23 research outputs found
The FORS Deep Field: Field selection, photometric observations and photometric catalog
The FORS Deep Field project is a multi-colour, multi-object spectroscopic
investigation of an approx. 7 times 7 region near the south galactic pole based
mostly on observations carried out with the FORS instruments attached to the
VLT telescopes. It includes the QSO Q 0103-260 (z = 3.36). The goal of this
study is to improve our understanding of the formation and evolution of
galaxies in the young Universe. In this paper the field selection, the
photometric observations, and the data reduction are described. The source
detection and photometry of objects in the FORS Deep Field is discussed in
detail. A combined B and I selected UBgRIJKs photometric catalog of 8753
objects in the FDF is presented and its properties are briefly discussed. The
formal 50% completeness limits for point sources, derived from the co-added
images, are 25.64, 27.69, 26.86, 26.68, 26.37, 23.60 and 21.57 in U, B, g, R,
I, J and Ks (Vega-system), respectively. A comparison of the number counts in
the FORS Deep Field to those derived in other deep field surveys shows very
good agreement.Comment: 15 pages, 11 figures (included), accepted for publication in A&
The UKIDSS Galactic Plane Survey
'The definitive version is available at www.blackwell-synergy.com .' Copyright Blackwell Publishing DOI: 10.1111/j.1365-2966.2008.13924.xThe UKIDSS Galactic Plane Survey (GPS) is one of the five near-infrared Public Legacy Surveys that are being undertaken by the UKIDSS consortium, using the Wide Field Camera on the United Kingdom Infrared TelescopePeer reviewe
Archiving multi-epoch data and the discovery of variables in the near infrared
We present a description of the design and usage of a new synoptic pipeline
and database model for time series photometry in the VISTA Data Flow System
(VDFS). All UKIRT-WFCAM data and most of the VISTA main survey data will be
processed and archived by the VDFS. Much of these data are multi-epoch, useful
for finding moving and variable objects. Our new database design allows the
users to easily find rare objects of these types amongst the huge volume of
data being produced by modern survey telescopes. Its effectiveness is
demonstrated through examples using Data Release 5 of the UKIDSS Deep
Extragalactic Survey (DXS) and the WFCAM standard star data. The synoptic
pipeline provides additional quality control and calibration to these data in
the process of generating accurate light-curves. We find that 0.6+-0.1% of
stars and 2.3+-0.6% of galaxies in the UKIDSS-DXS with K<15 mag are variable
with amplitudes \Delta K>0.015 magComment: 30 pages, 31 figures, MNRAS, in press Minor changes from previous
version due to refereeing and proof-readin
The UKIRT Hemisphere Survey: Definition and Full J-band Data Release
This paper defines the UK Infra-red Telescope (UKIRT) Hemisphere Survey (UHS) and release of the complete J-band dataset. The UHS provides continuous coverage in the northern hemisphere from a declination of 0 deg to 60 deg by combining the existing Large Area Survey, Galactic Plane Survey and Galactic Clusters Survey conducted under the UKIRT Infra-red Deep Sky Survey (UKIDSS) programme with a new additional ~12,700 sq.deg area not covered by UKIDSS. This data release includes J-band imaging and source catalogues over the new area, which, together with UKIDSS, completes the J-band UHS coverage over the full ~17,900 sq.deg area. 98 per cent of the data in this release have passed quality control criteria, the remaining 2 per cent being scheduled for re-observation. The median 5-sigma point source sensitivity of the released data is 19.6 mag (Vega). The median full width at half-maximum of the point spread function across the dataset is 0.75 arcsec. In this paper, we outline the survey management, data acquisition, processing and calibration, quality control and archiving as well as summarising the characteristics of the released data products. The data are initially available to a limited consortium with a world-wide release scheduled for August 2018
The GLEAMing of the first supermassive black holes: II. A new sample of high-redshift radio galaxy candidates
While unobscured and radio-quiet active galactic nuclei are regularly being
found at redshifts , their obscured and radio-loud counterparts remain
elusive. We build upon our successful pilot study, presenting a new sample of
low-frequency-selected candidate high-redshift radio galaxies (HzRGs) over a
sky area twenty times larger. We have refined our selection technique, in which
we select sources with curved radio spectra between 72-231 MHz from the
GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. In
combination with the requirements that our GLEAM-selected HzRG candidates have
compact radio morphologies and be undetected in near-infrared -band
imaging from the Visible and Infrared Survey Telescope for Astronomy
Kilo-degree Infrared Galaxy (VIKING) survey, we find 51 new candidate HzRGs
over a sky area of approximately 1200 deg. Our sample also includes two
sources from the pilot study: the second-most distant radio galaxy currently
known, at , with another source potentially at . We present
our refined selection technique and analyse the properties of the sample. We
model the broadband radio spectra between 74 MHz and 9 GHz by supplementing the
GLEAM data with both publicly available data and new observations from the
Australia Telescope Compact Array at 5.5 and 9 GHz. In addition, deep -band imaging from the High-Acuity Widefield -band Imager (HAWK-I) on the
Very Large Telescope and from the Southern Herschel Astrophysical Terahertz
Large Area Survey Regions -band Survey (SHARKS) is presented for
five sources. We discuss the prospects of finding very distant radio galaxies
in our sample, potentially within the epoch of reionisation at .Comment: 49 pages, 3 figures (one of which is a multi-page figure with 102
separate panels), 9 tables, accepted for publication in PAS
Patterns of long‐term vegetation change vary between different types of semi‐natural grasslands in Western and Central Europe
Questions: Has plant species richness in semi‐natural grasslands changed over recent decades? Do the temporal trends of habitat specialists differ from those of habitat generalists? Has there been a homogenization of the grassland vegetation?
Location: Different regions in Germany and the UK.
Methods: We conducted a formal meta‐analysis of re‐survey vegetation studies of semi‐natural grasslands. In total, 23 data sets were compiled, spanning up to 75 years between the surveys, including 13 data sets from wet grasslands, six from dry grasslands and four from other grassland types. Edaphic conditions were assessed using mean Ellenberg indicator values for soil moisture, nitrogen and pH. Changes in species richness and environmental variables were evaluated using response ratios.
Results: In most wet grasslands, total species richness declined over time, while habitat specialists almost completely vanished. The number of species losses increased with increasing time between the surveys and were associated with a strong decrease in soil moisture and higher soil nutrient contents. Wet grasslands in nature reserves showed no such changes or even opposite trends. In dry grasslands and other grassland types, total species richness did not consistently change, but the number or proportions of habitat specialists declined. There were also considerable changes in species composition, especially in wet grasslands that often have been converted into intensively managed, highly productive meadows or pastures. We did not find a general homogenization of the vegetation in any of the grassland types.
Conclusions: The results document the widespread deterioration of semi‐natural grasslands, especially of those types that can easily be transformed to high production grasslands. The main causes for the loss of grassland specialists are changed management in combination with increased fertilization and nitrogen deposition. Dry grasslands are most resistant to change, but also show a long‐term trend towards an increase in more mesotrophic species
The WFCAM Science Archive
We describe the WFCAM Science Archive (WSA), which is the primary point of
access for users of data from the wide-field infrared camera WFCAM on the
United Kingdom Infrared Telescope (UKIRT), especially science catalogue
products from the UKIRT Infrared Deep Sky Survey (UKIDSS). We describe the
database design with emphasis on those aspects of the system that enable users
to fully exploit the survey datasets in a variety of different ways. We give
details of the database-driven curation applications that take data from the
standard nightly pipeline-processed and calibrated files for the production of
science-ready survey datasets. We describe the fundamentals of querying
relational databases with a set of astronomy usage examples, and illustrate the
results.Comment: 28 pages, 18 figures; accepted for publication in MNRAS (2007
November 8