We measure the morphology-density relation ( MDR) and morphology-radius relation (MRR) for galaxies in seven z $ 1 clusters that have been observed with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope. Simulations and independent comparisons of our visually derived morphologies indicate that ACS allows one to distinguish between E, S0, and spiral morphologies down to z 850 ¼ 24, corresponding to L /L Ã ¼ 0:21 and 0.30 at z ¼ 0:83 and 1.24, respectively. We adopt density and radius estimation methods that match those used at lower redshift in order to study the evolution of the MDR and MRR. We detect a change in the MDR between 0:8 < z < 1:2 and that observed at z $ 0, consistent with recent work; specifically, the growth in the bulge-dominated galaxy fraction, f EþS0 , with increasing density proceeds less rapidly at z $ 1 than it does at z $ 0. At z $ 1 and AE ! 500 galaxies Mpc À2 , we find h f EþS0 i ¼ 0:72 AE 0:10. At z $ 0, an E+S0 population fraction of this magnitude occurs at densities about 5 times smaller. The evolution in the MDR is confined to densities AE k 40 galaxies Mpc À2 and appears to be primarily due to a deficit of S0 galaxies and an excess of Sp+Irr galaxies relative to the local galaxy population. The f E -density relation exhibits no significant evolution between z ¼ 1 and 0. We find mild evidence to suggest that the MDR is dependent on the bolometric X-ray luminosity of the intracluster medium. Implications for the evolution of the disk galaxy population in dense regions are discussed in the context of these observations.

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We have obtained long-slit observations of the circumnuclear region of M87 at three different locations, with a spatial sampling of 0. ′′ 028 using the Faint Object Camera f/48 spectrograph on board HST. These data allow us to determine the rotation curve of the inner ∼ 1 ′′ of the ionized gas disk in [O II]λ3727 to a distance as close as 0. ′′ 07 (≃ 5pc) to the dynamic center, thereby significantly improving on both the spatial resolution and coverage of previous FOS observations. We have modeled the kinematics of the gas under the assumption of the existence of both a central black hole and an extended central mass distribution, taking into account the effects of the instrumental PSF, the intrinsic luminosity distribution of the line, and the finite size of the slit. We find that the central mass must be concentrated within a sphere whose -2maximum radius is 0. ′′ 05 (≃3.5pc) and show that both the observed rotation curve and line profiles are consistent with a thin-disk in keplerian motion. We conclude that the most likely explanation for the observed motions is the presence of a supermassive black hole and derive a value of M BH = (3.2 ± 0.9)×10 9 M ⊙ for its mass.Subject headings: Galaxies -individual (M87); Galaxies -Seyfert; Galaxies -active; Black -Holes * Positions are nominally the same as the preceding ones but there was a small misplacement during observations.

We analyze deep multicolor Advanced Camera images of the largest known gravitational lens, A1689. Radial and tangential arcs delineate the critical curves in unprecedented detail, and many small counterimages are found near the center of mass. We construct a flexible light deflection field to predict the appearance and positions of counterimages. The model is refined as new counterimages are identified and incorporated to improve the model, yielding a total of 106 images of 30 multiply lensed background galaxies, spanning a wide redshift range, 1:0 < z < 5:5. The resulting mass map is more circular in projection than the clumpy distribution of cluster galaxies, and the light is more concentrated than the mass within r < 50 kpc h À1 . The projected mass profile flattens steadily toward the center with a shallow mean slope of dlog AE=dlog r ' À0:55 AE 0:1, over the observed range r < 250 kpc h À1 , matching well an NFW profile, but with a relatively high concentration, C vir ¼ 8:2 þ2:1 À1:8 . A softened isothermal profile (r core ¼ 20 AE 2 00 ) is not conclusively excluded, illustrating that lensing constrains only projected quantities. Regarding cosmology, we clearly detect the purely geometric increase of bend angles with redshift. The dependence on the cosmological parameters is weak owing to the proximity of A1689, z ¼ 0:18, constraining the locus, M þ Ã 1:2. This consistency with standard cosmology provides independent support for our model, because the redshift information is not required to derive an accurate mass map. Similarly, the relative fluxes of the multiple images are reproduced well by our best-fitting lens model.

In a previous paper we presented a homogeneous and 92% complete optical spectral dataset of the 3CR radio sources with redshift <0.3. Here we use the emission line measurements to explore the spectroscopic properties of the sample. The 3CR sources show a bimodal distribution of excitation index, a new spectroscopic indicator that measures the relative intensity of low and high excitation lines. This unveils the presence of two main sub-populations of radio-loud AGN to which we refer to, following previous studies, as high and low excitation galaxies (HEG and LEG, respectively). In addition to the two main classes, we find one source with a spectrum typical of star forming galaxies, and 3 objects of extremely low level of excitation. All broad-line objects are HEG from the point of view of their narrow emission line ratios and all HEG are FR II radio-galaxies with log L 178 [erg s −1 ] > ∼ 32.8. Conversely LEG cover the whole range of radio power encompassed by this 3CR subsample (30.7 < ∼ log L 178 < ∼ 35.4) and they are of both FR I and FR II type. The brightest LEG are all FR II. HEG and LEG obey to two (quasi) linear correlations between the optical line and extended radio luminosities, with HEG being brighter than LEG in the [O III] line by a factor of ∼10. HEG and LEG are offset also in a plane that compares the black hole mass and the ionizing nuclear luminosity. However, although HEG are associated with higher nuclear luminosities, we find LEG among the brightest radio sources of the sample and with a clear FR II morphology, indistinguishable from those seen in HEG. This suggests that LEG are not simply objects with a lower level of accretion. We speculate that the differences between LEG and HEG are related to a different mode of accretion: LEG are powered by hot gas, while HEG require the presence of cold accreting material. The high temperature of the accreting gas in LEG accounts for the lack of "cold" structures (i.e. molecular torus and broad line region), for the reduced radiative output of the accretion disk, and for the lower gas excitation.