11,896 research outputs found
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
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
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,
, as a function of host galaxy stellar mass, , 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
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 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
Ladies' Javelin: Aerodynamics, Flight Simulation and Biomechanical Considerations
The javelin event, using both men's old and new rules javelins, has been reported in the literature from various aspects including biomechanical studies (e.g. 1,2), aerodynamics (3), and computer modelling (4, 5, 6,7,8). However, consideration of the ladies' event, from the latter two aspects, has not previously been reported. If the flight of a javelin can be accurately simulated then it is possible to find, for any individual, an optimum set of release conditions which produce a maximum range. In previous papers, the authors have reported data for the aerodynamics (9) and computer simulation of javelin flight (10) for the men's new rules javelin. This paper presents the results of wind tunnel tests of the ladies' javelin, a consequent computer flight simulation of this implement and the implications for the biomechanics of the event
Lattice hadron matrix elements with the Schroedinger functional: the case of the first moment of non-singlet quark density
We present the results of a non-perturbative determination of the pion matrix
element of the twist-2 operator corresponding to the average momentum of
non-singlet quark densities. The calculation is made within the Schroedinger
functional scheme. We report the results of simulations done with the standard
Wilson action and with the non-perturbatively improved clover action and we
show that their ratio correctly extrapolates, in the continuum limit, to a
value compatible with the residual correction factor expected from perturbation
theory.Comment: LaTeX, 10 pages, 5 figure
A short survey on nonlinear models of the classic Costas loop: rigorous derivation and limitations of the classic analysis
Rigorous nonlinear analysis of the physical model of Costas loop --- a
classic phase-locked loop (PLL) based circuit for carrier recovery, is a
challenging task. Thus for its analysis, simplified mathematical models and
numerical simulation are widely used. In this work a short survey on nonlinear
models of the BPSK Costas loop, used for pre-design and post-design analysis,
is presented. Their rigorous derivation and limitations of classic analysis are
discussed. It is shown that the use of simplified mathematical models, and the
application of non rigorous methods of analysis (e.g., simulation and
linearization) may lead to wrong conclusions concerning the performance of the
Costas loop physical model.Comment: Accepted to American Control Conference (ACC) 2015 (Chicago, USA
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