Examinando por Autor "Bland Hawthorn, J."

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Acceso Abierto
Galaxy classification: Deep learning on the OTELO and COSMOS databases
(EDP Sciences, 2020-06-25) De Diego, J. A.; Nadolny, J.; Bongiovanni, Á.; Cepa, J.; Povic, M.; Pérez García, A. M.; Padilla Torres, C. P.; Lara López, M. A.; Cerviño, M.; Pérez Martínez, R.; Alfaro, Emilio J.; Castañeda, H. O.; Fernández Lorenzo, M.; Gallego, J.; González, J. J.; González Serrano, J. I.; Pintos Castro, I.; Sánchez Portal, M.; Cedrés, B.; González Otero, M.; Jones, D. Heath; Bland Hawthorn, J.; Ministerio de Economía y Competitividad (MINECO); Agencia Estatal de Investigación (AEI); De Diego, J. A. https://orcid.org/0000-0001-7040-069X; 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
Context. The accurate classification of hundreds of thousands of galaxies observed in modern deep surveys is imperative if we want to understand the universe and its evolution.Aims. Here, we report the use of machine learning techniques to classify early- and late-type galaxies in the OTELO and COSMOS databases using optical and infrared photometry and available shape parameters: either the Sersic index or the concentration index.Methods. We used three classification methods for the OTELO database: (1) u-r color separation, (2) linear discriminant analysis using u-r and a shape parameter classification, and (3) a deep neural network using the r magnitude, several colors, and a shape parameter. We analyzed the performance of each method by sample bootstrapping and tested the performance of our neural network architecture using COSMOS data.Results. The accuracy achieved by the deep neural network is greater than that of the other classification methods, and it can also operate with missing data. Our neural network architecture is able to classify both OTELO and COSMOS datasets regardless of small differences in the photometric bands used in each catalog.Conclusions. In this study we show that the use of deep neural networks is a robust method to mine the cataloged data.
Acceso Abierto
Hierarchical Bayesian approach for estimating physical properties in nearby galaxies: Age Maps (Paper II)
(Oxford Academics: Oxford University Press, 2019-02-15) Sánchez Gil, M. C.; Alfaro, Emilio J.; Cerviño, M.; Pérez, E.; Bland Hawthorn, J.; Death Jones, D.; Ministerio de Economía y Competitividad (MINECO); Junta de Andalucia; Agencia Estatal de Investigación (AEI); 0000-0002-2234-7035; 0000-0001-8009-231X; 0000-0001-9737-4559; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
One of the fundamental goals of modern astrophysics is to estimate the physical parameters of galaxies. We present a hierarchical Bayesian model to compute age maps from images in the H α line (taken with Taurus tunable filter, TTF), ultraviolet band (GALEX far UV, FUV), and infrared bands (Spitzer 24, 70, and 160 μm). We present the burst ages for young stellar populations in a sample of nearby and nearly face-on galaxies. The H α to FUV flux ratio is a good relative indicator of the very recent star formation history (SFH). As a nascent star-forming region evolves, the H α line emission declines earlier than the UV continuum, leading to a decrease in the H α/FUV ratio. Using star-forming galaxy models, sampled with a probabilistic formalism, and allowing for a variable fraction of ionizing photons in the clusters, we obtain the corresponding theoretical ratio H α/FUV to compare with our observed flux ratios, and thus to estimate the ages of the observed regions. We take into account the mean uncertainties and the interrelationships between parameters when computing H α/FUV. We propose a Bayesian hierarchical model where a joint probability distribution is defined to determine the parameters (age, metallicity, IMF) from the observed data (the observed flux ratios H α/FUV). The joint distribution of the parameters is described through independent and identically distributed (i.i.d.) random variables generated through MCMC (Markov Chain Monte Carlo) techniques.
Acceso Abierto
MAGNUM survey: Compact jets causing large turmoil in galaxies Enhanced line widths perpendicular to radio jets as tracers of jet-ISM interaction
(EDP Sciences, 2021-04-07) Venturi, G.; Cresci, G.; Marconi, A.; Mingozzi, M.; Nardini, E.; Carniani, S.; Mannucci, F.; Marasco, A.; Maiolino, R.; Perna, M.; Treister, E.; Bland Hawthorn, J.; Gallimore, J.; Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT); European Research Council (ERC); Science and Technology Facilities Council (STFC); Comunidad de Madrid; Venturi, G. [0000-0001-8349-3055]; Cresci, G. [0000-0002-5281-1417]; Marconi, A. [0000-0002-9889-4238]; Mingozzi, M. [0000-0003-2589-762X]; Nardini, E. [0000-0001-9226-8992]; Carniani, S. [0000-0002-6719-380X]; Mannucci, F. [0000-0002-4803-2381]; Marasco, A. [0000-0002-5655-6054]; Perna, M. [0000-0002-0362-5941]; Treister, E. [0000-0001-7568-6412]; Gallimore, J. [0000-0002-6972-2760]
Context. Outflows accelerated by active galactic nuclei (AGN) are commonly observed in the form of coherent, mildly collimated high-velocity gas directed along the AGN ionisation cones and kinetically powerful (≳1044 − 45 erg s−1) jets. Recent works found that outflows can also be accelerated by low-power (≲1044 erg s−1) jets, and the most recent cosmological simulations indicate that these are the dominant source of feedback on sub-kiloparsec scales, but little is known about their effect on the galaxy host. Aims. We study the relation between radio jets and the distribution and kinematics of the ionised gas in IC 5063, NGC 5643, NGC 1068, and NGC 1386 as part of our survey of nearby Seyfert galaxies called Measuring Active Galactic Nuclei Under MUSE Microscope (MAGNUM). All these objects host a small-scale (≲1 kpc) low-power (≲1044 erg s−1) radio jet that has small inclinations (≲45°) with respect to the galaxy disc. Methods. We employed seeing-limited optical integral field spectroscopic observations from the Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope to obtain flux, kinematic, and excitation maps of the extended ionised gas. We compared these maps with archival radio images and in one case, with Chandra X-ray observations. Results. We detect a strong (up to ≳800–1000 km s−1) and extended (≳1 kpc) emission-line velocity spread perpendicular to the direction of the AGN ionisation cones and jets in all four targets. The gas excitation in this region of line-width enhancement is entirely compatible with shock ionisation. These broad and symmetric line profiles are not associated with a single coherent velocity of the gas. A ‘classical’ outflow component with net blueshifted and redshifted motions is also present, but is directed along the ionisation cones and jets. Conclusions. We interpret the observed phenomenon as due to the action of the jets perturbing the gas in the galaxy disc. These intense and extended velocity spreads perpendicular to AGN jets and cones are indeed currently only observed in galaxies hosting a low-power jet whose inclination is sufficiently low with respect to the galaxy disc to impact on and strongly affect its material. In line with cosmological simulations, our results demonstrate that low-power jets are indeed capable of affecting the host galaxy.
Acceso Abierto
The OTELO survey I. Description, data reduction, and multi-wavelength catalogue
(EDP Sciences, 2019-10-14) Ramón Pérez, M.; Pérez García, A. M.; Cepa, J.; Cerviño, M.; Nadolny, J.; Pérez Martínez, R.; Alfaro, Emilio J.; Castañeda, H. O.; De Diego, J. A.; Ederoclite, A.; Fernández Lorenzo, M.; Gallego, J.; González, J. J.; González Serrano, J. I.; Lara López, M. A.; Oteo Gómez, I.; Padilla Torres, C. P.; Pintos Castro, I.; Povic, M.; Sánchez Portal, M.; Jones, H.; Bland Hawthorn, J.; Cabrera Lavers, A.; Bongiovanni, Á.; Agence Nationale de la Recherche (ANR); Ministerio de Economía y Competitividad (MINECO); Agencia Estatal de Investigación (AEI); Bongiovanni, Á. [0000-0002-3557-3234]
Context. The evolution of galaxies through cosmic time is studied observationally by means of extragalactic surveys. The usefulness of these surveys is greatly improved by increasing the cosmological volume, in either depth or area, and by observing the same targets in different wavelength ranges. A multi-wavelength approach using different observational techniques can compensate for observational biases. Aims. The OTELO survey aims to provide the deepest narrow-band survey to date in terms of minimum detectable flux and emission line equivalent width in order to detect the faintest extragalactic emission line systems. In this way, OTELO data will complements other broad-band, narrow-band, and spectroscopic surveys. Methods. The red tunable filter of the OSIRIS instrument on the 10.4 m Gran Telescopio Canarias (GTC) is used to scan a spectral window centred at 9175 Å, which is free from strong sky emission lines, with a sampling interval of 6 Å and a bandwidth of 12 Å in the most deeply explored EGS region. Careful data reduction using improved techniques for sky ring subtraction, accurate astrometry, photometric calibration, and source extraction enables us to compile the OTELO catalogue. This catalogue is complemented with ancillary data ranging from deep X-ray to far-infrared, including high resolution HST images, which allow us to segregate the different types of targets, derive precise photometric redshifts, and obtain the morphological classification of the extragalactic objects detected. Results. The OTELO multi-wavelength catalogue contains 11 237 entries and is 50% complete at AB magnitude 26.38. Of these sources, 6600 have photometric redshifts with an uncertainty δ zphot better than 0.2 (1+zphot). A total of 4336 of these sources correspond to preliminary emission line candidates, which are complemented by 81 candidate stars and 483 sources that qualify as absorption line systems. The OTELO survey results will be released to the public on the second half of 2019.