2,984 research outputs found
Photometric Redshifts for an Optical/Near-Infrared Catalogue in the Chandra Deep Field South
Photometric redshifts have proven a powerful tool in identifying galaxies
over a large range of lookback times. We have been generalising this technique
to incorporate the selection of candidate high redshift QSOs. We have applied
this to a large optical/near-infrared imaging survey in 6 wavebands aiming to
push farther in redshift (and fainter in luminosity) than previous studies. We
believe that study of these very faint and distant objects provides valuable
insights into galaxy formation and evolution.
Here we present work in progress and preliminary results for a catalogue of
objects detected as part of the Las Campanas Infrared Survey. This is a
stepping stone to the type of survey data that will become available in the
next few years from projects such as UKIDSS and VISTA.Comment: 4 pages LaTeX, submitted to the "Eurokiel 2002: Galaxy Evolution III:
From Simple Models to Self Consistant Approaches" Conference Proceeding
The new very small angle neutron scattering spectrometer at Laboratoire Leon Brillouin
The design and characteristics of the new very small angle neutron scattering
spectrometer under construction at the Laboratoire Leon Brillouin is described.
Its goal is to extend the range of scattering vectors magnitudes towards
2x10{-4} /A. The unique feature of this new spectrometer is a high resolution
two dimensional image plate detector sensitive to neutrons. The wavelength
selection is achieved by a double reflection supermirror monochromator and the
collimator uses a novel multibeam design
Radio-optical orientation of E/S0 galaxies: APM versus FIRST
We searched for extended radio sources in isolated E/S0 galaxies comparing
the FIRST and APM catalogues for a single POSS plate. The 35 most promising
candidates were visually inspected on the Digitized Sky Survey (DSS) and on
FIRST images: we find several spirals and interacting galaxies and a few E/S0s
with very weak, marginally extended radio cores. The only double-lobed
(previously known) radio source is a dumbbell. For the rest of the objects, all
hosting small and weak radio sources, the DSS is inadequate to determine
morphological types. Thus a significant increase in sample size will be a major
effort.Comment: 2 pages; no figures; to appear in Proc. "Observational Cosmology with
the New Radio Surveys", eds. M. Bremer, N. Jackson & I. Perez-Fournon, Kluwer
Acad. Pres
Picosecond photoisomerization and rotational reorientation dynamics in solution
The trans-cis isomerization rates for stiff-diphenylbutadiene (S-DPB) in n-alkane solvents were measured using single photon counting methods and the rotational reorientation times ÏR for S-DPB and trans stilbene were obtained by picosecond polarization spectroscopy. In neither case did ÏR VS viscosity show Stokes-Einstein-Debye (SED) behavior. The values of ÏR were used to calculate the angular velocity correlation frequencies ÎČ using the Hubbard relation. The variation of isomerization rate with ÎČ was found to be predicted well by the Kramers equation when barrier frequencies of 154 cm-1 for stilbene and 16 cm-1 for S-DPB were used. This Kramers-Hubbard fit finesses questions regarding the validity of the one dimensional Kramers model and focuses attention on the SED equation. The dynamical relationship between the torsional friction, important in isomerization, and rotational friction, which determines the overall angular motion of the molecules, is discussed
Efficient use of simultaneous multi-band observations for variable star analysis
The luminosity changes of most types of variable stars are correlated in the
different wavelengths, and these correlations may be exploited for several
purposes: for variability detection, for distinction of microvariability from
noise, for period search or for classification. Principal component analysis is
a simple and well-developed statistical tool to analyze correlated data. We
will discuss its use on variable objects of Stripe 82 of the Sloan Digital Sky
Survey, with the aim of identifying new RR Lyrae and SX Phoenicis-type
candidates. The application is not straightforward because of different noise
levels in the different bands, the presence of outliers that can be confused
with real extreme observations, under- or overestimated errors and the
dependence of errors on the magnitudes. These particularities require robust
methods to be applied together with the principal component analysis. The
results show that PCA is a valuable aid in variability analysis with multi-band
data.Comment: 8 pages, 5 figures, Workshop on Astrostatistics and Data Mining in
Astronomical Databases, May 29-June 4 2011, La Palm
Language abnormality in deaf people with schizophrenia: a problem with classifiers
Introduction: Although there is evidence for language abnormality in schizophrenia, few studies have examined sign language in deaf patients with the disorder. This is of potential interest because a hallmark of sign languages is their use of classifiers (semantic or entity classifiers), a reference-tracking device with few if any parallels in spoken languages. This study aimed to examine classifier production and comprehension in deaf signing adults with schizophrenia. Method: Fourteen profoundly deaf signing adults with schizophrenia and 35 age- and IQ-matched deaf healthy controls completed a battery of tests assessing classifier and noun comprehension and production. Results: The patients showed poorer performance than the healthy controls on comprehension and production of both nouns and entity classifiers, with the deficit being most marked in the production of classifiers. Classifier production errors affected handshape rather than other parameters such as movement and location. Conclusions: The findings suggest that schizophrenia affects language production in deaf patients with schizophrenia in a unique way not seen in hearing patients
A companion to a quasar at redshift 4.7
There is a growing consensus that the emergence of quasars at high redshifts
is related to the onset of galaxy formation, suggesting that the detection of
concentrations of gas accompanying such quasars should provide clues about the
early history of galaxies. Quasar companions have been recently identified at
redshifts up to . Here we report observations of Lyman-
emission (a tracer of ionised hydrogen) from the companion to a quasar at
=4.702, corresponding to a time when the Universe was less than ten per cent
of its present age. We argue that most of the emission arises in a gaseous
nebula that has been photoionised by the quasar, but an additional component of
continuum light -perhaps quasar light scattered from dust in the companion
body, or emission from young stars within the nebula- appears necessary to
explain the observations. These observations may be indicative of the first
stages in the assembly of galaxy-sized structures.Comment: 8 pages, 4 figures, plain LaTeX. Accepted for publication in Natur
The inevitable youthfulness of known high-redshift radio galaxies
Radio galaxies can be seen out to very high redshifts, where in principle
they can serve as probes of the early evolution of the Universe. Here we show
that for any model of radio-galaxy evolution in which the luminosity decreases
with time after an initial rapid increase (that is, essentially all reasonable
models), all observable high-redshift radio-galaxies must be seen when the
lobes are less than 10^7 years old. This means that high-redshift radio
galaxies can be used as a high-time-resolution probe of evolution in the early
Universe. Moreover, this result helps to explain many observed trends of
radio-galaxy properties with redshift [(i) the `alignment effect' of optical
emission along radio-jet axes, (ii) the increased distortion in radio
structure, (iii) the decrease in physical sizes, (iv) the increase in radio
depolarisation, and (v) the increase in dust emission] without needing to
invoke explanations based on cosmology or strong evolution of the surrounding
intergalactic medium with cosmic time, thereby avoiding conflict with current
theories of structure formation.Comment: To appear in Nature. 4 pages, 2 colour figures available on request.
Also available at http://www-astro.physics.ox.ac.uk/~km
Decadal changes of the Western Arabian sea ecosystem
Historical data from oceanographic expeditions and remotely sensed data on outgoing longwave radiation, temperature, wind speed and ocean color in the western Arabian Sea (1950â2010) were used to investigate decadal trends in the physical and biochemical properties of the upper 300 m. 72 % of the 29,043 vertical profiles retrieved originated from USA and UK expeditions. Increasing outgoing longwave radiation, surface air temperatures and sea surface temperature were identified on decadal timescales. These were well correlated with decreasing wind speeds associated with a reduced Siberian High atmospheric anomaly. Shoaling of the oxycline and nitracline was observed as well as acidification of the upper 300 m. These physical and chemical changes were accompanied by declining chlorophyll-a concentrations, vertical macrofaunal habitat compression, declining sardine landings and an increase of fish kill incidents along the Omani coast
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