64 research outputs found
Cosmology with redshift surveys of radio sources
We use the K-z relation for radio galaxies to illustrate why it has proved
difficult to obtain definitive cosmological results from studies based entirely
on catalogues of the brightest radio sources, e.g. 3C. To improve on this
situation we have been undertaking redshift surveys of complete samples drawn
from the fainter 6C and 7C radio catalogues. We describe these surveys, and
illustrate the new studies they are allowing. We also discuss our `filtered' 6C
redshift surveys: these have led to the discovery of a radio galaxy at z=4.4,
and are sensitive to similar objects at higher redshift provided the space
density of these objects is not declining too rapidly with z. There is
currently no direct evidence for a sharp decline in the space density of radio
galaxies for z > 4, a result only barely consistent with the observed decline
of flat-spectrum radio quasars.Comment: 8 pages Latex, To appear in the "Cosmology with the New Radio
Surveys" Conference - Tenerife 13-15 January 199
A complete sample of quasars from the 7C redshift survey
We present details of a new sample of radio-loud quasars drawn from 0.013 sr
of the 7C Redshift Survey. This sample is small (21 quasars) but complete in
that every object with an unresolved nucleus and/or broad emission lines with
S(151MHz) > 0.5 Jy has been discovered. The dependence of the quasar fraction
with redshift and radio luminosity is investigated, providing new evidence
supporting the unification of radio-loud quasars and powerful radio galaxies.
This 7C sample is compared with optically-selected quasars, in order to
determine whether there are systematic biases in the different selection
techniques. There are no lightly reddened (Av approx. 1) quasars in our sample
amongst the 14 with z < 2. The discovery of a reddened quasar at z = 2.034 and
its implications are discussed. A tight correlation between radio luminosity
and optical/near infrared continuum luminosity for a subset of the sample is
also found.Comment: 6 pages Latex, To appear in the "Cosmology with the New Radio
Surveys" Conference - Tenerife 13-15 January 199
H-ATLAS/GAMA: The nature and characteristics of optically red galaxies detected at submillimetre wavelengths
We combine Herschel/SPIRE sub-millimeter (submm) observations with existing multi-wavelength data to investigate the characteristics of low redshift, optically red galaxies detected in submm bands. We select a sample of galaxies in the redshift range 0.01z0.2, having >5 detections in the SPIRE 250 micron submm waveband. Sources are then divided into two sub-samples of and galaxies, based on their UV-optical colours. Galaxies in the sample account for 4.2 per cent of the total number of sources with stellar masses M10 Solar-mass. Following visual classification of the galaxies, we find that 30 per cent of them are early-type galaxies and 40 per cent are spirals. The colour of the -spiral galaxies could be the result of their highly inclined orientation and/or a strong contribution of the old stellar population. It is found that irrespective of their morphological types, and sources occupy environments with more or less similar densities (i.e., the parameter). From the analysis of the spectral energy distributions (SEDs) of galaxies in our samples based on MAGPHYS, we find that galaxies in the sample (of any morphological type) have dust masses similar to those in the sample (i.e. normal spiral/star-forming systems). However, in comparison to the -spirals and in particular systems, -ellipticals have lower mean dust-to-stellar mass ratios. Besides galaxies in the -elliptical sample have much lower mean star-formation/specific-star-formation rates in contrast to their counterparts in the sample. Our results support a scenario where dust in early-type systems is likely to be of an external origin
Effects of manganese on fat snook Centropomus parallelus (Carangaria: Centropomidae) exposed to different temperatures
A review of zoonotic infection risks associated with the wild meat trade in Malaysia.
The overhunting of wildlife for food and commercial gain presents a major threat to biodiversity in tropical forests and poses health risks to humans from contact with wild animals. Using a recent survey of wildlife offered at wild meat markets in Malaysia as a basis, we review the literature to determine the potential zoonotic infection risks from hunting, butchering and consuming the species offered. We also determine which taxa potentially host the highest number of pathogens and discuss the significant disease risks from traded wildlife, considering how cultural practices influence zoonotic transmission. We identify 51 zoonotic pathogens (16 viruses, 19 bacteria and 16 parasites) potentially hosted by wildlife and describe the human health risks. The Suidae and the Cervidae families potentially host the highest number of pathogens. We conclude that there are substantial gaps in our knowledge of zoonotic pathogens and recommend performing microbial food safety risk assessments to assess the hazards of wild meat consumption. Overall, there may be considerable zoonotic risks to people involved in the hunting, butchering or consumption of wild meat in Southeast Asia, and these should be considered in public health strategies
Publisher Correction: Discovery of rare variants associated with blood pressure regulation through meta-analysis of 1.3 million individuals
SARS-CoV-2 lineage dynamics in England from September to November 2021: high diversity of Delta sub-lineages and increased transmissibility of AY.4.2
Background: Since the emergence of SARS-CoV-2, evolutionary pressure has driven large increases in the transmissibility of the virus. However, with increasing levels of immunity through vaccination and natural infection the evolutionary pressure will switch towards immune escape. Genomic surveillance in regions of high immunity is crucial in detecting emerging variants that can more successfully navigate the immune landscape. Methods: We present phylogenetic relationships and lineage dynamics within England (a country with high levels of immunity), as inferred from a random community sample of individuals who provided a self-administered throat and nose swab for rt-PCR testing as part of the REal-time Assessment of Community Transmission-1 (REACT-1) study. During round 14 (9 September–27 September 2021) and 15 (19 October–5 November 2021) lineages were determined for 1322 positive individuals, with 27.1% of those which reported their symptom status reporting no symptoms in the previous month. Results: We identified 44 unique lineages, all of which were Delta or Delta sub-lineages, and found a reduction in their mutation rate over the study period. The proportion of the Delta sub-lineage AY.4.2 was increasing, with a reproduction number 15% (95% CI 8–23%) greater than the most prevalent lineage, AY.4. Further, AY.4.2 was less associated with the most predictive COVID-19 symptoms (p = 0.029) and had a reduced mutation rate (p = 0.050). Both AY.4.2 and AY.4 were found to be geographically clustered in September but this was no longer the case by late October/early November, with only the lineage AY.6 exhibiting clustering towards the South of England. Conclusions: As SARS-CoV-2 moves towards endemicity and new variants emerge, genomic data obtained from random community samples can augment routine surveillance data without the potential biases introduced due to higher sampling rates of symptomatic individuals. © 2022, The Author(s)
DETECTION OF A LARGE MASS OF DUST IN A RADIO GALAXY AT REDSHIFT Z=3.8
ELLIPTICAL galaxies are thought to have formed most of their stars in a rapid burst in the early Universe1, but an unambiguous example of a 'primaeval' elliptical galaxy (one undergoing its first major burst of star formation) has yet to be discovered. High-redshift radio galaxies are among the most promising candidates2'3, because their low-redshift counterparts are identified exclusively with ellipticals, but the presence of an active nucleus complicates the analysis of their evolutionary state from optical-infrared observations3"5. The failure of optical searches to detect primaeval ellipticals6"9 suggests that they may be very dusty, prompting us to search for thermal emission from the dust, which will be red-shifted to submillimetre wavelengths in our reference frame. Our detection of submillimetre emission from the radio galaxy 4C41.17, reported here, suggests that it contains a large mass of dust, probably located in a dust lane obscuring the centre of the galaxy10"14. The observations are consistent with the recent occurrence of a massive burst of star formation, but probably not the first such episode. We conclude that this galaxy was already in the final stages of its formation at a look-back time of 12-15 billion years
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