Roberto G. Abraham

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We have identified a population of faint red galaxies from a 0.62 deg region of the Las Campanas Infrared Survey whose properties are consistent with their being the progenitors of early-type galaxies. The optical and IR colors, number-magnitude relation, and angular clustering together indicate modest evolution and increased star formation rates among the(More)
The average mass density profile measured in the CNOC cluster survey is well described with the analytic form ρ(r) = Ar−1(r + aρ) −2, as advocated on the basis on n-body simulations by Navarro, Frenk & White. The predicted core radii are aρ = 0.20 (in units of the radius where the mean interior density is 200 times the critical density) for an Ω = 0.2 open(More)
In the first section of these lectures I outline the classical framework of the Hubble classification system. Because of space limitations I will focus on points of controversy concerning the physical interpretation of the Hubble sequence, showing how morphological ideas shape our understanding of galaxy evolution. I will then present an overview of the(More)
We have used the Hubble Space Telescope’s Advanced Camera for Surveys (Ford et al. 2003) to measure the cumulative mass density in morphologically-selected early-type galaxies over the redshift range 0.8 < z < 1.7. Our imaging data set covers four well-separated sight-lines, and is roughly intermediate (in terms of both depth and area) between the(More)
In this paper we present a new statistic for quantifying galaxy morphology based on measurements of the Gini coefficient of galaxy light distributions. This statistic is easy to measure and is commonly used in econometrics to measure how wealth is distributed in human populations. When applied to galaxy images, the Gini coefficient provides a quantitative(More)
The morphological properties of galaxies between 21 mag < I < 25 mag in the Hubble Deep Field are investigated using a quantitative classification system based on measurements of the central concentration and asymmetry of galaxian light. The class distribution of objects in the Hubble Deep Field is strongly skewed towards highly asymmetric objects, relative(More)
Hierarchical galaxy formation is the model whereby massive galaxies form from an assembly of smaller units. The most massive objects therefore form last. The model succeeds in describing the clustering of galaxies, but the evolutionary history of massive galaxies, as revealed by their visible stars and gas, is not accurately predicted. Near-infrared(More)
We investigate the visibility of galactic bars and spiral structure in the distant Universe by artificially redshifting 101 B-band CCD images of local spiral galaxies from the Ohio State University Bright Spiral Galaxy Survey. These local galaxy images represent a much fairer statistical baseline than the galaxy atlas images from Frei et al. (1995), the(More)
In order to establish an objective framework for studying galaxy morphology, we have developed a quantitative two-parameter description of galactic structure that maps closely on to Hubble’s original tuning fork. Any galaxy can be placed in this “Hubble space,” where the x-coordinate measures position along the early-to-late sequence, while the y-coordinate(More)