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S. Dye,
S. J. Warren,
N. C. Hambly,
N. J. G. Cross,
S. T. Hodgkin,
M. J. Irwin,
A. Lawrence,
A. J. Adamson,
O. Almaini,
A. C. Edge, [......],
D. J. Pinfield,
M. G. Rawlings,
M. A. Read,
M. Riello,
K. Sekiguchi,
A. J. Smith,
E. T. W. Sutorius,
W. Varricatt,
N. A. Walton, S. J. Weatherley
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ABSTRACT: This paper defines the UKIRT Infrared Deep Sky Survey (UKIDSS) Early Data Release (EDR). UKIDSS is a set of five large near-infrared surveys being undertaken with the United Kingdom Infrared Telescope Wide Field Camera (WFCAM). The programme began in 2005 May and has an expected duration of 7 yr. Each survey uses some or all of the broad-band filter complement ZY JHK. The EDR is the first public release of data to the European Southern Observatory (ESO) community. All worldwide releases occur after a delay of 18 months from the ESO release. The EDR provides a small sample data set, ∼50 deg2 (about 1 per cent of the whole of UKIDSS), that is a lower limit to the expected quality of future survey data releases. In addition, an EDR+ data set contains all EDR data plus extra data of similar quality, but for areas not observed in all of the required filters (amounting to ∼220 deg2). The first large data release, DR1, will occur in mid-2006. We provide details of the observational implementation, the data reduction, the astrometric and photometric calibration and the quality control procedures. We summarize the data coverage and quality (seeing, ellipticity, photometricity, depth) for each survey and give a brief guide to accessing the images and catalogues from the WFCAM Science Archive.
Monthly Notices of the Royal Astronomical Society 09/2006; 372(3):1227 - 1252. · 4.90 Impact Factor
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ABSTRACT: We present the detection of [O iii] emission lines from the galaxies responsible for two high-redshift z > 1.75 damped Lyman-α (DLA) absorption lines. We find two sources of [O iii] emission corresponding to the z= 1.92 DLA absorber towards the quasar Q 2206−1958, and we also detect [O iii] emission from the galaxy responsible for the z= 3.10 DLA absorber towards the quasar 2233.9+1381. These are the first detections of rest-frame optical emission lines from high-redshift DLA galaxies. Unlike the Lyα line, the [O iii] line provides a measure of the systemic velocity of the galaxy. We compare the [O iii] redshifts with the velocity profile of the low-ionization metal lines in these two absorbers, with the goal of distinguishing between the model of Prochaska and Wolfe of DLA absorbers as large rapidly rotating cold thick discs, and the standard hierarchical cold dark matter model of structure formation, in which DLAs arise in protogalactic fragments. We find some discrepancies with the predictions of the former model. Furthermore, the image of the DLA galaxy towards Q 2206−1958 shows a complex disturbed morphology, which is more in accord with the hierarchical picture. We use the properties of the rest-frame optical emission lines to further explore the question posed by Møller et al.: are high-redshift DLA galaxies Lyman-break galaxies (LBGs) selected by gas cross-section? The measured velocity dispersions of the DLA galaxies are in agreement with this picture, while the data on the [O iii] luminosities and the velocity differences between the Lyα and [O iii] lines are inconclusive, as there are insufficient LBG measurements overlapping in luminosity. Finally, we estimate the star formation rates in these two DLA galaxies, using a variety of diagnostics, and include a discussion of the extent to which the [O iii] line is useful for this purpose.
Monthly Notices of the Royal Astronomical Society 03/2005; 358(3):985 - 997. · 4.90 Impact Factor
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ABSTRACT: We present the detection of [OIII] emission lines from the galaxies
responsible for two high-redshift z>1.75 damped Lyman-alpha (DLA) absorption
lines. These are the first detections of rest-frame optical emission lines from
high-redshift DLA galaxies. Unlike the Lyman-alpha line, the [OIII] line
provides a measure of the systemic velocity of the galaxy. We compare the
[OIII] redshifts with the velocity profile of the low-ionisation metal lines in
these two absorbers, with the goal of distinguishing between the model of
Prochaska and Wolfe of DLA absorbers as large rapidly rotating cold thick
discs, and the standard hierarchical CDM model of structure formation, in which
DLAs arise in protogalactic fragments. We find some discrepancies with the
predictions of the former model. Furthermore the image of the DLA galaxy
towards Q2206-1958 shows a complex disturbed morphology, which is more in
accord with the hierarchical picture. We use the properties of the rest-frame
optical emission lines to further explore the question posed by Moller et al.:
are high-redshift DLA galaxies Lyman-break galaxies (LBGs) selected by gas
cross section? The measured velocity dispersions of the DLA galaxies are in
agreement with this picture, while the data on the [OIII] luminosities and the
velocity differences between the Lyman-alpha and [OIII] lines are inconclusive,
as there are insufficient LBG measurements overlapping in luminosity. Finally
we estimate the star formation rates in these two DLA galaxies, using a variety
of diagnostics, and include a discussion of the extent to which the [OIII] line
is useful for this purpose. (abridged)
01/2005;
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ABSTRACT: We present a combined galaxy-quasar approach to template-fitting photometric redshift techniques and show the method to be a powerful one. The code (ImpZ) is presented, developed and applied to two spectroscopic redshift catalogues, namely the Isaac Newton Telescope Wide Angle Survey ELAIS N1 and N2 fields and the Chandra Deep Field North. In particular, optical size information is used to improve the redshift determination. The success of the code is shown to be very good with Delta z/(1+z) constrained to within 0.1 for 92 per cent of the galaxies in our sample. The extension of template-fitting to quasars is found to be reasonable with Delta z/(1+z) constrained to within 0.25 for 68 per cent of the quasars in our sample. Various template extensions into the far-UV are also tested.
07/2004;
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ABSTRACT: In a recent paper Pello et al. reported observations of a faint galaxy, gravitationally lensed by the galaxy cluster Abell 1835. Deep J-band spectroscopy revealed a weak emission line near 1.34 microns, detected in two spectra with different central wavelengths. The line was interpreted as Lyman-alpha at redshift z=10.0. This interpretation is supported by the broad-band photometric spectral energy distribution, and by the location of the galaxy close to the lens critical line for this redshift. We have reanalysed the two spectra, just released from the data archive. Our analysis includes allowance for wavelength shifts due to transverse drift of the object in the slit. We do not detect a significant emission line at the reported location, or nearby, at either grating setting, nor in the combined spectrum. We provide a possible explanation for the reported detection as due to spurious positive flux introduced in the sky-subtraction stage as a result of variable hot pixels. We provide our final reduced 2D frame, and corresponding error array. Comment: 4 pages, 1 figure. To appear in A&A Letters. Added possible explanation for reported emission line as due to variable hot pixels
07/2004;
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ABSTRACT: We revisit the possibility that we inhabit a compact multi-connected flat, or nearly flat, Universe. Analysis of COBE data has shown that, for such a case, the size of the fundamental domain must be a substantial fraction of the horizon size. Nevertheless, there could be several copies of the Universe within the horizon. If the Milky Way was once a quasar we might detect its ‘ghost’ images. Using new large quasar catalogues we repeat the search by Fagundes & Wichoski for antipodal quasar pairs. By applying linear theory to account for the peculiar velocity of the Local Group, we are able to narrow the search radius to 134 arcsec. We find seven candidate antipodal quasar pairs within this search radius. However, a similar number would be expected by chance. We argue that, even with larger quasar catalogues, and more accurate values of the cosmological parameters, it is unlikely to be possible to identify putative ghost pairs unambiguously, because of the uncertainty of the correction for peculiar motion of the Milky Way.
Monthly Notices of the Royal Astronomical Society 05/2003; 342(1):L9 - L13. · 4.90 Impact Factor
