24 research outputs found
The SuperCOSMOS Sky Survey. Paper III: Astrometry
In this, the third in a series of three papers concerning the SuperCOSMOS Sky
Survey, we describe the astrometric properties of the database. We describe the
algorithms employed in the derivation of the astrometric parameters of the
data, and demonstrate their accuracies by comparison with external datasets
using the first release of data, the South Galactic Cap survey. We show that
the celestial coordinates, which are tied to the International Celestial
Reference Frame via the Tycho-2 reference catalogue, are accurate to better
than +/- 0.2 arcsec at J,R=19,18 rising to +/- 0.3 arcsec at J,R=22,21 with
positional dependent systematic effects from bright to faint magnitudes at the
+/- 0.1 arcsec level. The proper motion measurements are shown to be accurate
to typically +/- 10 mas/yr at J,R=19,18 rising to +/- 50 mas/yr at J,R=22,21
and are tied to zero using the extragalactic reference frame. We show that the
zeropoint errors in the proper motions are 17 and are no
larger than 10 mas/yr for R < 17 mas/yr.Comment: 15 pages, 12 figures; accepted for publication in MNRA
The SuperCOSMOS Sky Survey. Paper II: Image detection, parameterisation, classification and photometry
In this, the second in a series of three papers concerning the SuperCOSMOS
Sky Survey, we describe the methods for image detection, parameterisation,
classification and photometry. We demonstrate the internal and external
accuracy of our object parameters. Using examples from the first release of
data, the South Galactic Cap survey, we show that our image detection
completeness is close to 100% to within 1.5 mag of the nominal plate limits. We
show that for the Bj survey data, the image classification is externally > 99%
reliable to Bj = 19.5. Internally, the image classification is reliable at a
level of > 90% to Bj=21, R=19. The photometric accuracy of our data is
typically 0.3 mag with respect to external data for m > 15. Internally, the
relative photometric accuracy in restricted position and magnitude ranges can
be as accurate as 5% for well exposed stellar images. Colours (B-R or R-I) are
externally accurate to 0.07 mag at Bj = 16.5 rising to 0.16 mag at Bj = 20.Comment: 22 pages, 16 figures; accepted for publication in MNRA
Orientation of Galaxies in the Local Supercluster: A Review
The progress of the studies on the orientation of galaxies in the Local
Supercluster (LSC) is reviewed and a summary of recent results is given.
Following a brief introduction of the LSC, we describe the results of early
studies based on two-dimensional analysis, which were mostly not conclusive. We
describe next the three-dimensional analysis, which is used widely today.
Difficulties and systematic effects are explained and the importance of
selection effects is described. Then, results based on the new method and
modern databases are given, which are summarized as follows. When the LSC is
seen as a whole, galaxy planes tend to align perpendicular to the LSC plane
with lenticulars showing the most pronounced tendency. Projections onto the LSC
plane of the spin vectors of Virgo cluster member galaxies, and to some extent,
those of the total LSC galaxies, tend to point to the Virgo cluster center.
This tendency is more pronounced for lenticulars than for spirals. It is
suggested that 'field' galaxies, i.e., those which do not belong to groups with
more than three members, may be better objects than other galaxies to probe the
information at the early epoch of the LSC formation through the analysis of
galaxy orientations. Field lenticulars show a pronounced anisotropic
distribution of spin vectors in the sense that they lay their spin vectors
parallel to the LSC plane while field spirals show an isotropic spin-vector
distribution.Comment: 21 pages, 10 figures; Accepted for publication in Astrophysics and
Space Scienc
Whole-genome sequencing reveals host factors underlying critical COVID-19
Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease