iDEA Collection: Faculty Research and Publications (Physics)

The 2dF-SDSS LRG and QSO survey: QSO clustering and the L-z degeneracy

Sat, 02 Feb 2008 22:58:59 GMT

Title: The 2dF-SDSS LRG and QSO survey: QSO clustering and the L-z degeneracy

Authors: da Angela, J.; Shanks, T.; Croom, S. M.; Weilbacher, P.; Brunner, R. J.; Couch, W.J.; Miller, L.; Myers, A. D.; Nichol, R. C.; Pimbblet, K. A.; de Propris, R.; Richards, Gordon T.; Ross, N. P.; Schneider, D. P.; Wake, D. A.

Abstract: We combine the QSO samples from the 2dF QSO Redshift Survey (2QZ) and the 2dF-SDSS LRG and QSO Survey (2SLAQ) in order to investigate the clustering of z 1.4 QSOs and measure the correlation function ( ). The clustering signal in redshift-space and projected along the sky direction is similar to that previously obtained from the 2QZ sample alone. By fitting functional forms to ( , ), the correlation function measured along and across the line of sight, we find, as expected, that , the dynamical infall parameter and 0 m, the cosmological density parameter, are degenerate. However, this degeneracy can be lifted by using linear theory predictions under different cosmological scenarios. Using the combination of the 2QZ and 2SLAQ QSO data, we obtain: QSO(z = 1.4) = 0.60+0.14 −0.11, 0 m = 0.25+0.09 −0.07 which imply a value for the QSO bias, b(z = 1.4) = 1.5 ± 0.2. The combination of the 2QZ with the fainter 2SLAQ QSO sample further reveals that QSO clustering does not depend strongly on luminosity at fixed redshift. This result is inconsistent with the expectation of simple ‘high peaks’ biasing models where more luminous, rare QSOs are assumed to inhabit higher mass haloes. The data are more consistent with models which predict that QSOs of different luminosities reside in haloes of similar mass. By assuming ellipsoidal models for the collapse of density perturbations, we estimate the mass of the dark matter haloes which the QSOs inhabit. We find that halo mass does not evolve strongly with redshift nor depend on QSO luminosity. Assuming a range of relations which relate halo to black hole mass we investigate how black hole mass correlates with luminosity and redshift and ascertain the relation between Eddington efficiency and black hole mass. Our results suggest that QSOs of different luminosities may contain black holes of similar mass.

Imaging biomarkers of inflammation in situ with functionalized quantum dots in the dextran sodium sulfate (DSS) model of mouse colitis

Sun, 29 Oct 2006 22:58:59 GMT

Title: Imaging biomarkers of inflammation in situ with functionalized quantum dots in the dextran sodium sulfate (DSS) model of mouse colitis

Authors: Karwa, Amol; Papazoglou, Elisabeth; Pourrezaei, Kambiz; Tyagi, Som; Murthy, Sreekant

Abstract: Objective and Design: Myeloperoxidase (MPO) and proinflammatory cytokines play an important role in the development of inflammation. These markers are generally measured using tedious ELISA procedures. In this study, a novel technique utilizing antibody conjugated quantum dot nanoparticles was developed to detect myeloperoxidase, IL-1 α and TNF-α in vivo in the dextran sodium sulfate (DSS) model of experimental colitis. Materials and Methods: Colitis was induced in animals (n=8 animals/ group) by feeding 4% DSS solution ad libitum for seven to eight days. Quantum Dots exhibiting fluorescence at various wavelengths were conjugated to MPO, IL-1 α and TNF-α polyclonal antibodies and tested in vivo at various stages of colitis. Tissue sections obtained were imaged with confocal microscope. The image intensity obtained from the tissue specimen was correlated with clinical activity measured as Disease Activity Index (DAI). Results: Myeloperoxidase, IL-1α and TNF-α were visualized with quantum dots on various days of disease. The intensity of quantum dots increased with increase in inflammation. The increase in intensity showed an excellent correlation with the DAI based on the clinical parameters. Conclusion: The study demonstrated that multiple biomarkers can be detected simultaneously and their quantitative expression correlated well with clinical disease severity. This novel technology should facilitate design of a novel optical platform for imaging various biomarkers of inflammation, early detection of acute and chronic disease markers and inflammation-mediated cancer markers. This detection may also facilitate determination of therapeutic success.

Peeling bifurcations of toroidal chaotic attractors

Mon, 10 Dec 2007 22:58:59 GMT

Title: Peeling bifurcations of toroidal chaotic attractors

Authors: Letellier, Christophe; Gilmore, Robert; Jones, Timothy

Abstract: Chaotic attractors with toroidal topology van der Pol attractor have counterparts with symmetry that exhibit unfamiliar phenomena. We investigate double covers of toroidal attractors, discuss changes in their morphology under correlated peeling bifurcations, describe their topological structures and the changes undergone as a symmetry axis crosses the original attractor, and indicate how the symbol name of a trajectory in the original lifts to one in the cover. Covering orbits are described using a powerful synthesis of kneading theory with refinements of the circle map. These methods are applied to a simple version of the van der Pol oscillator.

A systems approach for the prediction of wild type MAPK pathway response to targeted drugs

Fri, 28 Sep 2007 22:58:59 GMT

Title: A systems approach for the prediction of wild type MAPK pathway response to targeted drugs

Authors: Miller, David J.; Ghosh, Avijit

Abstract: In this paper we simulate the wild type MAPK pathway response to twelve in silico drugs that were previously found to reduce elevated phosphorylated ERK levels (ERK*) in 40 top ranked mutations in a model of the MAPK signal transduction pathway. We nd that a subset of the simulated drugs (notably those targeting GEF and the G G-protein trimer) were able to e ectively inhibit the elevated ERK* levels of the mutated pathways, whilst simultaneously eliciting only minimal inhibition of the wild type pathway ERK* response to EGF stimulation.

Raman spectra of unfilled and filled carbon nanotubes: theory

Wed, 24 Oct 2007 22:58:59 GMT

Title: Raman spectra of unfilled and filled carbon nanotubes: theory

Authors: Gayen, S.; Behera, S. N.; Bose, Shyamalendu M.

Abstract: The Raman spectra of two G bands and a radial breathing mode RBM of unfilled and filled single-wall semiconducting and metallic carbon nanotubes have been investigated theoretically in the presence of electronphonon and phonon-phonon interactions. Excitation of low frequency optical plasmons in the metallic nanotube is responsible for the peak known as the Breit-Wigner-Fano BWF line shape in the G-band Raman spectra. In a filled nanotube, there is an additional peak due to excitation of the phonon of the filling atom or molecule. Positions, shapes, and relative strengths of these Raman peaks depend on the phonon frequencies of the nanotube and that of the filling atoms, and strengths and forms of the plasmon-phonon and phonon-phonon interactions. For example, filling atoms with phonon frequency close to the RBM frequency of the nanotube may broaden and lower the RBM Raman peak to such an extent that it may become barely visible. Hybridization between the G bands and the filling atom phonon is also strong when these two frequencies are close to each other, and it has important effects on the G band and the BWF line shapes. When the phonon frequency of the filling atom is far from the RBM and G-band frequencies, it gives rise to a separate peak with modest effects on the RBM and G-band spectra. The Raman spectra of semiconducting unfilled and filled nanotubes have similar behaviors as those of metallic nanotubes, except that normally they have Lorentzian line shapes and do not show a BWF line shape. However, if a semiconducting nanotube is filled with donor atoms, it is predicted that the BWF-type line shape may be observed near the RBM, or the G band, or the filling atom Raman peak.

Magnet therapy

Mon, 29 Oct 2001 22:58:59 GMT

Title: Magnet therapy

Authors: Finegold, Leonard; Flamm, Bruce L

A new quadruply lensed quasar: SDSS J125107.57+293540.5

Fri, 28 Sep 2007 22:58:59 GMT

Title: A new quadruply lensed quasar: SDSS J125107.57+293540.5

Authors: Kayo, Issha; Inada, Naohisa; Oguri, Masamune; Hall, Patrick B.; Kochanek, Christopher S.; Richards, Gordon T.; Schneider, Donald P.; York, Donald G.; Pan, Kaike

Abstract: We report the discovery of a quadruply imaged quasar, SDSS J125107.57+293540.5, selected from the Sloan Digital Sky Survey. Follow-up imaging reveals that the system consists of four blue pointlike components in a typical cusp lens geometry surrounding a central red galaxy. The source redshift is 0.802, and the lens redshift is 0.410. The maximum image separation between the lensed components is 1.7900. While the image configuration is well reproduced by standard mass models with reasonable parameter values, the flux ratios predicted by these models differ from the observed ratios in all bands. This is suggestive of small-scale structure in this lens, although a definitive identification of the anomaly requires more accurate photometry and astrometry

The fifth data release of the sloan digital sky survey

Fri, 28 Sep 2007 22:58:59 GMT

Title: The fifth data release of the sloan digital sky survey

Authors: Adelman-McCarthy, Jennifer K.; Agueros, Marcel A.; Allam, Sahar S.; Anderson, Kurt S. J.; et al.

Abstract: This paper describes the Fifth Data Release (DR5) of the Sloan Digital Sky Survey (SDSS). DR5 includes all survey quality data taken through 2005 June and represents the completion of the SDSS-I project (whose successor, SDSS-II, will continue through mid-2008). It includes five-band photometric data for 217 million objects selected over 8000 deg2 and 1,048,960 spectra of galaxies, quasars, and stars selected from 5713 deg2 of that imaging data. These numbers represent a roughly 20% increment over those of the Fourth Data Release; all the data from previous data releases are included in the present release. In addition to ‘‘standard’’ SDSS observations,DR5 includes repeat scans of the southern equatorial stripe, imaging scans across M31 and the core of the Perseus Cluster of galaxies, and the first spectroscopic data from SEGUE, a survey to explore the kinematics and chemical evolution of the Galaxy. The catalog database incorporates several new features, including photometric redshifts of galaxies, tables of matched objects in overlap regions of the imaging survey, and tools that allowprecise computations of survey geometry for statistical investigations.

A dynamical origin for early mass segregation in young star clusters

Mon, 18 Sep 2006 22:58:59 GMT

Title: A dynamical origin for early mass segregation in young star clusters

Authors: McMillan, Stephen L.W.; Vesperini, Enrico; Zwart, Simon F. Portegies

Abstract: Some young star clusters show a degree of mass segregation that is inconsistent with the effects of standard two-body relaxation from an initially unsegregated system without substructure, in virial equilibrium, and it is unclear whether cur- rent cluster formation models can account for this degree of initial segregation in clusters of significant mass. In this Letter we demonstrate that mergers of small clumps that are either initially mass segregated, or in which mass segrega- tion can be produced by two-body relaxation before they merge, generically lead to larger systems which inherit the progenitor clumps’ segregation. We conclude that clusters formed in this way are naturally mass segregated, accounting for the anomalous observations and suggesting that this process of prompt mass segre- gation due to initial clumping should be taken fully into account in constructing cluster dynamical models.

SDSS J1029_2623: a gravitationally lensed quasar with an image separation of 22.5 inches

Tue, 19 Dec 2006 22:58:59 GMT

Title: SDSS J1029_2623: a gravitationally lensed quasar with an image separation of 22.5 inches

Authors: Inada, Naohisa; Oguri, Masamune; Morokuma, Tomoki; Doi, Mamoru; Yasuda, Naoki; Becker, Robert H.; Richards, Gordon T.; Kochanek, Christopher S.; Kayo, Issha; Konishi, Kohki; Utsunomiya, Hiroyuki; Shin, Min-Su; Strauss, Michael A.; Sheldon, Erin; York, Donald G.; Hennawi, Joseph F.; Schneider, Donald P.; Dai, Xinyu; Fukugita, Masataka

Abstract: We report the discovery of a cluster-scale lensed quasar, SDSS J1029+2623, selected from the Sloan Digital Sky Survey. The lens system exhibits two lensed images of a quasar at z p 2.197. The image separation of s 22.5 inches makes it the largest separation lensed quasar discovered to date. The similarity of the optical spectra and the radio loudnesses of the two components support the lensing hypothesis. Images of the field show a cluster of galaxies at z1 ~ 0.55 that is responsible for the large image separation. The lensed images and the cluster light l center are not collinear, which implies that the lensing cluster has a complex structure.