Examinando por Autor "Varela, J."

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Acceso Abierto
Deriving stellar parameters from GALANTE photometry: bias and precision
(Oxford Academics: Oxford University Press, 2020-04-09) Lorenzo Gutiérrez, A.; Alfaro, E. J.; Maíz Apellániz, J.; Barbá, R. H.; Marín Franch, A.; Ederoclite, A.; Cristóbal Hornillos, D.; Varela, J.; Vázquez Ramió, H.; Cenarro, A. J.; Lennon, D. J.; García Lario, P.; Daflon, S.; Borges Fernandes, M.; Agencia Estatal de Investigación (AEI); Maíz Apellániz, J. [0000-0003-0825-3443]; Marín Franch, A. [0000-0002-9026-3933]; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
In this paper, we analyse how to extract the physical properties from the GALANTE photometry of a stellar sample. We propose a direct comparison between the observational colours (photometric bands normalized to the 515 nm central wavelength) and the synthetic colours derived from different stellar libraries. We use the reduced χ2 as the figure of merit for selecting the best fitting between both colour sets. The synthetic colours of the Next Generation Spectral Library (NGSL) provide a valuable sample for testing the uncertainty and precision of the stellar parameters derived from observational data. Reddening, as an extrinsic stellar physical parameter becomes a crucial variable for accounting for the errors and bias in the derived estimates: the higher the reddenings, the larger the errors and uncertainties in the derived parameters. NGSL colours also enable us to compare different theoretical stellar libraries for the same set of physical parameters, where we see how different catalogues of models can provide very different solutions in a, sometimes, non-linear way. This peculiar behaviour makes us to be cautious with the derived physical parameters obtained from GALANTE photometry without previous detailed knowledge of the theoretical libraries used to this end. In addition, we carry out the experiment of deriving physical stellar parameters from some theoretical libraries, using some other libraries as observational data. In particular, we use the Kurucz and Coelho libraries, as input observational data, to derive stellar parameters from Coelho + TLUSTY and Kurucz + TLUSTY stellar libraries, respectively, for different photometric errors and colour excesses.© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
Acceso Abierto
J-PLUS: photometric calibration of large-area multi-filter surveys with stellar and white dwarf loci
(EDP Sciences, 2019-11-05) López Sanjuan, C.; Varela, J.; Cristóbal Hornillos, D.; Vázquez Ramió, H.; Carrasco, J. M.; Tremblay, P. E.; Whitten, D. D.; Placco, V. M.; Marín Franch, A.; Cenarro, A. J.; Ederoclite, A.; Alfaro, Emilio J.; Coelho, P. R. T.; Civera, T.; Hernández Fuertes, J.; Jiménez Esteban, F. M.; Jiménez Teja, Y.; Maíz Apellániz, J.; Sobral, D.; Vílchez, J. M.; Alcaniz, J. S.; Angulo, R. E.; Dupke, R. A.; Hernández Monteagudo, C.; Mendes de Oliveira, Claudia L.; Moles, M.; Sodré, L.; Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); National Aeronautics and Space Administration (NASA); Carrasco Martínez, J. M. [0000-0002-3029-5853]; Sobral, D. [0000-0001-8823-4845]; Mendes de Oliveira, C. [0000-0002-5267-9065]; Vilchez, J. M. [0000-0001-7299-8373]; Jiménez Esteban, F. M. [0000-0002-6985-9476]; Placco, V. [0000-0003-4479-1265]; López Sanjuan, C. [0000-0002-5743-3160]; Coelho, P. R. T. [0000-0003-1846-4826]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737; Unidad de Excelencia Científica María de Maeztu Instituto de Ciencias del Cosmos (ICCUB), MDM-2014-0369
Aims. We present the photometric calibration of the 12 optical passbands observed by the Javalambre Photometric Local Universe Survey (J-PLUS). Methods. The proposed calibration method has four steps: (i) definition of a high-quality set of calibration stars using Gaia information and available 3D dust maps; (ii) anchoring of the J-PLUS gri passbands to the Pan-STARRS photometric solution, accounting for the variation in the calibration with the position of the sources on the CCD; (iii) homogenization of the photometry in the other nine J-PLUS filters using the dust de-reddened instrumental stellar locus in (𝒳 − r) versus (g − i) colours, where 𝒳 is the filter to calibrate. The zero point variation along the CCD in these filters was estimated with the distance to the stellar locus. Finally, (iv) the absolute colour calibration was obtained with the white dwarf locus. We performed a joint Bayesian modelling of 11 J-PLUS colour–colour diagrams using the theoretical white dwarf locus as reference. This provides the needed offsets to transform instrumental magnitudes to calibrated magnitudes outside the atmosphere. Results. The uncertainty of the J-PLUS photometric calibration, estimated from duplicated objects observed in adjacent pointings and accounting for the absolute colour and flux calibration errors, are ∼19 mmag in u, J0378, and J0395; ∼11 mmag in J0410 and J0430; and ∼8 mmag in g, J0515, r, J0660, i, J0861, and z. Conclusions. We present an optimized calibration method for the large-area multi-filter J-PLUS project, reaching 1–2% accuracy within an area of 1022 square degrees without the need for long observing calibration campaigns or constant atmospheric monitoring. The proposed method will be adapted for the photometric calibration of J-PAS, that will observe several thousand square degrees with 56 narrow optical filters.
Acceso Abierto
J-PLUS: Tools to identify compact planetary nebulae in the Javalambre and southern photometric local Universe surveys
(EDP Sciences, 2020-01-21) Gutiérrez Soto, L. A.; Gonçalves, D. R.; Akras, S.; Cortesi, A.; López Sanjuan, C.; Guerrero, Martín A.; Daflon, S.; Borges Fernandes, M.; Mendes de Oliveira, Claudia L.; Ederoclite, A.; Sodré, L.; Pereira, C. B.; Kanaan, A.; Werle, A.; Vázquez Ramió, H.; Alcaniz, J. S.; Angulo, R. E.; Cenarro, A. J.; Cristóbal Hornillos, D.; Dupke, R. A.; Hernández Monteagudo, C.; Marín Franch, A.; Moles, M.; Varela, J.; Ribeiro, T.; Schoenell, W.; Álvarez Candal, A.; Galbany, L.; Jiménez Esteban, F. M.; Logroño García, R.; Sobral, D.; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); European Research Council (ERC); Ministerio de Economía y Competitividad (MINECO); Guitiérrez Soto, L. A. [0000-0002-9891-8017]
Context. From the approximately 3500 planetary nebulae (PNe) discovered in our Galaxy, only 14 are known to be members of the Galactic halo. Nevertheless, a systematic search for halo PNe has never been performed. Aims. In this study, we present new photometric diagnostic tools to identify compact PNe in the Galactic halo by making use of the novel 12-filter system projects, Javalambre Photometric Local Universe Survey (J-PLUS) and Southern-Photometric Local Universe Survey (S-PLUS). Methods. We reconstructed the Isaac Newton Telescope Photometric H alpha Survey of the Northern Galactic Plane diagnostic diagram and propose four new ones using (i) the J-PLUS and S-PLUS synthetic photometry for a grid of photo-ionisation models of halo PNe, (ii) several observed halo PNe, as well as (iii) a number of other emission-line objects that resemble PNe. All colour-colour diagnostic diagrams are validated using two known halo PNe observed by J-PLUS during the scientific verification phase and the first data release (DR1) of S-PLUS and the DR1 of J-PLUS. Results. By applying our criteria to the DR1s (similar to 1190 deg(2)), we identified one PN candidate. However, optical follow-up spectroscopy proved it to be a HII region belonging to the UGC 5272 galaxy. Here, we also discuss the PN and two HII galaxies recovered by these selection criteria. Finally, the cross-matching with the most updated PNe catalogue (HASH) helped us to highlight the potential of these surveys, since we recover all the known PNe in the observed area. Conclusions. The tools here proposed to identify PNe and separate them from their emission-line contaminants proved to be very efficient thanks to the combination of many colours, even when applied - like in the present work - to an automatic photometric search that is limited to compact PNe.
Restringido
The GALANTE photometric survey of the northern Galactic plane: project description and pipeline
(Oxford Academics: Oxford University Press, 2021-07-02) Maíz Apellániz, J.; Alfaro, E. J.; Barbá, R. H.; Holgado, G.; Vázquez Ramió, H.; Varela, J.; Ederoclite, A.; Lorenzo Gutiérrez, A.; García Lario, P.; García Escudero, H.; García, M.; Coelho, P. R. T.; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709; European Space Agency (ESA); Gobierno de Aragón; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Coelho, P. R. T. [0000-0003-1846-4826]
The GALANTE optical photometric survey is observing the northern Galactic plane and some adjacent regions using seven narrow- and intermediate-filters, covering a total of 1618 deg2. The survey has been designed with multiple exposure times and at least two different air masses per field to maximize its photometric dynamic range, comparable to that of Gaia, and ensure the accuracy of its photometric calibration. The goal is to reach at least 1 per cent accuracy and precision in the seven bands for all stars brighter than AB magnitude 17 while detecting fainter stars with lower values of the signal-to-noise ratio. The main purposes of GALANTE are the identification and study of extinguished O+B+WR stars, the derivation of their extinction characteristics, and the cataloguing of F and G stars in the solar neighbourhood. Its data will be also used for a variety of other stellar studies and to generate a high-resolution continuum-free map of the Hα emission in the Galactic plane. We describe the techniques and the pipeline that are being used to process the data, including the basis of an innovative calibration system based on Gaia DR2 and 2MASS photometry.