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Recent studies have found that the oldest and most luminous galaxies in the early Universe are surprisingly compact, having stellar masses similar to present-day elliptical galaxies but much smaller sizes. This finding has attracted…
A model is proposed for determining the distances to falling interstellar clouds in the galactic halo by measuring the cloud velocity and column density and assuming a model for the vertical density distribution of the Galactic interstellar…
Maximum disk mass models fitted to galaxy rotation curves are used to show that dark matter (DM) halos in late-type and dwarf spheroidal (dSph) galaxies satisfy well defined scaling laws. Halos in less luminous galaxies have smaller core…
The fact that the spatial nonlocality of galaxy formation is controlled by some short length scale like the Lagrangian radius is the cornerstone of the bias expansion for large-scale-structure tracers. However, the first sources of ionizing…
We review a range of stastistical methods for analyzing the structures of star clusters, and derive a new measure ${\cal Q}$ which both quantifies, and distinguishes between, a (relatively smooth) large-scale radial density gradient and…
Ionized gas and stellar kinematical parameters have been measured along the major axis of 20 nearby disc galaxies. We discuss the properties of each sample galaxy distinguishing between those characterized by regular or peculiar kinematics.…
The statistical uncertainty in measuring the primordial density perturbations on a given comoving scale is dictated by the number of independent regions of that scale that are accessible to an observer. This number varies with cosmic time…
In this paper, the first in a series on galaxy formation before reionization, we focus on understanding what determines the size and morphology of stellar objects in the first low mass galaxies, using parsec- scale cosmological simulations…
We study the clustering properties of the first galaxies formed in the Universe. We find that, due to chemical enrichment of the inter-stellar medium by isolated Population III stars formed in mini-halos at redshift z>30, the…
The past decade has witnessed impressive progress in our understanding of the physical properties of massive stars in the Magellanic Clouds, and how they compare to their cousins in the Galaxy. I summarise new results in this field,…
We present a new technique in order to quantify the dynamics of spatially extended systems. Using a test on the existence of unstable periodic orbits, we identify intermediate spatial scales, wherein the dynamics is characterized by maximum…
At cosmic dawn, the 21-centimeter signal from intergalactic hydrogen was driven by Lyman-$\alpha$ photons from some of the earliest stars, producing a spatial pattern that reflected the distribution of galaxies at that time. Due to the…
Early-type galaxies from CfA catalogue were assotiated with IRAS FSC sources. In given sample IR and optical properties were used to obtain some classification of these objects. The existance of significant classes can be evidence of…
The local space density of galaxies as a function of their basic structural parameters -luminosity, surface brightness and scale size- is still poorly known. Our poor knowledge is the result of strong selection biases against low surface…
We inspect the coupled dependence of physical parameters of the SDSS galaxies on the small-scale (distance to and morphology of the nearest neighbor galaxy) and the large-scale (background density smoothed over 20 nearby galaxies)…
We present a coarse-grained field theory of density fluctuations for a Newtonian self-gravitating many-body system and apply it to a homogeneous Universe with small density fluctuations. The theory treats the clustering of galaxies and…
Here I summarize constraints on the nature of the dark matter halos of field galaxies that have been obtained from the most recent investigations of (i) weak galaxy-galaxy lensing and (ii) the dynamics of satellite galaxies in orbit about…
We investigate the relationship between the colors, luminosities, and environments of galaxies in the Sloan Digital Sky Survey spectroscopic sample, using environmental measurements on scales ranging from 0.2 to 6 Mpc/h. We find: (1) that…
Halos of similar mass and redshift exhibit a large degree of variability in their differential properties, such as dark matter, hot gas, and stellar mass density profiles. This variability is an indicator of diversity in the formation…
Peculiar velocities thoughout the region of the local supercluster are reconstructed by two different orbit-retracing methods. The requirement of the optimal correlation between the radial components of reconstructed velocities and the…