No description available.

We present the 1.4-GHz catalog of the galaxy cluster field RCS J022434-0002.5, at a redshift of z = 0.773. A total of 194 sources were found within a ∼0.28 degree2 region to a 5sigma depth of ∼75 muJy. We show that the differential source counts for the cluster field are in good agreement with other radio surveys, and therefore do not indicate a strong excess of radio sources in the cluster compared to the field. We find 13 sources have optical counterparts with photometric redshifts within 1sigma of the cluster redshift and an additional 5 within 2sigma, and we consider these objects to be candidate cluster members. We use their radio luminosities to attempt to diagnose the presence of active galactic nuclei or star formation activity. We find that the cluster candidates are statistically more likely to be powered by active galactic nuclei, rather than star formation.

Diss. (sammanfattning) Uppsala : Univ., 2003. / Härtill 3 uppsatser.

A dilemma is posed by studies of galaxy evolution at intermediate redshifts. If evolutionary effects are neglected, simple models predict number densities of faint galaxies which are 2—5x lower than observed at z ≅ 0.4. Yet the faint galaxy redshift distribution appears to be well modelled by the same no—evolution models. If low-mass starbursting galaxies are responsible for the excess, then the excess faint galaxy population should have rotation velocities lower than those of quiescent galaxies with the same luminosity. This thesis describes the results of a limited survey of the internal kinematics of intermediate redshift (z = 0.25—0.45) field galaxies. The goal of this survey was to find the unmistakable kinematical signature of low-mass starbursting galaxies. Using the Canada-France-Hawaii Telescope, spatially resolved spectra of the [O II] λλ 3726—3729 Å doublet emission line have been obtained for 22 galaxies. High-spatial resolution has made it possible to extract [special characters omitted] and [O II] disk scale length from each galaxy spectrum using synthetic galaxy rotation curve fitting. It is found that about 25% of the galaxies in the sample have [OIl] kinematics unrelated to rotation. [OIl] emission is concentrated in the nucleus in these “kinematically anomalous" galaxies. A Doppler ellipse similar to those found in local dwarf irregular galaxies has been observed in a z = 0.35 galaxy. An intermediate redshift Tully-Fisher (TF) relation defined by 12 kinematically normal galaxies shows that these galaxies have a systematically lower rotation velocity (i.e. mass) for their luminosity than expected from the local TF relation. These galaxies would have to fade by ~ 1.5-2 mag to lie on the local TF relation. This is consistent with starbursting dwarf galeixy models. Although the sample is small, there is also a hint that massive galaxies do not lie as far off the local TF relation as low-mass ones. However, as shown using a large sample of local galaxies, the scatter in the local TF relation is large, especially for late-type galaxies. Selection effects, particularly [OIl] emission strength, could be responsible for part of the observed TF shift if different star formation rates are responsible for the local TF scatter. A comparison with other works indicates that the luminosity-dependent luminosity evolution scenario neatly explains all the available internal kinematics and surface brightness data. / Graduate

New techniques are developed for relating the statistics of close galaxy pairs to the galaxy merger and accretion rates. Unlike the traditional pair fraction approach, these methods are shown to be robust to a number of selection effects related to the depth and completeness of the sample. These techniques are applied to the large, well-defined SSRS2 (z ∼ 0) and CNOC2 (0.1 ≤ ± ≤ 0.55) redshift surveys, yielding the first secure measurements of close pair statistics at low and moderate redshift. These results imply that the galaxy merger and accretion rates increase with redshift, approximately as (1 + z)2±1.5, for galaxies brighter than MB = –18. The CNOC2 survey is used to carry out a detailed comparison between close companions and field galaxies. Paired galaxies are found to be of slightly earlier spectral type, with a larger spread in properties. In particular, the spectral indices of close companions imply a more complex star formation history, as would be expected if galaxy interactions and mergers are prevalent. / Graduate

No description available.

A Simultaneous Photometer for Infrared and Visual light (hereafter SPIV) has been constructed. SPIV uses three dichroic filters to divide light from a common aperture in the telescope focal plane into four colors with bandpasses (in microns) of: 0.42 to 0.7 (V(B)); 0.7 to 0.95 (I(B)); 1.45 to 1.8 (H); 1.97 to 2.27 (K). The H and K bands are detected by liquid helium cooled InSb diodes. I(B) is detected by a helium cooled Si diode, and V(B) by an uncooled EMI 9658R photomultiplier tube. The instrument response function (IRF) including the effect of atmospheric transmission is shown. The maximum usable aperture size of 2 mm corresponds to 7 arcseconds on the Multiple Mirror Telescope and to 20 arcseconds on the UAO 61" and 90" telescopes. Information about the sky brightness is combined with the IRF to calculate the expected background noise. These calculations show SPIV should be background noise limited in all bands. Observations show this is true except for I(B), which is detector noise limited. The optical alignment of the four channels is shown to be satisfactory. The SPIV instrumental magnitude system is defined. Observations of 40 radio galaxies and 39 non-radio first ranked cluster galaxies with known redshifts ranging from 0.019 to 1.6 are reduced on this system, correcting for atmospheric extinction, reddening, and aperture. The transformation to standard magnitude systems is derived. The reduced V(B)-H, I(B)-H and H-K colors as a function of redshift are compared for the radio and non-radio galaxies using statistical tests. No convincing differences are found, with the possible exception of H-K in the z = 0.2 to 0.4 range. These colors are also compared to a "no evolution" prediction generated by redshifting a composite spectrum of nearby elliptical galaxies, and to evolutionary models from Bruzual (1981). Passively evolving models with little residual star formation and a galaxy formation epoch z(f) > 3 are slightly favored by H-K observations. These models predict about one magnitude brightening at H by a redshift of one. The I(B)-H color becomes redder with redshift much faster than the reddest model, and shows large scatter for z 3. Residual star formation models require an older universe than is allowed by qₒ = 0.5, Hₒ = 80 km/sec/Mpc to fit the red V(B)-H envelope at high redshift. Some galaxies show strong blueward deviations for z > 0.4. This behavior is most easily explained by episodes of star formation involving small fractions of the total number of stars. Because of the flatness of H-K and I(B)-H at high redshift, and the scatter in V(B)-H, determining redshifts > 0.4 from broadband colors will be difficult.

This thesis presents the results of a spectroscopic survey of the RCS2319+00 supercluster field using the VIMOS instrument on the 8-meter Very Large Telescope. This system is a rare and massive high-redshift structure, comprising at least three galaxy clusters at z = 0.9, separated by less than 3 Mpc, and is one of the few examples of the progenitors of present-day massive galaxy clusters. / We measure 638 new redshifts from a sample of 1134 target sources, 49 of which are consistent with the supercluster redshift. Redshifts are also obtained for 24 radio galaxies within the field, with 6 of these identified as cluster members. We combine the VIMOS redshift catalogue with the data analyzed by Gilbank et al. (2008) from the IMACS spectrograph on the 6-meter Magellan telescope for a total of 1051 redshifts over an area of ∼ 30 x 30 square arcminutes, with 94 spectroscopically confirmed supercluster members. From this combined data set the mean spectroscopic redshifts of the three galaxy clusters were refined and found to be zspec = 0.9056, 0.9041, and 0.9047 for clusters A, B, and C respectively. A new velocity dispersion of sigmav = (1300 +/- 410) km S-1 was calculated for the largest component cluster, A, and was used to estimate a new cluster membership redshift range of 0.8857 ≤ z ≤ 0.9239. / These data will facilitate further scientific study of RCS2319+00 and will shed light on the evolution of massive clusters, hierarchical structure formation, and galaxy evolution. In combination with other spectroscopy this data will allow: the full extent of the supercluster and its substructure in redshift space to be traced; a determination of the dynamical masses of the individual sub-clusters; and a study of the galaxy population within the structure, in particular the star-forming galaxies and active galactic nuclei as traced by radio and infrared emission.

Thesis (Ph. D.)--School of Physics, Faculty of Science, University of Sydney, 2004. / Bibliography: p. 123-129.

Thesis (Ph. D.)--University of Sydney, 2004. / Title from title screen (viewed 14 May 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Physics, Faculty of Science. Degree awarded 2004; thesis submitted 2003. Includes bibliographical references. Also available in print form.