bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic control of sodium exclusion in durum wheat
Authors: Munns Rana , Rebetzke Gregory J. , Husain Shazia , James Richard A. , Hare Ray A.
Published: August 2003

Salt tolerance in the genus Triticum is associated with low accumulation of Na+ in leaves. Durum and other tetraploid wheats generally have high accumulation of Na+ relative to bread wheat, and are salt sensitive, but a durum wheat landrace, Line 149, was found to have unusually low leaf Na+ accumulation. Populations were developed from crosses between 149 and the high Na+ accumulation variety Tamaroi, as well as between 149 and a durum wheat landrace with very high Na+ accumulation, Line 141. The third leaf of parental lines, F1, F2, and low- and high-selected F2:3 progeny was assayed for Na+ uptake when grown in 150 mM NaCl. Sodium concentrations were significantly (P < 0.01) lower in the low Na+ uptake Line 149 compared with high Na+ uptake Tamaroi (5-fold greater Na+ accumulation) and Line 141 (7-fold greater Na+ accumulation). There was no evidence of any maternal genetic effect on Na+ accumulation. The F1 progeny mean was intermediate to the mid- and low-parent means, suggesting incomplete dominance gene action. Progeny in the F2 generation of both populations segregated for Na+ accumulation in a 15 (low Na+) : 1 (high Na+) ratio (χ215:1 = 0.27 and 0.46, P > 0.50n.s. for 149/Tamaroi and 149/141, respectively), indicating duplicate dominance epistasis arising from segregation of 2 interacting dominant genes. Small yet significant (P < 0.01) genotypic variation was also observed for minor genes affecting Na+ accumulation. Realised heritabilities were moderate to high (h2R = 0.43–0.90) across populations, indicating good response to selection for low Na+ accumulation in the F2 generation. The simple genetic control of Na+ accumulation suggests relative ease of selection of lines with low Na+ accumulation. However, presence of dominance will require selection to be delayed until after 1 or 2 generations of inbreeding, or after progeny-testing of selected low Na+ accumulation families.
Genetic parameters for meat quality and carcass traits and their correlation with wool traits in Australian Merino sheep
Authors: Fogarty N. M. , Safari E. , Taylor P. J. , Murray W.
Published: August 2003

Estimates of genetic parameters for carcass traits in Merino sheep are presented, including muscle pH and colour, which are indicators of meat quality. The inclusion of these in the parameter set for genetic evaluation will provide the basis for more accurate estimated breeding values and the design of better breeding programs for improving meat traits in straightbred Merino sheep and crossbred lamb production. Data from 1045, nineteen-month-old Merino rams, the progeny of 125 sires from 3 strains that are representative of the industry, were used. Heritability and genetic correlations were estimated by fitting an animal model using a REML procedure in univariate and multivariate analyses. The traits included fasted pre-slaughter liveweight; dressing %; carcass tissue depth at the GR site (FATGR); fat depth at the C site (FATC); eye muscle depth (EMD), width (EMW), and area (EMA); ultimate pH and colour (L*, a*, b*) of the eye muscle. Multivariate analyses were used to estimate genetic correlations among meat traits and between wool traits (clean wool weight and mean fibre diameter) and selected carcass and meat traits. Estimates of heritability were: liveweight 0.51 (±0.10), dressing % 0.39 (±0.10), FATGR 0.33 (±0.09), FATC 0.20 (±0.08), EMD 0.27 (±0.08), EMW 0.15 (±0.07), EMA 0.23 (±0.08), muscle pH 0.27 (±0.09), and 0.14 (±0.07), 0.02 (±0.06), and 0.04 (±0.06) for the meat colour measurements L*, a*, and b* respectively. There was a favourable genetic correlation between muscle pH and colour L* of –0.56 (±0.23). There were also significant genetic correlations between wool weight and FATGR (–0.34 ± 0.16) and between mean fibre diameter and muscle colour L* (–0.66 ± 0.27). The study indicates that there is genetic variation for carcass traits, including indicators of meat quality, with scope for selection to improve meat production and quality in Merino sheep.
Water use, competition, and crop production in low rainfall, alley farming systems of south-eastern Australia
Authors: Unkovich Murray , Blott Kerrin , Knight Alex , Mock Ivan , Rab Abdur , Portelli Michael
Published: August 2003

Annual crops were grown in alleys between belts of perennial shrubs or trees over 3–4 years at 3 sites across low rainfall (<450 mm) south-eastern Australia. At the two lower rainfall sites (Pallamana and Walpeup), crop grain yields within 2–5 m of shrub belts declined significantly with time, with a reduction equivalent to 45% over 9 m in the final year of cropping. At the third, wetter site (Bridgewater), the reduction in crop grain yields adjacent to tree belts was not significant until the final year of the study (12% over 11 m) when the tree growth rates had increased. The reductions in crop yield were associated with increased competition for water between the shrub or tree belts and the crops once the soil profile immediately below the perennials had dried. At all 3 sites during the establishment year, estimates of water use under the woody perennials were less than under annual crops, but after this, trends in estimates of water use of alley farming systems varied between sites. At Pallamana the perennial shrubs used a large amount of stored soil water in the second summer after establishment, and subsequently were predominantly dependent on rainfall plus what they could scavenge from beneath the adjacent crop. After the establishment year at the Walpeup site, water use under the perennial shrubs was initially 67 mm greater than under the annual crop, declining to be only 24 mm greater in the final year. Under the trees at Bridgewater, water use consistently increased to be 243 mm greater than under the adjacent annual crop by the final year. Although the shrub belts used more water than adjacent crop systems at Walpeup and Pallamana, this was mostly due to the use of stored soil water, and since the belts occupied only 7–18% of the land area, increases in total water use of these alley farming systems compared with conventional crop monocultures were quite small, and in terms of the extent of recharge control this was less than the area of crop yield loss. At the wetter, Bridgewater site, alley farming appeared to be using an increasing amount of water compared with conventional annual cropping systems. Overall, the data support previous work that indicates that in lower rainfall environments (<350 mm), alley farming is likely to be dogged by competition for water between crops and perennials.
The Optical Emission from Gamma-Ray Quasars
Authors: Whiting M. T. , Majewski P. , Webster R. L.
Published: August 2003

We present photometric observations of six radio-loud quasars that were detected by the COMPTEL gamma-ray telescope. The data encompass seven wavebands in the optical and near infrared. After correction for Galactic extinction, we find a wide range in optical slopes. Two sources are as blue as optically-selected quasars, and are likely to be dominated by the accretion disc emission, while three others show colours consistent with a red synchrotron component. We discuss the properties of the COMPTEL sample of quasars, as well as the implications our observations have for multiwavelength modelling of gamma-ray quasars.
Orbit of Comet C/1850 Q1 (Bond)
Authors: Branham Richard L.
Published: August 2003

Comet C/1850 Q1 (Bond) is one of a number of comets catalogued with parabolic orbits. Given that there are sufficient observations, 104 in right ascension and 103 in declination, it proves possible to calculate a better orbit. Some of the difficulties of working with 19th century observations, which show considerable scatter, are discussed. Rectangular coordinates, both of the comet and the Sun, are interpolated by a recursive version of Aitken's method, rendering unnecessary the need to specify an order for the interpolation. Comet Bond's orbit is slightly hyperbolic.
Photometry of R Coronae Borealis Stars during the Recovery Phase of their Declines
Authors: Skuljan Lj. , Cottrell P. L. , Gilmore A. C. , Kilmartin P. M.
Published: August 2003

The photometric observations (UBVRI) of nine cool R Coronae Borealis (RCB) stars have been collected at Mt John University Observatory, New Zealand, over a period of twelve years. The analysis of the magnitude–colour and colour–colour diagrams for the recovery phase demonstrates that all declines exhibit a similar asymptotic approach to their normal brightness. Declines return to maximum brightness along a line with essentially the same slope that does not depend on the star or the depth of the decline. Assuming a uniform obscuration of the photosphere by the dust cloud during the recovery phase, the extinction properties of the material were determined. The ratio of total to selective extinction (RV) for the RCB stars in our sample is in the range 2.5 to 4.6, indicating that the obscuring dust has extinction properties similar to that of the interstellar dust. Observations have been compared with the theoretical extinction curves for different sorts of grains.
Optical and UV Spectral Diagnostics for GPS and CSS Sources
Authors: Dopita Michael A.
Published: August 2003

In this paper I examine the use of optical and UV spectral diagnostic ratios to distinguish between gas which is locally shock-excited by the interaction with a jet and that which is photoionised by the central engine. In many cases key UV lines remain unobserved except in the case of high redshift radio galaxies. However, in one case, the nearby GPS galaxy NGC1052, UV data was obtained with the FOS. This object shows LINER characteristics at optical wavelengths, but has a rich coronal-line spectrum in the UV. We conclude that jet-driven shocks tend to evolve from shock-excited to photoionised later in their evolution.
HST/STIS Spectroscopy of CSS Sources: Kinematics and Ionisation of the Aligned Nebulae
Authors: Labiano A. , O'Dea C. P. , Gelderman R. , Vries W. H. de , Axon D. J. , Barthel P. D. , Baum S. A. , Capetti A. , Fanti R. , Koekemoer A. M. , Morganti R. , Tadhunter C. N.
Published: August 2003

We have obtained long slit spectra of 3C 67 and 3C 277.1 with the HST/STIS spectrograph. We present our preliminary results on the diagnostic emission line ratios along the radio source axes in 3C 67 and 3C 277.1.
New Metallicity Calibration Down to [Fe/H] = −2.75 dex
Authors: Karaali S. , Bilir S. , Karataş Y. , Ak S. G.
Published: August 2003

We have taken 88 dwarfs, covering the colour-index interval 0.37 ≤ (B–V)0 ≤ 1.07 mag, with metallicities –2.70 ≤ [Fe/H] ≤ +0.26 dex, from three different sources for new metallicity calibration. The catalogue of Cayrel de Stroble et al. (2001), which includes 65% of the stars in our sample, supplies detailed information on abundances for stars with determination based on high-resolution spectroscopy. In constructing the new calibration we have used as ‘corner stones’ 77 stars which supply at least one of the following conditions: (i) the parallax is larger than 10 mas (distance relative to the Sun less than 100 pc) and the galactic latitude is absolutely higher than 30°; (ii) the parallax is rather large, if the galactic latitude is absolutely low and vice versa. Contrary to previous investigations, a third-degree polynomial is fitted for the new calibration: [Fe/H] = 0.10 – 2.76δ – 24.04δ2 + 30.00δ3. The coefficients were evaluated by the least-squares method, without regard to the metallicity of Hyades. However, the constant term is in the range of metallicity determined for this cluster, i.e. 0.08 ≤ [Fe/H] ≤ 0.11 dex. The mean deviation and the mean error in our work are equal to those of Carney (1979), for [Fe/H] ≥ –1.75 dex where Carney's calibration is valid.
The Extraordinary Radio Galaxy MRC B1221–423
Authors: Safouris V. , Hunstead R. W. , Prouton O. R.
Published: August 2003

MRC B1221–423 is a compact steep spectrum (CSS) radio source in the core of a remarkable elliptical galaxy. We examine its environment with long-slit spectra and multicolour images. A high-resolution synthesis image shows the radio source to have a 1″.5 (5.7 kpc) double structure. We use the empirical relationship between jet kinetic power and narrow line luminosity to infer a source age of ˜105 yr. The z = 0.1706 host galaxy is clearly disturbed, with tidal features and shells providing plausible evidence for a merger with one or more close companions. This evidence leads us to conclude that B1221–423 may be the progenitor of a much larger source, caught at an early stage in its radio evolution. We speculate that it is the interaction and accompanying events which have triggered this young powerful radio source.
Properties of Radio Source Host Galaxies
Authors: Vries Wim de
Published: August 2003

A brief overview of the current radio source host galaxy state of affairs is given. All the evidence appears to point towards a scenario in which the young radio source expands through the host galaxy on timescales of 105–106 yr, before it ends its life as a large scale FR II radio galaxy. The place and role of the quasars in this evolutionary picture is unclear, however, and remains an issue of debate.
Polarimetry of GPS and CSS Sources
Authors: Cotton W. D. , Dallacasa D. , Fanti C. , Fanti R. , Foley A. R. , Schilizzi R. T. , Spencer R. , Saikia D. J. , Garrington S.
Published: August 2003

The role of radio polarimetry in the understanding of GPS and CSS sources is explored. After an initial discussion of what can be learned from polarimetry, the expectations of a simple evolutionary sequence of GPS/CSO to CSS to FR I/FR II sources are explored. Observational results are then compared with the expectations. Conclusions include: the GPS category is likely not a single homogeneous class of objects; Faraday depth effects are very strong inside the inner 3 kpc of CSS and CSO sources; in at least 3C 138 the Faraday screen has very fine scale (subparsec) structure; and there is evidence for increased ionisation near bends in some CSS jets probably due to jet–ISM interaction. New results on 3C 138, 3C 43, and 3C 454 are given.
1245+676 — A CSO/GPS Source being an Extreme Case of a Double-Double Structure
Authors: Marecki Andrzej , Barthel Peter D. , Polatidis Antonis , Owsianik Izabela
Published: August 2003

AGN with the so-called 'double-double' radio structure have been interpreted as restarted AGN where the inner structure is a manifestation of a new phase of activity which happened to begin before the outer radio lobes resulting from the previous one had faded completely. The radio galaxy 1245+676 is an extreme example of such a double-double object — its outer structure, measuring 970 h−1 kpc, is five orders of magnitude larger than the 9.6 h−1 pc inner one. We present a series of VLBI observations of the core of 1245+676 which appears to be a compact symmetric object (CSO). We have detected the motion of the CSOs lobes, measured its velocity, and inferred the kinematic age of that structure.
Spectral Ages of CSOs and CSS Sources
Authors: Murgia Matteo
Published: August 2003

This paper deals with the spectral ageing study of a representative sample of compact symmetric objects (CSOs) and compact steep spectrum (CSS) sources. Observations reveal a distinctive high-frequency steepening of the radio spectra of many of these sources. The existence of such a spectral feature is expected or may be naturally interpreted in terms of radiative ageing of synchrotron emitting electrons. The small angular size of CSS sources makes it relatively easy to measure their integrated spectra over a wide frequency range for a conspicuous number of objects. For those sources whose emission is dominated by the mini-lobes, the integrated spectra can be used to constrain the source age. Assuming equipartition magnetic fields, the spectral ages we found are in the range from 102 to 105 yr. Multifrequency VLBA observations allow us to study the spectral properties of two CSOs: B1323+321 and B1943+546. The case of B1943+546 is particularly interesting since for this source a kinematic age has been derived from the proper motion of the hot spots. We found that spectral and kinematic ages agree within a factor of 2. The overall results presented here confirm that the CSOs and CSS sources are indeed young objects. Finally, we show some examples of compact sources characterised by an extraordinary steep and curved spectrum. It is plausible that these are relic sources in which the injection of fresh electrons has ceased for a significant fraction of their lifetime. These observations may indicate either the presence of intermittent activity or a class of short-living objects.

Throughout this paper we adopt H0 = 100 h km s−1 Mpc−1 and q0 = 0.5.
Search for CSS and GPS Candidates from the Peacock and Wall Catalogue
Authors: Rossetti A. , Mantovani F. , Fanti C. , Fanti R.
Published: August 2003

Samples of CSS/GPS sources suitable for statistical studies have been selected from the 3CR catalogue and from the Peacock & Wall catalogue. The selection criterion used for the Peacock & Wall catalogue CSS/GPS sources selects sources which peak below about 2 GHz and are therefore larger than ˜200 pc. Our main aim is to find among the flat spectrum sources in the Peacock & Wall catalogue smaller size CSS/GPS sources by means of systematic high resolution observations. The discovery of a few more would be important in order to finally have a complete flux limited sample of this class of objects. We discuss the results obtained so far for three of the observed sources.
The Shroud around the ‘Compact, Symmetric’ Radio Jets in NGC 1052
Authors: Vermeulen R. C. , Ros E. , Kellermann K. I. , Cohen M. H. , Zensus J. A. , van Langevelde H. J.
Published: August 2003

This is a paper on young jet material in a frustratingly complex environment.

NGC 1052 has a compact, flat or GHz peaked spectrum radio nucleus consisting of bi-symmetric jets, oriented close to the plane of the sky. Many features on both sides move away at υapp ˜0.26 c (H0 = 65 km s−1 Mpc−1). VLBI at seven frequencies shows a wide range of spectral shapes and brightness temperatures; there is clearly free–free absorption, probably together with synchrotron self-absorption, on both sides of the core. The absorbing structure is likely to be geometrically thick and oriented roughly orthogonal to the jets, but it is patchy.

HI VLBI shows atomic gas in front of the approaching as well as the receding jet. There appear to be three velocity systems, at least two of which are local to the AGN environment. The ‘high velocity system’, 125–200 km s−1 redward of systemic, seems restricted to a shell 1–2 pc away from the core. Closer to the centre, this gas might be largely ionised; it could cause the free–free absorption.

WSRT spectroscopy shows 1667 and 1665 MHz OH absorption over a wide velocity range. OH and HI profile similarity suggests co-location of molecular and atomic ‘high velocity’ gas; the connection to H2O masing gas is unclear. Further, at ‘high velocity’ we detected the OH 1612 MHz satellite line in absorption and the 1720 MHz line in emission, with complementary strengths.
Extreme Emission Line Outflows in the GPS Source 4C 12.50 (PKS 1345+12)
Authors: Holt J. , Tadhunter C. N. , Morganti R.
Published: August 2003

We present high resolution spectra (0.7 Å/pix) of the GPS source 4C 12.50 with large spectral coverage (˜4500 Å) taken with the 4.2 m William Herschel Telescope, La Palma. The slit was aligned along PA 160° to include the nucleus and emission line region to the NW. An asymmetric halo extending 20 kpc NW and 12 kpc SE from the nucleus is clearly seen. At the position of the nucleus we observe unusually broad forbidden emission line components (broadest component: FWHM ˜ 2000 km s−1), blue shifted by up to 2000 km s−1 with respect to the halo of the galaxy and HI absorption. We interpret this as material in outflow. We measure E(B–V) = 1.44 for the broadest, most kinematically disturbed component, corresponding to an actual Hβ flux 130 times brighter than that measured. We calculate an upper limit for the mass of the line emitting gas of order 106 M⊙ for both the intermediate and broad components. Our results are consistent with 4C 12.50 being a young radio source.
On the Reliability of Initial Conditions for Dissipationless Cosmological Simulations
Authors: Knebe Alexander , Domínguez Alvaro
Published: August 2003

We present the study of ten random realisations of a density field characterised by a cosmological power spectrum P(k) at redshift z = 50. The reliability of such initial conditions for N-body simulations is tested with respect to their correlation properties. The power spectrum P(k) and the mass variance σM(r) do not show detectable deviations from the desired behaviour in the intermediate range of scales between the mean interparticle distance and the simulation volume. The estimator for ξ(r) is too noisy to detect any reliable signal at the initial redshift z = 50. The particle distributions are then evolved forward until z = 0. This allows us to explore the cosmic variance stemming from the random nature of the initial conditions. With cosmic variance we mean the fact that a simulation represents a single realisation of the stochastic initial conditions whereas the real Universe contains many realisations of regions of the size of the box; this problem affects most importantly the scales at about the fundamental mode. We study morphological descriptors of the matter distribution such as the genus, as well as the internal properties of the largest object(s) forming in the box. We find that the scatter is at least comparable to the scatter in the fundamental mode.
Constraining the Evolution of Young Radio-Loud AGN
Authors: Snellen I. A. G. , Mack K.-H. , Schilizzi R. T. , Tschager W.
Published: August 2003

GPS and CSS radio sources are the objects of choice to investigate the evolution of young radio-loud AGN. Previous investigations, mainly based on number counts and source size distributions, indicate that GPS/CSS sources decrease significantly in radio power when evolving into old, extended objects. We suggest this is preceded by a period of increase in radio luminosity, which lasts as long as the radio source is confined within the core-radius of its host galaxy. We have selected a sample of nearby compact radio sources, unbiased by radio spectrum, to determine their luminosity function, size distribution, dynamical ages, and emission line properties in a complete and homogeneous way. First results indicate that the large majority of objects (>80%) exhibit classical GPS/CSS radio spectra, and show structures consistent with them being compact double or compact symmetric objects. This sample provides an ideal basis to further test and constrain possible evolution scenarios, and to investigate the relation between radio spectra and morphologies, orientation and Doppler boosting in samples of young radio-loud AGN, in an unbiased way.
GPS and CSS Sources — Theory and Modelling
Authors: Bicknell Geoffrey V. , Saxton Curtis J. , Sutherland Ralph S.
Published: August 2003

We review theoretical ideas that seem to be currently important for the physics of GPS and CSS radio sources. These include models for their evolution, the production of emission lines, and the origin of the low frequency turnover. We also describe the initial phases of a program of simulations that is aimed at understanding the radiative interactions between jets, lobes, and dense clouds in the nuclei of these objects.
VLBA Observations of Bright High Frequency Peakers
Authors: Tinti Sara , Dallacasa Daniele , Stanghellini Carlo , Celotti Annalisa
Published: August 2003

The anticorrelation between the turnover frequency in the radio spectrum and the projected linear size (indicative of the age in the currently favoured youth model) in powerful and intrinsically compact radio sources suggests that the youngest objects must have the highest turnover frequencies. We present preliminary results of new VLBA observations of a sample of sources peaking at frequencies higher than a few GHz, making them good candidates for being newly born sources. Our initial analysis deals with the morphological classification which allows us to study the contamination from beamed sources dominated by a single unresolved component.
Radio Spectral Variability of the Nearby GPS Galaxy PKS 1718–649
Authors: Tingay S. J. , de Kool M.
Published: August 2003

Data from new Australia Telescope Compact Array observations of a nearby gigahertz peaked spectrum radio source, PKS 1718–649, show significant variability both below and above the spectral turnover frequency during a nine month period. Simple models of synchrotron self-absorption (SSA) and free–free absorption (FFA) cannot explain the individual spectra or the spectral variability. Novel SSA or FFA models will need to be investigated in order to explain the complex variability in this source. Some potential explanations for the spectral variability are explored here but we can make no strong conclusion about which of SSA or FFA (or alternative mechanisms) causes the peaked spectrum in PKS 1718–649.
Deriving the Metallicity Distribution Function of Galactic Systems
Authors: Fenner Yeshe , Gibson Brad K.
Published: August 2003

The chemical evolution of the Milky Way is investigated using a dual-phase metal-enriched infall model in which primordial gas fuels the earliest epoch of star formation, followed by the ongoing formation of stars from newly accreted gas. The latest metallicity distribution of local K-dwarfs is reproduced by this model, which allows the Galactic thin disk to form from slightly metal-enriched gas with α-element enhancement. Our model predicts ages for the stellar halo and thin disk of 12.5 and 7.4 Gyr respectively, in agreement with empirically determined values. The model presented in this paper is compared with a similar dual-phase infall model from Chiappini et al. (2001). We discuss a degeneracy that enables both models to recover the K-dwarf metallicity distribution while yielding different star formation histories.

The metallicity distribution function (MDF) of K-dwarfs is proposed to be more directly comparable to chemical evolution model results than the G-dwarf distribution because lower mass K-dwarfs are less susceptible to stellar evolutionary effects. The K-dwarf MDF should consequently be a better probe of star formation history and provide a stronger constraint to chemical evolution models than the widely used G-dwarf MDF. The corrections that should be applied to a G-dwarf MDF are quantified for the case of the outer halo of NGC 5128.
Hi Absorption in GPS/CSS Sources
Authors: Pihlström Ylva , Conway John , Vermeulen Rene
Published: August 2003

Combining our own observations with data from the literature, we consider the incidence of HI absorption in gigahertz peaked spectrum (GPS) and compact steep spectrum (CSS) sources. Here we present our preliminary results, where we find that the smaller GPS sources (<1 kpc) on average have larger HI column densities than the larger CSS sources (>1 kpc). Both a spherical and an axi-symmetric gas distribution, with a radial power law density profile, can be used to explain this anti-correlation between projected linear size and HI column density. Since most detections occur in galaxy classified objects, we argue that if the unified schemes apply to the GPS/CSS sources, a disk distribution for the HI is more likely.
Weak CSS Sources from the FIRST Survey
Authors: Marecki Andrzej , Niezgoda Jacek , Włodarczak Jacek , Kunert Magdalena , Spencer Ralph E. , Kus Andrzej J.
Published: August 2003

We report early results of an observational campaign targeted on a sample of compact steep spectrum sources selected from the FIRST survey which are significantly weaker than those investigated before. The selection criteria and procedure are given in detail. We present here an assortment of MERLIN and VLBI observations and make some general comments based on the morphologies of the sources presented.
Location of Weak CSS Sources on the Evolutionary Path of Radio-Loud AGN
Authors: Marecki Andrzej , Spencer Ralph E. , Kunert Magdalena
Published: August 2003

According to the currently accepted paradigm compact steep spectrum (CSS) sources are precursors of larger/older objects and gigahertz peaked spectrum (GPS) sources may be earlier stages of CSS sources. In this paper we confront this paradigm with the outcome of recent observations of CSS sources that are significantly weaker than those known before. In particular we claim that not all CSS sources must end up as large scale objects; if the activity phase of an AGN's central engine is shorter than the lifetime of a large scale radio source (up to ˜108 yr) the radio source associated with such an AGN decays earlier, e.g. at the CSS stage. We point out that a theory of thermal–viscous instabilities in the accretion disks of AGN may explain many features of radio sources at all stages of their evolution.
X-ray Emission from Gigahertz Peaked/Compact Steep Spectrum Sources
Authors: Siemiginowska Aneta , Aldcroft Thomas L. , Bechtold Jill , Brunetti Gianfranco , Elvis Martin , Stanghellini Carlo
Published: August 2003

The high spatial resolution of the Chandra X-ray Observatory allows us to study the environment of GPS/CSS sources to within an arcsec of the strong compact core. We present the discovery of X-ray jets in two GPS quasars, PKS1127–145 and B2 0738+313, indicating that X-ray emission associated with the relativistic plasma is present at large distances from the GPS nucleus. We also discuss first results from Chandra observations of our GPS/CSS sample. We find that six out of ten sources show intrinsic absorption at a level which may be sufficient to confine the GPS source.
Proper Motions in Compact Symmetric Objects
Authors: Polatidis A. G. , Conway J. E.
Published: August 2003

We discuss recent measurements of proper motions of the hotspots of compact symmetric objects (CSOs). Source expansion has been detected in 10 CSOs so far and all these objects are very young (≤ 3 × 103 yr). In a few sources ages have also been estimated from energy supply and spectral ageing arguments and these estimates are comparable. This argues that these sources are close to equipartition and that standard spectral ageing models apply. Proper motion studies are now constraining hotspot accelerations, side-to-side motions, and differences in hotspot advance speeds between the two hotspots of a source. Although most CSOs are young sources their evolution is unclear. There is increasing evidence that in some objects the CSO structure represents a new phase of activity within a recurrent source.
Two-Sided Radio Jets in B1524–136
Authors: Mantovani F. , Bondi M. , Saikia D. J. , Junor W. , Salter C. J. , Ricci R.
Published: August 2003

We present global VLBI and VLBA observations of the compact steep spectrum quasar B1524–136. These observations reveal well-defined radio jets on both sides of the active nucleus. Also, the overall radio structure appears highly distorted and asymmetric with the counter-jet exhibiting several oscillations. A possible scenario is one in which jet and counter-jet are inclined at about 25° and 75° to the line of sight respectively and an environment which is dense on the jet side. Possible implications of these results are discussed.
Radio Properties of GPS and CSS Sources: Galaxies versus Quasars
Authors: Stanghellini Carlo
Published: August 2003

On the basis of the different radio properties (especially different radio morphologies) between GPS galaxies and GPS quasars, I suggest that GPS galaxies are a more homogeneous class mainly consisting of compact symmetric objects, while the majority of GPS quasars are an intrinsically different type of radio source, similar to the common flat spectrum radio sources. For CSS radio sources the difference between galaxies and quasars is less evident. This is interpreted as a bias correlated with size: samples of smaller objects are more likely to be contaminated by unrelated objects. This is consistent also with the high percentage of blazar/quasar objects present in a sample of the even smaller HFP radio sources.
The Impact of the Early Stages of Radio Source Evolution on the ISM of the Host Galaxies
Authors: Morganti R. , Tadhunter C. N. , Oosterloo T. A. , Holt J. , Tzioumis A. , Wills K.
Published: August 2003

The study of both neutral and ionised gas in young radio sources is providing key information on the effect the radio plasma has on the ISM of these objects. We present results obtained for the compact radio sources PKS 1549–79, 4C 12.50 and PKS 1814–63 and for the intermediate-size radio galaxy 3C 459. At least in the first two, low ionisation optical emission lines and HI absorption appear to be associated with the extended, but relatively quiescent, dusty cocoon surrounding the nucleus. The [OIII] lines are, on the other hand, mostly associated with the region of interaction between the radio plasma and the ISM, indicating a fast outflow from the centre. A case of fast outflow (up to ∼1000 km s-1) is also observed in HI in the radio source 4C 12.50. As the radio source evolves, any obscuring material along the radio axis is swept aside until, eventually, cavities (of the same kind as observed e.g. in Cygnus A) are hollowed out on either side of the nucleus. We may witness this phase in the evolution of a radio source in the radio galaxy 3C 459.
Radio-Excess IRAS Galaxies: Low Power CSS/GPS Sources?
Authors: Drake Catherine L. , McGregor Peter J. , Bicknell Geoffrey V. , Dopita Michael A.
Published: August 2003

Amongst our sample of radio-excess IRAS galaxies, we have identified compact steep spectrum radio sources that fall into the classes of CSS or GPS sources, but have not previously been identified as such. The sample includes objects that have radio powers as low as ˜1022 W Hz−1. We suggest that these are low-power analogues of CSS and GPS sources, with weaker radio jets. These may be precursors to FR I radio galaxies or may ‘fade’ into radio-quiet galaxies.
Symmetry Parameters of CSS Sources: Evidence of Fuelling?
Authors: Saikia D. J. , Jeyakumar S. , Mantovani F. , Salter C. J. , Spencer R. E. , Thomasson P. , Wiita P. J.
Published: August 2003

The compact steep spectrum (CSS) and gigahertz peaked spectrum (GPS) sources are widely believed to be young radio sources, with ages ≤106yr. If the activity in the nucleus is fuelled by the supply of gas, one might find evidence of this gas by studying the structural and polarisation characteristics of CSS sources and their evolution through this gas. In this paper we discuss some of the possible ‘smoking-gun’ evidence of this gas which may have triggered and fuelled the radio source.
The Polarised Bent Jet of 3C 43
Authors: Mantovani F. , Junor W. , Saikia D. J. , Salter C. J.
Published: August 2003

Radio observations of linear polarisation provide a useful probe of the physical conditions in the gaseous environments of compact steep spectrum (CSS) sources. Here, we present polarimetric VLBA observations at 8.4 GHz of the CSS quasar 3C 43. The jet in this source curves gently up to about 220 mas from the core, at which point it bends sharply, probably due to a jet–cloud encounter. Regions of polarised emission are detected along the jet, while the core component shows no significant polarisation.
III Zw 2: Evolution of a Radio Galaxy in a Nutshell
Authors: Brunthaler A. , Falcke H. , Bower G. C. , Aller M. F. , Aller H. D. , Teräsranta H. , Krichbaum T. P.
Published: August 2003

III Zw 2 shows dramatic radio outbursts roughly every five years. Here we present the light curves and VLBA observations of the latest flare with an excellent time sampling. We have detected superluminal motion with a lower limit for the apparent expansion speed of 1.25±0.09 c at 43 GHz. Spectral and spatial evolution are closely linked and the evolution of III Zw 2 in a turnover frequency vs. linear size diagram is similar to the correlation for GPS and CSS sources. Before and after this rapid expansion we observe a period of virtually no expansion. However, at 15 GHz III Zw 2 shows a constant slow expansion (∼0.6 c). The difference is qualitatively explained by optical depth effects in an ‘inflating-balloon model’, describing the evolution of radio lobes on an ultra-compact scale. The stop-and-go behaviour could be explained by a jet interacting with a molecular cloud or the molecular torus.
A Dynamical Model for the Evolution of Hot Spots in Powerful Radio Sources
Authors: Perucho M. , Martí J. M.
Published: August 2003

Compact symmetric objects are considered the young counterparts of large doubles according to advance speeds measured or inferred from spectral ageing. Here we present a simple power law model for the CSO/FR II evolution based on the study of sources with well defined hot spots. The luminosity of the hot spots is estimated under minimum energy conditions. The advance of the source is considered to proceed in ram pressure equilibrium with the ambient medium. Finally, we also assume that the jets feeding the hot spots are relativistic and have a time dependent power. Comparison with observational data points to an interpretation of the CSO–FR II evolution in terms of decreasing jet power with time.
Luminosity Evolution of Double Radio Sources
Authors: Carvalho Joel C. , O'Dea Christopher P.
Published: August 2003

We have recently developed a detailed analytical model for powerful radio sources based on the results of a series of 2-D numerical hydrodynamical simulations. Here we make use of the model results to investigate the radio source luminosity evolution. Changes in the radio spectrum due to radiation losses were calculated in two different scenarios for energy gains/losses: Kardashev–h;Pacholczyk (KP) and ‘continuous injection’ (CI). The magnetic field was calculated in two limiting cases: (1) assuming equipartition of energy between relativistic particles and fields and (2) magnetic flux conservation inside the cocoon. The effect of the surrounding medium was taken into account by considering three different ambient density profiles. The evolutionary tracks were plotted in a power–diameter (P-D) diagram and compared with the predictions of self-similar models. In general, the evolutionary tracks cannot be represented by a simple power law and have a complex form that is most probably the result of the nonself-similar evolution of the source.
Dense Plasma Torus in the GPS Galaxy NGC 1052
Authors: Kameno Seiji , Inoue Makoto , Wajima Kiyoaki , Sawada-Satoh Satoko , Shen Zhi-Qiang
Published: August 2003

We report results from nearly simultaneous pentachromatic VLBI observations towards a nearby GPS galaxy NGC 1052. The observations at 1.6 and 4.8 GHz with the VSOP, and at 2.3, 8.4, and 15.4 GHz with VLBA, provide linear resolutions of ∼0.1 pc. Convex spectra of a double-sided jet imply that synchrotron emission is obscured through foreground cold dense plasma, in terms of free–free absorption (FFA). We found a central condensation of the plasma which covers about 0.1 and 1 pc of the approaching and receding jets, respectively. A simple model with a geometrically thick plasma torus perpendicular to the jets is established to explain the asymmetric distribution of FFA opacities.
A Population Study of Faint Compact Steep Spectrum Radio Sources: Self-Similar Growth
Authors: Tschager Wolfgang , Schilizzi Richard , Röttgering Huub , Snellen Ignas , Miley George , Perley Rick
Published: August 2003

The main topic of this contribution is the investigation of the morphological self-similarity of the growth process during the gigahertz peaked spectrum (GPS) and compact steep spectrum (CSS) phase of evolving radio galaxies. By investigating a new sample of faint CSS radio sources we establish that self-similar evolution must hold for peaked spectrum sources over a wide range of luminosities as well as physical sizes. Thus, we argue that self-similarity should be regarded as an essential, intrinsic characteristic of the growth process of young radio sources, and be treated as such, and not merely as a supplementary constraint for evolution models.
High Frequency Peakers
Authors: Dallacasa Daniele
Published: August 2003

There is quite a clear anticorrelation between the intrinsic peak frequency and the overall radio source size in compact steep spectrum (CSS) and gigahertz peaked spectrum (GPS) radio sources. This feature is interpreted in terms of synchrotron self-absorption (although free–free absorption may play a role as well) of the radiation emitted by a small radio source which is growing within the inner region of the host galaxy. This leads to the hypothesis that these objects are young and that the radio source is still developing/expanding within the host galaxy itself.

Very young radio sources must have the peak in their radio spectra occurring above a few tens of gigahertz, and for this reason they are termed high frequency peakers (HFPs). These newly born radio sources must be very rare given that they spend very little time in this stage. Ho = 100 km s−1 Mpc−1 and qo = 0.5 are used throughout this paper.
Jet–Cloud Interactions in Compact Steep Spectrum Radio Sources
Authors: O'Dea C. P. , Vries W. H. de , Koekemoer A. M. , Baum S. A. , Axon D. J. , Barthel P. D. , Capetti A. , Fanti R. , Gelderman R. , Morganti R. , Tadhunter C. N.
Published: August 2003

We have obtained HST/STIS long slit spectroscopy of the aligned emission line nebulae in three compact steep spectrum (CSS) radio sources — 3C 67, 3C 277.1, and 3C 303.1. We find systematic offsets (˜300–500 kms) of the emission line velocities on one or both sides of the radio sources. We also see evidence for broad lines (FWHM ˜500 kms) and complex emission line profiles. In 3C 303.1 the data are consistent with multiple components and possibly split lines. The amplitude of the velocity variations is not so large as to exclude gravitationally-induced motions. However, the complex kinematics, the lack of a signature of Keplerian rotation, and the association of the velocity variations with the radio lobes are consistent with the observed ˜300–500 kms velocities being driven by the expansion of the radio source. Acceleration of the clouds by the bow shock is plausible given the estimated densities in the clouds and the velocities observed in the much smaller compact symmetric objects and with expansion velocities estimated from spectral ageing. This conclusion is unchanged if we consider the scenario in which the cloud acceleration is dominated by the post bow shock flow.
Rotation Measure and Opacity Asymmetry in 2134+004
Authors: Mutoh M. , Inoue M. , Kameno S. , Asada K.
Published: August 2003

Based on the free–free absorption (FFA) model of gigahertz peaked spectrum (GPS) sources, we explain both Faraday rotation asymmetry and opacity asymmetry consistently between two components of a GPS quasar 2134+004. The FFA model assumes dense plasma around the central core to produce FFA, and the difference of path lengths in the plasma toward each component could cause these asymmetries. The component that is closer to the observer has a shorter path length, and consequently, smaller opacity of FFA and lower Faraday rotation. In a simple case, the ratio of Faraday rotation between two components is a function of the ratio of path length, and is the same as the ratio of opacity. Then these two ratios are shown to be essentially the same by our observations. We could thus distinguish between near-side and far-side components by the asymmetries.
Emission Line Properties of GPS/CSS Galaxies
Authors: Koekemoer Anton M. , O'Dea Christopher P. , Baum Stefi A.
Published: August 2003

We present initial results from a program that we have begun, aimed at increasing the number of GPS and CSS sources for which good spectroscopic data are available for a variety of emission lines. We combine new observational data with previously published results to investigate whether there are any relationships between the excitation state of the gas and the radio properties of the sources, retaining distinctions between GPS and GSS galaxies and quasars. In scenarios where the youngest, most compact sources interact most strongly with the gas, it is perhaps to be expected that this can have an effect on the overall excitation state of the gas, which could therefore correlate with radio properties such as turnover frequency that plausibly trace the source size and age. However, we find a degree of scatter between the turnover frequency and gas excitation state that is several times larger than the characteristic degree of uncertainty in our line ratio measurements. This would suggest that either there is no underlying relationship between turnover frequency and excitation state, or alternatively that any potential relationship is completely diluted by variations in the intrinsic properties of the gas from one source to the next, which would thus be an important factor in determining the source properties.
Variability in GPS Sources
Authors: Jauncey D. L. , King Edward A. , Bignall Hayley E. , Lovell J. E. J. , Kedziora-Chudczer Lucyna , Tzioumis A. K. , Tingay S. J. , Macquart Jean-Pierre , McCulloch P. M.
Published: August 2003

Flux density monitoring data at 2.3 and 8.4 GHz is presented for a sample of 33 southern hemisphere GPS sources, drawn from the 2.7 GHz Parkes survey. This monitoring data, together with VLBI monitoring data, shows that a small fraction of these sources, ∼10%, vary. Their variability falls into several categories: sources whose spectral classification is, at best, ephemeral on a timescale of years; sources with a stable GPS classification that vary, but retain their classification; and a small number of sources that exhibit interstellar scintillation, but that maintain a mean GPS spectrum. Existing data on GPS sources with higher frequency peaks, ≥3 GHz, reveals that many such sources vary. However, the majority of these sources possess a GPS spectrum only during outbursts, and hence should perhaps be classified as ephemeral GPS sources. In addition, significant levels of circular polarisation have been found in a number of GPS sources, both amongst the variables and non-variables. Remarkable amongst these is PKS 1519–273, which possesses strong and variable circular polarisation, and which exhibits IDV in all Stokes parameters.
Solar-like Oscillations
Authors: Bedding Timothy R. , Kjeldsen Hans
Published: August 2003

The five-minute oscillations in the Sun have provided a wealth of information about the solar interior. After many attempts, positive detections of similar oscillations in solar-type stars have now been made. This review discusses the properties of solar-like oscillations, the methods used to observe them, and the results on individual stars. We conclude that the study of solar-like oscillations from the ground and space has an exciting future.
Free–Free Absorption and the Unified Scheme
Authors: Kameno Seiji , Inoue Makoto , Wajima Kiyoaki , Sawada-Satoh Satoko , Shen Zhi-Qiang
Published: August 2003

We report very long baseline array (VLBA) observations at 2.3, 8.4, and 15.4 GHz towards nine gigahertz peaked spectrum (GPS) sources. One Seyfert 1 galaxy, one Seyfert 2 galaxy, three radio galaxies, and four quasars were included in our survey. We obtained spatial distributions of the free–free absorption (FFA) opacity with milliarcsecond resolution for all sources. It is found that type 1 (Seyfert 1 and quasars) and type 2 (Seyfert 2 and radio galaxies) sources showed different distributions of the FFA opacities. The type 1 sources tend to show more asymmetric opacity distributions towards a double lobe, while those of the type 2 sources are rather symmetric. Our results imply that the different viewing angle of the jet causes the difference of FFA opacity along the external absorber. This idea supports the unified scheme between quasars and radio galaxies, proposed by Barthel (1989).