arXiv subjects

H. M. Hernández-Toledo

Publications and source records attributed to H. M. Hernández-Toledo.

15 recordsLinked to original sources

arXiv2026

Asymmetries in spatially unresolved 21-cm emission line profiles of isolated galaxies

The origin of asymmetry in the ${\rm H}\,{\scriptsize{\rm I}}$ of galaxies remains an elusive problem, largely due to the difficulties associated with distinguishing between its secular and external contributors. We have compiled a sample of local isolated galaxies from the UNAM-KIAS and the latest AMIGA samples with near-complete beam coverage and robust estimates of ${\rm H}\,{\scriptsize{\rm I}}$ line asymmetry. The ${\rm H}\,{\scriptsize{\rm I}}$ measurements are based on single-dish spectra sourced from five surveys: ${\rm H}\,{\scriptsize{\rm I}}$-MaNGA, NIBLES, KLUN, ALFALFA, and xGASS. Our galaxies tend to be late-type, star-forming centrals at all masses but exhibit slightly lower specific star formation rates (sSFRs) and higher ${\rm H}\,{\scriptsize{\rm I}}$ contents than expected. The latter is likely driven by lower star formation efficiency, weaker outflows, and additionally, higher accretion rate of gas onto the galaxy at $M_\star\lesssim 10^{10.3}\,\mathrm{M}_\odot$. AMIGA, however, shows systematically higher ${\rm H}\,{\scriptsize{\rm I}}$ masses than UNAM-KIAS, which we attribute to higher local densities probed by the latter. Furthermore, both samples show bar frequencies similar to normal spirals, indicating that the gravitational instabilities leading to bars predominantly stem from internal processes, as suggested by recent works. Our galaxies show unexpectedly high merger fractions, possibly due to sampling bias and/or the inability of the classification method to distinguish between flybys and encounters leading to coalescence. We also find higher sSFRs for asymmetric galaxies below $M_\star\sim 10^{10.3}\,\mathrm{M}_\odot$, in agreement with the predictions for centrals from the ${\scriptsize{\rm EAGLE}}$ simulation. We release the ${\rm H}\,{\scriptsize{\rm I}}$ measurements along with ancillary galaxy and halo properties for public use.

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arXiv2025

Visual morphological classification of the full MaNGA DR17 sample: a general characterization

We present the MaNGA Visual Morphology (MVM) catalogue, featuring a visual morphological classification of 10,059 galaxies in the final MaNGA sample. By combining SDSS and DESI Legacy Survey (DLS) images, we classified galaxies into 13 Hubble types, detected tidal features, categorized bars into different families, and estimated concentration, asymmetry, and clumpiness. The depth of the DLS images allowed us to identify structural details that were not evident in the SDSS images, resulting in a more reliable classification. After correcting for volume completeness, we find a bimodal distribution in galaxy morphology, with peaks in S0 and Scd types, and a transition zone around S0a-Sa types. Bars are present in 54% of disc galaxies with inclinations < 70, following a bimodal trend with peaks in Sab-Sb and Scd-Sd types. Tidal structures are identified in ~13% of galaxies, particularly in massive E-Sa and low-mass Sdm-Irr galaxies. We derive the galaxy stellar mass function (GSMF) and decompose it into each morphological type. Schechter functions accurately describe the latter, while a triple Schechter function describes the total GSMF, associating three characteristic masses with different galaxy types. The abundance of early-type galaxies remains constant at low masses; they are predominantly satellites. We confirm that later-type galaxies are generally younger, bluer, more star-forming, and less metal-rich compared to early-type galaxies. Additionally, we find evidence connecting morphology and stellar mass to the star formation history of galaxies. The MVM catalogue provides a robust dataset for investigating galaxy evolution, secular processes, and machine learning-based morphological classifications.

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arXiv2025

The MaNGA Dwarf Galaxy Sample (MaNDala): stellar profiles and gradients characterization

We derived radial profiles and inner/outer gradients of various stellar population (SP) properties for 124 bright dwarf galaxies, $10^{7.53}\leq M_*/M_\odot\leq 10^{9.06}$, from the MaNDala sample, using integral field spectroscopy observations. Given the complex structure of dwarf galaxies, we used four different methods to derive SP radial profiles: two based on concentric elliptical rings, and two exploiting the spatially resolved data. For each method, we applied four approaches to calculate the inner ($0 \leq R/R_e \leq 1$) and outer ($0.75 \leq R/R_e \leq 1.5$) gradients of: luminosity- and mass-weighted age and stellar metallicity, dust attenuation, $D_{n4000}$ index, stellar mass and star formation rate (SFR) surface densities, and specific SFR. While the PSF has a minor impact on the SP gradients, the methodology for characterizing radial profiles significantly affects them. At fixed property, differences in inner gradients from concentric rings methods are $\sim0.05\text{-}0.1 \text{ dex/}R_e$, while outer gradients can reach $0.5\text{-}1 \text{ dex/}R_e$, relative to the median of all gradients of that property, $\text{med}\left(\{\nabla \mathcal{G}\}_i\right)$. Spatially resolved methods yield smaller differences, $\lesssim0.1 \text{ dex/}R_e$. For some SP gradients, e.g. $\nabla_\text{SFR}$, the dispersion among the methods is comparable to $\text{med}\left(\{\nabla \mathcal{G}\}_i\right)$. While it is not possible to select a single preferred method for determining SP gradients, we suggest to use $\text{med}\left(\{\nabla \mathcal{G}\}_i\right)$ for each SP property. The resulting median age and metallicity suggest that, overall, bright dwarfs experienced moderate inside-out formation, and significant early SF from low-metallicity gas with outward radial migration of old SPs. The derived SP gradients provide strong constraints on feedback mechanisms in dwarf galaxies.

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arXiv2025

Morphological Classification of Galaxies Through Structural and Star Formation Parameters Using Machine Learning

We employ the XGBoost machine learning (ML) method for the morphological classification of galaxies into two (early-type, late-type) and five (E, S0--S0a, Sa--Sb, Sbc--Scd, Sd--Irr) classes, using a combination of non-parametric ($C,\,A,\,S,\,A_S,\,\mathrm{Gini},\,M_{20},\,c_{5090}$), parametric (Sérsic index, $n$), geometric (axial ratio, $BA$), global colour ($g-i,\,u-r,\,u-i$), colour gradient ($Δ(g - i)$), and asymmetry gradient ($ΔA_{9050}$) information, all estimated for a local galaxy sample ($z<0.15$) compiled from the Sloan Digital Sky Survey (SDSS) imaging data. We train the XGBoost model and evaluate its performance through multiple standard metrics. Our findings reveal better performance when utilizing all fourteen parameters, achieving accuracies of 88\% and 65\% for the two-class and five-class classification tasks, respectively. In addition, we investigate a hierarchical classification approach for the five-class scenario, combining three XGBoost classifiers. We observe comparable performance to the ``direct'' five-class classification, with discrepancies of only up to 3\%. Using SHAP (an advanced interpretation tool), we analyse how galaxy parameters impact the model's classifications, providing valuable insights into the influence of these features on classification outcomes. Finally, we compare our results with previous studies and find them consistently aligned.

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arXiv2023

The evolution of radial gradients of MaNGA quiescent elliptical galaxies: inside-out quenching or outer mass growth?

Using spatially-resolved fossil record analysis on a large sample of 'red and dead' elliptical galaxies (classical ellipticals, CLEs) from the MaNGA/SDSS-IV DR15 survey, we reconstruct the archaeological evolution of their radial gradients in mass-to-luminosity ratio ($M/L$), $g-r$ color, and specific star formation (SF) rate. We also calculate other metrics that quantify the inside-out SF quenching and external mass growth processes. The $M/L$ gradients, $\nablaΥ_{\star}$, are approximately flat at high look-back times ($t_{\rm lb}$), but then they become negative and steeper until an epoch, when this trend reverses. These trends are shifted to later epochs the less massive the galaxies are. Color gradients follow qualitatively similar trends. We find that these trends are mainly driven by strong inside-out quenching, without significant outer growth or structural changes overall. Our results suggest a scenario where the main progenitors of local CLE galaxies evolved quasi-passively after an early dissipative phase, but underwent radial photometric changes due to the inside-out quenching that led to the systematic decrease of $\nablaΥ_{\star}$ and to an increase of the light-weighted radius. The late reversing of $\nablaΥ_{\star}$, $t_{\rm lb}\approx2-4$ Gyr, roughly coincides with the global quenching of the CLE galaxies. We have pushed archaeological inferences to the limit, but thanks to the large number of objects and an understanding of how the caveats and assumptions affect our results, we conclude that they offer an average description of evolutionary behaviors of CLE progenitors that is valid at least qualitatively.

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arXiv2022

SDSS-IV MaNGA: The MaNGA Dwarf Galaxy Sample

We present the MaNGA Dwarf galaxy, MaNDala, Value-Added-Catalog, VAC, from the final release of the Sloan Digital Sky Survey-IV program. MaNDala consists of 136 randomly selected bright dwarf galaxies with $M_{*}<10^{9.1}\odot$ and $M_{g}>-18.5$ making it the largest Integral Field Spectroscopy homogeneous sample of dwarf galaxies. We release a photometric analysis of the $g,r$ and $z$ broadband imaging based on the DESI Legacy Imaging Surveys as well as the spectroscopic analysis based on the Pipe3D SDSS-IV VAC. Our release includes the surface brightness (SB), geometric parameters and color profiles, Sérsic fits as well as stellar population properties (such as, stellar ages, metallicities, star formation histories), and emission lines fluxes within the FOV and the effective radii of the galaxies. We find that the majority of the MaNDala galaxies are star forming late-type galaxies with $\langle{}n_{\text{Sersic,r}}\rangle\sim1.6$ that are centrals (central/satellite dichotomy). MaNDala covers a large range of SB values (we find 11 candidates of ultra diffuse galaxies and 3 compact ones), filling the gap between classical dwarfs and low-mass galaxies in the Kormendy Diagram and in the size-mass/luminosity relation, whichseems to flatten at $10^8 2$, while the last $20\%$ was at $\langle{}z\rangle<0.3$. Finally, a bending of the sSFR-$M_{*}$ relation at $M_{*}\sim10^{9}\odot$ for the main sequence galaxies seems to be supported by MaNDala.

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arXiv2022

Preparing for low surface brightness science with the Vera C. Rubin Observatory: characterisation of tidal features from mock images

Tidal features in the outskirts of galaxies yield unique information about their past interactions and are a key prediction of the hierarchical structure formation paradigm. The Vera C. Rubin Observatory is poised to deliver deep observations for potentially of millions of objects with visible tidal features, but the inference of galaxy interaction histories from such features is not straightforward. Utilising automated techniques and human visual classification in conjunction with realistic mock images produced using the NEWHORIZON cosmological simulation, we investigate the nature, frequency and visibility of tidal features and debris across a range of environments and stellar masses. In our simulated sample, around 80 per cent of the flux in the tidal features around Milky Way or greater mass galaxies is detected at the 10-year depth of the Legacy Survey of Space and Time (30-31 mag / sq. arcsec), falling to 60 per cent assuming a shallower final depth of 29.5 mag / sq. arcsec. The fraction of total flux found in tidal features increases towards higher masses, rising to 10 per cent for the most massive objects in our sample (M*~10^{11.5} Msun). When observed at sufficient depth, such objects frequently exhibit many distinct tidal features with complex shapes. The interpretation and characterisation of such features varies significantly with image depth and object orientation, introducing significant biases in their classification. Assuming the data reduction pipeline is properly optimised, we expect the Rubin Observatory to be capable of recovering much of the flux found in the outskirts of Milky Way mass galaxies, even at intermediate redshifts (z<0.2).

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arXiv2022

SDSS IV MaNGA: Visual Morphological and Statistical Characterization of the DR15 sample

We present a detailed visual morphological classification for the 4614 MaNGA galaxies in SDSS Data Release 15, using image mosaics generated from a combination of r-band (SDSS and deeper DESI Legacy Surveys) images and their digital post-processing. We distinguish 13 Hubble types and identify the presence of bars and bright tidal debris. After correcting the MaNGA sample for volume completeness, we calculate the morphological fractions, the bi-variate distribution of type and stellar mass M*-where we recognise a morphological transition "valley" around S0a-Sa types- and the variations of the g-i colour and luminosity-weighted age over this distribution. We identified bars in 46.8% of galaxies, present in all Hubble types later than S0. This fraction amounts to a factor ~2 larger when compared with other works for samples in common. We detected 14% of galaxies with tidal features, with the fraction changing with M* and morphology. For 355 galaxies, the classification was uncertain; they are visually faint, mostly of low/intermediate masses, low concentrations, and disky in nature. Our morphological classification agrees well with other works for samples in common, though some particular differences emerge, showing that our image procedures allow us to identify a wealth of added value information as compared to SDSS-based previous estimates. Based on our classification, we also propose an alternative criteria for the E-S0 separation, in the structural semi-major to semi-minor axis versus bulge to total light ratio (b/a-B/T) and concentration versus semi-major to semi-minor axis (C-b/a) space.

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arXiv2021

The differences between mass- and light-derived structural parameters over time for MaNGA Elliptical galaxies

We apply stellar population synthesis analysis to obtain spatially-resolved archaeological inferences for a large sample of "red and dead" Elliptical galaxies (Classical Ellipticals; CLEs) from the MaNGA/SDSS-IV DR15 survey. From their 2D stellar light and mass maps, we explore the differences between the radial mass and light distributions in the rest-frame bands $g,$ $r,$ and $i$ as functions of look-back time, $t_{\rm lb}$, or redshift, $z$. We characterize these differences through the ratios between the following mass- and light-derived global properties: sizes, concentrations, and effective surface densities. We find that the mass-to-light ratios of these properties change with $t_{\rm lb}$, more the more massive the galaxies are. The CLE galaxy archaeological progenitors are, on average, less compact, concentrated, and dense in light than in mass as $z$ decreases. However, at later times, when also the evolution of the progenitors becomes passive at all radii, there is an upturn in these trends and the differences between mass and light in compactness/concentration decrease towards $z\sim 0$. The trends in the ratios of mass to light sizes agree qualitatively with results from direct observations in galaxy surveys at different redshifts. We discuss the caveats and interpretations of our results, and speculate that the strong structural evolution found in some previous studies for early-type galaxies could be explained partially by photometric changes rather than by intrinsic structural changes.

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arXiv2021

SDSS-IV MaNGA: global and local stellar population properties of elliptical galaxies

We study the spatially resolved properties of 343 elliptical galaxies with the MaNGA/SDSS-IV survey. We used the DESI Legacy Imaging Surveys for morphological classification. Based on integrated spectroscopic properties and colors, we classified seven classes of ellipticals. We inferred the stellar age and metallicity ($Z$) gradients out to a 1.5 effective radius of classical "red and dead", recently quenched, and blue star-forming ellipticals (CLEs, RQEs, and BSFs), corresponding to 73%, 10%, and 4% of the sample, respectively. We reconstructed their global and radial histories of star formation and mass growth. We find the mass- and luminosity-weighted age gradients of CLEs are nearly flat or mildly negative. The respective $Z$ gradients are negative, being flatter as the mass is smaller. The more massive CLEs formed stars earlier and quenched faster than the less massive ones. The CLEs show a weak inside-out growth and a clear inside-out quenching. They finished their quenching globally 3.8 $\pm$ 1.2 Gyr ago, with quenching time-scales of 3.4 $\pm$ 0.8 Gyr. At masses < 10$^{11}$ $M_{\bigodot}$, the age and $Z$ gradients of the RQEs and BSFs are flatter than those of the CLEs but with larger scatters. They show very weak inside-out growth and quenching, which is slow and even not completed at $z\sim0$ for the BSFs. Instead, the massive RQEs show an outside-in quenching and positive gradients in the luminosity-weighted age and stellar metallicities. The RQEs of all masses quenched 1.2 $\pm$ 0.9 Gyr ago on average. Our results for the CLEs are consistent with a two-phase scenario where their inner parts formed by an early and coeval dissipative collapse with a consequent burst of star formation and further quenching, whereas the outer parts continued their assembly likely by dry mergers. We also discuss some evolutionary scenarios for the RQE and BSF galaxies.

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arXiv2019

SDSS-IV MaNGA: Effects of Morphology in the global and local Star Formation Main Sequences

We study the global star-formation rate (SFR) vs. stellar mass (M$_*$) correlation, and the spatially-resolved SFR surface density ($Σ_{SFR}$) vs. stellar mass surface density (\Sm) correlation, in a sample of $\sim2,000$ galaxies from the MaNGA MPL-5 survey. We classify galaxies and spatially-resolved areas into star-forming and retired according to their ionization processes. We confirm the existence of a Star-Forming Main Sequence (SFMS) for galaxies and spatially-resolved areas, and show that they have the same nature, with the global as a consequence of the local one. The latter presents a bend below a limit \Sm value, $\approx 3\times 10^7$ M$_\odot$kpc$^{-2}$, which is not physical. Using only star-forming areas (SFAs) above this limit, a slope and a scatter of $\approx1$ and $\approx0.27$ dex are determined. The retired galaxies/areas strongly segregate from their respective SFMS's, by $\sim -1.5$ dex on average. We explore how the global/local SFMS's depend on galaxy morphology, finding that for star-forming galaxies and SFAs, there is a trend to lower values of star-formation activity with earlier morphological types, which is more pronounced for the local SFMS. The morphology not only affects the global SFR due to the diminish of SFAs with earlier types, but also affects the local SF process. Our results suggest that the local SF at all radii is established by some universal mechanism partially modulated by morphology. Morphology seems to be connected to the slow aging and sharp decline of the SF process, and on its own it may depend on other properties as the environment.

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arXiv2011

The Bulgeless Seyfert/LINER Galaxy NGC 3367: Disk, Bar, Lopsidedness and Environment

NGC3367 is a nearby isolated active galaxy that shows a radio jet, a strong bar and evidence of lopsidedness. We present a quantitative analysis of the stellar and gaseous structure of the galaxy disk and a search for evidence of recent interaction based on new UBVRI Halpha and JHK images and on archival Halpha Fabry-Perot and HI VLA data. From a coupled 1D/2D GALFIT bulge/bar/disk decomposition an (B/D ~ 0.07-0.1) exponential pseudobulge is inferred in all the observed bands. A NIR estimate of the bar strength = 0.44 places NGC 3367 bar among the strongest ones. The asymmetry properties were studied using (1) optical and NIR CAS indexes (2) the stellar (NIR) and gaseous (Halpha, HI) A_1 Fourier mode amplitudes and (3) the HI integrated profile and HI mean intensity distribution. While the average stellar component shows asymmetry values close to the average found in the Local Universe for isolated galaxies, the young stellar component and gas values are largely decoupled showing significantly larger A_1 mode amplitudes suggesting that the gas has been recently perturbed. Our search for (1) faint stellar structures in the outer regions (up to u_R ~ 26 mag arcsec^{-2}), (2) (Halpha) star-forming satellite galaxies and (3) regions with different colors (stellar populations) along the disk all failed. Such an absence is interpreted using recent numerical simulations to constrain a tidal event with an LMC like galaxy to some dynamical times in the past or to a current very low mass, gas rich accretion. We conclude that a cold accretion mode (gas and small/dark galaxies) may be responsible of the nuclear activity and peculiar (young stars and gas) morphology regardless of the highly isolated environment. Black hole growth in bulgeless galaxies may be triggered by cosmic smooth mass accretion.

astro-ph.CO↗

arXiv2010

The UNAM-KIAS Catalog of Isolated Galaxies

A new catalog of isolated galaxies from The Sloan Digital Sky Survey (DR5) is presented. 1520 isolated galaxies were found in 1.4 steradians of sky. The selection criteria in this so called UNAM-KIAS catalog was implemented from a variation on the criteria developed by Karachentseva 1973 including full redshift information. Through an image processing pipeline that takes advantage from the high resolution (~ 0.4 ''/pix) and high dynamic range of the SDSS images, a uniform g band morphological classification for all these galaxies is presented. We identify 80% (SaSm) spirals (50% later than Sbc types) on one hand, and a scarce population of early-type E(6.5%) and S0(8%) galaxies amounting to 14.5% on the other hand. This magnitude-limited catalog is ~ 80% complete at 16.5, 15.6, 15.0, 14.6 and 14.4 magnitudes in the ugriz bands respectively. Some representative physical properties including SDSS magnitudes and color distributions, color-color diagrams, absolute magnitude-color, and concentration-color diagrams as a function of morphological type are presented. The UNAM-KIAS Morphological Atlas is also released along with this paper. For each galaxy of type later than Sa, a mosaic is presented that includes: (1) a g-band logarithmic image, (2) a g band filtered-enhanced image where a Gaussian kernel of various sizes was applied and (3) an RGB color image from the SDSS database. For E/S0/Sa galaxies, in addition to the images in (1), (2) and (3), plots of r band surface brightness and geometric profiles (ellipticity, Position Angle PA and A4/B4 coefficients of the Fourier series expansions of deviations of a pure ellipse) are provided...

astro-ph.CO↗

arXiv2008

On the baryonic, stellar, and luminous scaling relations of disk galaxies

We explore how the slopes and scatters of the scaling relations of disk galaxies (Vm-L[-M], R-L[-M], and Vm-R) do change when moving from B to K bands and to stellar and baryonic quantities. For our compiled sample of 76 normal, non-interacting high and low surface brightness galaxies, we find some changes, which evidence evolution effects, mainly related to gas infall and star formation (SF). We also explore correlations among the (B-K) color, stellar mass fraction fs, mass M (luminosity L), and surface density (SB), as well as correlations among the residuals of the scaling relations. Some of our findings are: (i) the scale length Rb is a third parameter in the baryonic TF relation and the residuals of this relation follow a trend (slope ~-0.15) with the residuals of the Rb-Mb relation; for the stellar and K band cases, R is not anymore a third parameter and the mentioned trend disappears; (ii) among the TFRs, the B-band TFR is the most scattered; in this case, the color is a third parameter; (iii) the LSB galaxies break some observed trends, which suggest a threshold in the gas surface density Sg, below which the SF becomes independent of the gas infall rate and Sg. Our results are interpreted and discussed in the light of LCDM-based models of galaxy evolution. The models explain not only the baryonic scaling relations, but also most of the processes responsible for the observed changes in the slopes, scatters, and correlations among the residuals when changing to stellar and luminous quantities. The baryon fraction is required to be smaller than 0.05 on average. We detect some potential difficulties for the models: the observed color-M and surface density-M correlations are steeper, and the intrinsic scatter in the baryonic TFR is smaller than those predicted. [abridged]

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arXiv2008

A morphology revaluation of galaxies in common from the Catalog of Isolated Galaxies and the Sloan Digital Sky Survey (DR6)

We present a revaluation of the optical morphology for 549 galaxies from the Catalog of Isolated Galaxies (Karachentseva 1973) that are available in the SDSS (DR6). Both the high resolution and high dynamic range of the SDSS images and our semi-automatic image processing scheme, allow for a major quality and uniform morphological analysis. The processing scheme includes (1) sky-subtracted, cleaned, and logarithmic scaled g-band images; (2) filtered-enhanced versions of the images in (1); and (3) the RGB images available in the SDSS database. Special attention was paid for distinguishing between E, S0, and Sa candidates through an additional analysis of (4) the surface brightness, ε, PA, and A_4/B_4 Fourier series expansion profiles. The median type in the sample corresponds to Sbc, with 65% of the sample being of this type or later. A scarce population of E (3.5%) and S0 (5%) galaxies, and a non-negligible 14% fraction of SaSab spirals are identified. We calculate also the gri absolute magnitudes corrected by Galactic and internal extinctions and present the g-i color distribution and the color-magnitude diagram. Among the spirals, we find fractions of strong and suspected bars of 65.8% and of 33.3% of rings. For the E galaxies we find a richness of distinct substructure in their isophotal shape and also of morphological distortions. At least 78% of the ellipticals show some kind of distortion, suggesting that these galaxies suffered late dry mergers. Finally, we calculate the CAS (concentration, asymmetry and clumpiness) structural parameters in the ugriz bands. We analyze the loci of our isolated galaxies in different projections of the CAS volume and discuss some trends of these parameters with the color band, as well as with the type and the galaxy color. [abridged]

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