high-resolution and large-scale extinction map presented here is readily available to the community through a web query interface.Peer reviewe

The VVV Templates Project. Towards an Automated Classification of VVV Light-Curves. I. Building a database of stellar variability in the near-infrared

Context. The Vista Variables in the V\'ia L\'actea (VVV) ESO Public Survey is a variability survey of the Milky Way bulge and an adjacent section of the disk carried out from 2010 on ESO Visible and Infrared Survey Telescope for Astronomy (VISTA). VVV will eventually deliver a deep near-IR atlas with photometry and positions in five passbands (ZYJHK_S) and a catalogue of 1-10 million variable point sources - mostly unknown - which require classifications. Aims. The main goal of the VVV Templates Project, that we introduce in this work, is to develop and test the machine-learning algorithms for the automated classification of the VVV light-curves. As VVV is the first massive, multi-epoch survey of stellar variability in the near-infrared, the template light-curves that are required for training the classification algorithms are not available. In the first paper of the series we describe the construction of this comprehensive database of infrared stellar variability. Methods. First we performed a systematic search in the literature and public data archives, second, we coordinated a worldwide observational campaign, and third we exploited the VVV variability database itself on (optically) well-known stars to gather high-quality infrared light-curves of several hundreds of variable stars. Results. We have now collected a significant (and still increasing) number of infrared template light-curves. This database will be used as a training-set for the machine-learning algorithms that will automatically classify the light-curves produced by VVV. The results of such an automated classification will be covered in forthcoming papers of the series.Comment: 12 pages, 16 figures, 3 tables, accepted for publication in A&A. Most of the data are now accessible through http://www.vvvtemplates.org

Infrared photometry and CaT spectroscopy of globular cluster M 28 (NGC 6626)

Recent studies show that the inner Galactic regions host genuine bulge globular clusters, but also halo intruders, complex remnants of primordial building blocks, and objects likely accreted during major merging events. In this study we focus on the properties of M 28, a very old and massive cluster currently located in the Galactic bulge. We analysed wide-field infrared photometry collected by the VVV survey, VVV proper motions, and intermediate-resolution spectra in the calcium triplet range for 113 targets in the cluster area. Our results in general confirm previous estimates of the cluster properties available in the literature. We find no evidence of differences in metallicity between cluster stars, setting an upper limit of Delta[Fe/H]<0.08 dex to any internal inhomogeneity. We confirm that M 28 is one of the oldest objects in the Galactic bulge (13-14 Gyr). From this result and the literature data, we find evidence of a weak age-metallicity relation among bulge globular clusters that suggests formation and chemical enrichment. In addition, wide-field density maps show that M 28 is tidally stressed and that it is losing mass into the general bulge field. Our study indicates that M 28 is a genuine bulge globular cluster, but its very old age and its mass loss suggest that this cluster could be the remnant of a larger structure, possibly a primeval bulge building block.Comment: Accepted for publication in Astronomy & Astrophysic

Blue Straggler Stars in Globular Clusters: a powerful tool to probe the internal dynamical evolution of stellar systems

This chapter presents an overview of the main observational results obtained to date about Blue Straggler Stars (BSSs) in Galactic Globular Clusters (GCs). The BSS specific frequency, radial distribution, chemical composition and rotational properties are presented and discussed in the framework of using this stellar population as probe of GC internal dynamics. In particular, the shape of the BSS radial distribution has been found to be a powerful tracer of the dynamical age of stellar systems, thus allowing the definition of the first empirical "dynamical clock".Comment: Chapter 5, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G. Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe