As part of a research program exploring how and why dwarf elliptical (dE) galaxies depart from the Fundamental Plane defined by luminous elliptical (E) galaxies, we have analyzed archival Hubble Space Telescope F606W images of a sample of 18 dE galaxy candidates in the Coma Cluster. We model the full radial extent of their light-profiles by simultaneously fitting a PSFconvolved Sérsic R 1/n model and, when necessary, either a central point-source or a central PSF-convolved Gaussian. Nucleation was detected in all but two of our final sample of 15 dE galaxies. When detected, the luminosities of the central component L nuc scale with the host galaxy luminosity L gal such that L nuc = 10 4.76±0.10 L gal /10 7 0.87±0.26 . We confirm that the lightprofiles of the underlying host galaxies display systematic departures from an exponential model that are correlated with the model-independent host galaxy luminosity and are not due to biasing from the nuclear component. The Pearson correlation coefficient between log(n) and central galaxy surface brightness µ 0 (excluding the flux from extraneous central components) is -0.83 at a significance level of 99.99%. Excluding one outlier, the Pearson correlation coefficient between the logarithm of the Sérsic index n and the host galaxy magnitude is -0.77 at a significance of 99.9%. We explain the observed relationship between dE galaxy luminosity and the inner logarithmic profile slope γ′ as a by-product of the correlation between luminosity and Sérsic index n. Including, from the literature, an additional 232 dE and E galaxies spanning 10 mag in absolute magnitude (M ), the dE galaxies are shown to display a continuous sequence with the brighter E galaxies such that µ 0 brightens linearly with M until core formation causes the most luminous (M B −20.5 mag) E galaxies to deviate from this relation. The different behavior of dE and E galaxies in the M -<µ> e (and M -µ e ) diagram, and the <µ> e -log R e diagram have nothing to do with core formation, and are in fact expected from the continuous and linear relation between M and µ 0 , and M and log(n).

We have obtained spectra with the 10-m Keck telescope of a sample of 24 galaxies having colors consistent with star-forming galaxies at redshifts 2 < ∼ z < ∼ 4.5 in the Hubble Deep Field (HDF). Eleven of these galaxies are confirmed to be at high redshift (z med = 3.0), one is at z = 0.5, and the other 12 have uncertain redshifts but have spectra consistent with their being at z > 2. The spectra of the confirmed high-redshift galaxies show a diversity of features, including weak Lyα emission, strong Lyα breaks or damped Lyα absorption profiles, and the stellar and interstellar rest-UV absorption lines common to local starburst galaxies and high-redshift star-forming galaxies reported recently by others. The narrow profiles and low equivalent widths of C IV, Si IV, and N V absorption lines may imply low stellar metallicities. Combined with the 5 high-redshift galaxies in the HDF previously confirmed with Keck spectra by Steidel et al. (1996b), the 16 confirmed sources yield a comoving volume density of n ≥ 2.5 × 10 −4 h 3 50 Mpc −3 for q 0 = 0.05, or n ≥ 1.2 × 10 −3 h 3 50 Mpc −3 for q 0 = 0.5. These densities are 3 − 4 times higher than the recent estimates of 1 Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the

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We present a spectroscopic study of 51 compact field galaxies with redshifts z < 1.4 and apparent magnitudes I 814 < 23.74 in the flanking fields of the Hubble Deep Field. These galaxies are compact in the sense that they have small apparent half-light radii (r 1/2 ≤ 0.5 arcsec) and high surface brightnesses (µ I814 ≤ 22.2 mag arcsec −2 ). The spectra, taken at the Keck telescope, show emission lines in 88% of our sample, and only absorption lines in the remaining 12%. Emission-line profiles are roughly Gaussian with velocity widths that range from the measurement limit of σ ∼ 35 km s −1 to 150 km s −1 . Rest-frame[OII]λ3727 equivalent widths range from 5 Å to 94 Å, yielding star formation rates (SFR) of ∼0.1 to 14 M ⊙ yr −1 . The analysis of various line diagnostic diagrams reveals that ∼60% of compact emission-line galaxies have velocity widths, excitations, Hβ luminosities, SFRs, and mass-to-light ratios characteristic of young star-forming HII galaxies. The remaining 40% form a more heterogeneous class of evolved starbursts, similar to local starburst disk galaxies. We find that, although the compact galaxies at z > 0.7 have similar SFRs per unit mass to those at z < 0.7, they are on average ∼10 times more massive. Our sample implies a lower limit for the global comoving SFR density of ∼0.004 M ⊙ yr −1 Mpc −3 at z = 0.55, and ∼0.008 M ⊙ yr −1 Mpc −3 at z = 0.85 (assuming Salpeter IMF, H 0 = 50 km s −1 Mpc −1 , and q 0 = 0.5). These values, when compared to estimates for a sample of local compact galaxies selected in a similar fashion, support a history of the universe in which the SFR density declines by a factor ∼10 from z = 1 to today. From the comparison with the SFR densities derived for magnitude-limited samples of field galaxies, we conclude that compact emission-line galaxies, though only ∼20% of the general field population, may contribute as much as ∼45% to the global SFR of the universe at 0.4 < z < 1.

Intracluster stellar populations are a natural result of tidal interactions in galaxy clusters. Measuring these populations is difficult, but important for understanding the assembly of the most massive galaxies. The Coma cluster of galaxies is one of the nearest truly massive galaxy clusters, and is host to a correspondingly large system of globular clusters (GCs). We use imaging from the HST/ACS Coma Cluster Survey to present the first definitive detection of a large population of intracluster GCs (IGCs) that fills the Coma cluster core and is not associated with individual galaxies. The GC surface density profile around the central massive elliptical galaxy, NGC 4874, is dominated at large radii by a population of IGCs that extend to the limit of our data (R < 520 kpc). We estimate that there are 47000 ± 1600 (random) +4000 −5000 (systematic) IGCs out to this radius, and that they make up ∼ 70% of the central GC system, making this the largest GC system in the nearby Universe. Even including the GC systems of other cluster galaxies, the IGCs still make up ∼ 30-45% of the GCs in the cluster core. Observational limits from previous studies of the intracluster light (ICL) suggest that the IGC population has a high specific frequency. If the IGC population has a specific frequency similar to high-S N dwarf galaxies, then the ICL has a mean surface brightness of µ V ≈ 27 mag arcsec −2 and a total stellar mass of roughly 10 12 M ⊙ within the cluster core. The ICL makes up approximately half of the stellar luminosity and one-third of the stellar mass of the central (NGC4874+ICL) system. The color distribution of the IGC population is bimodal, with blue, metal-poor GCs outnumbering red, metal-rich GCs by a ratio of 4:1. The inner GCs associated with NGC 4874 also have a bimodal distribution in color, but with a redder metal-poor population. The fraction of red IGCs (20%), and the red color of those GCs, implies that IGCs can originate from the halos of relatively massive, L * galaxies, and not solely from the disruption of dwarf galaxies.