5,002 research outputs found

    An Early Bronze Age 'dagger grave' from Rameldry Farm, near Kingskettle, Fife

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    In February 2000, ploughing disturbed the capstone of a cist, located on the side of a prominent knowe at Rameldry Farm, near Kingskettle in central Fife. Excavation by Headland Archaeology Ltd on behalf of Historic Scotland revealed a short cist which contained the crouched inhumation of a man aged 40-50, who had suffered from arthritis, some tooth loss and possibly Paget's Disease. He had been buried wearing a garment adorned with six V-pelforated buttons. Five of these are of Whitby jet (including one with unique decoration including inlaid tin); the sixth is of the mineral lizardite, and has an enigmatic coating, possibly a glaze. Behind his shoulder was a dagger, of 'Milston type (East Kennet variant) it had had a fancy horn hilt and a scabbard lined with animal skin. The scabbard yielded two A MS radiocarbon dates, with a mean value of 2280-1970 cal Bc at 2

    The Number Density of Intermediate and High Luminosity Active Galactic Nuclei at z~2-3

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    We use the combination of the 2 Ms Chandra X-ray image, new J and H band images, and the Spitzer IRAC and MIPS images of the Chandra Deep Field-North to obtain high spectroscopic and photometric redshift completeness of high and intermediate X-ray luminosity sources in the redshift interval z=2-3. We measure the number densities of z=2-3 active galactic nuclei (AGNs) and broad-line AGNs in the rest-frame 2-8 keV luminosity intervals 10^44-10^45 and 10^43-10^44 ergs/s and compare with previous lower redshift results. We confirm a decline in the number densities of intermediate-luminosity sources at z>1. We also measure the number density of z=2-3 AGNs in the luminosity interval 10^43-10^44.5 ergs/s and compare with previous low and high-redshift results. Again, we find a decline in the number densities at z>1. In both cases, we can rule out the hypothesis that the number densities remain flat to z=2-3 at above the 5-sigma level.Comment: 8 pages, Accepted by The Astrophysical Journal (scheduled for 10 Dec 2005

    Star Formation History since z = 1.5 as Inferred from Rest-Frame Ultaviolet Luminosity Density Evolution

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    We investigate the evolution of the universal rest-frame ultraviolet luminosity density from z = 1.5 to the present. We analyze an extensive sample of multicolor data (U', B, V = 24.5) plus spectroscopic redshifts from the Hawaii Survey Fields and the Hubble Deep Field. Our multicolor data allow us to select our sample in the rest-frame ultraviolet (2500 angstrom) over the entire redshift range to z = 1.5. We conclude that the evolution in the luminosity density is a function of the form (1+z)^{1.7\pm1.0} for a flat lambda cosmology and (1+z)^{2.4\pm1.0} for an Einstein-de Sitter cosmology.Comment: 12 pages, 7 figs, 5 tables, submitted to A

    A Flux-Limited Sample of z~1 Ly-alpha Emitting Galaxies in the CDFS

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    We describe a method for obtaining a flux-limited sample of Ly-alpha emitters from GALEX grism data. We show that the multiple GALEX grism images can be converted into a three-dimensional (two spatial axes and one wavelength axis) data cube. The wavelength slices may then be treated as narrowband images and searched for emission-line galaxies. For the GALEX NUV grism data, the method provides a Ly-alpha flux-limited sample over the redshift range z=0.67-1.16. We test the method on the Chandra Deep Field South field, where we find 28 Ly-alpha emitters with faint continuum magnitudes (NUV>22) that are not present in the GALEX pipeline sample. We measure the completeness by adding artificial emitters and measuring the fraction recovered. We find that we have an 80% completeness above a Ly-alpha flux of 10^-15 erg/cm^2/s. We use the UV spectra and the available X-ray data and optical spectra to estimate the fraction of active galactic nuclei in the selection. We report the first detection of a giant Ly-alpha blob at z<1, though we find that these objects are much less common at z=1 than at z=3. Finally, we compute limits on the z~1 Ly-alpha luminosity function and confirm that there is a dramatic evolution in the luminosity function over the redshift range z=0-1.Comment: 18 pages, in press at The Astrophysical Journa
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