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We compare the properties of galaxy groups extracted from the Updated Zwicky Catalogue (UZC) with those of groups extracted from N-body simulations of the local Universe, in a LambdaCDM and a tauCDM cosmology. In the simulations, the…
The current hierarchical merging paradigm and $\Lambda$CDM predict that the $z \sim 4-8$ universe should be a time in which the most massive galaxies are transitioning from their initial halo assembly to the later baryonic evolution seen in…
The hierarchical theory of galaxy formation rests on the idea that smaller galactic structures merge to form the galaxies that we see today. The past decade has provided remarkable observational support for this scenario, driven in part by…
Observations on galactic scales seem to be in contradiction with recent high resolution N-body simulations. This so-called cold dark matter (CDM) crisis has been addressed in several ways, ranging from a change in fundamental physics by…
The abundance of the faintest galaxies provides insight into the nature of dark matter and the process of dwarf galaxy formation. In the LCDM scenario, low mass halos are so numerous that the efficiency of dwarf formation must decline…
In their evolution, star-forming galaxies are known to follow scaling relations between some fundamental physical quantities, such as the mass-metallicity and the main sequence relations. We aim at studying the evolution of galaxies that,…
We study the stellar population history and chemical evolution of the Milky Way (MW) in a hierarchical LCDM model for structure formation. Using a Monte Carlo method based on the semi-analytical EPS formalism, we reconstruct the merger tree…
A large amount of observations have constrained cosmological parameters and the initial density fluctuation spectrum to a very high accuracy. However, cosmological parameters change with time and the power index of the power spectrum varies…
We explore trends in galaxy properties with Mpc-scale structures using catalogues of environment and large scale structure from the Galaxy And Mass Assembly (GAMA) survey. Existing GAMA catalogues of large scale structure, group and pair…
Theory and observations reveal fatal flaws in the standard LambdaCDM model. The cold dark matter hierarchical clustering paradigm predicts a gradual bottom-up growth of gravitational structures assuming linear, collisionless, ideal flows…
We use cosmological hydrodynamical simulations of Milky-Way-mass galaxies from the FIRE project to evaluate various strategies for estimating the mass of a galaxy's stellar halo from deep, integrated-light images. We find good agreement…
The James Webb Space Telescope has found an unexpected population of high-mass galaxies ($\log (M^\star / {\rm M} _\odot) \gtrsim 10$) with extremely small effective radii ($\sim 100\,\rm pc$) at $z \gtrsim 6$. Also, the existence of an…
We examine the projected correlation of galaxies with mass from small scales (<few hundred kpc) where individual dark matter halos dominate, out to 15 Mpc where correlated large-scale structure dominates. We investigate these profiles as a…
Numerical simulations have revealed the presence of long-lived substructure in Cold Dark Matter (CDM) halos. These surviving cores of past merger and accretion events vastly outnumber the known satellites of the Milky Way. This finding has…
We investigate possible signatures of halo assembly bias for spectroscopically selected galaxy groups from the GAMA survey using weak lensing measurements from the spatially overlapping regions of the deeper, high-imaging-quality…
We numerically simulate some of the most critical physical processes in galaxy formation: The supernova feedback, in conjunction with gasdynamics and gravity, plays a crucial role in determining how galaxies arise within the context of a…
Timescales in astronomy comprise the largest range of any scientific discipline. In the construction of physical models, this circumstance may both be a blessing and a curse. For example, galaxy evolution occurs on typical timescales of…
A number of recent challenges to the standard Lambda-CDM paradigm relate to discrepancies that arise in comparing the abundance and kinematics of local dwarf galaxies with the predictions of numerical simulations. Such arguments rely…
A semi-analytical model for the evolution of galaxies and supermassive black holes (SMBHs) within the $\Lambda$CDM paradigm has been shown to yield stellar mass-BH mass relations that reproduce both the JWST and pre-JWST observations.…
Current theories of galaxy formation have tended to focus on hierarchical structure formation, which is the most likely scenario for cosmological models with lots of power at small scales (e.g. standard cold dark matter). Models with little…