Vicent Martínez - Profile on Academia.edu (original) (raw)
Book Chapters by Vicent Martínez
Teaching Astronomy and Astrophysics online at the Valencian International University
In the last decade, the development of information and communication technologies (ICTs) has impl... more In the last decade, the development of information and communication technologies (ICTs) has imply a significant change in the traditional distance learning and specifically in e-learning. The new tools developed are consolidating the online learning modality at the university level all over the world and in all disciplines.In this study, we present the case of the Master of Astronomy and Astrophysics which is running from 2010 in the Valencian International University (http://www.viu.es). Unlike other more consolidated distance universities in Spain, the teaching method which has opted in this case includes an element of presence via webcam. This method could be considered as a kind of blended learning, combining the advantages of traditional e-learning with the humanity of personal and direct contact with the students.The results of participation in the master beyond the initial expectations with 37 students enrolled, of which approximately 80% were Spanish and the other 20% were mostly from Latin American countries. The feedback provided by students in the first months of teaching appreciates favorably the presence component, while casting doubt on the usefulness of certain tools traditionally used in the field of e-learning.
Papers by Vicent Martínez
Desvelant l'univers: fòssils cosmològics a Terol
Mètode: Revista de difusió de la investigació de la Universitat de Valencia, 2013
Monthly Notices of the Royal Astronomical Society, 2021
This paper proposes a morphostatistical characterization of the galaxy distribution through spati... more This paper proposes a morphostatistical characterization of the galaxy distribution through spatial statistical modelling based on inhomogeneous Gibbs point processes. The galaxy distribution is supposed to exhibit two components. The first one is related to the major geometrical features exhibited by the observed galaxy field, here, its corresponding filamentary pattern. The second one is related to the interactions exhibited by the galaxies. Gibbs point processes are statistical models able to integrate these two aspects in a probability density, controlled by some parameters. Several such models are fitted to real observational data via the ABC shadow algorithm. This algorithm provides simultaneous parameter estimation and posterior-based inference, hence allowing the derivation of the statistical significance of the obtained results.
Preprint typeset using L ATEX style emulateapj v. 10/09/06 NGC1600- CLUSTER OR FIELD ELLIPTICAL?
A study of the galaxy distribution in the field of the elliptical galaxy NGC1600 has been underta... more A study of the galaxy distribution in the field of the elliptical galaxy NGC1600 has been undertaken. Although this galaxy is often classified as a member of a loose group, all the neighbouring galaxies are much fainter and could be taken as satellites of NGC1600. The number density profile of galaxies in the field of this galaxy shows a decline with radius, with evidence of a background at approximately 1.3 Mpc. The density and number density profile are consistent with that found for other isolated early-type galaxies. NGC1600 appears as an extended source in X-rays, and the center of the X-ray emission seems not to coincide with the center of the galaxy. The velocity distribution of neighbouring galaxies has been measured from optical spectroscopic observations and shows that the mean radial velocity is approximately 85 km s −1 less than that of NGC1600, indicating that the centre of mass could lie outside the galaxy. The velocity dispersion of the ‘group ’ is estimated at 429 ± ...
Arrokoth, el món més distant mai explorat
Desvelant l'univers: dels 'little green men' als púlsars
Astronomy & Astrophysics, 2021
The Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS) will scan thousa... more The Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS) will scan thousands of square degrees of the northern sky with a unique set of 56 filters using the dedicated 2.55 m Javalambre Survey Telescope (JST) at the Javalambre Astrophysical Observatory. Prior to the installation of the main camera (4.2 deg2 field-of-view with 1.2 Gpixels), the JST was equipped with the JPAS-Pathfinder, a one CCD camera with a 0.3 deg2 field-of-view and plate scale of 0.23 arcsec pixel−1. To demonstrate the scientific potential of J-PAS, the JPAS-Pathfinder camera was used to perform miniJPAS, a ∼1 deg2 survey of the AEGIS field (along the Extended Groth Strip). The field was observed with the 56 J-PAS filters, which include 54 narrow band (FWHM ∼ 145 Å) and two broader filters extending to the UV and the near-infrared, complemented by the u, g, r, i SDSS broad band filters. In this miniJPAS survey overview paper, we present the miniJPAS data set (images and catalogs), as we hi...
Desvelant l'univers: the dark side of the Moon
Metode Revista De Difusio De La Investigacio De La Universitat De Valencia, 2014
Entrevista amb Virginia Trimble: em preocupa que les estudiants tinguen menys oportunitats que els seus companys masculins
Metode Revista De Difusio De La Investigacio De La Universitat De Valencia, 2010
Desvelando el universo: el inventario cósmico
Metode Revista De Difusion De La Investigacion, 2011
Virginia Trimble: me preocupa que las estudiantes tengan menos oportunidades que sus compañeros masculinos
Metode Revista De Difusion De La Investigacion, 2010
Desvelant l'univers: fotografiant papallones galàctiques
Metode Revista De Difusio De La Investigacio De La Universitat De Valencia, 2010
Recovering the real-space correlation function from
Astronomy & Astrophysics, 2015
Aims. We present MUFFIT, a new generic code optimized to retrieve the main stellar population par... more Aims. We present MUFFIT, a new generic code optimized to retrieve the main stellar population parameters of galaxies in photometric multi-filter surveys, and check its reliability and feasibility with real galaxy data from the ALHAMBRA survey. Methods. Making use of an error-weighted χ 2-test, we compare the multi-filter fluxes of galaxies with the synthetic photometry of mixtures of two single stellar populations at different redshifts and extinctions, to provide the most likely range of stellar population parameters (mainly ages and metallicities), extinctions, redshifts, and stellar masses. To improve the diagnostic reliability, MUFFIT identifies and removes from the analysis those bands that are significantly affected by emission lines. The final parameters and their uncertainties are derived by a Monte Carlo method, using the individual photometric uncertainties in each band. Finally, we discuss the accuracies, degeneracies, and reliability of MUFFIT using both simulated and real galaxies from ALHAMBRA, comparing with results from the literature. Results. MUFFIT is a precise and reliable code to derive stellar population parameters of galaxies in ALHAMBRA. Using the results from photometric-redshift codes as input, MUFFIT improves the photometric-redshift accuracy by ∼10-20%. MUFFIT also detects nebular emissions in galaxies, providing physical information about their strengths. The stellar masses derived from MUFFIT show excellent agreement with the COSMOS and SDSS values. In addition, the retrieved age-metallicity locus for a sample of z ≤ 0.22 early-type galaxies in ALHAMBRA at different stellar mass bins are in very good agreement with the ones from SDSS spectroscopic diagnostics. Moreover, a one-to-one comparison between the redshifts, ages, metallicities, and stellar masses derived spectroscopically for SDSS and by MUFFIT for ALHAMBRA reveals good qualitative agreements in all the parameters, hence reinforcing the strengths of multi-filter galaxy data and optimized analysis techniques, like MUFFIT, to conduct reliable stellar population studies.
SPIE Proceedings, 2002
The main tools in cosmology for comparing theoretical models with the observations of the galaxy ... more The main tools in cosmology for comparing theoretical models with the observations of the galaxy distribution are statistical. We will review the applications of spatial statistics to the description of the large-scale structure of the universe. Special topics discussed in this talk will be: description of the galaxy samples, selection effects and biases, correlation functions, Fourier analysis, nearest neighbor statistics, Minkowski functionals and structure statistics. Special attention will be devoted to scaling laws and the use of the lacunarity measures in the description of the cosmic texture.
Nuovo Cimento della Societa Italiana di Fisica B, 2007
First results from the ALHAMBRA-Survey A. Fernández-Soto(1), on behalf of the ALHAMBRA-Survey Cor... more First results from the ALHAMBRA-Survey A. Fernández-Soto(1), on behalf of the ALHAMBRA-Survey Core Team(*) (1) Universitat de València, Spain Summary.-We present the first results from the ALHAMBRA survey. ALHAM-BRA will cover a relatively wide area (4 square degrees) using a purposely-designed set of 20 medium-band filters, down to an homogeneous magnitude limit AB ≈ 25 in most of them, adding also deep near-infrared imaging in JHKs. To this aim we are using the Calar Alto 3.5m telescope. A small area of the ALHAMBRA survey has already been observed through our complete filter set, and this allows for the first time to check all the steps of the survey, including the pipelines that have been designed for the project, the fulfilment of the data quality expectations, the calibration procedures, and the photometric redshift machinery for which ALHAMBRA has been optimised. We present here the basic results regarding the properties of the galaxy sample selected in a 15 × 15 arcmin 2 area of the ALHAMBRA-8 field, which includes approximately 10000 galaxies with precise photometric redshift measurements. In a first estimate, approximately 500 of them must be galaxies with z > 2.
The Astrophysical Journal, 2009
The ALHAMBRA survey aims to cover 4 square degrees using a system of 20 contiguous, equal width, ... more The ALHAMBRA survey aims to cover 4 square degrees using a system of 20 contiguous, equal width, medium-band filters spanning the range 3500Å to 9700Å plus the standard JHKs filters. Here we analyze deep near-IR number counts of one of our fields (ALH08) for which we have a relatively large area (0.5 square degrees) and faint photometry (J=22.4, H=21.3 and K=20.
The Astrophysical Journal, 2005
We have developed a method based on wavelets to obtain the true underlying smooth density from a ... more We have developed a method based on wavelets to obtain the true underlying smooth density from a point distribution. The goal has been to reconstruct the density field in an optimal way ensuring that the morphology of the reconstructed field reflects the true underlying morphology of the point field which, as the galaxy distribution, has a genuinely multiscale structure, with near-singular behavior on sheets, filaments and hotspots. If the discrete distributions are smoothed using Gaussian filters, the morphological properties tend to be closer to those expected for a Gaussian field. The use of wavelet denoising provide us with a unique and more accurate morphological description.
The Astrophysical Journal, 1999
We present the function J as a morphological descriptor for point patterns formed by the distribu... more We present the function J as a morphological descriptor for point patterns formed by the distribution of galaxies in the Universe. This function was recently introduced in the field of spatial statistics, and is based on the nearest neighbor distribution and the void probability function. The J descriptor allows to distinguish clustered (i.e. correlated) from "regular" (i.e. anti-correlated) point distributions. We outline the theoretical foundations of the method, perform tests with a Matérn cluster process as an idealised model of galaxy clustering, and apply the descriptor to galaxies and loose groups in the Perseus-Pisces Survey. A comparison with mock-samples extracted from a mixed dark matter simulation shows that the J descriptor can be profitably used to constrain (in this case reject) viable models of cosmic structure formation.
The Astrophysical Journal, 1994
We apply fractal analysis methods to investigate the scaling properties in the Abell and ACO cata... more We apply fractal analysis methods to investigate the scaling properties in the Abell and ACO catalogs of rich galaxy clusters. The methods are adapted to account for the incompleteness of the samples by appropriately using the known selection functions in the partition sums. We also discuss dierent technical aspects of the method when applied to data sets with small number of points as the cluster catalogs. Results are compared with simulations based on the Zel'dovich approximation. We limit our analysis to scales less than 100 h 1 Mpc. The cluster distribution show a scale invariant m ultifractal behavior in a limited scale range. For the Abell catalog this range is 15{60 h 1 Mpc, while for the ACO sample it extends to smaller scales. Despite this dierence in the extension of the scale{range where scale{invariant clustering takes place, both samples are characterized by remarkably similar multifractal spectra in the corresponding scaling regime. In particular, the correlation dimension turns out to be D 2 ' 2:2 for both Abell and ACO clusters. Although it is dicult to point out the scale at which homogeneity is reached with the present size of these redshift surveys, our results indicate that the cluster distribution shows a tendency to homogeneity at large scales, disproving the picture of a pure scale invariant fractal structure extending to arbitrarily large distances.
Teaching Astronomy and Astrophysics online at the Valencian International University
In the last decade, the development of information and communication technologies (ICTs) has impl... more In the last decade, the development of information and communication technologies (ICTs) has imply a significant change in the traditional distance learning and specifically in e-learning. The new tools developed are consolidating the online learning modality at the university level all over the world and in all disciplines.In this study, we present the case of the Master of Astronomy and Astrophysics which is running from 2010 in the Valencian International University (http://www.viu.es). Unlike other more consolidated distance universities in Spain, the teaching method which has opted in this case includes an element of presence via webcam. This method could be considered as a kind of blended learning, combining the advantages of traditional e-learning with the humanity of personal and direct contact with the students.The results of participation in the master beyond the initial expectations with 37 students enrolled, of which approximately 80% were Spanish and the other 20% were mostly from Latin American countries. The feedback provided by students in the first months of teaching appreciates favorably the presence component, while casting doubt on the usefulness of certain tools traditionally used in the field of e-learning.
Desvelant l'univers: fòssils cosmològics a Terol
Mètode: Revista de difusió de la investigació de la Universitat de Valencia, 2013
Monthly Notices of the Royal Astronomical Society, 2021
This paper proposes a morphostatistical characterization of the galaxy distribution through spati... more This paper proposes a morphostatistical characterization of the galaxy distribution through spatial statistical modelling based on inhomogeneous Gibbs point processes. The galaxy distribution is supposed to exhibit two components. The first one is related to the major geometrical features exhibited by the observed galaxy field, here, its corresponding filamentary pattern. The second one is related to the interactions exhibited by the galaxies. Gibbs point processes are statistical models able to integrate these two aspects in a probability density, controlled by some parameters. Several such models are fitted to real observational data via the ABC shadow algorithm. This algorithm provides simultaneous parameter estimation and posterior-based inference, hence allowing the derivation of the statistical significance of the obtained results.
Preprint typeset using L ATEX style emulateapj v. 10/09/06 NGC1600- CLUSTER OR FIELD ELLIPTICAL?
A study of the galaxy distribution in the field of the elliptical galaxy NGC1600 has been underta... more A study of the galaxy distribution in the field of the elliptical galaxy NGC1600 has been undertaken. Although this galaxy is often classified as a member of a loose group, all the neighbouring galaxies are much fainter and could be taken as satellites of NGC1600. The number density profile of galaxies in the field of this galaxy shows a decline with radius, with evidence of a background at approximately 1.3 Mpc. The density and number density profile are consistent with that found for other isolated early-type galaxies. NGC1600 appears as an extended source in X-rays, and the center of the X-ray emission seems not to coincide with the center of the galaxy. The velocity distribution of neighbouring galaxies has been measured from optical spectroscopic observations and shows that the mean radial velocity is approximately 85 km s −1 less than that of NGC1600, indicating that the centre of mass could lie outside the galaxy. The velocity dispersion of the ‘group ’ is estimated at 429 ± ...
Arrokoth, el món més distant mai explorat
Desvelant l'univers: dels 'little green men' als púlsars
Astronomy & Astrophysics, 2021
The Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS) will scan thousa... more The Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS) will scan thousands of square degrees of the northern sky with a unique set of 56 filters using the dedicated 2.55 m Javalambre Survey Telescope (JST) at the Javalambre Astrophysical Observatory. Prior to the installation of the main camera (4.2 deg2 field-of-view with 1.2 Gpixels), the JST was equipped with the JPAS-Pathfinder, a one CCD camera with a 0.3 deg2 field-of-view and plate scale of 0.23 arcsec pixel−1. To demonstrate the scientific potential of J-PAS, the JPAS-Pathfinder camera was used to perform miniJPAS, a ∼1 deg2 survey of the AEGIS field (along the Extended Groth Strip). The field was observed with the 56 J-PAS filters, which include 54 narrow band (FWHM ∼ 145 Å) and two broader filters extending to the UV and the near-infrared, complemented by the u, g, r, i SDSS broad band filters. In this miniJPAS survey overview paper, we present the miniJPAS data set (images and catalogs), as we hi...
Desvelant l'univers: the dark side of the Moon
Metode Revista De Difusio De La Investigacio De La Universitat De Valencia, 2014
Entrevista amb Virginia Trimble: em preocupa que les estudiants tinguen menys oportunitats que els seus companys masculins
Metode Revista De Difusio De La Investigacio De La Universitat De Valencia, 2010
Desvelando el universo: el inventario cósmico
Metode Revista De Difusion De La Investigacion, 2011
Virginia Trimble: me preocupa que las estudiantes tengan menos oportunidades que sus compañeros masculinos
Metode Revista De Difusion De La Investigacion, 2010
Desvelant l'univers: fotografiant papallones galàctiques
Metode Revista De Difusio De La Investigacio De La Universitat De Valencia, 2010
Recovering the real-space correlation function from
Astronomy & Astrophysics, 2015
Aims. We present MUFFIT, a new generic code optimized to retrieve the main stellar population par... more Aims. We present MUFFIT, a new generic code optimized to retrieve the main stellar population parameters of galaxies in photometric multi-filter surveys, and check its reliability and feasibility with real galaxy data from the ALHAMBRA survey. Methods. Making use of an error-weighted χ 2-test, we compare the multi-filter fluxes of galaxies with the synthetic photometry of mixtures of two single stellar populations at different redshifts and extinctions, to provide the most likely range of stellar population parameters (mainly ages and metallicities), extinctions, redshifts, and stellar masses. To improve the diagnostic reliability, MUFFIT identifies and removes from the analysis those bands that are significantly affected by emission lines. The final parameters and their uncertainties are derived by a Monte Carlo method, using the individual photometric uncertainties in each band. Finally, we discuss the accuracies, degeneracies, and reliability of MUFFIT using both simulated and real galaxies from ALHAMBRA, comparing with results from the literature. Results. MUFFIT is a precise and reliable code to derive stellar population parameters of galaxies in ALHAMBRA. Using the results from photometric-redshift codes as input, MUFFIT improves the photometric-redshift accuracy by ∼10-20%. MUFFIT also detects nebular emissions in galaxies, providing physical information about their strengths. The stellar masses derived from MUFFIT show excellent agreement with the COSMOS and SDSS values. In addition, the retrieved age-metallicity locus for a sample of z ≤ 0.22 early-type galaxies in ALHAMBRA at different stellar mass bins are in very good agreement with the ones from SDSS spectroscopic diagnostics. Moreover, a one-to-one comparison between the redshifts, ages, metallicities, and stellar masses derived spectroscopically for SDSS and by MUFFIT for ALHAMBRA reveals good qualitative agreements in all the parameters, hence reinforcing the strengths of multi-filter galaxy data and optimized analysis techniques, like MUFFIT, to conduct reliable stellar population studies.
SPIE Proceedings, 2002
The main tools in cosmology for comparing theoretical models with the observations of the galaxy ... more The main tools in cosmology for comparing theoretical models with the observations of the galaxy distribution are statistical. We will review the applications of spatial statistics to the description of the large-scale structure of the universe. Special topics discussed in this talk will be: description of the galaxy samples, selection effects and biases, correlation functions, Fourier analysis, nearest neighbor statistics, Minkowski functionals and structure statistics. Special attention will be devoted to scaling laws and the use of the lacunarity measures in the description of the cosmic texture.
Nuovo Cimento della Societa Italiana di Fisica B, 2007
First results from the ALHAMBRA-Survey A. Fernández-Soto(1), on behalf of the ALHAMBRA-Survey Cor... more First results from the ALHAMBRA-Survey A. Fernández-Soto(1), on behalf of the ALHAMBRA-Survey Core Team(*) (1) Universitat de València, Spain Summary.-We present the first results from the ALHAMBRA survey. ALHAM-BRA will cover a relatively wide area (4 square degrees) using a purposely-designed set of 20 medium-band filters, down to an homogeneous magnitude limit AB ≈ 25 in most of them, adding also deep near-infrared imaging in JHKs. To this aim we are using the Calar Alto 3.5m telescope. A small area of the ALHAMBRA survey has already been observed through our complete filter set, and this allows for the first time to check all the steps of the survey, including the pipelines that have been designed for the project, the fulfilment of the data quality expectations, the calibration procedures, and the photometric redshift machinery for which ALHAMBRA has been optimised. We present here the basic results regarding the properties of the galaxy sample selected in a 15 × 15 arcmin 2 area of the ALHAMBRA-8 field, which includes approximately 10000 galaxies with precise photometric redshift measurements. In a first estimate, approximately 500 of them must be galaxies with z > 2.
The Astrophysical Journal, 2009
The ALHAMBRA survey aims to cover 4 square degrees using a system of 20 contiguous, equal width, ... more The ALHAMBRA survey aims to cover 4 square degrees using a system of 20 contiguous, equal width, medium-band filters spanning the range 3500Å to 9700Å plus the standard JHKs filters. Here we analyze deep near-IR number counts of one of our fields (ALH08) for which we have a relatively large area (0.5 square degrees) and faint photometry (J=22.4, H=21.3 and K=20.
The Astrophysical Journal, 2005
We have developed a method based on wavelets to obtain the true underlying smooth density from a ... more We have developed a method based on wavelets to obtain the true underlying smooth density from a point distribution. The goal has been to reconstruct the density field in an optimal way ensuring that the morphology of the reconstructed field reflects the true underlying morphology of the point field which, as the galaxy distribution, has a genuinely multiscale structure, with near-singular behavior on sheets, filaments and hotspots. If the discrete distributions are smoothed using Gaussian filters, the morphological properties tend to be closer to those expected for a Gaussian field. The use of wavelet denoising provide us with a unique and more accurate morphological description.
The Astrophysical Journal, 1999
We present the function J as a morphological descriptor for point patterns formed by the distribu... more We present the function J as a morphological descriptor for point patterns formed by the distribution of galaxies in the Universe. This function was recently introduced in the field of spatial statistics, and is based on the nearest neighbor distribution and the void probability function. The J descriptor allows to distinguish clustered (i.e. correlated) from "regular" (i.e. anti-correlated) point distributions. We outline the theoretical foundations of the method, perform tests with a Matérn cluster process as an idealised model of galaxy clustering, and apply the descriptor to galaxies and loose groups in the Perseus-Pisces Survey. A comparison with mock-samples extracted from a mixed dark matter simulation shows that the J descriptor can be profitably used to constrain (in this case reject) viable models of cosmic structure formation.
The Astrophysical Journal, 1994
We apply fractal analysis methods to investigate the scaling properties in the Abell and ACO cata... more We apply fractal analysis methods to investigate the scaling properties in the Abell and ACO catalogs of rich galaxy clusters. The methods are adapted to account for the incompleteness of the samples by appropriately using the known selection functions in the partition sums. We also discuss dierent technical aspects of the method when applied to data sets with small number of points as the cluster catalogs. Results are compared with simulations based on the Zel'dovich approximation. We limit our analysis to scales less than 100 h 1 Mpc. The cluster distribution show a scale invariant m ultifractal behavior in a limited scale range. For the Abell catalog this range is 15{60 h 1 Mpc, while for the ACO sample it extends to smaller scales. Despite this dierence in the extension of the scale{range where scale{invariant clustering takes place, both samples are characterized by remarkably similar multifractal spectra in the corresponding scaling regime. In particular, the correlation dimension turns out to be D 2 ' 2:2 for both Abell and ACO clusters. Although it is dicult to point out the scale at which homogeneity is reached with the present size of these redshift surveys, our results indicate that the cluster distribution shows a tendency to homogeneity at large scales, disproving the picture of a pure scale invariant fractal structure extending to arbitrarily large distances.
The Astrophysical Journal, 2004
Using well-defined selection criteria applied to the LEDA galaxy catalogue we have constructed a ... more Using well-defined selection criteria applied to the LEDA galaxy catalogue we have constructed a sample of elliptical galaxies that can be taken to lie in the field. Such criteria can easily be applied to theoretical simulations for direct comparison with observations. The variation of the number of 'isolated' ellipticals with selection criteria is also investigated. A preliminary study of the environment of the field ellipticals shows that, in the mean, they are surrounded by a population of dwarf galaxies, out to projected radii of at least 500 kpc, with a radial density profile of r −0.6±0.2 and a luminosity function slope of α ∼ −1.8. The results are compared and contrasted to the satellite population around isolated spiral galaxies.