ﻻ يوجد ملخص باللغة العربية
Color-color diagrams for the clump and interclump emission in 10 clump-cluster galaxies of the Ultra Deep Field are made from B,V,i, and z images and compared with models to determine redshifts, star formation histories, and galaxy masses. The clump colors suggest declining star formation over the last ~0.3 Gy, while the interclump emission is older. The clump luminous masses are typically 6x10^8 Msun and their diameters average 1.8 kpc. Total galaxy luminous masses average 6.5x10^10 Msun. The distribution of axial ratios is consistent with a thick disk geometry. The ages of the clumps are longer than their internal dynamical times by a factor of ~8, so they are stable clusters, but the clump densities are only ~10 times the limiting tidal densities, so they could be deformed by tidal forces. This is consistent with the observation that some clumps have tails. The clumps could form by gravitational instabilities in accreting disk gas, or they could be captured as gas-rich dwarf galaxies. Support for this second possibility comes from the high abundance of nearly identical bare clumps in the UDF field. Several clump-clusters have disk densities that are much larger than in local disks, suggesting they do not survive but get converted into ellipticals by collisions.
We study the nature of faint, red-selected galaxies at z ~ 2-3 using the Hubble Ultra Deep Field (HUDF) and Spitzer IRAC photometry. We detect candidate galaxies to H < 26 mag, probing lower-luminosity (lower mass) galaxies at these redshifts. We ide
Clump clusters and chain galaxies in the Hubble Ultra Deep Field are examined for bulges in the NICMOS images. Approximately 50% of the clump clusters and 30% of the chains have relatively red and massive clumps that could be young bulges. Magnitudes
We measure the build-up of the stellar mass of galaxies from z=6 to z=1. Using 15 band multicolor imaging data in the NICMOS Ultra Deep Field we derive photometric redshifts and masses for 796 galaxies down to H(AB)=26.5. The derived evolution of the
This paper is part of a series devoted to the study of the stellar populations in brightest cluster galaxies (BCGs), aimed at setting constraints on the formation and evolution of these objects. We have obtained high signal-to-noise ratio, long-slit
Based on FORS2-VLT long-slit spectroscopy, the analysis of the central absorption line indices of 9 S0 galaxies in the Fornax Cluster is presented. Central indices correlate with central velocity dispersions as observed in ellipticals. However, the s