Evaluación preliminar de emisiones de plomo en automóviles

El presente trabajo reporta emisiones de plomo contenido en el material particulado emitido por el escape. de una muestra típica de automóviles a gasolina, mediame muestreo isocinético a volumen constante según normas de la Environmental Protection Agency de USA. Los resultados obtenidos muestran ww emisión promedio de 7.4 ± 0.68 (mg Pb · km- 1) obtenido al aplicar un ciclo de conducción representativo de la A 1·enida Bemardo O'Higgins en el área de restricción vehicular. simulado en dinamómetro de rodillos y a través de dilución variable de gases de escape. Este valor sugiere que la información utilizada en la evaluación de los inventarios de emisiones en Santiago, sobredimensiona la contribución del material particulado proveniente de vehículos livianos a gasolina

Comparación de efectos de un aditivo comercial y un encendido por descarga continua sobre las emisiones primarias de un motor de automóvil

El presente trabajo muestra un estudio comparativo de las emisiones de S02 , NOx, HCHO, CO y HC producidas por un motor Datsun 1 .5 L acoplado a un dinanómetro hidráulico. En un caso, se usó un sistema de encendido por "descarga continua" y en el otro, se usó un aditivo comercial "For Gas" marca Wynn' s. En las condiciones analizadas, el aditivo comercial mostró una mayor eficiencia en la reducción de contaminames, que el encendido electrónico. En particular, las emisiones de S02 se redujeron hasta un 20% comparativas al sistema convencional

J-NEP: 60-band photometry and photometric redshifts for the James Webb Space Telescope North Ecliptic Pole Time-Domain Field

The J-PAS survey will observe ~1/3 of the northern sky with a set of 56 narrow-band filters using the dedicated 2.55 m JST telescope at the Javalambre Astrophysical Observatory. Prior to the installation of the main camera, in order to demonstrate the scientific potential of J-PAS, two small surveys were performed with the single-CCD Pathfinder camera: miniJPAS (~1 deg2 along the Extended Groth Strip), and J-NEP (~0.3 deg2 around the JWST North Ecliptic Pole Time Domain Field), including all 56 J-PAS filters as well as u, g, r, and i. J-NEP is ~0.5-1.0 magnitudes deeper than miniJPAS, providing photometry for 24,618 r-band detected sources and photometric redshifts (photo-z) for the 6,662 sources with r<23. In this paper we describe the photometry and photo-z of J-NEP and demonstrate a new method for the removal of systematic offsets in the photometry based on the median colours of galaxies, dubbed "galaxy locus recalibration". This method does not require spectroscopic observations except in a few reference pointings and, unlike previous methods, is applicable to the whole J-PAS survey. We use a spectroscopic sample of 787 galaxies to test the photo-z performance for J-NEP and in comparison to miniJPAS. We find that the deeper J-NEP observations result in a factor ~1.5-2 decrease in sigma_NMAD (a robust estimate of the standard deviation of the photo-z error) and the outlier rate relative to miniJPAS for r>21.5 sources, but no improvement in brighter ones. We find the same relation between sigma_NMAD and odds in J-NEP and miniJPAS, suggesting sigma_NMAD can be predicted for any set of J-PAS sources from their odds distribution alone, with no need for additional spectroscopy to calibrate the relation. We explore the causes for photo-z outliers and find that colour-space degeneracy at low S/N, photometry artifacts, source blending, and exotic spectra are the most important factors.Comment: 16 pages, 25 figures, accepted for publication in Astronomy and Astrophysic

The miniJPAS and J-NEP surveys: Identification and characterization of the Ly

We present the Lyman-α (Lyα) luminosity function (LF) at 2.05  43.5. This work serves as a proof of concept for the results that can be obtained with the upcoming data releases of the J-PAS survey

The miniJPAS survey quasar selection I: Mock catalogues for classification

In this series of papers, we employ several machine learning (ML) methods to classify the point-like sources from the miniJPAS catalogue, and identify quasar candidates. Since no representative sample of spectroscopically confirmed sources exists at present to train these ML algorithms, we rely on mock catalogues. In this first paper we develop a pipeline to compute synthetic photometry of quasars, galaxies and stars using spectra of objects targeted as quasars in the Sloan Digital Sky Survey. To match the same depths and signal-to-noise ratio distributions in all bands expected for miniJPAS point sources in the range $17.5\leq r<24$, we augment our sample of available spectra by shifting the original $r$-band magnitude distributions towards the faint end, ensure that the relative incidence rates of the different objects are distributed according to their respective luminosity functions, and perform a thorough modeling of the noise distribution in each filter, by sampling the flux variance either from Gaussian realizations with given widths, or from combinations of Gaussian functions. Finally, we also add in the mocks the patterns of non-detections which are present in all real observations. Although the mock catalogues presented in this work are a first step towards simulated data sets that match the properties of the miniJPAS observations, these mocks can be adapted to serve the purposes of other photometric surveys