arXiv subjects

Héctor J. Martínez

Publications and source records attributed to Héctor J. Martínez.

16 recordsLinked to original sources

arXiv2026

Reconstructing orbits of galaxies in extreme regions (roger v2.0): an extension to intermediate mass systems

In this paper, we present an updated version of the roger code, called roger v2.0, developed to perform the orbital classification of galaxies residing in and around galaxy groups and clusters. In addition to the projected phase-space coordinates, the new version incorporates the host halo mass as an additional input parameter. Although the inclusion of the halo mass leads to only modest changes in the classification, it contributes to improving the overall robustness of the method. We also extend the range of host halo masses over which roger can be applied, enabling the analysis of systems with masses down to $10^{13.5} h^{-1} M_{\odot}$. We further provide a Python implementation of the new code, which will be made publicly available. This implementation enables users to efficiently and robustly classify arbitrary galaxy samples using either version of the method. Moreover, it allows users to train a customized classifier on an alternative training set, providing the flexibility to adapt the method to different datasets and scientific applications.

astro-ph.GA↗

arXiv2026

Linking X-ray emission to galaxy populations in GAMA groups

We study how the presence of a detectable hot intragroup medium affects galaxy colour and star-formation properties, and how these trends depend on dynamical stage within the group. We analysed galaxies in GAMA groups with and without X-ray detection (XG and NXG) at 0.1 <= z <= 0.2, using samples with similar halo-mass distributions, compared with a field control sample. Galaxies were classified as red, green, or blue by UV-optical colour, and group galaxies further classified into dynamical classes based on projected phase-space position and host halo mass. We examined galaxy populations as a function of orbital class, star-formation activity, nuclear activity, and cluster-centric distance. The galaxy population is systematically more evolved in XG than NXG, with lower blue and star-forming fractions and higher red and passive fractions. The green fraction is stable across environments and orbital classes, though high-mass recent arrivals show a mild excess of green systems while retaining relatively high star-forming and low passive fractions, suggesting an intermediate quenching stage. The active galactic nucleus fraction shows no environmental dependence, while the post-starburst fraction increases strongly in XG, reaching nearly 20 percent, consistent with enhanced rapid quenching. Galaxy properties show stronger radial segregation in XG than NXG, with colour fractions differing from field values even at R/R200 ~ 3, consistent with preprocessing. Despite similar halo-mass distributions, the systematic differences between XG and NXG show that halo mass alone does not determine galaxy properties. A detectable hot intragroup medium is associated with enhanced environmental processing, stronger quenching, and more frequent rapid transitions, highlighting the role of the intragroup medium's thermodynamical state, beyond halo mass, in shaping galaxy evolution at group scales.

astro-ph.GA↗

arXiv2026

Cluster-green galaxy correlations: where do these galaxies live?

Green valley (GV) galaxies are thought to represent a transitional population between star-forming and quiescent systems. However, their spatial distribution relative to galaxy systems remains unclear, particularly in relation to the large-scale environmental influence on galaxy quenching. We aim to determine whether GV galaxies preferentially inhabit specific environments within galaxy systems. We analyse the spatial distribution of GV galaxies using the cluster-galaxy cross-correlation function (CCF), based on the hydrodynamical simulation Illustris TNG300-1 (TNG) and observational data from the Sloan Digital Sky Survey (SDSS). Galaxy systems with $\log(M_{200}/M_{\odot}) \geq 13.5$ are used as cluster centres, while galaxies classified as blue, green, or red serve as tracers for the correlation analysis. In TNG, GV galaxies show an increasing relative fraction with cluster-centric distance, peaking in the outskirts, particularly for low-mass galaxies and haloes, and in some cases the GV fraction exceeds that of red galaxies. SDSS data reveal qualitatively similar trends, with the GV fraction remaining below that of red galaxies at all scales. Mock catalogues built from TNG and matched to SDSS selection functions reproduce the observational signal, indicating that projection effects drive the differences between datasets. GV galaxies preferentially reside in the outskirts of galaxy systems as satellites bound to the central halo, supporting a scenario in which they are transitioning objects influenced by environmental quenching.

astro-ph.GA↗

arXiv2025

Galaxy evolution in groups: Transition galaxies in the IllustrisTNG simulations

The evolution of galaxies is significantly influenced by the environments they inhabit. While high-density regions, such as clusters of galaxies have been widely studied, the dynamics and quenching processes in intermediate environments remain less explored. These systems provide a valuable context for understanding the transition of galaxies from active star formation to quiescence. This study aims to characterise the astrophysical properties of galaxies in intermediate-mass galaxy groups $(13.5 \leq \log(M_{200}/M_{\odot}) \leq 13.7)$, with a focus on their evolutionary pathways and the key processes driving their transition through the green valley (GV) and green zone (GZ). Using the Illustris TNG300-1 hydrodynamical cosmological simulations, we classified galaxies based on their trajectories and environment into five categories: group galaxies (GRs), backsplash galaxies (BSs), recent infallers (RINs), infall galaxies (INs), and field galaxies (FGs). We examined their optical colours in the $(u-r)$-stellar mass diagram, specific star formation rates (sSFRs), gas fractions, and stellar mass evolution from $z=0.5$ to $z=0$. At $z=0$, FGs dominate the blue cloud, while GRs show progressive reddening. BSs exhibit the highest fraction of green galaxies, highlighting their transitional nature, whereas RINs show a rapid quenching upon entering $R_{200}$. Our results reveal that the timing of group entry and environmental effects, such as gas depletion, play a critical role in galaxy quenching. Green BS and RINs follow distinct evolutionary tracks, with the latter undergoing more rapid changes due to later infall into more massive systems.

astro-ph.GA↗

arXiv2025

Dust sub-millimetre emission in green valley galaxies

Context. Green valley (GV) galaxies are objects defined on a colour-magnitude diagram, or a colour-mass diagram, as being associated with a transition from a star-forming to a quiescent state (quenching), or vice versa (rejuvenation). Aims. We studied the sub-millimetre emission of galaxies in the GV and linked it with their physical evolutionary properties. Methods. We exploited a semi-analytic model (SAM) for galaxy evolution that includes a detailed treatment of dust production and evolution in galactic contexts. We modelled the observational properties of simulated galaxies by post-processing the SAM catalogues with the spectral synthesis and radiative transfer code GRASIL. Results. Our model produces a clear bimodality (and thus a GV) in the colour-mass diagram, although some tensions arise when compared to observations. After introducing a new criterion for identifying the GV in any dataset, we find that GV galaxies, at fixed stellar mass, have $250 μ$m luminosities approximately half those of blue galaxies, while red galaxies exhibit luminosities of up to an order of magnitude lower. While specific star formation rates drop sharply during quenching, the dust content remains relatively high during the GV transition, powering sub-millimetre emission. Rejuvenating galaxies in the GV, which were previously red, have experienced a star formation burst that shifts their colour to green, but their $S_{250\, μ\rm m}$ fluxes remain low due to their still low dust masses. Conclusions. Our galaxy evolution model highlights the delay between star formation and dust evolution, showing that sub-millimetre emission is not always a safe indicator of star formation activity, with quenching (rejuvenating) GV galaxies featuring relatively high (low) sub-millimetre emission.

astro-ph.GA↗

arXiv2025

Reconstructing orbits of galaxies in extreme regions (ROGER). IV. Unveiling galaxy evolution patterns in OmegaWINGS clusters

Clusters of galaxies have proven to be efficient systems in modifying various properties of galaxies, such as star formation or morphology. However, projection effects impose serious challenges in determining how, when, and to what extent galaxies are affected by the cluster environment. Using innovative techniques to classify galaxies based on their history within the cluster, we aim to determine how galaxies of different classes are affected by the cluster environment. We applied the ROGER code to select trajectories of galaxies in the phase space for 35 galaxy clusters from the OmegaWINGS survey. A new algorithm was applied to minimize contamination effects. We found that both morphological transformation and the quenching of star formation begin shortly after galaxies enter the cluster. Even though over the last $2-3$ Gyr, galaxies entering clusters have undergone significant transformations in both their star formation and morphology these transformation processes are not complete, that is, they are not completely quenched and are not early type yet. Backsplash galaxies and recent infallers show a higher fraction of jellyfish galaxies compared to older cluster members, suggesting that the timescale of this phenomenon is typically less than 3 Gyr.

astro-ph.GA↗

arXiv2025

Improving the accuracy of observable distributions for galaxies classified in the Projected Phase Space Diagram

Studies of galaxy populations classified according to their kinematic behaviours and dynamical state using the Projected Phase Space Diagram (PPSD) are affected by misclassification and contamination, leading to systematic errors in determining the characteristics of the different galaxy classes. We propose a method to statistically correct the determination of galaxy properties' distributions accounting for the contamination caused by misclassified galaxies from other classes. Using a sample of massive clusters and galaxies in their surroundings taken from the MultiDark Planck 2 simulation combined with the semi-analytic model of galaxy formation SAG, we compute the confusion matrix associated to a classification scheme in the PPSD. Based on positions in the PPSD, galaxies are classified as cluster members, backsplash galaxies, recent infallers, infalling galaxies, and interlopers. This classification is determined using probabilities calculated by the code ROGER, along with a threshold criterion. By inverting the confusion matrix, we are able to get better determinations of distributions of galaxy properties such as colour. Compared to a direct estimation based solely on the predicted galaxy classes, our method provides better estimates of the mass-dependent colour distribution for the galaxy classes most affected by misclassification: cluster members, backsplash galaxies, and recent infallers. We apply the method to a sample of observed X-ray clusters and galaxies. Our method can be applied to any classification of galaxies in the PPSD, and to any other galaxy property besides colour, provided an estimation of the confusion matrix. Blue, low-mass galaxies in clusters are almost exclusively recent infaller galaxies that have not yet been quenched by the environmental action of the cluster. Backsplash galaxies are on average redder than expected.

astro-ph.GA↗

arXiv2024

Star Formation and Dust in the Cosmic Web

The large-scale environment of the cosmic web is believed to impact galaxy evolution, but there is still no consensus regarding the mechanisms. We use a semi-analytic model (SAM) galaxy catalog to study the star formation and dust content of local galaxies in different cosmic environments of the cosmic web, namely voids, filaments, walls, and nodes. We find a strong impact of the environment only for galaxies with $M_{\rm stars}\lesssim10^{10.8}\, M_\odot$: the less dense the environment, the larger the star formation rate and dust content at fixed stellar mass. This is attributed to the fact that galaxies in less dense environments typically feature younger stellar populations, a slower evolution of their stellar mass and a delayed star formation compared to galaxies in denser environments. As for galaxies with $M_{\rm stars}\gtrsim 10^{10.8}\, M_\odot$ differences among environments are milder due to the disc instability (DI) driven supermassive black hole (SMBH) growth implemented in the SAM, which makes SMBH growth, and thus galaxy quenching, environment insensitive. We qualitatively test our predictions against observations by identifying environments in the SDSS-DR16 using dust masses derived from the GAMA survey. The agreement is encouraging, particularly at ${\rm log} \, M_{\rm stars}/M_\odot\gtrsim 10.5-11$, where sSFRs and dust masses appear quite environment-insensitive. This result confirms the importance of in situ growth channels of SMBHs.

astro-ph.GA↗

arXiv2023

Backsplash galaxies and their impact on galaxy evolution: a three-stage, four-type perspective

We study the population of backsplash galaxies at $z=0$ in the outskirts of massive, isolated clusters of galaxies taken from the MDPL2-SAG semi-analytic catalogue. We consider four types of backsplash galaxies according to whether they are forming stars or passive at three stagesin their lifetimes: before entering the cluster, during their first incursion through the cluster, and after they exit the cluster. We analyse several geometric, dynamic, and astrophysical aspects of the four types at the three stages. Galaxies that form stars at all stages account for the majority of the backsplash population ($58\%$) and have stellar masses typically below $M_\star\sim 3\times 10^{10} h^{-1}{\rm M}_\odot$ that avoid the innermost cluster's regions and are only mildly affected by it. In a similar mass range, galaxies that become passive after exiting the cluster ($26\%$) follow orbits characterised by small pericentric distance and a strong deflection by the cluster potential well while suffering a strong loss of both dark matter and gas content. Only a small fraction of our sample ($4\%$) become passive while orbiting inside the cluster. These galaxies have experienced heavy pre-processing and the cluster's tidal stripping and ram pressure provide the final blow to their star formation. Finally, galaxies that are passive before entering the cluster for the first time ($12\%$) are typically massive and are not affected significantly by the cluster. Using the bulge/total mass ratio as a proxy for morphology, we find that a single incursion through a cluster do not result in significant morphological changes in all four types.

astro-ph.GA↗

arXiv2021

Reconstructing Orbits of Galaxies in Extreme Regions (ROGER) II: reliability of projected phase-space in our understanding of galaxy populations

We connect galaxy properties with their orbital classification by analysing a sample of galaxies with stellar mass $M_{\star} \geq 10^{8.5}h^{-1}M_\odot$ residing in and around massive and isolated galaxy clusters with mass $M_{200} > 10^{15}h^{-1}M_\odot$ at redshift $z=0$. The galaxy population is generated by applying the semi-analytic model of galaxy formation SAG on the cosmological simulation MultiDark Planck 2. We classify galaxies considering their real orbits (3D) and their projected phase-space position using the ROGER code (2D). We define five categories: cluster galaxies, galaxies that have recently fallen into a cluster, backsplash galaxies, infalling galaxies, and interloper galaxies. For each class, we analyse the $g-r$ colour, the specific star formation rate (sSFR), and the stellar age, as a function of the stellar mass. For the 3D classes, we find that cluster galaxies have the lowest sSFR, and are the reddest and the oldest, as expected from environmental effects. Backsplash galaxies have properties intermediate between the cluster and recent infaller galaxies. For each 2D class, we find an important contamination by other classes. We find it necessary to separate the galaxy populations in red and blue to perform a more realistic analysis of the 2D data. For the red population, the 2D results are in good agreement with the 3D predictions. Nevertheless, when the blue population is considered, the 2D analysis only provides reliable results for recent infallers, infalling galaxies and interloper galaxies.

astro-ph.GA↗

arXiv2020

Anisotropic infall in the outskirts of OmegaWINGS galaxy clusters

We study the effects of the environment on galaxy quenching in the outskirts of clusters at $0.04 < z < 0.08$. We use a subsample of 14 WINGS and OmegaWINGS clusters that are linked to other groups/clusters by filaments and study separately galaxies located in two regions in the outskirts of these clusters according to whether they are located towards the filaments' directions or not. We also use samples of galaxies in clusters and field as comparison. Filamentary structures linking galaxy groups/clusters were identified over the Six Degree Field Galaxy Redshift Survey Data Release 3. We find a fraction of passive galaxies in the outskirts of clusters intermediate between that of the clusters and the field's. We find evidence of a more effective quenching in the direction of the filaments. We also analyse the abundance of post-starburst galaxies in the outskirts of clusters focusing our study on two extreme sets of galaxies according to their phase-space position: backsplash and true infallers. We find that up to $\sim70\%$ of post-starburst galaxies in the direction of filaments are likely backsplash, while this number drops to $\sim40\%$ in the isotropic infall region. The presence of this small fraction of galaxies in filaments that are falling into clusters for the first time and have been recently quenched, supports a scenario in which a significant number of filament galaxies have been quenched long time ago.

astro-ph.GA↗

arXiv2020

A comparison of cosmological filaments catalogues

In this work we compare three catalogues of cosmological filaments identified in the Sloan Digital Sky Survey by means of different algorithms by Tempel et al., Pereyra et al., and Martínez et al. We analyse how different identification techniques determine differences in the filament statistical properties: length, elongation, redshift distribution, and abundance. We find that the statistical properties of the filaments strongly depend on the identification algorithm. We use a volume limited sample of galaxies to characterise other properties of filaments such as: galaxy overdensity, luminosity function of galaxies, mean galaxy luminosity, filament luminosity, and the overdensity profile of galaxies around filaments. In general, we find that these properties primarily depended on filament length. Shorter filaments have larger overdensities, are more populated by red galaxies, and have better defined galaxy overdensity profiles, than longer filaments. Concluding that galaxies belonging to filaments have characteristic signatures depending on the identification algorithm used.

astro-ph.GA↗

arXiv2019

Filaments in VIPERS: galaxy quenching in the infalling regions of groups

We study the quenching of galaxies in different environments and its evolution in the redshift range $0.43 \leq z \leq 0.89$. For this purpose, we identify galaxies inhabiting filaments, the isotropic infall region of groups, the field, and groups in the VIMOS Public Extragalactic Redshift Survey (VIPERS). We classify galaxies as quenched (passive), through their $NUV-r$ versus $r-K$ colours. We study the fraction of quenched galaxies ($F_{r}$) as a function of stellar mass and environment at two redshift intervals. Our results confirm that stellar mass is the dominant factor determining galaxy quenching over the full redshift range explored. We find compelling evidence of evolution in the quenching of intermediate mass galaxies $(9.3 \leq \log(M_{*}/M_{\odot}) \leq 10.5)$ for all environments. For this mass range, $F_{r}$ is largest for galaxies in groups and smallest for galaxies in the field, while galaxies in filaments and in the isotropic infall regions appear to have intermediate values with the exception of the high redshift bin, where the latter show similar fraction of quenched galaxies as in the field. Galaxies in filaments are systematically more quenched than their counterparts infalling from other directions, in agreement to similar results found at low redshift. The least massive galaxies in our samples do not show evidence of internal or environmental quenching.

astro-ph.GA↗

arXiv2017

Green Valley galaxies as a transition population in different environments

We present a comparative analysis of the properties of passive, star-forming and transition (green valley) galaxies, in four discrete environments: field, groups, the outskirts and the core of X-ray clusters. We construct samples of galaxies from the SDSS in these environments so that they are bound to have similar redshift distributions. The classification of galaxies into the three sequences is based on the UV-optical colour $NUV-r$. We study a number of galaxy properties: stellar mass, morphology, specific star formation rate and the history of star formation. The analysis of green valley galaxies reveals that the physical mechanisms responsible for external quenching become more efficient moving from the field to denser environments. We confirm previous findings that green valley galaxies have intermediate morphologies, moreover, we find that this appears to be independent of the environment. Regarding the stellar mass of green valley galaxies, we find that they tend to be more massive in the field than in denser environments. On average, green valley galaxies account for $\sim 20\%$ of all galaxies in groups and X-ray clusters. We find evidence that the field environment is inefficient in transforming low mass galaxies. Green valley galaxies have average star formation histories intermediate between passive and star forming galaxies, and have a clear and consistent dependence on the environment: both, the quenching time, and the amplitude of the star formation rate, decrease towards higher density environments.

astro-ph.GA↗

arXiv2014

Comparing galaxy populations in compact and loose groups of galaxies III. Effects of environment on star formation

This paper is part of a series in which we perform a systematic comparison of the galaxy properties inhabiting compact groups, loose groups and the field. In this paper we focus our study to the age and the star formation in galaxies. For galaxies in selected samples of compact groups, loose groups and field, we compare the distributions of the following parameters: D$_n(4000)$ as an age indicator, and the specific star formation rate as indicator of ongoing star formation. We analyse the dependence of these parameters on galaxy type, stellar mass and, for group galaxies, their dependence on the dynamic state of the system. We also analyse the fraction of old, and of high star forming galaxies as a function of galaxy stellar mass in the environments we probe. Galaxies in compact groups have, on average, older stellar populations than their loose group or field counterparts. Early-type galaxies in compact groups formed their stars and depleted their gas content more rapidly than in the other environments. We have found evidence of two populations of late-type galaxies in dynamically old compact groups: one with normal specific star formation rates and another with markedly reduced star formation. Processes that transform galaxies from star forming to quiescent act upon galaxies faster and more effectively in compact groups. The unique characteristics of compact groups make them an extreme environment for galaxies, where the transition to quiescence occurs rapidly.

astro-ph.GA↗

arXiv2013

Comparing galaxy populations in compact and loose groups of galaxies II: brightest group galaxies

The properties of the brightest galaxies (BCGs) are studied in both compact and loose groups of galaxies in order to better understand the physical mechanisms influencing galaxy evolution in different environments. Samples of BCGs are selected in the compact groups identified by McConnachie et al. (2009), and in loose groups taken from Zandivarez & Martínez (2011). The following physical properties of the BCGs in compact groups and in subsamples of loose groups are compared, defined by their mass and total luminosity. The fraction of BCGs classified as red and/or early-type as a function of galaxy luminosity are studied. The fraction of the group's total luminosity contained in the BCG and the difference in luminosity between the BCG and the second-ranked galaxy, are also analysed. Some properties of BCGs in compact and loose groups are comparable. However, BCGs in compact groups are systematically more concentrated and have larger surface brightness than their counterparts in both, high- and low-mass loose groups. The fractions of red and early-type BCGs in compact groups are consistent with those of high-mass loose groups. Comparing BCGs in subsamples of compact and loose groups selected for their similar luminosities, BCGs in compact groups are found to be, on average, brighter, more massive, larger, redder and more frequently classified as elliptical. In compact groups, the BCG contains a larger fraction of the system's total luminosity and differs more in absolute magnitude from the second-ranked galaxy. BCGs in compact and loose groups are found to be different. Some mechanisms responsible for transforming late-type galaxies into early types, such as mergers, may be more effective within compact groups due to their high densities and small velocity dispersion, which would lead their BCGs along somewhat different evolutionary paths.

astro-ph.CO↗