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We present a maximum-likelihood analysis of galaxy-galaxy lensing effects in galaxy clusters and in the field. The aim is to determine the accuracy and robustness of constraints that can be obtained on galaxy halo properties in both…
The aperture photometry method is a powerful tool that enables us to study large star cluster systems efficiently. However, its accuracy depends on various factors, including the stochasticity of the stellar initial mass function and…
We present measurements of the V and I band magnitudes of red clump stars in 15 nearby galaxies obtained from recently published homogenous HST photometry. Supplementing these results with similar data for another 8 galaxies available in…
We investigate the color-magnitude diagram (CMD) of cluster galaxies in the hierarchical $\Lambda$-CDM cosmological scenario using both single stellar populations and simple galaxy models. First, we analyze the effect of bursts and mergers…
We use the Wide Field Camera 3 onboard the Hubble Space Telescope to obtain deep, high-resolution photometry of the young (~ 100 Myr) star cluster NGC1850 in the Large Magellanic Cloud. We analyze the cluster colour-magnitude diagram (CMD)…
The Global-Multi Conjugated Adaptive Optics (GMCAO) approach offers an alternative way to correct an adequate scientific Field of View (FoV) using only natural guide stars (NGSs) to extremely large ground-based telescopes. Thus, even in the…
Follow-up observations at high-angular resolution of submillimeter galaxies showed that the single-dish sources are comprised of a blend of several galaxies. Consequently, number counts derived from low and high angular resolution…
We study the efficiency of numerically simulated galaxy clusters for producing strong gravitational lensing events in different dark-energy cosmologies with constant and time-variable equation of state and we compare it with ``standard''…
Arc statistics is known to be a powerful cosmological tool. Numerical lensing simulations show that orders of magnitude differences in the number of {\em giant} arcs on the whole sky are expected in different cosmological models. In this…
The abundance and mass distribution of galaxy clusters is a sensitive probe of cosmological parameters, through the sensitivity of the high-mass end of the halo mass function to $\Omega_m$ and $\sigma_8$. While galaxy cluster surveys have…
We study the effect of magnification in the Dark Energy Survey Year 3 analysis of galaxy clustering and galaxy-galaxy lensing, using two different lens samples: a sample of Luminous red galaxies, redMaGiC, and a sample with a…
In the present work we show a comprehensive comparison of our new stellar population synthesis MIUSCAT models with photometric data of globular clusters and early-type galaxies. The models compare remarkably well with the colours of Milky…
CONTEXT. Massive stars have high-multiplicity fractions, and many of them have still undetected components, thus hampering the study of their properties. AIMS. I study a sample of massive stars with high angular resolution to better…
We present halo model predictions for the expected angular clustering and associated errors from the completed Sloan Digital Sky Survey (SDSS) photometric galaxy sample. These results are used to constrain halo model parameters under the…
Weak gravitational lensing has been used extensively in the past decade to constrain the masses of galaxy clusters, and is the most promising observational technique for providing the mass calibration necessary for precision cosmology with…
Adaptive optics (AO) instruments for the future extremely large telescopes (ELTs) are characterized by advanced optical systems with diffraction-limited optical quality. Low geometric distortion is also crucial for high accuracy astrometric…
We forecast the constraints on the values of sigma_8, Omega_m, and cluster scaling relation parameters which we expect to obtain from the XMM Cluster Survey (XCS). We assume a flat Lambda-CDM Universe and perform a Monte Carlo Markov Chain…
We make an exploratory study of how well dark energy models can be constrained using lensed arcs at different redshifts behind cluster lenses. Arcs trace the critical curves of clusters, and the growth of critical curves with source…
We study the stellar cluster population in two adjacent fields in the nearby, face-on spiral galaxy, M83, using WFC3/HST imaging. The clusters are selected through visual inspection to be centrally concentrated, symmetric, and resolved on…
Maximizing the utility of upcoming photometric cluster surveys requires a thorough understanding of the richness-mass relation of galaxy clusters. We use Monte Carlo simulations to study the impact of various sources of observational…