We used Hubble Space Telescope WFPC2 images to identify six early-type galaxies with surface brightness profiles that decrease inward over a limited range of radii near their centers. The inferred luminosity density profiles of these galaxies have local minima interior to their core break radii. NGC 3706 harbors a high surface brightness ring of starlight with radius approximate to20 pc. Its central structure may be related to that in the double-nucleus galaxies M31 and NGC 4486B. NGC 4406 and NGC 6876 have nearly at cores that, on close inspection, are centrally depressed. Colors for both galaxies imply that this is not due to dust absorption. The surface brightness distributions of both galaxies are consistent with stellar tori that are more diffuse than the sharply defined system in NGC 3706. The remaining three galaxies are the brightest cluster galaxies in A260, A347, and A3574. Color information is not available for these objects, but they strongly resemble NGC 4406 and NGC 6876 in their cores. The thin ring in NGC 3706 may have formed dissipatively. The five other galaxies resemble the endpoints of some simulations of the merging of two gas-free stellar systems, each harboring a massive nuclear black hole. In one version of this scenario, diffuse stellar tori are produced when stars initially bound to one black hole are tidally stripped away by the second black hole. Alternatively, some inward-decreasing surface brightness profiles may reflect the ejection of stars from a core during the hardening of the binary black hole created during the merger.

The Inamori-Magellan Areal Camera and Spectrograph is nearing completion. This reimaging spectrograph will have fields of view of 15 arcmin and 27 arcmin in its relecting grating and grism spectrographic modes, respectively, the largest such areas available on one of the new generation of large optical-IR ground-based telescopes. In addition to wide field imaging and a range of low- to medium-resolution spectroscopic modes, IMACS will have a 2 x 1000 fiber-fed integral field unit built by Durham University, an ecellette mode, and the potential for a full-field tunable filter. We review some of the planned science programs for IMACS, ranging from spectroscopy of stars in the Galactic halo and nearby dwarf spheroidal galaxies, the search for stars between galaxies, internal kinematics in normal galaxies and AGN, and the evolution of high redshift galaxies and galaxy clusters.

The Inamori Magellan Areal Camera and Spectrograph (IMACS) will soon be one of the three first-generation instruments for the Magellan 6.5m telescopes. This instrument drove the specification and design of the f/11 Gregorian focus on Magellan, which it uses to feed an all-spherical, refracting wide-field collimator with a 30 arcmin field of view. Two Epps cameras are used to re-image the field of view for imaging and spectroscopy. The aspheric, f/2 ("short") camera images a field of 27 x 27 arcmin at 0.2 arcsec/pixel, and produces 0.32 arcsec images averaged over all field positions across the 0.39-1.05 micron-bandpass. The all-spherical f/4 ("long") camera images a field 15 x 15 arcmin at 0.11 arcsec/pixel, and produces 0.16 arcsec images averaged over all field positions across the 0.365-1.0 micron bandpass. This paper describes the final specifications for the multiple spectrographic and imaging modes, and provides a status report on the current state of the instrument project.

We present axisymmetric, orbit superposition models for 12 galaxies using data taken with the Hubble Space Telescope (HST) and ground-based observatories. In each galaxy, we detect a central black hole (BH) and measure its mass to accuracies ranging from 10% to 70%. We demonstrate that in most cases the BH detection requires both the HST and ground-based data. Using the ground-based data alone does provide an unbiased measure of the BH mass (provided that they are fitted with fully general models), but at a greatly reduced significance. The most significant correlation with host galaxy properties is the relation between the BH mass and the velocity dispersion of the host galaxy; we find no other equally strong correlation and no second parameter that improves the quality of the mass-dispersion relation. We are also able to measure the stellar orbital properties from these general models. The most massive galaxies are strongly biased to tangential orbits near the BH, consistent with binary BH models, while lower mass galaxies have a range of anisotropies, consistent with an adiabatic growth of the BH.

We present stellar kinematics for a sample of 10 early-type galaxies observed using the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope and the Modular Spectrograph on the MDM Observatory 2.4 m telescope. These observations are a part of an ongoing program to understand the coevolution of supermassive black holes and their host galaxies. Our spectral ranges include either the calcium triplet absorption lines at 8498, 8542, and 8662 Angstrom or the Mg b absorption at 5175 Angstrom. The lines are used to derive line-of-sight velocity distributions (LOSVDs) of the stars using a maximum penalized likelihood method. We use Gauss-Hermite polynomials to parameterize the LOSVDs and find predominantly negative h4 values (boxy distributions) in the central regions of our galaxies. One galaxy, NGC 4697, has significantly positive central h4 (high tail weight). The majority of galaxies have a central velocity dispersion excess in the STIS kinematics over ground-based velocity dispersions. The galaxies with the strongest rotational support, as quantified with v(max)/sigma(STIS), have the smallest dispersion excess at STIS resolution. The best-fitting, general, axisymmetric dynamical models (described in a companion paper) require black holes in all cases, with masses ranging from 10(6.5) to 10(9.3) M-.. We replot these updated masses on the M-BH-sigma relation and show that the fit to only these 10 galaxies has a slope consistent with the fits to larger samples. The greatest outlier is NGC 2778, a dwarf elliptical with relatively poorly constrained black hole mass. The two best candidates for pseudobulges, NGC 3384 and NGC 7457, do not deviate significantly from the established relation between M-BH and sigma. Neither do the three galaxies that show the most evidence of a recent merger, NGC 3608, NGC 4473, and NGC 4697.

We report the discovery of two new gravitationally lensed quasars, WFI J2026-4536 and WFI J2033-4723, at respective source redshifts of z = 2.23 and z = 1.66. Both systems are quadruply imaged and have similar PG 1115 - like image configurations. WFI J2026 - 4536 has a maximum image separation of 1."4, a total brightness of g = 16.5, and a relatively simple lensing environment, while WFI J2033 - 4723 has a maximum image separation of 2."5, an estimated total brightness of g approximate to 17.9, and a more complicated environment of at least six galaxies within 2000. The primary lensing galaxies are detected for both systems after point-spread function subtraction. Several of the broadband flux ratios in these systems show a strong (0.1 - 0.4 mag) trend with wavelength, suggesting either microlensing or differential extinction through the lensing galaxy. For WFI J2026 - 4536, the total quasar flux has dimmed by 0.1 mag in the blue but only half as much in the red over 3 months, suggestive of microlensing-induced variations. For WFI J2033 - 4723, resolved spectra of some of the quasar components reveal emission-line flux ratios that agree better with the macromodel predictions than either the broadband or continuum ratios, also indicative of microlensing. The predicted differential time delays for WFI J2026 - 4536 are short, ranging from 1 to 2 weeks for the long delay, but are longer for WFI J2033 - 4723, ranging from 1 to 2 months. Both systems hold promise for future monitoring campaigns aimed at microlensing or time delay studies.

We have formed "composite spectra'' by combining the integrated-light spectra of individual galaxies in eight intermediate-redshift and 12 low-redshift clusters of galaxies. Because these composite spectra have much higher signal-to-noise ratios than individual galaxy spectra, they are particularly useful in quantifying general trends in star formation for galaxy populations in distant clusters, z > 0.3. By measuring diagnostic features that represent stellar populations of very different ages, a grand composite spectrum can reflect the fractions of those populations as accurately as if excellent spectral measurements were available for each galaxy. Such composite spectra can also be useful in the study of finer spectral signatures, for example, spectral indices that break the age-metallicity degeneracy, and the shape of the Hdelta absorption line as an indicator of the age and duration of an epoch of starbursting galaxies in a cluster. Measuring the equivalent widths of spectral features in composite spectra is especially well suited for comparing the cosmic variance of star formation in clusters at a given redshift or comparing clusters over a range of redshifts. When we do this we find that [O II] emission and especially Balmer absorption is strong in each of our intermediate-redshift clusters and completely separable from a sample of 12 present-epoch clusters, where these features are weak. Cluster-to-cluster variations at a given epoch seem to be smaller than the strong trend in redshift, which suggests that cosmic evolution is the major factor in the star formation histories of cluster galaxies. Specifically, we show by comparison with the Hdelta strengths of present-epoch populations of continuously star-forming galaxies that the higher redshift samples must contain a much higher fraction of starburst galaxies than are found today in any environment.

We measure the morphology-density relation of galaxies at z = 1 across the full 3 orders of magnitude in projected galaxy density available in low-redshift studies. Our study adopts techniques that are comparable with those applied at lower redshifts, allowing a direct investigation of how the morphological segregation of galaxies has evolved over the last 8 Gyr. Although the morphology-density relation, as described by the fraction of early-type (E+S0) galaxies, was in place at z = 1, its form differs from that observed at both z = 0 and z = 0.5. In the highest density regions the early-type fraction has increased steadily with time from f(E+S0) = 0.7+/-0.1 at z = 1 to f(E+S0) = 0.9+/-0.1 at the present epoch. However, in intermediate-density regions corresponding to groups and the accretion regions of rich clusters, significant evolution appears to begin only after z = 0.5. Finally, at the lowest densities, no evolution is observed for the early-type fraction of field galaxies, which remains constant at f(E+S0) = 0.4+/-0.1 at all epochs. We examine a simple picture consistent with these observations where the early-type population at z = 1 is comprised largely of elliptical galaxies. Subsequent evolution in both intermediate and dense regions is attributed to the transformation of spirals into lenticulars. Further progress in verifying our hypothesis may be achieved through distinguishing ellipticals and lenticulars at these redshifts through resolved dynamical studies of representative systems.

We present observations of 77 early-type galaxies imaged with the PC1 CCD of the Hubble Space Telescope (HST) WFPC2. "Nuker-law'' parametric fits to the surface brightness profiles are used to classify the central structure into "core'' or "power-law'' forms. Core galaxies are typically rounder than power-law galaxies. Nearly all power-law galaxies with central ellipticities epsilon >= 0.3 have stellar disks, implying that disks are present in power-law galaxies with epsilon < 0.3 but are not visible because of unfavorable geometry. A few low-luminosity flattened core galaxies also have disks; these may be transition forms from power-law galaxies to more luminous core galaxies, which lack disks. Several core galaxies have strong isophote twists interior to their break radii, although power-law galaxies have interior twists of similar physical significance when the photometric perturbations implied by the twists are evaluated. Central color gradients are typically consistent with the envelope gradients; core galaxies have somewhat weaker color gradients than power-law galaxies. Nuclei are found in 29% of the core galaxies and 60% of the power-law galaxies. Nuclei are typically bluer than the surrounding galaxy. While some nuclei are associated with active galactic nuclei (AGNs), just as many are not; conversely, not all galaxies known to have a low-level AGN exhibit detectable nuclei in the broadband filters. NGC 4073 and 4382 are found to have central minima in their intrinsic starlight distributions; NGC 4382 resembles the double nucleus of M31. In general, the peak brightness location is coincident with the photocenter of the core to a typical physical scale of < 1 pc. Five galaxies, however, have centers significantly displaced from their surrounding cores; these may be unresolved asymmetric double nuclei. Finally, as noted by previous authors, central dust is visible in about half of the galaxies. The presence and strength of dust correlates with nuclear emission; thus, dust may outline gas that is falling into the central black hole. The prevalence of dust and its morphology suggest that dust clouds form, settle to the center, and disappear repeatedly on similar to 10(8) yr timescales. We discuss the hypothesis that cores are created by the decay of a massive black hole binary formed in a merger. Apart from their brightness profiles, there are no strong differences between core galaxies and power-law galaxies that demand this scenario; however, the rounder shapes of core, their lack of disks, and their reduced color gradients may be consistent with it.