54 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
PKS 0537-441: extended [O II] emission and a binary QSO?
We present high-resolution imaging and low-resolution spectroscopy of the BL
Lac object PKS 0537-441 (z = 0.893) and its environment. The observations were
designed to clarify, whether the properties of PKS 0537-441 are affected by
gravitational microlensing, or whether PKS 0537-441 and its environment act as
a lensing system itself. Our observations show that neither case seems to be
likely. We did not find a galaxy along the line-of-sight to the BL Lac as
claimed previously, our spectroscopy shows that none of the four closest
companion galaxies is at high redshift. Two of the four nearby companion
galaxies to PKS 0537-441 are within 200 km/s of the systemic velocity of the BL
Lac (z = 0.892 and 0.895, respectively). The third companion galaxy is at
higher redshift (z = 0.947). The fourth companion galaxy shows evidence of Mg
II absorption redwards of its systemic velocity and is perhaps a mini low
ionization BAL QSO at z = 0.885. If the latter can be confirmed, PKS 0537-441
is the first BL Lacertae object being a member of a binary Quasar. We also
detected extended [O II] emission in the off-nuclear spectrum of PKS 05371-441,
which is most likely due to photoionization from the active nucleus.
Alternatively, the extended [O II] emission is due to jet-cloud interaction
with the counterjet of PKS 0537-441. Our clustering analysis indicates that PKS
0537-441 is located in a cluster environment as rich as Abell type 0-1. This is
supported by the detection of four galaxies in the field with similar redshifts
as the BL Lac (Delta z < 0.002). We found serendipitously even more galaxies at
somewhat higher redshifts (z = 0.9-1). Thus, PKS0537-441 might be located in
front of a galaxy cluster at somewhat higher redshift or even be part of a
large-scale structure with an extension towards the BL Lac.Comment: 13 pages, 9 figures, accepted for publication in A&
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 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
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
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