S. A. Cora

Universidad Nacional de La Plata

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Cristian A Vega-Martínez

University of La Serena

Nelson Padilla

Instituto de Astronomía Teórica y Experimental

Andrés N. Ruiz

Consejo Nacional de Investigaciones Científicas y Técnicas

Ignacio D. Gargiulo

Universidad Nacional de La Plata

P. B. Tissera

Universidad Andrés Bello

Darren Croton

Swinburne University of Technology

T. E. Tecce

Pontificia Universidad Católica de Chile

Claudia del P. Lagos

University of Copenhagen

D. G. Lambas

Universidad Nacional de Córdoba

L. P. Bassino

Universidad Nacional de La Plata

Cooperative Institutions

Centre National de la Recherche Scientifique

Consejo Nacional de Investigaciones Científicas y Técnicas

Universidad Nacional de La Plata

Universidad Autónoma de Madrid

Max Planck Society

Argentine National Observatory

Universidad Nacional de Córdoba

Centro Científico Tecnológico - San Juan

Pontificia Universidad Católica de Chile

Max Planck Institute for Astrophysics

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Galaxy Formation and Chemical Evolution in Hierarchical Hydrodynamical Simulations

arXiv (Cornell University) (2000)

S. A. Cora M. B. Mosconi P. B. Tissera D. G. Lambas

We report first results of an implementation of a chemical model in a cosmological code, based on the Smoothed Particle Hydrodynamics (SPH) technique. We show that chemical SPH simulations are a promising tool to provide clues for the understanding of the chemical properties of galaxies in relation to their formation and evolution in a cosmological framework.

10.48550/arxiv.astro-ph/0007072

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The Three Hundred project: a large catalogue of theoretically modelled galaxy clusters for cosmological and astrophysical applications

Monthly Notices of the Royal Astronomical Society (2018)

Weiguang Cui Alexander Knebe Gustavo Yepes F. R. Pearce Chris Power

We introduce the THE THREE HUNDRED project, an endeavour to model 324 large galaxy clusters with full-physics hydrodynamical re-simulations. Here we present the data set and study the differences to observations for fundamental galaxy cluster properties and scaling relations. We find that the modelled galaxy clusters are generally in reasonable agreement with observations with respect to baryonic fractions and gas scaling relations at redshift z = 0. However, there are still some (model-dependent) differences, such as central galaxies being too massive, and galaxy colours (g - r) being bluer (about 0.2 dex lower at the peak position) than in observations. The agreement in gas scaling relations down to 10^{13} h^{-1} M_{\odot} between the simulations indicates that particulars of the sub-grid modelling of the baryonic physics only has a weak influence on these relations. We also include - where appropriate - a comparison to three semi-analytical galaxy formation models as applied to the same underlying dark-matter-only simulation. All simulations and derived data products are publicly available.

10.1093/mnras/sty2111

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Citations (182)

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

arXiv (Cornell University) (2025)

Héctor J. Martínez Martín de los Rios Valeria Coenda H. Muriel Andrés N. Ruiz

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.

10.48550/arxiv.2502.04446

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Improving the accuracy of observable distributions for galaxies classified in the projected phase space diagram

Astronomy and Astrophysics (2025)

Héctor J. Martínez Martín de los Rios Valeria Coenda H. Muriel Andrés N. Ruiz

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 for statistically correcting the determination of galaxy properties' distributions that accounts for the contamination caused by misclassified galaxies from other classes. Using a sample of massive clusters and the galaxies in their surroundings taken from the MultiDark Planck 2 simulation combined with the semi-analytic model of galaxy formation we computed the confusion matrix associated with a classification scheme in the PPSD. Based on positions in the PPSD, galaxies are classified as cluster members, backsplash galaxies, recent infallers, infalling galaxies, or interlopers. This classification is determined using probabilities calculated by the code 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 applied 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 is available. 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.

10.1051/0004-6361/202451999

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ROGER: Reconstructing orbits of galaxies in extreme regions using machine learning techniques

Monthly Notices of the Royal Astronomical Society (2020)

Martín de los Rios Héctor J. Martínez Valeria Coenda H. Muriel Andrés N. Ruiz

We present the ROGER (Reconstructing Orbits of Galaxies in Extreme Regions) code, which uses three different machine learning techniques to classify galaxies in, and around, clusters, according to their projected phase-space position. We use a sample of 34 massive, $M_{200}>10^{15} h^{-1} M_{\odot}$, galaxy clusters in the MultiDark Planck 2 (MDLP2) simulation at redshift zero. We select all galaxies with stellar mass $M_{\star} \ge 10^{8.5} h^{-1}M_{\odot}$, as computed by the semi-analytic model of galaxy formation SAG, that are located in, and in the vicinity of, the clusters and classify them according to their orbits. We train ROGER to retrieve the original classification of the galaxies out of their projected phase-space positions. For each galaxy, ROGER gives as output the probability of being a cluster galaxy, a galaxy that has recently fallen into a cluster, a backsplash galaxy, an infalling galaxy, or an interloper. We discuss the performance of the machine learning methods and potential uses of our code. Among the different methods explored, we find the K-Nearest Neighbours algorithm achieves the best performance.

10.1093/mnras/staa3339

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Citations (14)

On the Effect of Chaotic Orbits on Dynamical Friction

The Astrophysical Journal (2001)

S. A. Cora M. M. Vergne J. C. Muzzio

Chaotic orbits suffer significant changes as a result of small perturbations. One can thus wonder whether the dynamical friction suffered by a satellite on a regular orbit, and interacting with the stars of a galaxy, will be different if the bulk of the stars of the galaxy are in regular or chaotic orbits. In order to check that idea, we investigated the orbital decay (caused by dynamical friction) of a rigid satellite moving within a larger stellar system (a galaxy) whose potential is nonintegrable. We performed numerical experiments using two kinds of triaxial galaxy models: (1) the triaxial generalization of Dehnen's spherical mass model (Dehnen; Merritt & Fridman); (2) a modified Satoh model (Satoh; Carpintero, Muzzio, & Wachlin). The percentages of chaotic orbits present in these models were increased by perturbing them. In the first case, a central compact object (black hole) was introduced; in the second case, the perturbation was produced by allowing the galaxy to move on a circular orbit in a logarithmic potential. The equations of motion were integrated with a non-self-consistent code. Our results show that the presence of chaotic orbits does not affect significantly the orbital decay of the satellite.

Dynamical friction

Orbit (dynamics)

Circular orbit

Stellar dynamics

Orbital mechanics

Satellite galaxy

10.1086/318223

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Chemical properties of the intracluster medium

Boletin de la Asociacion Argentina de Astronomia La Plata Argentina (2013)

Cristian A Vega-Martínez S. A. Cora Ignacio D. Gargiulo Nelson Padilla Andrés N. Ruiz

Intracluster medium

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Modeling the Color Magnitude Relation for Galaxy Clusters

Noelia Jiménez S. A. Cora A. V. Smith Castelli L. P. Bassino

Fil: Jimenez, Noelia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico La Plata. Instituto de Astrofisica de La Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronomicas y Geofisicas; Argentina

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Influence of black hole spin on galaxy properties

Boletin de la Asociacion Argentina de Astronomia La Plata Argentina (2008)

S. A. Cora Claudia del P. Lagos Nelson Padilla

We use a hybrid model that combines a cosmological Nbody simulation of the concordance Λ Cold Dark Matter paradigm and a semi-analytic model of galaxy formation (Lagos, Cora & Padilla 2008a) to study the development of the spin of central super-massive black holes (SMBHs), and the relations between the BH spin and mass, and the morphology and radio-loudness of host galaxies. BH spins are computed using the α model (Shakura & Sunyaev 1973) and considering a warped disc treatment (King et al. 2005). The direction of the BH spin is inferred from the angular momentum of the source of the accreted material, which encodes information on the evolution of the surrounding large-scale structure. Resumen. Usamos un modelo hibrido que combina una simulacion cosmologica de N-cuerpos del paradigma de materia oscura fŕia (Λ Cold Dark Matter) y un modelo semianaĺitico de formacion de galaxias (Lagos, Cora & Padilla 2008a) para estudiar el desarrollo del spin de agujeros negros centrales super-masivos, y las relaciones entre la masa y el spin de los agujeros negros, y la morfoloǵia e intensidad en radio de las galaxias que los albergan. El spin del agujero negro es estimado usando el modelo α (Shakura & Sunyaev 1973) y considerando un tratamiento de disco alabeado (King et al. 2005). La direccion del spin del agujero negro es inferido a partir del momento angular de la fuente que provee el material acretado, la cual guarda informacion sobre la evolucion de la estructura a gran escala circundante.

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Overdensity of VVV galaxies behind the Galactic bulge

Astronomy and Astrophysics (2020)

Daniela Galdeano Luis Pereyra Fernanda Duplancic Georgina Coldwell Sol Alonso

We studied a region of 1.636 square degrees corresponding to the VVV tile $b204$. Using SExtractor, we analysed photometric data generating a catalogue of extended sources in this area. In order to confirm these sources as galaxy candidates we visually inspected RGB images looking for typical galaxy features. Using 2MASX and GCMW catalogued sources we tested completeness and contamination of our catalogue and define suitable colour cuts to select galaxies. We also compared the observational results with those obtained from two semi-analytical models on Dark Matter simulations. One galaxy catalogue was constructed with the SAG semi-analytic model of galaxy formation, and the other one was constructed with the L-Galaxies semi-analytic model.By adopting CLASS-STAR$< 0.5$, $r_{1/2} > 0.7$ arcsec and specific colour cuts (J-Ks$>$0.97, J-H$>$0 and H-Ks$>$0) we generated an automatic catalogue of extended sources. After visual inspection we identified 624 sources with 10$

Effective radius

10.1051/0004-6361/201937432

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Citations (7)