We investigate the dependence of stellar population properties of galaxies on group dynamical stage for a subsample of the Yang catalog. We classify groups according to their galaxy velocity distribution into Gaussian (G) and Non-Gaussian (NG). Using two totally independent approaches, we have shown that our measurement of Gaussianity is robust and reliable. Our sample covers Yang’s groups in the redshift range 0.03 z 0.1, with mass . The new method, called Hellinger Distance, to determine whether a group has a velocity distribution Gaussian or NG is very effective in distinguishing between the two families. NG groups present halo masses higher than the G ones, confirming previous findings. Examining the skewness and kurtosis of the velocity distribution of G and NG groups, we find that faint galaxies in NG groups are mainly infalling, for the first time, into the groups. We show that considering only faint galaxies in the outskirts; those in NG groups are older and more metal-rich than those in G groups. Also, examining the Projected Phase Space of cluster galaxies, we see that bright and faint galactic systems in G groups are in dynamical equilibrium—which does not seem to be the case in NG groups. These findings suggest that NG systems have a higher infall rate, assembling more galaxies that have experienced preprocessing before entering the group.

Motivated by the existence of the relationship between the dynamical state of clusters and the shape of the velocity dispersion profiles (VDPs), we study the VDPs for Gaussian (G) and non-Gaussian (NG) systems for a subsample of clusters from the Yang catalogue. The groups cover a redshift interval of 0.03 ≤ z ≤ 0.1 with halo mass ≥10¹⁴ M_⊙. We use a robust statistical method, Hellinger Distance, to classify the dynamical state of the systems according to their velocity distribution. The stacked VDP of each class, G and NG, is then determined using either Bright or Faint galaxies. The stacked VDP for G groups displays a central peak followed by a monotonically decreasing trend which indicates a predominance of radial orbits, with the Bright stacked VDP showing lower velocity dispersions in all radii. The distinct features we find in NG systems are manifested not only by the characteristic shape of VDP, with a depression in the central region, but also by a possible higher infall rate associated with galaxies in the Faint stacked VDP.

We analyse the dependence of galaxy evolution on cluster dynamical state and galaxy luminosity for a sample of 146 galaxy clusters from the Yang SDSS catalogue. Clusters were split according to their velocity distribution in Gaussians (G) and Non-Gaussians (NG), and further divided by luminosity regime. We performed a classification in the plane of mean stellar age versus specific star formation rate, providing three classes: star-forming (SF), passive (PAS) and intermediate (GV – green valley). We show that galaxies evolve in the same way in G and NG systems, but also suggest that their formation histories lead to different mixtures of galactic types and infall patterns. Separating the GV into star-forming and passive components, we find more bright galaxies in the passive mode of NG systems than in that of G systems. We also find more intermediate faint galaxies in the star-forming component of NG systems than in that of G systems. Our results suggest that GV is the stage where the transition from types Sab and Scd to S0 must be taking place, but the conversion between morphological types is independent of the dynamical stage of the clusters. Analysing the velocity dispersion profiles, we find that objects recently infalling onto clusters have a different composition between G and NG systems. While all galaxy types infall on to G systems, Sab and Scd dominate the infall on to NG systems. Finally, we find that faint Scd galaxies in the outskirts of NG systems present higher asymmetries relative to the mean asymmetry of field galaxies, suggesting that there are environmental effects acting on these objects.

This paper is the third of a series in which we investigate the discrimination between Gaussian (G) and Non-Gaussian (NG) clusters, based on the velocity distribution of the member galaxies. We study a sample of 177 groups from the Yang catalog in the redshift interval of 0.03 ≤ z ≤ 0.1 and masses ${\ge }10^{14}\, \rm M_{\odot }$. Examining the projected stellar mass density distributions of G and NG groups, we find strong evidence of a higher infall rate in the outskirts of NG groups over the G ones. There is a 61 per cent excess of faint galaxies in NGs when contrasted with G groups, when integrating $\rm from \, 0.8 \,to\, 2.0R/R_{200}$. The study of the star formation history (SFH) of ellipticals and spirals in the three main regions of the projected phase space reveals also that the star formation in faint spirals of NG groups is significantly different from their counterpart in the G groups. The assembled mass for faint spirals varies from 59 per cent at 12.7 Gyr to 75 per cent at 8.0 Gyr, while in G systems this variation is from 82 per cent to 91 per cent. This finding may also be interpreted as a higher infall rate of gas-rich systems in NG groups. This accretion process through the filaments, disturbing the velocity distribution and modifying not only the stellar population of the incoming galaxies but also their SFH, should be seriously considered in modelling galaxy evolution.

In this work we investigate the influence of the dynamic state of galaxy clusters on segregation effects and velocity dispersion profiles (VDPs) for a sample of 111 clusters extracted from SDSS-DR7. We find that 73 clusters have Gaussian (G) velocity distribution and 38 clusters have a complex or non-Gaussian (NG) velocity distribution. We also split the G and NG samples into ‘active’ and ‘passive’ galaxies, according to their specific star formation rates and stellar masses. Our results indicate a strong spatial segregation between active and passive galaxies both in G and NG systems, with passive galaxies being more central. We also found that the passive population in G systems is the only family with lower velocity dispersions for the brightest galaxies (Mr ≲ −22.75), thus presenting velocity segregation with luminosity. The similarity found between the VDPs of the galaxy populations in NG systems indicates that these sets probably share a similar mix of orbits. We also found a clear evolutionary trend for G systems, with brighter galaxies in massive clusters having flatter VDPs. The scenario emerging from this study suggests a direct relationship between segregation effects, VDPs, and the dynamic state of clusters.

In this work we improve the dynamic-evolutionary framework of two massive clusters at intermediate redshifts: Cl 0024+17 at z ∼ 0.4 and MS 0451-03 at z ∼ 0.5. The spectroscopic galaxy members were selected from Moran et al. (2007a), which combine optical and UV imaging with spectroscopy. Using a set of dynamic estimators with different approaches, our results show that both Cl 0024+17 and MS 0451-03 are non-relaxed systems with distinct dynamical configurations. Cl 0024+17 exhibits a disturbed kinematics, displaying significant gaps and a velocity dispersion profile suggesting a merger. This is confirmed by the presence of previously reported substructures and new ones identified in this study. MS 0451-03 appears less disturbed than Cl 0024+17, indicating by the significant segregation between late and early-type galaxies, with the latter occupying more central regions of the projected phase-space. However, five previously unobserved substructures and non-Gaussianity in the velocity distribution indicate that MS 0451-03 is also out of equilibrium. In both clusters, there are substructures infalling onto the systems, indicating key moments in their assembly histories and potential effects on the pre-processing of galaxies within these subgroups. This is suggested by the high percentage of early-type galaxies outside R₂₀₀ (approximately |$83\%$|⁠) in the case of CL 0024+17. This work reinforces the importance of more detailed dynamical analysis of clusters to better characterize their evolutionary picture.