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

The triggering probability of radio-loud AGN: A comparison of high and low excitation radio galaxies in hosts of different colors

Low luminosity radio-loud active galactic nuclei (AGN) are generally found in massive red elliptical galaxies, where they are thought to be powered through gas accretion from their surrounding hot halos in a radiatively inefficient manner. These AGN are often referred to as "low-excitation" radio galaxies (LERGs). When radio-loud AGN are found in galaxies with a young stellar population and active star formation, they are usually high-power radiatively-efficient radio AGN ("high-excitation", HERG). Using a sample of low-redshift radio galaxies identified within the Sloan Digital Sky Survey (SDSS), we determine the fraction of galaxies that host a radio-loud AGN, $f_{RL}$, as a function of host galaxy stellar mass, $M_*$, star formation rate, color (defined by the 4000 \angstrom break strength), radio luminosity and excitation state (HERG/LERG). We find the following: 1. LERGs are predominantly found in red galaxies. 2. The radio-loud AGN fraction of LERGs hosted by galaxies of any color follows a $f^{LE}_{RL} \propto M^{2.5}_*$ power law. 3. The fraction of red galaxies hosting a LERG decreases strongly for increasing radio luminosity. For massive blue galaxies this is not the case. 4. The fraction of green galaxies hosting a LERG is lower than that of either red or blue galaxies, at all radio luminosities. 5. The radio-loud AGN fraction of HERGs hosted by galaxies of any color follows a $f^{HE}_{RL} \propto M^{1.5}_*$ power law. 6. HERGs have a strong preference to be hosted by green or blue galaxies. 7. The fraction of galaxies hosting a HERG shows only a weak dependence on radio luminosity cut. 8. For both HERGs and LERGs, the hosting probability of blue galaxies shows a strong dependence on star formation rate. This is not observed in galaxies of a different color.[abridged]Comment: 7 pages, 6 figure

Theoretical and experimental research on parameter tracking systems Final report, 15 Jul. 1964 - Aug. 1965

Parameter tracking systems based on equation error approach for mathematical model of unknown plan

A jet-cloud interaction in 3C34 at redshift z = 0.69

We report the detection of a strong jet-cloud interaction at a distance of 120 kpc from the nucleus of the radio galaxy 3C34, which has redshift z=0.69. Hubble Space Telescope images of the radio galaxy show a long narrow region of blue emission orientated along the radio axis and directed towards a radio hotspot. The William Herschel Telescope has been used to provide long-slit spectroscopic data of this object, and infrared observations made with the United Kingdom InfraRed Telescope have enabled its spectral energy distribution to be modelled. We propose that the aligned emission is associated with a region of massive star-formation, induced by the passage of the radio jet through a galaxy within the cluster surrounding 3C34. A star-formation rate of about 100 solar masses per year is required, similar to the values necessary to produce the alignment effect in high-redshift radio galaxies. The consequences of this result for models of star formation in distant radio galaxies are discussed.Comment: 12 pages including 11 figures, LaTeX. To appear in MNRA

Contraction Obstructions for Connected Graph Searching

We consider the connected variant of the classic mixed search game where, in each search step, cleaned edges form a connected subgraph. We consider graph classes with bounded connected (and monotone) mixed search number and we deal with the question whether the obstruction set, with respect of the contraction partial ordering, for those classes is finite. In general, there is no guarantee that those sets are finite, as graphs are not well quasi ordered under the contraction partial ordering relation. In this paper we provide the obstruction set for $k=2$, where $k$ is the number of searchers we are allowed to use. This set is finite, it consists of 177 graphs and completely characterises the graphs with connected (and monotone) mixed search number at most 2. Our proof reveals that the "sense of direction" of an optimal search searching is important for connected search which is in contrast to the unconnected original case. We also give a double exponential lower bound on the size of the obstruction set for the classes where this set is finite

HST, radio and infrared observations of 28 3CR radio galaxies at redshift z ~ 1: I. The observations

Hubble Space Telescope images are presented of a sample of 28 3CR radio galaxies with redshifts in the range 0.6 < z < 1.8, together with maps at comparable angular resolution of their radio structure, taken using the Very Large Array. Infrared images of the fields, taken with the United Kingdom InfraRed Telescope, are also presented. The optical images display a spectacular range of structures. Many of the galaxies show highly elongated optical emission aligned along the directions of the radio axes, but this is not a universal effect; a small number of sources are either symmetrical or misaligned. Amongst those sources which do show an alignment effect, the morphology of the optical emission varies greatly, from a single bright elongated emission region to strings of optical knots stretching from one radio hotspot to the other. The infrared images display much less complexity. Although their significantly lower angular resolution would wash out some of the smaller structures seen in the HST images, it is clear that these galaxies are less aligned at infrared wavelengths than in the optical. In this paper, we discuss the galaxies individually, but defer a statistical analysis of the multi-waveband properties of the complete sample of sources to later papers in this series.Comment: 39 pages including 52 figures, LaTeX. Accepted for publication in MNRA