Galaxy formation and evolution

Abstract:

One of the most important techniques for astrophysics with adaptive optics is the ability to do spectroscopy at diffraction limited scales. The extreme difficulty of positioning a faint target accurately on a very narrow slit can be avoided by using an integral field unit, which provides the added benefit of full spatial coverage. During 1998, working with ALFA and the 3D integral field spectrometer, we demonstrated the validity of this technique by extracting and distinguishing spectra from binary stars separated by only 0.26 inch. The combination of ALFA & 3D is also ideally suited to imaging distant galaxies or the nuclei of nearby ones, as its field of view can be changed between 1.2 inches×1.2 inches and 4 inches×4 inches, depending on the pixel scale chosen. In this contribution we present new results both on galactic targets, namely young stellar objects, as well as extra-galactic objects including a Seyfert and a starburst nucleus.

Abstract:

We fit axisymmetric three-integral dynamical models to NGC 3379 using the line-of-sight velocity distribution obtained from Hubble Space Telescope FOS spectra of the galaxy center and ground-based long-slit spectroscopy along four position angles, with the light distribution constrained by WFPC2 and ground-based images. We have fitted models with inclinations from 29° (intrinsic galaxy type E5) to 90° (intrinsic E1) and black hole masses from 0 to 109 M⊙. The best-fit black hole masses range from 6 × 107 to 2 × 108 M⊙, depending on inclination. The preferred inclination is 90° (edge-on); however, the constraints on allowed inclination are not very strong, owing to our assumption of constant M/LV. The velocity ellipsoid of the best model is not consistent with either isotropy or a two-integral distribution function. Along the major axis, the velocity ellipsoid becomes tangential at the innermost bin, radial in the midrange radii, and tangential again at the outermost bins. The rotation rises quickly at small radii owing to the presence of the black hole. For the acceptable models, the radial-to-tangential [(σ2θ + σ2φ)/2] dispersion in the midrange radii ranges over 1.1 < σr/σt < 1.7, with the smaller black holes requiring larger radial anisotropy. Compared with these three-integral models, two-integral isotropic models overestimate the black hole mass since they cannot provide adequate radial motion. However, the models presented in this paper still contain restrictive assumptions - namely, assumptions of constant M/LV and spheroidal symmetry - requiring yet more models to study black hole properties in complete generality.

Abstract:

LUCIFER (LBT NIR-Spectroscopic Utility with Camera and Integral-Field Unit for Extragalactic Research) is a full cryogenic NIR spectrograph and imager (λ 0.9μ - 2.5μ, zJHK-bands) to be built by a consortium of five institutes (Landessternwarte Heidelberg (LSW), Max Planck Institut fuer Astronomie in Heidelberg (MPIA), Max Planck Institut fuer Extraterrestrische Physik (MPE) in Garching, Astronomisches Institut der Ruhr Universitaet Bochum (AIRUB) and Fachhochschule fuer Technik und Gestaltung (FHTG) in Mannheim). The instrument has been selected as one of three first-light instruments for the Large Binocular Telescope (LBT) on Mt. Graham, Arizona which first mirror becomes available to the community in early 2003. The second mirror and a second more or less identical spectrograph/imager follows 18 month later. Both LUCIFER instruments will be mounted at the bent Gregorian foci of the two individual LBT-mirrors and include six observing modes: seeing and diffraction limited imaging, seeing and diffraction limited longslit spectroscopy, seeing limited multi-object spectroscopy (MOS) and integral-field spectroscopy (IFU). The detector will be a Rockwell HAWAII-2 HgCdTe-array with a pixel-size of 18μ.

Abstract:

We present new near-infrared images of z > 0.8 radio galaxies from the flux-limited 7C-III sample of radio sources for which we have recently obtained almost complete spectroscopic redshifts. The 7C objects have radio luminosities ≈20 times fainter than 3C radio galaxies at a given redshift. The absolute magnitudes of the underlying host galaxies and their scale sizes are only weakly dependent on radio luminosity. Radio galaxy hosts at z ∼ 2 are significantly brighter than the hosts of radio-quiet quasars at similar redshifts and the recent model AGN hosts of Kauffmann & Haehnelt. There is no evidence for strong evolution in scale size, which shows a large scatter at all redshifts. The hosts brighten significantly with redshift, consistent with the passive evolution of a stellar population that formed at z ≳ 3. This scenario is consistent with studies of host galaxy morphology and submillimeter continuum emission, both of which show strong evolution at z ≳ 2.5. The lack of a strong "redshift cutoff" in the radio luminosity function to z > 4 suggests that the formation epoch of the radio galaxy host population lasts ≳ 1 Gyr, from z ≳ 5 to z ∼ 3. We suggest these facts are best explained by models in which the most massive galaxies and their associated AGN form early because of high baryon densities in the centers of their dark matter haloes.

Abstract:

In the context of the CNOC1 cluster survey, redshifts were obtained for galaxies in 16 clusters. The resulting sample is ideally suited for an analysis of the internal velocity and mass distribution of clusters. Previous analyses of this data set used the Jeans equation to model the projected velocity dispersion profile. However, the results of such an analysis always yield a strong degeneracy between the mass density profile and the velocity dispersion anisotropy profile. Here we analyze the full (R, v) data set of galaxy positions and velocities in an attempt to break this degeneracy. We build an "ensemble cluster" from the individual clusters under the assumption that they form a homologous sequence; if clusters are not homologous then our results are probably still valid in an average sense. To interpret the data we study a one-parameter family of spherical models with different constant velocity dispersion anisotropy, chosen to all provide the same acceptable fit to the projected velocity dispersion profile. The best-fit model is sought using a variety of statistics, including the likelihood of the data set and the shape and Gauss-Hermite moments of the grand-total velocity histogram. The confidence regions and goodness of fit for the best-fit model are determined using Monte Carlo simulations. Although the results of our analysis depend slightly on which statistic is used to judge the models, all statistics agree that the best-fit model is close to isotropic. For none of the statistics does the 1 σ confidence region extend below σr/σt = 0.74, or above σr/σt, = 1.05. This result derives primarily from the fact that the observed grand-total velocity histogram is close to Gaussian, which is not expected to be the case for a strongly anisotropic model. The best-fitting models have a mass-to-number density ratio that is approximately independent of radius over the range constrained by the data. They also have a mass density profile that is consistent with the dark matter halo profile advocated by Navarro, Frenk, & White in terms of both the profile shape and the characteristic scale length. This adds important new weight to the evidence that clusters do indeed follow this proposed universal mass density profile. We present a detailed discussion of a number of possible uncertainties in our analysis, including our treatment of interlopers and brightest cluster galaxies, our use of a restricted one-parameter family of distribution functions, our use of spherical models for what is in reality an ensemble of nonspherical clusters, and our assumption that clusters form a homologous set. These issues all constitute important approximations in our analysis. However, none of the tests that we have done indicates that these approximations influence our results at a significant level.