Gustavo Luis Baume
Star populations in the NGC 2403 galaxy

Using images and multiband photometric data, obtained with the Advanced Camera for Surveys of the Hubble Space Telescope (HST/ACS), we performed a systematic and homogeneous identification of different star populations placed in the central region of the spiral galaxy NGC 2403. Bassed on the location over global color-magnitude diagrams, we split the objects among probable young blue population, a bright intermediate group, and the old red population. In particular, we focused our atention on a selection of bright blue stars, employing over them two different searching methods: a) stellar density maps for the identification of the most relevant and large scale galactic structures, and b) the PLC method, that takes into account the spatial distance between objects, for those low scale star groups. As a result, we have estimated sizes and densities of the identified groups and we have built their individual colour-magnitude diagrams and luminosity functions. These tools have allowed us to derive the fundamental characteristics of the groups. Moreover, we were able to establish different structures at several levels of stellar density that revealed the hierarchical structure of the young population in NGC 2403. On the other hand, we could map the spatial distribution of the intermediate and old populations over the covered galactic field.

JoaquĆ­n Armijo
Void properties in modified gravity models

Theories of modified gravity have been proposed to explain cosmic acceleration without invoking dark energy. Distinguishing modify gravity versus dark energy is one of the most important problem to address in cosmology. Significant differences between modified gravity and general relativity (GR) have to be studied in low density regions of the Universe, which lead to cosmic voids being proposed as promising test laboratory for gravity. Using N-body simulations of the f(R) model and GR, even with the same clustering of simulated galaxies, voids still have the power to distinguish them. I will present statistical analysis of void properties in these simulations, highlighting results from mark correlation functions.