M. V. Costa-Duarte — Page 2

arXiv2012

Stellar populations in superclusters of galaxies

A catalogue of superclusters of galaxies is used to investigate the influence of the supercluster environment on galaxy populations, considering galaxies brighter than M$_r<$-21+5$\log$ h. Empirical spectral synthesis techniques are applied to obtain the stellar population properties of galaxies which belong to superclusters and representative values of stellar population parameters are attributed to each supercluster. We show that richer superclusters present denser environments and older stellar populations. The galaxy populations of superclusters classified as filaments and pancakes are statistically similar, indicating that the morphology of superclusters does not have a significative influence on the stellar populations. Clusters of galaxies within superclusters are also examined in order to evaluate the influence of the supercluster environment on their galaxy properties. Our results suggest that the environment affects galaxy properties but its influence should operate on scales of groups and clusters, more than on the scale of superclusters.

astro-ph.CO↗

arXiv2010

Morphological Properties of Superclusters of Galaxies

We studied superclusters of galaxies in a volume-limited sample extracted from the Sloan Digital Sky Survey Data Release 7 (SDSS/DR7) and from mock catalogues based on a semi-analytical model of galaxy evolution in the Millenium Simulation. A density field method was applied to a sample of galaxies brighter than $M_r= -21+5 \log h_{100}$ to identify superclusters, taking into account selection and boundary effects. In order to evaluate the influence of threshold density, we have chosen two thresholds: the first maximizes the number of objects (D1), and the second constrains the maximum supercluster size to $\sim$120~h$^{-1}$Mpc (D2). We have performed a morphological analysis, using Minkowski Functionals, based on a parameter which increases monotonically from filaments to pancakes. An anti-correlation was found between supercluster richness (and total luminosity or size) and the morphological parameter, indicating that filamentary structures tend to be richer, larger and more luminous than pancakes in both observed and mock catalogues. We have also used the mock samples to compare supercluster morphologies identified in position and velocity spaces, concluding that our morphological classification is not biased by the peculiar velocities. Monte Carlo simulations designed to investigate the reliability of our results with respect to random fluctuations show that these results are robust. Our analysis indicates that filaments and pancakes present different luminosity and size distributions.

astro-ph.CO↗