arXiv subjects

H. Domínguez-Sánchez

Publications and source records attributed to H. Domínguez-Sánchez.

15 recordsLinked to original sources

arXiv2026

J-PLUS: Spectral classification and photometric redshifts for 79 million sources in the fourth data release

We present spectral classifications and photometric redshifts for 79.2 million sources up to an r-band magnitude of 22 in Data Release 4 of the Javalambre Photometric Local Universe Survey (J-PLUS). Leveraging the 12-band J-PLUS filter system, we compare a template-fitting approach (LePhare) against LeMoNNADE, a morphology-blind machine learning pipeline that uses spectral mixing augmentation to overcome training set limitations. LeMoNNADE consistently outperforms template fitting in precision, robust scatter, and outlier rates. Including WISE infrared photometry breaks optical degeneracies between stars and quasars, reducing the catastrophic outlier rate for quasars from ~40% to ~23% and constraining systemic redshift bias to <1% up to z = 4. We find LeMoNNADE is also less susceptible to redshift aliasing, particularly when adopting the probability density function median. Because the spectroscopic training samples severely under-represent stars, we apply an Expectation-Maximization Bayesian calibration to recover unbiased class probabilities for the magnitude-limited sample. This reveals that extragalactic counts agree with the literature down to the r ~ 20.5 completeness limit. The inferred redshift distribution for r < 21 extragalactic sources peaks at z ~ 0.3, showing broad agreement with existing literature up to z ~ 0.6. The resulting catalogues represent a significant milestone for local Universe science, offering probabilistically calibrated classifications and distances while explicitly characterising faint-end limits and contamination.

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arXiv2025

J-PLUS: Spectroscopic validation of H$α$ emission line maps in spatially resolved galaxies

We present a dedicated automated pipeline to construct spatially resolved emission H$α$+[NII] maps and to derive the spectral energy distributions (SEDs) in 12 optical filters (five broad and seven narrow/medium) of H$α$ emission line regions in nearby galaxies (z $<$ 0.0165) observed by the Javalambre Photometric Local Universe Survey (J-PLUS). We used the $J0660$ filter of $140$Å width centered at $6600$Å to trace H$α$ + [NII] emission and $r$ and $i$ broad bands were used to estimate the stellar continuum. We create pure emission line images after the continnum subtraction, where the H$α$ emission line regions were detected. This method was also applied to Integral Field Unit (IFU) spectroscopic data from PHANGS-MUSE, CALIFA and MaNGA surveys by building synthetic narrow-bands based on J-PLUS filters. The studied sample includes the cross-matched catalog of these IFU surveys with J-PLUS third data release (DR3), amounting to $2$ PHANGS-MUSE, $78$ CALIFA, and $78$ MaNGA galaxies at $z < 0.0165$, respectively. We compared the H$α$+[NII] radial profiles from J-PLUS and the IFU surveys, finding good agreement within the expected uncertainties. We also compared the SEDs from the emission line regions detected in J-PLUS images, reproducing the main spectral features present in the spectroscopic data. Finally, we compared the emission fluxes from the J-PLUS and IFU surveys accounting for scale differences, finding a difference of only 2% with a dispersion of 7% in the measurements. The J-PLUS data provides reliable spatially resolved H$α$+[NII] emission maps for nearby galaxies. We provide the J-PLUS DR3 catalog for the $158$ galaxies with IFU data, including emission maps, SEDs of star-forming clumps, and radial profiles.

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arXiv2024

J-PLUS: Bayesian object classification with a strum of BANNJOS

With its 12 optical filters, the Javalambre-Photometric Local Universe Survey (J-PLUS) provides an unprecedented multicolor view of the local Universe. The third data release (DR3) covers 3,192 deg$^2$ and contains 47.4 million objects. However, the classification algorithms currently implemented in its pipeline are deterministic and based solely on the sources morphology. Our goal is classify the sources identified in the J-PLUS DR3 images into stars, quasi-stellar objects (QSOs), and galaxies. For this task, we present BANNJOS, a machine learning pipeline that uses Bayesian neural networks to provide the probability distribution function (PDF) of the classification. BANNJOS is trained on photometric, astrometric, and morphological data from J-PLUS DR3, Gaia DR3, and CatWISE2020, using over 1.2 million objects with spectroscopic classification from SDSS DR18, LAMOST DR9, DESI EDR, and Gaia DR3. Results are validated using $1.4 10^5$ objects and cross-checked against theoretical model predictions. BANNJOS outperforms all previous classifiers in terms of accuracy, precision, and completeness across the entire magnitude range. It delivers over 95% accuracy for objects brighter than $r = 21.5$ mag, and ~90% accuracy for those up to $r = 22$ mag, where J-PLUS completeness is < 25%. BANNJOS is also the first object classifier to provide the full probability distribution function (PDF) of the classification, enabling precise object selection for high purity or completeness, and for identifying objects with complex features, like active galactic nuclei with resolved host galaxies. BANNJOS has effectively classified J-PLUS sources into around 20 million galaxies, 1 million QSOs, and 26 million stars, with full PDFs for each, which allow for later refinement of the sample. The upcoming J-PAS survey, with its 56 color bands, will further enhance BANNJOS's ability to detail each source's nature.

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arXiv2024

Galaxy merger challenge: A comparison study between machine learning-based detection methods

Various galaxy merger detection methods have been applied to diverse datasets. However, it is difficult to understand how they compare. We aim to benchmark the relative performance of machine learning (ML) merger detection methods. We explore six leading ML methods using three main datasets. The first one (the training data) consists of mock observations from the IllustrisTNG simulations and allows us to quantify the performance metrics of the detection methods. The second one consists of mock observations from the Horizon-AGN simulations, introduced to evaluate the performance of classifiers trained on different, but comparable data. The third one consists of real observations from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) survey. For the binary classification task (mergers vs. non-mergers), all methods perform reasonably well in the domain of the training data. At $0.1<z<0.3$, precision and recall range between $\sim$70\% and 80\%, both of which decrease with increasing $z$ as expected (by $\sim$5\% for precision and $\sim$10\% for recall at $0.76<z<1.0$). When transferred to a different domain, the precision of all classifiers is only slightly reduced, but the recall is significantly worse (by $\sim$20-40\% depending on the method). Zoobot offers the best overall performance in terms of precision and F1 score. When applied to real HSC observations, all methods agree well with visual labels of clear mergers but can differ by more than an order of magnitude in predicting the overall fraction of major mergers. For the multi-class classification task to distinguish pre-, post- and non-mergers, none of the methods offer a good performance, which could be partly due to limitations in resolution and depth of the data. With the advent of better quality data (e.g. JWST and Euclid), it is important to improve our ability to detect mergers and distinguish between merger stages.

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arXiv2024

The miniJPAS survey: Maximising the photo-z accuracy from multi-survey datasets with probability conflation

We present a new method for obtaining photometric redshifts (photo-z) for sources observed by multiple photometric surveys using a combination (conflation) of the redshift probability distributions (PDZs) obtained independently from each survey. The conflation of the PDZs has several advantages over the usual method of modelling all the photometry together, including modularity, speed, and accuracy of the results. Using a sample of galaxies with narrow-band photometry in 56 bands from J-PAS and deeper grizy photometry from the Hyper-SuprimeCam Subaru Strategic program (HSC-SSP), we show that PDZ conflation significantly improves photo-z accuracy compared to fitting all the photometry or using a weighted average of point estimates. The improvement over J-PAS alone is particularly strong for i>22 sources, which have low signal-to-noise ratio in the J-PAS bands. For the entire i<22.5 sample, we obtain a 64% (45%) increase in the number of sources with redshift errors |Dz|<0.003, a factor 3.3 (1.9) decrease in the normalised median absolute deviation of the errors (sigma_NMAD), and a factor 3.2 (1.3) decrease in the outlier rate compared to J-PAS (HSC-SSP) alone. The photo-z accuracy gains from combining the PDZs of J-PAS with a deeper broadband survey such as HSC-SSP are equivalent to increasing the depth of J-PAS observations by ~1.2--1.5 magnitudes. These results demonstrate the potential of PDZ conflation and highlight the importance of including the full PDZs in photo-z catalogues.

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arXiv2024

The local Universe in the era of large surveys -- III. Radial activity profiles of S0 galaxies

Spatially resolved MaNGA's optical spectra of 1072 present-day lenticular (S0) galaxies, dimensionally reduced from a principal component analysis (PCA), are used to determine their radial activity structure shaped by any possible nebular ionization source. Activity profiles within $1.5\,R_{\mathrm e}$ are examined in tandem with the mass, age, ellipticity and kinematics of the stars, as well as environmental density. Among the results of this comparison, we find that the sign of the radial activity gradient of S0s is tightly related to their PCA classification, BPT designation, and star formation status. PCA-passive lenticulars often show low-level, flat activity profiles, although there is also a significant number of systems with positive gradients, while their less common active counterparts generally have negative gradients, usually associated with high SSFRs and, sometimes, moderate Seyfert emission. A fraction of the latter also shows radial activity profiles with positive gradients, which become more abundant with increasing stellar mass regardless of environmental density. Our analysis also reveals that the subset of active S0s with negative gradients experiences at all galactocentric radii a systematic reduction in its median activity level with stellar mass, consistent with expectations for main sequence galaxies. In contrast, passive S0s with positive gradients show the opposite behaviour. Furthermore, systems whose activity is dominated by star formation are structurally rounder than the rest of S0s, while those classified as Seyfert exhibit higher rotational support. The possibility that negative and positive activity gradients in S0s may result from rejuvenation by two distinct types of minor mergers is raised.

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arXiv2023

Bridging the gap in the mass-size relation of compact galaxies with MaNGA

We present the analysis of the full MaNGA DR17 sample to characterize its population of compact galaxies. We focus on galaxies that fill the stellar mass (M$_{\star}$) gap between compact elliptical galaxies (cEs; $8 \lesssim \log \left(M_{\star} / M_{\odot} \right) \lesssim 10$) and compact massive galaxies (CMGs; $10 \lesssim \log \left(M_{\star} / M_{\odot} \right)$). We study their stellar populations and kinematics to reveal how their properties depend on stellar mass. We select compact galaxies in the MaNGA DR17 sample according to their effective radius ($R_e$) and stellar mass. 37 galaxies fulfill our selection criteria in the bridging region between cEs and CMGs. We derive their kinematics and stellar population parameters from the stacked spectra at 1~$R_e$ using a full spectral fitting routine. We then classify the selected compact galaxies in three main groups based on their stellar population properties. One of the groups shows characteristics compatible with relic galaxies, i.e. galaxies that have remained mostly unchanged since their early formation epoch ($z \sim 2$). Another group shows more extended and continuous star formation histories (SFHs). The third group shows a low star-forming rate at initial times, which increases at around $\sim4$ Gyr. We compare the derived properties of the selected galaxies with those of previously studied compact galaxies at different mass ranges. The selected galaxies successfully fill the mass gap between cEs and CMGs. Their properties are compatible with the assumption that the scaling relations of compact galaxies at different mass ranges are related, although galaxies in the first group are clear outliers in the fundamental plane, suggesting different formation mechanisms for this relic population.

astro-ph.GA↗

arXiv2023

The origin of star-forming rings in S0 galaxies

Spatially resolved integral field spectroscopic maps in a sample of $532$ S0 galaxies from the MaNGA survey have unveiled the existence of inner rings ($\langle R\rangle\sim 1\,R_\mathrm{e}$) betraying ongoing star formation in a number of these objects. Activity gradients averaged over bins of galactocentric radius up to $\sim 1.5\,R_\mathrm{e}$ have been measured in the subspace defined by the first two principal components of the optical spectra of these galaxies. We find that the sign of the gradients is closely related to the presence of such rings in the spectral maps, which are especially conspicuous in the equivalent width of the H$α$ emission line, EW(H$α$), with a fractional abundance $\unicode{x2014}21\unicode{x2013}34\%\unicode{x2014}$ notably larger than that inferred from optical images. While the numbers of S0s with positive, negative, and flat activity gradients are comparable, star-forming rings are largely found in objects for which quenching proceeds from the inside out, in good agreement with predictions from cosmological simulations studying S0 buildup. Assessment of these ringed structures indicates that their frequency increases with the mass of their hosts, that they have shorter lifetimes in galaxies with ongoing star formation, that they may feed on gas from the disks, and that the local environment does not play a relevant role in their formation. We conclude that the presence of inner rings in the EW(H$α$) is a common phenomenon in fully formed S0s, possibly associated with annular disk resonances driven by weakly disruptive mergers preferentially involving a relatively massive primary galaxy and a tiny satellite strongly bound to the former.

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arXiv2021

A duality in the origin of bulges and spheroidal galaxies

Studying the resolved stellar populations of the different structural components which build massive galaxies directly unveils their assembly history. We aim at characterizing the stellar population properties of a representative sample of bulges and pure spheroids in massive galaxies ($M_{\star}>10^{10}$ M$_{\odot}$) in the GOODS-N field. We take advantage of the spectral and spatial information provided by SHARDS and HST data to perform the multi-image spectro-photometrical decoupling of the galaxy light. We derive the spectral energy distribution separately for bulges and disks in the redshift range $0.14<z\leq1$ with spectral resolution $R\sim50$. Analyzing these SEDs, we find evidences of a bimodal distribution of bulge formation redshifts. We find that 33% of them present old mass-weighted ages, implying a median formation redshift $z_{\rm{form}}={6.2}_{-1.7}^{+1.5}$. They are relics of the early Universe embedded in disk galaxies. A second wave, dominant in number, accounts for bulges formed at median redshift $z_{\rm{form}}={1.3}_{-0.6}^{+0.6}$. The oldest (1$^{\rm{st}}$-wave) bulges are more compact than the youngest. Virtually all pure spheroids (i.e., those without any disk) are coetaneous with the 2$^{\rm{nd}}$-wave bulges, presenting a median redshift of formation $z_{\rm{form}}={1.1}_{-0.3}^{+0.3}$. The two waves of bulge formation are not only distinguishable in terms of stellar ages, but also in star formation mode. All 1$^{\rm st}$-wave bulges formed fast at $z\sim6$, with typical timescales around 200 Myr. A significant fraction of the 2$^{\rm{nd}}$-wave bulges assembled more slowly, with star formation timescales as long as 1 Gyr. The results of this work suggest that the centers of massive disk-like galaxies actually harbor the oldest spheroids formed in the Universe.

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arXiv2019

A deeper look at the dust attenuation law of star-forming galaxies at high redshift

A diverse range of dust attenuation laws is found in star-forming galaxies. In particular, Tress et al. (2018) studied the SHARDS survey to constrain the NUV bump strength (B) and the total-to selective ratio (Rv) of 1,753 star-forming galaxies in the GOODS-N field at 1.5<z<3. We revisit here this sample to assess the implications and possible causes of the correlation found between Rv and B. The UVJ bicolour plot and main sequence of star formation are scrutinised to look for clues into the observed trend. The standard boundary between quiescent and star-forming galaxies is preserved when taking into account the wide range of attenuation parameters. However, an additional degeneracy, regarding the effective attenuation law, is added to the standard loci of star-forming galaxies in the UVJ diagram. A simple phenomenological model with an age-dependent extinction (at fixed dust composition) is compatible with the observed trend between Rv and B, whereby the opacity decreases with the age of the populations, resulting in a weaker NUV bump when the overall attenuation is shallower (greyer). In addition, we compare the constraints obtained by the SHARDS sample with dust models from the literature, supporting a scenario where geometry could potentially drive the correlation between Rv and B

astro-ph.GA↗

arXiv2019

The Hubble Sequence at $z\sim0$ in the IllustrisTNG simulation with deep learning

We analyze the optical morphologies of galaxies in the IllustrisTNG simulation at $z\sim0$ with a Convolutional Neural Network trained on visual morphologies in the Sloan Digital Sky Survey. We generate mock SDSS images of a mass complete sample of $\sim12,000$ galaxies in the simulation using the radiative transfer code SKIRT and include PSF and noise to match the SDSS r-band properties. The images are then processed through the exact same neural network used to estimate SDSS morphologies to classify simulated galaxies in four morphological classes (E, S0/a, Sab, Scd). The CNN model finds that $\sim95\%$ of the simulated galaxies fall in one the four main classes with high confidence. The mass-size relations of the simulated galaxies divided by morphological type also reproduce well the slope and the normalization of observed relations which confirms the realism of optical morphologies in the TNG suite. However, the Stellar Mass Functions decomposed into different morphologies still show significant discrepancies with observations both at the low and high mass end. We find that the high mass end of the SMF is dominated in TNG by massive disk galaxies while early-type galaxies dominate in the observations according to the CNN classifications. The present work highlights the importance of detailed comparisons between observations and simulations in comparable conditions.

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arXiv2018

Deep Learning Identifies High-z Galaxies in a Central Blue Nugget Phase in a Characteristic Mass Range

We use machine learning to identify in color images of high-redshift galaxies an astrophysical phenomenon predicted by cosmological simulations. This phenomenon, called the blue nugget (BN) phase, is the compact star-forming phase in the central regions of many growing galaxies that follows an earlier phase of gas compaction and is followed by a central quenching phase. We train a Convolutional Neural Network (CNN) with mock "observed" images of simulated galaxies at three phases of evolution: pre-BN, BN and post-BN, and demonstrate that the CNN successfully retrieves the three phases in other simulated galaxies. We show that BNs are identified by the CNN within a time window of $\sim0.15$ Hubble times. When the trained CNN is applied to observed galaxies from the CANDELS survey at $z=1-3$, it successfully identifies galaxies at the three phases. We find that the observed BNs are preferentially found in galaxies at a characteristic stellar mass range, $10^{9.2-10.3} M_\odot$ at all redshifts. This is consistent with the characteristic galaxy mass for BNs as detected in the simulations, and is meaningful because it is revealed in the observations when the direct information concerning the total galaxy luminosity has been eliminated from the training set. This technique can be applied to the classification of other astrophysical phenomena for improved comparison of theory and observations in the era of large imaging surveys and cosmological simulations.

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arXiv2018

SHARDS: Constraints on the dust attenuation law of star-forming galaxies at z~2

We make use of SHARDS, an ultra-deep (<26.5AB) galaxy survey that provides optical photo-spectra at resolution R~50, via medium band filters (FWHM~150A). This dataset is combined with ancillary optical and NIR fluxes to constrain the dust attenuation law in the rest-frame NUV region of star-forming galaxies within the redshift window 1.5<z<3. We focus on the NUV bump strength (B) and the total-to-selective extinction ratio (Rv), targeting a sample of 1,753 galaxies. By comparing the data with a set of population synthesis models coupled to a parametric dust attenuation law, we constrain Rv and B, as well as the colour excess, E(B-V). We find a correlation between Rv and B, that can be interpreted either as a result of the grain size distribution, or a variation of the dust geometry among galaxies. According to the former, small dust grains are associated with a stronger NUV bump. The latter would lead to a range of clumpiness in the distribution of dust within the interstellar medium of star-forming galaxies. The observed wide range of NUV bump strengths can lead to a systematic in the interpretation of the UV slope ($β$) typically used to characterize the dust content. In this study we quantify these variations, concluding that the effects are $Δβ$~0.4.

astro-ph.GA↗

arXiv2013

Serendipitous detection of an overdensity of Herschel-SPIRE 250 micron sources south of MRC1138-26

We report the serendipitous detection of a significant overdensity of Herschel-SPIRE 250 micron sources in the vicinity of MRC1138-26. We use an adaptive kernel density estimate to quantify the significance, including a comparison with other fields. The overdensity has a size of ~3.5-4' and stands out at ~5sigma with respect to the background estimate. No features with similar significance were found in four extragalactic control fields: GOODS-North, Lockman, COSMOS and UDS. The chance of having a similar overdensity in a field with the same number but randomly distributed sources is less than 2%. The clump is also visible as a low surface brightness feature in the Planck 857 GHz map. We detect 76 sources at 250 micron (with a signal-to-noise ratio greater than 3), in a region of 4' radius; 43 of those are above a flux density limit of 20 mJy. This is a factor of 3.6 in excess over the average in the four control fields, considering only the sources above 20 mJy. We also find an excess in the number counts of sources with 250 micron flux densities between 30 and 40 mJy, compared to deep extragalactic blank-field number counts. Assuming a fixed dust temperature (30 K) and emissivity (beta=1.5) a crude, blackbody-derived redshift distribution, zBB, of the detected sources is significantly different from the distributions in the control fields and exhibits a significant peak at zBB ~ 1.5, although the actual peak redshift is highly degenerate with the temperature. We tentatively suggest, based on zBB and the similar S250/S350 colours of the sources within the peak, that a significant fraction of the sources in the clump may be at a similar redshift. Since the overdensity lies ~7' south of the z=2.16 Spiderweb protocluster MRC1138-26, an intriguing possibility (that is presently unverifiable given the data in hand) is that it lies within the same large-scale structure.(abridged)

astro-ph.CO↗

arXiv2013

Multi-wavelength landscape of the young galaxy cluster RXJ1257.2+4738 at z=0.866: I. The infrared view

We performed a thorough analysis of the star formation activity in the young massive galaxy cluster RXJ1257+4738 at z=0.866, with emphasis on the relationship between the local environment of the cluster galaxies and their star formation activity. We present an optical and IR study that benefited from the large amount of data available for this cluster, including new OSIRIS/GTC and Herschel imaging observations. Using a optical-to-NIR multi-wavelength catalogue, we measured photometric redshifts through a chi2 SED-fitting procedure. We implemented a reliable and carefully chosen cluster membership selection criterion including Monte Carlo simulations and derived a sample of 292 reliable cluster member galaxies for which we measured the following properties: optical colours, stellar masses, ages, ultraviolet luminosities and local densities. Using the MIPS 24um and Herschel data, we measured total IR luminosities and SFR. Of the sample of 292 cluster galaxies, 38 show FIR emission with an SFR between 0.5 and 45 Msun/yr. The spatial distribution of the FIR emitters within the cluster density map and the filament-like overdensities observed suggest that RXJ1257 is not virialised, but is in the process of assembly. The average star formation as a function of the cluster environment parametrised by the local density of galaxies does not show any clear trend. However, the fraction of SF galaxies unveils that the cluster intermediate-density regions is preferred for the SF activity to enhance, since we observe a significant increase of the FIR-emitter fraction in this environment. Focusing on the optically red SF galaxies, we can support the interpretation of this population as dusty red galaxies, since we observe an appreciable difference in their extinction compared with the blue population.

astro-ph.CO↗