The final two redshifts for radio sources from the equatorial BRL sample

Best, Rottgering and Lehnert (1999, 2000a) defined a new sample of powerful radio sources from the Molonglo Reference Catalogue, for which redshifts were compiled or measured for 177 of the 178 objects. For the final object, MRC1059-010 (3C249), the host galaxy is here identified using near-infrared imaging, and the redshift is determined from VLT spectroscopy. For one other object in the sample, MRC0320+053 (4C05.14), the literature redshift has been questioned: new spectroscopic observations of this object are presented, deriving a corrected redshift. With these two results, the spectroscopic completeness of this sample is now 100%. New redshifts are also presented for PKS0742+10 from the Wall & Peacock 2.7 GHz catalogue, and PKS1336+003 from the Parkes Selected Regions. PKS0742+10 shows a strong neutral hydrogen absorption feature in its Lyman-alpha emission profile.Comment: 4 pages. LaTeX. Accepted for publication in MNRA

Clustering around radio galaxies at z~1.5

The importance of studying old elliptical galaxies at redshift z ~ 1.5 is reviewed, considering both what can be learned by extending studies of the evolution of cluster galaxy scaling relations to earlier cosmic epochs, and the age-dating of old elliptical galaxies at high redshifts. Following this, the first results are provided of an on-going project to find such distant elliptical galaxies, through an investigation of the cluster environments of powerful radio sources with redshifts 1.44 < z < 1.7. These studies show a considerable excess of red galaxies in the radio sources fields, with the magnitudes (K >~ 17.5) and colours (R-K > 4) expected of old passively evolving galaxies at the radio source redshift. The red galaxy overdensities are found on two different scales around the radio sources; a pronounced small-scale peak at radial distances of <~ 150 kpc, and a weaker large-scale excess extending out to 1 - 1.5 Mpc. The presence and richness of these red galaxy excesses varies considerably from source to source. An interpretation of these results is provided.Comment: LaTeX, 6 pages, Elsevier Science format. To appear in "Radio galaxies: past, present & future". eds. M. Jarvis et al., Leiden, Nov 200

Extreme host galaxy growth in powerful early-epoch radio galaxies

During the first half of the universe's age, a heyday of star-formation must have occurred because many massive galaxies are in place after that epoch in cosmic history. Our observations with the revolutionary Herschel Space Observatory reveal vigorous optically obscured star-formation in the ultra-massive hosts of many powerful high-redshift 3C quasars and radio galaxies. This symbiotic occurrence of star-formation and black hole driven activity is in marked contrast to recent results dealing with Herschel observations of X-ray selected active galaxies. Three archetypal radio galaxies, at redshifts 1.132,1.575, and 2.474 are presented here, with inferred star-formation rates of hundreds of solar masses per year. A series of spectacular coeval AGN/starburst events may have formed these ultra-massive galaxies and their massive central black holes during their relatively short lifetimes.Comment: To appear in Astrophysical Journal Letter

Feature-based motion control for near-repetitive structures

In many manufacturing processes, production steps are carried out on repetitive structures which consist of identical features placed in a repetitive pattern. In the production of these repetitive structures one or more consecutive steps are carried out on the features to create the final product. Key to obtaining a high product quality is to position the tool with respect to each feature of the repetitive structure with a high accuracy. In current industrial practice, local position sensors such as motor encoders are used to separately measure the metric position of the tool and the stage where the repetitive structure is on. Here, the final accuracy of alignment directly relies on assumptions like thermal stability, infinite machine frame stiffness and constant pitch between successive features. As the size of these repetitive structures is growing, often these assumptions are difficult to satisfy in practice. The main goal of this thesis is to design control approaches for accurately positioning the tool with respect to the features, without the need of the aforementioned assumptions. In this thesis, visual servoing, i.e., using machine vision data in the servo loop to control the motion of a system, is used for controlling the relative position between the tool and the features. By using vision as a measurement device the relevant dynamics and disturbances are therefore measurable and can be accounted for in a non-collocated control setting. In many cases, the pitch between features is subject to small imperfections, e.g., due to the finite accuracy of preceding process steps or thermal expansion. Therefore, the distance between two features is unknown a priori, such that setpoints can not be constructed a priori. In this thesis, a novel feature-based position measurement is proposed, with the advantage that the feature-based target position of every feature is known a priori. Motion setpoints can be defined from feature to feature without knowing the exact absolute metric position of the features beforehand. Next to feature-to-feature movements, process steps involving movements with respect to the features, e.g., engraving or cutting, are implemented to increase the versatility of the movements. Final positioning accuracies of 10 µm are attained. For feature-to-feature movements with varying distances between the features a novel feedforward control strategy is developed based on iterative learning control (ILC) techniques. In this case, metric setpoints from feature to feature are constructed by scaling a nominal setpoint to handle the pitch imperfections. These scale varying setpoints will be applied during the learning process, while second order ILC is used to relax the classical ILC boundary of setpoints being the same every trial. The final position accuracy is within 5 µm, while scale varying setpoints are applied. The proposed control design approaches are validated in practice on an industrial application, where the task is to position a tool with respect to discrete semiconductors of a wafer. A visual servoing setup capable of attaining a 1 kHz frame rate is realized. It consists of an xy-stage on which a wafer is clamped which contains the discrete semiconductor products. A camera looks down onto the wafer and is used for position feedback. The time delay of the system is 2.5 ms and the variation of the position measurement is 0.3 µm (3s)

HST and UKIRT imaging observations of z~1 6C radio galaxies - II. Galaxy morphologies and the alignment effect

(abridged) Powerful radio galaxies often display enhanced optical/UV emission regions, elongated and aligned with the radio jet axis. The aim of this series of papers is to separately investigate the effects of radio power and redshift on the alignment effect, together with other radio galaxy properties. In this second paper, we present a deeper analysis of the morphological properties of these systems, including both the host galaxies and their surrounding aligned emission. The host galaxies of our 6C subsample are well described as de Vaucouleurs ellipticals, with typical scale sizes of ~10kpc. This is comparable to the host galaxies of low-z radio sources of similar powers, and also the more powerful 3CR sources at the same redshift. The contribution of nuclear point source emission is also comparable, regardless of radio power. The 6C alignment effect is remarkably similar to that seen around more powerful 3CR sources at the same redshift in terms of extent and degree of alignment with the radio source axis, although it is generally less luminous. The bright, knotty features observed in the case of the z~1 3CR sources are far less frequent in our 6C subsample; neither do we observe such strong evidence for evolution in the strength of the alignment effect with radio source size/age. However, we do find a very strong link between the most extreme alignment effects and emission line region properties indicative of shocks, regardless of source size/age or power. In general, the 6C alignment effect is still considerably stronger than that seen around lower redshift galaxies of similar radio powers. (abridged)Comment: 23 pages, 15 figures, accepted for publication in MNRAS. See http://www.mrao.cam.ac.uk/~kji/MorphPaper/ for version of paper with full resolution images of Figs 1-1