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Clustering in the 2dF QSO Redshift Survey

ArXiv astro-ph/0205039 (2002)

Authors:

SM Croom, BJ Boyle, NS Loaring, L Miller, P Outram, T Shanks, RJ Smith, F Hoyle

Abstract:

We present clustering results from the 2dF QSO Redshift Survey (2QZ) which currently contains over 20,000 QSOs at z<3. The two-point correlation function of QSOs averaged over the entire survey (~1.5) is found to be similar to that of local galaxies. When sub-dividing the sample as a function of redshift, we find that for an Einstein-de Sitter universe QSO clustering is constant (in comoving coordinates) over the entire redshift range probed by the 2QZ, while in a universe with Omega_0=0.3 and Lambda_0=0.7 there is a marginal increase in clustering with redshift. Sub-dividing the 2QZ on the basis of apparent magnitude we find only a slight difference between the clustering of QSOs of different apparent brightness, with the brightest QSOs having marginally stronger clustering. We have made a first measurement of the redshift space distortion of QSO clustering, with the goal of determining the value of cosmological parameters (in partcular Lambda_0) from geometric distortions. The current data do not allow us to discriminate between models, however, in combination with constraints from the evolution of mass clustering we find Omega_0=1-Lambda_0=0.23 +0.44-0.13 and beta(z~1.4)=0.39 +0.18-0.17. The full 2QZ data set will provide further cosmological constraints.
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The 2dF QSO Redshift Survey - IX. A measurement of the luminosity dependence of QSO clustering

ArXiv astro-ph/0205036 (2002)

Authors:

Scott M Croom, BJ Boyle, NS Loaring, L Miller, PJ Outram, T Shanks, RJ Smith

Abstract:

In this Paper we present a clustering analysis of QSOs as a function of luminosity over the redshift range z=0.3-2.9. We use a sample of 10566 QSOs taken from the preliminary data release catalogue of the 2dF QSO Redshift Survey (2QZ). We analyse QSO clustering as a function of apparent magnitude. The strong luminosity evolution of QSOs means that this is approximately equivalent to analysing the data as a function of absolute magnitude relative to M* over the redshift range that the 2QZ probes. Over the relatively narrow range in apparent magnitude of the 2QZ we find no significant (>2sigma) variation in the strength of clustering, however, there is marginal evidence for QSOs with brighter apparent magnitudes having a stronger clustering amplitude. QSOs with 18.25
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Deep Westerbork 1.4 GHz Imaging of the Bootes Field

\aj 123 (2002) 1784-1800-1784-1800

Authors:

WH de Vries, R Morganti, HJA Röttgering, R Vermeulen, W van Breugel, R Rengelink, MJ Jarvis
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Source-lens clustering effects on the skewness of the lensing convergence

Monthly Notices of the Royal Astronomical Society 330:2 (2002) 365-377

Authors:

T Hamana, ST Colombi, A Thion, JEGT Devriendt, Y Mellier, F Bernardeau

Abstract:

potentials causes a systematic effect on measurements of cosmic shear statistics, known as the source-lens clustering (SLC) effect. The SLC effect on the skewness of lensing convergence, S3, is examined using a non-linear semi-analytic approach and is checked against numerical simulations. The semi-analytic calculations have been performed in a wide variety of generic models for the redshift distribution of source galaxies and power-law models for the bias parameter between the galaxy and dark matter distributions. The semi-analytic predictions are tested successfully against numerical simulations. We find the relative amplitude of the SLC effect on S3 to be of the order of 5 -40 per cent. It depends significantly on the redshift distribution of sources and on the way in which the bias parameter evolves. We discuss possible measurement strategies to minimize the SLC effects.
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The 2dF BL Lac Survey

ArXiv astro-ph/0202386 (2002)

Authors:

D Londish, SM Croom, BJ Boyle, T Shanks, PJ Outram, EM Sadler, NS Loaring, RJ Smith, L Miller, PFL Maxted

Abstract:

We have optically identified a sample of 56 featureless continuum objects without significant proper motion from the 2dF QSO Redshift Survey (2QZ). The steep number--magnitude relation of the sample, $n(\bj) \propto 10^{0.7\bj}$, is similar to that derived for QSOs in the 2QZ and inconsistent with any population of Galactic objects. Follow up high resolution, high signal-to-noise, spectroscopy of five randomly selected objects confirms the featureless nature of these sources. Assuming the objects in the sample to be largely featureless AGN, and using the QSO evolution model derived for the 2QZ, we predict the median redshift of the sample to be $z=1.1$. This model also reproduces the observed number-magnitude relation of the sample using a renormalisation of the QSO luminosity function, $\Phi^* = \Phi^*_{\rm \sc qso}/66 \simeq 1.65 \times 10^{-8} $mag$^{-1}$Mpc$^{-3}$. Only $\sim$20 per cent of the objects have a radio flux density of $S_{1.4}>3 $mJy, and further VLA observations at 8.4 GHz place a $5\sigma$ limit of $S_{8.4} < 0.2$mJy on the bulk of the sample. We postulate that these objects could form a population of radio-weak AGN with weak or absent emission lines, whose optical spectra are indistinguishable from those of BL Lac objects.
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