Adaptive Optics observations of LBQS 0108+0028: K-band detection of the host galaxy of a radio-quiet QSO at z=2

We report the first unambiguous detection of the host galaxy of a normal radio-quiet QSO at high-redshift in K-band. The luminosity of the host comprises about 35% of the total K-band luminosity. Assuming the average colour of QSOs at z=2, the host would be about 5 to 6 mag brighter than an unevolved L* galaxy placed at z=2, and 3 to 4 mag brighter than a passively evolved L* galaxy at the same redshift. The luminosity of the host galaxy of the QSO would thus overlap with the highest found in radio-loud QSOs and radio-galaxies at the same redshift.Comment: Accepted to be published in MNRAS. 4 pages, 2 postscript figures. Also available at http://www.mpa-garching.mpg.de/~itzia

Hardware and software status of QCDOC

QCDOC is a massively parallel supercomputer whose processing nodes are based on an application-specific integrated circuit (ASIC). This ASIC was custom-designed so that crucial lattice QCD kernels achieve an overall sustained performance of 50% on machines with several 10,000 nodes. This strong scalability, together with low power consumption and a price/performance ratio of $1 per sustained MFlops, enable QCDOC to attack the most demanding lattice QCD problems. The first ASICs became available in June of 2003, and the testing performed so far has shown all systems functioning according to specification. We review the hardware and software status of QCDOC and present performance figures obtained in real hardware as well as in simulation.Comment: Lattice2003(machine), 6 pages, 5 figure

QSO clustering and the AAT 2dF redshift survey

We review previous results on the clustering and environments of QSOs. We show that the correlation length for QSOs derived from existing surveys is r~5/h Mpc, similar to the observed correlation length for field galaxies at the present epoch. The galaxy environment for z<1 radio-quiet QSOs is also consistent with field galaxies. The evolution of the QSO correlation length with redshift is currently uncertain, largely due to the small numbers of QSOs (~2000) in surveys suitable for clustering analysis. We report on intial progress with the AAT 2dF QSO redshift survey, which, once completed will comprise almost 30000 QSOs. With over 1000 QSOs already observed, it is already the largest single homogeneous QSO survey. We discuss prospects for deriving limits on cosmological parameters from this survey, and on the evolution of large-scale structure in the Universe.Comment: Invited talk at RS meeting on 'Large Scale Structure in the Universe' held at the Royal Society on 25-26 March 1998 14 pages, 11 figre

Haplotype analysis of the PPARgamma Pro12Ala and C1431T variants reveals opposing associations with body weight.

BACKGROUND: Variation at the PPARG locus may influence susceptibility to type 2 diabetes and related traits. The Pro12Ala polymorphism may modulate receptor activity and is associated with protection from type 2 diabetes. However, there have been inconsistent reports of its association with obesity. The silent C1431T polymorphism has not been as extensively studied, but the rare T allele has also been inconsistently linked to increases in weight. Both rare alleles are in linkage disequilibrium and the independent associations of these two polymorphisms have not been addressed. RESULTS: We have genotyped a large population with type 2 diabetes (n = 1107), two populations of non-diabetics from Glasgow (n = 186) and Dundee (n = 254) and also a healthy group undergoing physical training (n = 148) and investigated the association of genotype with body mass index. This analysis has demonstrated that the Ala12 and T1431 alleles are present together in approximately 70% of the carriers. By considering the other 30% of individuals with haplotypes that only carry one of these polymorphisms, we have demonstrated that the Ala12 allele is consistently associated with a lower BMI, whilst the T1431 allele is consistently associated with higher BMI. CONCLUSION: This study has therefore revealed an opposing interaction of these polymorphisms, which may help to explain previous inconsistencies in the association of PPARG polymorphisms and body weight

The IRAS 1-Jy Survey of Ultraluminous Infrared Galaxies: I. The sample and Luminosity Function

A complete flux-limited sample of 118 ultraluminous infrared galaxies (ULIGs) has been identified from the IRAS Faint Source Catalog (FSC). The selection criteria were a 60 micron flux density greater than 1 Jy in a region of the sky delta > -40 deg, |b| > 30 deg. All sources were subsequently reprocessed using coadded IRAS maps in order to obtain the best available flux estimates in all four IRAS wavelength bands. The maximum observed infrared luminosity is L_ir = 10^{12.90} L_{sun}, and the maximum redshift is z = 0.268. The luminosity function for ULIGs over the decade luminosity range L_ir = 10^{12} - 10^{13} L_{sun} can be approximated by a power law Phi (L) ~= L^{-2.35} Mpc^{-3} mag^{-1}. In the local Universe z < 0.1, the space density of ULIGs appears to be comparable to or slightly larger than that of optically selected QSOs at comparable bolometric luminosities. A maximum likelihood test suggests strong evolution for our sample; assuming density evolution proportional to (1+z)^{alpha} we find alpha = 7.6+/-3.2. Examination of the two-point correlation function shows a barely significant level of clustering, xi (r) = 1.6 +/- 1.2, on size scales r ~= 22 h^{-1} Mpc.Comment: 18 pages of text, 10 pages of figures 1 to 6, 6 pages of tables 1 to 3, ApJS accepte

The Dust Content of Galaxy Clusters

We report on the detection of reddening toward z ~ 0.2 galaxy clusters. This is measured by correlating the Sloan Digital Sky Survey cluster and quasar catalogs and by comparing the photometric and spectroscopic properties of quasars behind the clusters to those in the field. We find mean E(B-V) values of a few times 10^-3 mag for sight lines passing ~Mpc from the clusters' center. The reddening curve is typical of dust but cannot be used to distinguish between different dust types. The radial dependence of the extinction is shallow near the cluster center suggesting that most of the detected dust lies at the outskirts of the clusters. Gravitational magnification of background z ~ 1.7 sources seen on Mpc (projected) scales around the clusters is found to be of order a few per cent, in qualitative agreement with theoretical predictions. Contamination by different spectral properties of the lensed quasar population is unlikely but cannot be excluded.Comment: 4 pages, 3 figure

Discovery of a luminous white dwarf in a young star cluster in the Large Magellanic Cloud

We have identified a candidate 1-2 x 10^5 year old luminous white dwarf in NGC 1818, a young star cluster in the Large Magellanic Cloud. This discovery strongly constrains the boundary mass M_c at which stars stop forming neutron stars and start forming white dwarfs, to M_c > 7.6 Msun.Comment: 4 pages, 2 figures, greyscale image available by ftp from [email protected]. ApJLetters, accepted 17 March 199

The Fall of the Quasar Population

We derive quantitative predictions of the optical and X-ray luminosity functions (LF) for QSs in the redshift range $z<3$. Based on BH paradigm, we investigate how the accretion is controlled by the surrounding structures, as these grow hierarchically. We argue that for $z < 3$ efficient black hole fueling is triggered by the encounters of a gas-rich host with its companions in a group. The dispersion of the dynamical parameters in the encounters produces a double power-law LF. Strong luminosity evolution (LE) is produced as these encounters deplete the gas supply in the host; an additional, milder density evolution obtains since the interactions become progressively rarer as the groups grow richer but less dense. From the agreement with the optical and the X-ray data, we conclude that the evolution of the bright quasars is articulated in two ways. Earlier than $z~3$ the gas-rich protogalaxies grow by merging, which also induces parallel growth of central holes accreting at Eddington rates. In the later era of group assemblage the host encounters with companions drive onto already existing holes further but meager accretion; these consume the gas in the hosts, and cause supply-limited emissions which are intermittent, go progressively sub-Eddington and peter out. Then other fueling processes come to the foreground; we discuss the faint emissions, especially noticeable in X-rays, which are expected when hosts in the field cannibalize satellite galaxies with their meager gas contents.Comment: 12 pages Latex + 3 EPS figures, ApJ in press, we have corrected the previous printing problems with the style \ca

Spectral Variability of Quasars in the Sloan Digital Sky Survey. II: The C IV Line

We examine the variability of the high-ionizaton C IV line in a sample of 105 quasars observed at multiple epochs by the Sloan Digital Sky Survey. We find a strong correlation between the change in the C IV line flux and the change in the line width, but no correlations between the change in flux and changes in line center and skewness. The relation between line flux change and line width change is consistent with a model in which a broad line base varies with greater amplitude than the line core. The objects studied here are more luminous and at higher redshift than those normally studied for variability, ranging in redshift from 1.65 to 4.00 and in absolute r-band magnitude from roughly -24 to -28. Using moment analysis line-fitting techniques, we measure line fluxes, centers, widths and skewnesses for the C IV line at two epochs for each object. The well-known Baldwin Effect is seen for these objects, with a slope beta = -0.22. The sample has a median intrinsic Baldwin Effect slope of beta = -0.85; the C IV lines in these high-luminosity quasars appear to be less responsive to continuum variations than those in lower luminosity AGN. Additionally, we find no evidence for variability of the well known blueshift of the C IV line with respect to the low-ionization Mg II line in the highest flux objects, indicating that this blueshift might be useful as a measure of orientation.Comment: 52 pages, 14 figures, accepted for publication in Ap