Recent Publications
“The origin of kinematically-persistent planes of satellite galaxies as driven by the early evolution of the local Cosmic Web in Λ CDM”
date: 2023-05-01
Kinematically-persistent planes of satellites (KPPs) are fixed sets of satellites co-orbiting around their host galaxy, whose orbital poles are conserved and clustered across long cosmic time intervals. They play the role of ‘skeletons’, ensuring the long-term durability of positional planes. We explore the physical processes behind their formation in terms of the dynamics of the local Cosmic Web (CW), characterized via the so-called Lagrangian Volumes (LVs) built up around two zoom-in, cosmological hydro-simulations of MW-mass disk galaxy + satellites systems, where three KPPs have been identified. By analyzing the LVs deformations in terms of the reduced Tensor of Inertia (TOI), we find an outstanding alignment between the LV principal directions and KPP satellites’ orbital poles. The most compressive local mass flows (along the e^3 eigenvector) are strong at early times, feeding the so-called e^3 -structure, while the smallest TOI axis rapidly decreases. The e^3 -structure collapse marks the end of this regime and is the timescale for the establishment of satellite orbital pole clustering when the Universe is ≲ 4 Gyr old. KPP proto-satellites aligned with e^3 are those whose orbital poles are either aligned from early times, or have been successfully bent at e^3 -structure collapse. KPP satellites associated to e^1 tend to have early trajectories already parallel to e^3 . We show that KPPs can arise as a result of the Λ CDM-predicted large-scale dynamics acting on particular sets of proto-satellites, the same dynamics that shape the local CW environment.
Recommended citation: Gámez-Marín, et. al. (2024)
venue: ‘ arXiv e-prints’
“Application of dimensionality reduction and clustering algorithms for the classification of kinematic morphologies of galaxies”
date: 2023-05-01
Context. The morphological classification of galaxies is considered a relevant issue and can be approached from different points of view. The increasing growth in the size and accuracy of astronomical data sets brings with it the need for the use of automatic methods to perform these classifications. Aims: The aim of this work is to propose and evaluate a method for the automatic unsupervised classification of kinematic morphologies of galaxies that yields a meaningful clustering and captures the variations of the fundamental properties of galaxies. Methods.We obtained kinematic maps for a sample of 2064 galaxies from the largest simulation of the EAGLE project that mimics integral field spectroscopy images. These maps are the input of a dimensionality reduction algorithm followed by a clustering algorithm. We analysed the variation of physical and observational parameters among the clusters obtained from the application of this procedure to different inputs. The inputs studied in this paper are (a) line-of-sight velocity maps for the whole sample of galaxies observed at fixed inclinations; (b) line-of-sight velocity, dispersion, and flux maps together for the whole sample of galaxies observed at fixed inclinations; (c) line-of-sight velocity, dispersion, and flux maps together for two separate subsamples of edge-on galaxies with similar amount of rotation; and (d) line-of-sight velocity, dispersion, and flux maps together for galaxies from different observation angles mixed. Results: The application of the method to solely line-of-sight velocity maps achieves a clear division between slow rotators (SRs) and fast rotators (FRs) and can differentiate rotation orientation. By adding the dispersion and flux information at the input, low-rotation edge-on galaxies are separated according to their shapes and, at lower inclinations, the clustering using the three types of maps maintains the overall information obtained using only the line-of-sight velocity maps. This method still produces meaningful groups when applied to SRs and FRs separately, but in the first case the division into clusters is less clear than when the input includes a variety of morphologies. When applying the method to a mixture of galaxies observed from different inclinations, we obtain results that are similar to those in our previous experiments with the advantage that in this case the input is more realistic. In addition, our method has proven to be robust: it consistently classifies the same galaxies viewed from different inclinations.
Recommended citation: Rosito, et. al. (2023a)
venue: ‘A&A’
“Redshift evolution of the dark matter haloes shapes”
date: 2023-05-01
In this work, we aim at investigating the morphology evolution of Milky Way mass-like dark matter haloes selected from the CIELO and IllustrisTNG Projects. The connection between halo shapes and their environment has been studied in previous works at z=0 but their connection remains yet to be fully understood. We focus on the evolution across cosmic time of the halo shapes and the relation with the infalling material, using hydrodynamical simulations
Recommended citation: Cataldi, et. al. (2023a)
venue: ‘MNRAS’
“Galaxy segmentation using U-Net deep-learning algorithm”
date: 2023-08-01
Automation in image segmentation is crucial to study the morphology of galaxies from large-scale surveys. In this work we use the Galaxy Zoo 3D dataset to train a series of convolutional neural networks for spiral arms detection in galaxy images. Six different deep-learning models were built according to the levels of confidence for the region marked as an arm. Using an architecture called U-Net, we trained an algorithm capable of generating spiral arms binary masks over a new set of images with high precision. This allows, not only to identify which galaxies have spiral arms, but to easily position the pixels from the spiral arms and measure their relative size for six different degrees of certainty.
Recommended citation: Deutsch, et. al. (2023)
venue: ‘BAAA’
“Planes of Satellites around Simulated Disk Galaxies. II. Time-persistent Planes of Kinematically Coherent Satellites in ΛCDM”
date: 2023-01-01
We use two zoom-in ΛCDM hydrodynamical simulations of massive disk galaxies to study the possible existence of fixed satellite groups showing a kinematically coherent behavior across evolution (angular momentum conservation and clustering). We identify three such groups in the two simulations, defining kinematically coherent persistent planes (KPPs) that last at least from virialization to z = 0 (more than 7 Gyr). This proves that orbital pole clustering is not necessarily set in at low redshift, representing a long-lived property of galaxy systems. KPPs are thin and oblate, represent ~25%-40% of the total number of satellites in the system, and are roughly perpendicular to their corresponding central disk galaxies during certain periods, consistently with Milky Way z = 0 data. KPP satellite members are statistically distinguishable from satellites outside KPPs: they show higher specific orbital angular momenta, orbit more perpendicularly to the central disk galaxy, and have larger pericentric distances than the latter. We numerically prove, for the first time, that KPPs and the best-quality positional planes share the same space configuration across time, such that KPPs act as “skeletons” preventing the latter from being washed out in short timescales. In one of the satellite-host systems, we witness the late capture of a massive dwarf galaxy endowed with its own satellite system, also organized into a KPP configuration prior to its capture. We briefly explore the consequences this event has on the host’s KPP and on the possible enhancement of the asymmetry in the number of satellites rotating in one sense or the opposite within the KPP.
Recommended citation: Santos-Santos, et. al. (2020)
venue: ‘The Astrophysical Journal’
“Non-parametric morphologies of galaxies in the EAGLE simulation”
date: 2020-06-01
We study the optical morphology of galaxies in a large-scale hydrodynamic cosmological simulation, the EAGLE simulation. Galaxy morphologies were characterized using non-parametric statistics (Gini, M20, Concentration, and Asymmetry) derived from mock images computed using a 3D radiative transfer technique and post-processed to approximate observational surveys. The resulting morphologies were contrasted to observational results from a sample of log {10}(M{*}/{M}_⊙) > 10 galaxies at z ∼ 0.05 in the GAMA survey. We find that the morphologies of EAGLE galaxies reproduce observations, except for asymmetry values which are larger in the simulated galaxies. Additionally, we study the effect of spatial resolution in the computation of non-parametric morphologies, finding that Gini and Asymmetry values are systematically reduced with decreasing spatial resolution. Gini values for lower mass galaxies are especially affected. Comparing against other large-scale simulations, the non-parametric statistics of EAGLE galaxies largely agree with those found in ILLUSTRISTNG. Additionally, EAGLE galaxies mostly reproduce observed trends between morphology and star formation rate and galaxy size. Finally, We also find a significant correlation between optical and kinematic estimators of morphologies, although galaxy classification based on an optical or a kinematic criteria results in different galaxy subsets. The correlation between optical and kinematic morphologies is stronger in central galaxies than in satellites, indicating differences in morphological evolution.
Recommended citation: Bignone, et. al. (2020)
venue: ‘MNRAS’
“Evolution of dark matter haloes in CIELO simulations “
date: 2023-02-01
‘This article analyze the dark matter (dm) halo evolution through time. For this study we use a Milky Way like haloes subsample from CIELO (ChemodynamIcal propertiEs of gaLaxies and the cOsmic web) project. This project aims at studying the formation of galaxies in different environments using zoom-ins simulations.
Recommended citation: Cataldi, et. al. (2023b)
venue: ‘BAAA64’
“Fingerprints of modified gravity on galaxies in voids”
date: 2022-10-01
In this work, we search for detectable signatures of f(R) gravity and its chameleon screening mechanism in the baryonic and dark matter properties of simulated void galaxies. The enhancement of the gravitational acceleration can have a meaningful impact on the scaling relations as well as on the halo morphology. The galaxy rotational velocity field (calculated with the velocity of the gas disc and the acceleration fields) deviates from the typical values of the Tully-Fisher Relation (TFR) in GR
Recommended citation: Cataldi, et. al. (2022)
venue: ‘MNRAS’
“Baryons shaping dark matter haloes “
date: 2020-12-01
In this work we aim at investigating the effects of baryons on the dark matter haloes structure, focusing on the correlation between the presence and importance of stellar discs and the halo shapes. We study the properties of a subsample of DM haloes from Fenix and eagle cosmological simulations.
Recommended citation: Cataldi, et. al. (2020)
venue: ‘MNRAS’
“Dark matter response to galaxy assembly history “
date: 2019-02-01
In this article, we study the properties of four Milky Way mass dark matter haloes from the Aquarius project during their assembly history, between z = 0−4.
Recommended citation: Artale, et. al. (2019)
venue: ‘A&A’