arXiv subjects

Miguel Cerviño

Publications and source records attributed to Miguel Cerviño.

34 records · Page 2Linked to original sources

arXiv2021

The OTELO survey: Faint end of the luminosity function of [OII] emitters at = 1.43

In this paper, we aim to study the main properties and luminosity function (LF) of the [OII] emitters detected in the OTELO survey in order to characterise the star formation processes in low-mass galaxies at $z\sim1.43$ and to constrain the faint-end of the LF. Here, we describe the selection method and analysis of the emitters obtained from narrow-band scanning techniques. In addition, we present several relevant properties of the emitters and discuss the selection biases and uncertainties in the determination of the LF and the star formation rate density (SFRD). We confirmed a total of 60 sources from a preliminary list of 332 candidates as [OII] emitters. Approximately 93% of the emitters have masses in the range of $10^{8}<M_{*}/{\rm M_{\odot}}<10^{9}$. All of our emitters are classified as late-type galaxies, with a lower value of $(u-v)$\, when compared with the rest of the emitters of the OTELO survey. We find that the cosmic variance strongly affects the normalisation ($ϕ^*$) of the LF and explains the discrepancy of our results when compared with those obtained from surveys of much larger volumes. However, we are able to determine the faint-end slope of the LF, namely, $α=-1.42\pm0.06$, by sampling the LF down to $\sim1$\,dex lower than in previous works. We present our calculation of the SFRD of our sample and compare it to the value obtained in previous studies from the literature.

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arXiv2021

The OTELO survey as a morphological probe. Last ten Gyr of galaxy evolution. The mass--size relation up to z=2

The morphology of galaxies provide us with a unique tool for relating and understanding other physical properties and their changes over the course of cosmic time. It is only recently that we have been afforded access to a wealth of data for an unprecedented number galaxies thanks to large and deep surveys, We present the morphological catalogue of the OTELO survey galaxies detected with the Hubble Space Telescope (HST)-ACS F814W images. We explore various methods applied in previous works to separate early-type (ET) and late-type (LT) galaxies classified via spectral energy distribution (SED) fittings using galaxy templates. Together with this article, we are releasing a catalogue containing the main morphological parameters in the F606W and F814W bands derived for more than 8\,000 sources. The morphological analysis is based on the single-Sérsic profile fit. We used the GALAPAGOS2 software to provide multi-wavelength morphological parameters fitted simultaneously in two HST-ACS bands. The GALAPAGOS2 software detects, prepares guess values for GALFTI-M, and provides the best-fitting single-Sérsic model in both bands for each source. Stellar masses were estimated using synthetic rest-frame magnitudes recovered from SED fittings of galaxy templates. The morphological catalogue is complemented with concentration indexes from a separate SExtractor dual, high dynamical range mode. A total of 8,812 sources were successfully fitted with single-Sérsic profiles. The analysis of a carefully selected sample of ~3,000 sources up to phot_z=2 is presented in this work, of which 873 sources were not detected in previous studies. We found no statistical evidence for the evolution of the low-mass end of mass-size relation for ET and LT since z=2. Furthermore, we found a good agreement for the median size evolution for ET and LT galaxies, for a given stellar mass, with the data from the literature.

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arXiv2020

GLACE survey: galaxy activity in ZwCl0024+1652 cluster from strong optical emission lines

Although ZwCl0024+1652 galaxy cluster at $z\sim0.4$ has been thoroughly analysed, it lacks a comprehensive study of star formation and nuclear activity of its members. With GaLAxy Cluster Evolution (GLACE) survey, a total of 174 H$α$ emission-line galaxies (ELGs) were detected, most of them having [NII}]. We reduced and analysed a set of [OIII] and H$β$ tunable filter (TF) observations within GLACE survey. Using H$α$ priors, we identified [OIII] and H$β$ in 35 ($\sim$20%) and 59 ($\sim$34%) sources, respectively, with 21 of them having both emission lines, and 20 having in addition [NII]. Applying BPT-NII diagnostic diagram, we classified these ELGs into 40% star-forming (SF), 55% composites, and 5% LINERs. Star formation rate (SFR) measured through extinction corrected H$α$ fluxes increases with stellar mass ($\mathrm{M}_{*}$), attaining its peak at $\mathrm{M}_{*}\sim10^{9.8}\mathrm{M}_\odot$. We observed that the cluster centre to $\sim$1.3Mpc is devoid of SF galaxies and AGN. Our results suggest that the star formation efficiency declines as the local density increases in the cluster medium. Moreover, the SF and AGN fractions drop sharply towards high-density environments. We observed a strong decline in SF fraction in high $\mathrm{M}_*$, confirming that star formation is highly suppressed in high-mass cluster galaxies. Finally, we determined that SFR correlates with $\mathrm{M}_*$ while specific SFR (sSFR) anti-correlates with $\mathrm{M}_*$, both for cluster and field. This work shows the importance and strength of TF observations when studying ELGs in clusters at higher redshifts. We provide with this paper a catalogue of ELGs with H$β$ and/or [OIII] lines in ZwCl0024+1652 cluster.

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arXiv2020

Galaxy classification: deep learning on the OTELO and COSMOS databases

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

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arXiv2020

The OTELO survey: Nature and mass-metallicity relation for H$α$ emitters at $z\sim\,0.4$

A sample of low-mass H$α$ emission line sources (ELS) at $z\,\sim\,0.4$ was studied in the context of the mass-metallicty relation (MZR) and its possible evolution. We drew our sample from the OSIRIS Tunable Emission Line Object (OTELO) survey, which exploits the red tunable filter of OSIRIS at the Gran Telescopio Canarias to perform a blind narrow-band spectral scan in a selected field of the Extended Groth Strip. We were able to directly measure emission line fluxes and equivalent widths from the analysis of OTELO pseudo-spectra. This study aims to explore the MZR in the very low-mass regime. Our sample reaches stellar masses ($M_*$) as low as $10^{6.8}\,M_\odot$, where 63\% of the sample have $M_*\,<10^9\,M_\odot$. We also explore the relation of the star formation rate (SFR) and specific SFR (sSFR) with $M_*$ and gas-phase oxygen abundances, as well as the $M_*$-size relation and the morphological classification. The $M_*$ were estimated using synthetic rest-frame colours. Using an $χ^2$ minimization method, we separated the contribution of \Nii$λ$6583 to the H$α$ emission lines. Using the N2 index, we separated active galactic nuclei from star-forming galaxies (SFGs) and estimated the gas metallicity. We studied the morphology of the sampled galaxies qualitatively (visually) and quantitatively (automatically) using high-resolution data from the \textit{Hubble Space Telescope}-ACS. The physical size of the galaxies was derived from the morphological analysis using \texttt{GALAPAGOS2/GALFIT}, where we fit a single-Sérsic 2D model to each source.

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arXiv2020

The OTELO survey. A case study of [O III]4959,5007 emitters at = 0.83

The OTELO survey is a very deep, blind exploration of a selected region of the Extended Groth Strip and is designed for finding emission-line sources (ELSs). The survey design, observations, data reduction, astrometry, and photometry, as well as the correlation with ancillary data used to obtain a final catalogue, including photo-z estimates and a preliminary selection of ELS, were described in a previous contribution. Here, we aim to determine the main properties and luminosity function (LF) of the [O III] ELS sample of OTELO as a scientific demonstration of its capabilities, advantages, and complementarity with respect to other surveys. The selection and analysis procedures of ELS candidates obtained using tunable filter (TF) pseudo-spectra are described. We performed simulations in the parameter space of the survey to obtain emission-line detection probabilities. Relevant characteristics of [O III] emitters and the LF([O III]), including the main selection biases and uncertainties, are presented. A total of 184 sources were confirmed as [O III] emitters at a mean redshift z=0.83. The minimum detectable line flux and equivalent width (EW) in this ELS sample are $\sim$5 $\times$ 10$^{-19}$ erg s$^{-1}$ cm$^{2}$ and $\sim$6 Å, respectively. We are able to constrain the faint-end slope ($α= -1.03\pm0.08$) of the observed LF([O III]) at z=0.83. This LF reaches values that are approximately ten times lower than those from other surveys. The vast majority (84\%) of the morphologically classified [O III] ELSs are disc-like sources, and 87\% of this sample is comprised of galaxies with stellar masses of M$_\star$ $<$ 10$^{10}$ M$_{\odot}$.

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arXiv2020

The OTELO survey. III. Demography, morphology, IR luminosity and environment of AGN hosts

We take advantage of the capabilities of the OTELO survey to select and study the AGN population in the field. We performed an analysis of the properties of these objects, including their demography, morphology, and IR luminosity. Focusing on the population of H$α$ emitters at $z \sim 0.4$, we also aim to study the environments of AGN and non-AGN galaxies at that redshift. We make use of the multiwavelength catalog of objects in the field compiled by the OTELO survey, unique in terms of minimum line flux and equivalent width. The OTELO pseudo-spectra allow the identification of emission lines and the spectral classification of the sources. We obtained a sample of 72 AGNs in the field of OTELO, selected with four different methods in the optical, X-rays, and mid-infrared bands. We find that using X-rays is the most efficient way to select AGNs. An analysis was performed on the AGN population of OTELO in order to characterize its members. At $z \sim 0.4$, we find that up to 26\% of our H$α$ emitters are AGNs. At that redshift, AGNs are found in identical environments to non-AGNs, although they represent the most clustered group when compared to passive and star-forming galaxies. The majority of our AGNs at any redshift were classified as late-type galaxies, including a 16\% proportion of irregulars. Another 16\% of AGNs show signs of interactions or mergers. Regarding the infrared luminosity, we are able to recover all the luminous infrared galaxies (LIRGs) in the field of OTELO up to $z\sim 1.6$. We find that the proportion of LIRGs and ultra-luminous infrared galaxies (ULIRGs) is higher among the AGN population, and that ULIRGs show a higher fraction of AGNs than LIRGs.

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arXiv2020

The OTELO survey. I. Description, data reduction, and multi-wavelength catalogue

The evolution of galaxies through cosmic time is studied observationally by means of extragalactic surveys. 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. 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 Extended Groth Strip 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. The OTELO multi-wavelength catalogue contains 11237 entries and is 50\% complete at AB magnitude 26.38. Of these sources, 6600 have photometric redshifts with an uncertainty $z_{phot}$ better than $0.2 (1+z_{phot})$. 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 products were released to the public on 2019.

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arXiv2020

The OTELO survey. II. The faint-end of the H$α$ luminosity function at z $\sim$ 0.40

We take advantage of the capability of the OTELO survey to obtain the H$α$ luminosity function (LF) at ${\rm z}\sim0.40$. Because of the deepest coverage of OTELO, we are able to determine the faint end of the LF, and thus better constrain the star formation rate and the number of galaxies at low luminosities. The AGN contribution to this LF is estimated as well. We make use of the multi-wavelength catalogue of objects in the field compiled by the OTELO survey, which is unique in terms of minimum flux and equivalent width. We also take advantage of the pseudo-spectra built for each source, which allow the identification of emission lines and the discrimination of different types of objects. The H$α$ luminosity function at $z\sim0.40$ is obtained, which extends the current faint end by almost 1 dex, reaching minimal luminosities of $\log_{10}L_{\rm lim}=38.5$ erg s$^{-1}$ (or $\sim0.002\, \text{M}_\odot\text{ yr}^{-1})$. The AGN contribution to the total H$α$ luminosity is estimated. We find that no AGN should be expected below a luminosity of $\log_{10}L=38.6$ erg s$^{-1}$. From the sample of non-AGN (presumably, pure SFG) at $z\sim0.40$ we estimated a star formation rate density of $ρ_{\rm SFR}=0.012\pm0.005\ {\rm \text{M}_{\odot}\ yr^{-1}\ Mpc^{-3}}$.

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arXiv2019

System IMF of the 25 Ori Group from Planetary-Mass Objects to Intermediate/High-Mass Stars

The stellar initial mass function (IMF) is an essential input for many astrophysical studies but only in a few cases it has been determined over the whole cluster mass range, limiting the conclusions about its nature. The 25 Orionis group (25 Ori) is an excellent laboratory to investigate the IMF across the entire mass range of the population, from planetary-mass objects to intermediate/high-mass stars. We combine new deep optical photometry with optical and near-infrared data from the literature to select 1687 member candidates covering a 1.1$^\circ$ radius area in 25 Ori. With this sample we derived the 25 Ori system IMF from 0.012 to 13.1 $M_\odot$. This system IMF is well described by a two-segment power-law with $Γ=-0.74\pm0.04$ for $m<0.4\ M_\odot$ and $Γ=1.50\pm0.11$ for $m\ge0.4\ M_\odot$. It is also well described over the whole mass range by a tapered power-law function with $Γ=1.10\pm0.09$, $m_p=0.31\pm0.03$ and $β=2.11\pm0.09$. The best lognormal representation of the system IMF has $m_c=0.31\pm0.04$ and $σ=0.46\pm0.05$ for $m<1\ M_\odot$. This system IMF does not present significant variations with the radii. We compared the resultant system IMF as well as the BD/star ratio of $0.16\pm0.03$ we estimated for 25 Ori with that of other stellar regions with diverse conditions and found no significant discrepancies. These results support the idea that general star formation mechanisms are probably not strongly dependent to environmental conditions. We found that the substellar and stellar objects in 25 Ori have similar spatial distributions and confirmed that 25 Ori is a gravitationally unbound stellar association.

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arXiv2019

A morphological study of galaxies in ZwCl0024+1652, a galaxy cluster at redshift z $\sim$ 0.4

The well-known cluster of galaxies ZwCl0024+1652 at z $\sim$ 0.4, lacks an in-depth morphological classification of its central region. While previous studies provide a visual classification of a patched area, we used the public code called galaxy Support Vector Machine (galSVM) and HST/ACS data as well as WFP2 master catalogue to automatically classify all cluster members up to 1 Mpc. galSVM analyses galaxy morphologies through Support Vector Machine (SVM). From the 231 cluster galaxies, we classified 97 as early-types (ET) and 83 as late-types (LT). The remaining 51 stayed unclassified (or undecided, UD). By cross-matching our results with the existing visual classification, we found an agreement of 81%. In addition to previous Zwcl0024 morphological classifications, 121 of our galaxies were classified for the first time in this work. In addition, we tested the location of classified galaxies on the standard morphological diagrams, colour-colour and colour-magnitude diagrams. Out of all cluster members, $\sim$20% are emission line galaxies (ELG), taking into account previous GLACE results. We have verified that the ET fraction is slightly higher near the cluster core and decreases with the clustercentric distance, while the opposite trend has been observed for LT galaxies. We found higher fraction of ET (54%) than LT (46%) throughout the analysed central region, as expected. In addition, we analysed the correlation between the five morphological parameters (Abraham concentration, Bershady-Concelice concentration, Asymmetry, Gini and M20 moment of light) and clustercentric distance, without finding a clear trend. Finally, as a result of our work, the morphological catalogue of 231 galaxies containing all the measured parameters and the final classification is available in the electronic form of this paper.

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arXiv2018

Hierarchical Bayesian approach for estimating physical properties in nearby galaxies: Age Maps (Paper II)

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 \Ha\ line (taken with Taurus Tunable Filter, TTF), ultraviolet band (GALEX far UV, FUV), and infrared bands (Spitzer 24, 70, and 160 $μ$m). We present the burst ages for young stellar populations in a sample of nearby and nearly face-on galaxies. The \Ha\ 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 \Ha\ line emission declines earlier than the UV continuum, leading to a decrease in the \Ha/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 \Ha/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 \Ha/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 \Ha/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.

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arXiv2015

Galaxy clusters and groups in the ALHAMBRA Survey

We present a catalogue of 348 galaxy clusters and groups with $0.2<z<1.2$ selected in the 2.78 $deg^2$ ALHAMBRA Survey. The high precision of our photometric redshifts, close to $1\%$, and the wide spread of the seven ALHAMBRA pointings ensure that this catalogue has better mass sensitivity and is less affected by cosmic variance than comparable samples. The detection has been carried out with the Bayesian Cluster Finder (BCF), whose performance has been checked in ALHAMBRA-like light-cone mock catalogues. Great care has been taken to ensure that the observable properties of the mocks photometry accurately correspond to those of real catalogues. From our simulations, we expect to detect galaxy clusters and groups with both $70\%$ completeness and purity down to dark matter halo masses of $M_h\sim3\times10^{13}\rm M_{\odot}$ for $z<0.85$. Cluster redshifts are expected to be recovered with $\sim0.6\%$ precision for $z<1$. We also expect to measure cluster masses with $σ_{M_h|M^*_{CL}}\sim0.25-0.35\, dex$ precision down to $\sim3\times10^{13}\rm M_{\odot}$, masses which are $50\%$ smaller than those reached by similar work. We have compared these detections with previous optical, spectroscopic and X-rays work, finding an excellent agreement with the rates reported from the simulations. We have also explored the overall properties of these detections such as the presence of a colour-magnitude relation, the evolution of the photometric blue fraction and the clustering of these sources in the different ALHAMBRA fields. Despite the small numbers, we observe tentative evidence that, for a fixed stellar mass, the environment is playing a crucial role at lower redshifts (z$<$0.5).

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arXiv2013

The stochastic nature of stellar population modelling

Since the early 1970s, stellar population modelling has been one of the basic tools for understanding the physics of unresolved systems from observation of their integrated light. Models allow us to relate the integrated spectra (or colours) of a system with the evolutionary status of the stars of which it is composed and hence to infer how the system has evolved from its formation to its present stage. On average, observational data follow model predictions, but with some scatter, so that systems with the same physical parameters (age, metallicity, total mass) produce a variety of integrated spectra. The fewer the stars in a system, the larger is the scatter. Such scatter is sometimes much larger than the observational errors, reflecting its physical nature. This situation has led to the development in recent years (especially since 2010) of Monte Carlo models of stellar populations. Some authors have proposed that such models are more realistic than state-of-the-art standard synthesis codes that produce the mean of the distribution of Monte Carlo models. In this review, I show that these two modelling strategies are actually equivalent, and that they are not in opposition to each other. They are just different ways of describing the probability distributions intrinsic in the very modelling of stellar populations. I show the advantages and limitations of each strategy and how they complement each other. I also show the implications of the probabilistic description of stellar populations in the application of models to observational data obtained with high-resolution observational facilities. Finally, I outline some possible developments that could be realized in stellar population modelling in the near future. Open your window and take a look at the night sky on a clear night.....

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arXiv2011

The 100 Myr Star Formation History of NGC 5471 from Cluster and Resolved Stellar Photometry

We show that star formation in the giant HII region NGC 5471 has been ongoing during the past 100 Myr. Using HST/WFPC2 F547M and F675W, ground based JHKs, and GALEX FUV and NUV images, we have conducted a photometric study of the star formation history in the massive giant extragalactic HII region NGC 5471 in M101. We perform a photometric study of the colour-magnitude diagram (CMD) of the resolved stars, and an integrated analysis of the main individual star forming clusters and of NGC 5471 as a whole. The integrated UV-optical-nIR photometry for the whole region provides two different reference ages, 8 Myr and 60 Myr, revealing a complex star formation history, clearly confirmed by the CMD resolved stellar photometry analysis. The spatial distribution of the stars shows that the star formation in NGC 5471 has proceeded along the whole region during, at least, the last 100 Myr. The current ionizing clusters are enclosed within a large bubble, which is likely to have been produced by the stars that formed in a major event < 20 Myr ago.

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arXiv2005

The ALHAMBRA Survey: For a systematic Study of Cosmic Evolution

ALHAMBRA is a project to gather data to sample a fraction of the Universe with enough precision to follow the evolution of its content and properties with z, a kind of Cosmic Tomography. It is defined as a 4 square degrees photometric survey with 20 contiguous, equal width, medium band filters covering from 3500 to 9700 A, plus the JHKs NIR bands. It was optimized to get (for a fixed observing time) the maximum number of objects with accurate classification and redshift and to be sensitive to relatively faint emission features. The observations will be carried out with the 3.5m telescope in Calar Alto (Spain). We intend to reach the limit AB=25 in all the optical filters from the bluest to 8300 A, and from 24.7 to 23.4 for the remainder. The expected limit in the NIR is fixed at Ks=20, H=21, J=22. The homogeneous and contiguous spectral coverage will result in several hundred thousand objects with accurate SED identification and z-values. The accuracy of the survey will allow to make detailed studies, including galactic, without the need for any further follow-up. Indeed, it will provide exciting targets for large telescopes, the GTC in particular.

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