The effect of reionization on the CMB-density correlation

In this paper we show how the rescattering of CMB photons after cosmic reionization can give a significant linear contribution to the temperature-matter cross-correlation measurements. These anisotropies, which arise via a late time Doppler effect, are on scales much larger than the typical scale of non-linear effects at reionization; they can contribute to degree scale cross-correlations and could affect the interpretation of similar correlations resulting from the integrated Sachs-Wolfe effect. While expected to be small at low redshifts, these correlations can be large given a probe of the density at high redshift, and so could be a useful probe of the cosmic reionization history.Comment: 8 pages, 8 figure

An optimal estimator for the CMB-LSS angular power spectrum and its application to WMAP and NVSS data

We use a Quadratic Maximum Likelihood (QML) method to estimate the angular power spectrum of the cross-correlation between cosmic microwave background and large scale structure maps as well as their individual auto-spectra. We describe our implementation of this method and demonstrate its accuracy on simulated maps. We apply this optimal estimator to WMAP 7-year and NRAO VLA Sky Survey (NVSS) data and explore the robustness of the angular power spectrum estimates obtained by the QML method. With the correction of the declination systematics in NVSS, we can safely use most of the information contained in this survey. We then make use of the angular power spectrum estimates obtained by the QML method to derive constraints on the dark energy critical density in a flat $\Lambda$CDM model by different likelihood prescriptions. When using just the cross-correlation between WMAP 7 year and NVSS maps with 1.8$^\circ$ resolution, the best-fit model has a cosmological constant of approximatively 70% of the total energy density, disfavouring an Einstein-de Sitter Universe at more than 2 $\sigma$ CL (confidence level).Comment: 12 pages, 12 figure

Integrated Sachs-Wolfe map recovery from NVSS and WMAP 7yr data

We present a map of the Cosmic Microwave Background (CMB) anisotropies induced by the late Integrated Sachs Wolfe effect. The map is constructed by combining the information of the WMAP 7-yr CMB data and the NRAO VLA Sky Survey (NVSS) through a linear filter. This combination improves the quality of the map that would be obtained using information only from the Large Scale Structure data. In order to apply the filter, a given cosmological model needs to be assumed. In particular, we consider the standard LCDM model. As a test of consistency, we show that the reconstructed map is in agreemet with the assumed model, which is also favoured against a scenario where no correlation between the CMB and NVSS catalogue is considered.Comment: 6 pages, 4 figures. Minor revision, accepted for publication in MNRA

The large-scale bias of the hard X-ray background

Recent deep X-ray surveys combined with spectroscopic identification of the sources have allowed the determination of the rest-frame 2-8 keV luminosity as a function of redshift. In addition, an analysis of the HEAO1 A2 2-10 keV full-sky map of the X-ray background (XRB) reveals clustering on the scale of several degrees. Combining these two results in the context of the currently favored Lambda-CDM cosmological model implies an average X-ray bias factor, b_x, of b_x^2 = 1.12 +- 0.33, i.e., b_x = 1.06 +- 0.16. These error estimates include only statistical error; the systematic error sources, while comparable, appear to be sub-dominant. This result is in contrast to the large biases of some previous estimates and is more in line with current estimates of the optical bias of L* galaxies.Comment: 6 pages, 3 eps figures, accepted for ApJ, vol. 612, 10 September 200

Probabilistic Cross-Identification of Astronomical Sources

We present a general probabilistic formalism for cross-identifying astronomical point sources in multiple observations. Our Bayesian approach, symmetric in all observations, is the foundation of a unified framework for object matching, where not only spatial information, but physical properties, such as colors, redshift and luminosity, can also be considered in a natural way. We provide a practical recipe to implement an efficient recursive algorithm to evaluate the Bayes factor over a set of catalogs with known circular errors in positions. This new methodology is crucial for studies leveraging the synergy of today's multi-wavelength observations and to enter the time-domain science of the upcoming survey telescopes.Comment: Accepted for publication in the Astrophysical Journal, 8 pages, 1 figure, emulateapj w/ apjfont

Cliff-height and slope-angle relationships in a chronosequence of Quaternary marine terraces, San Clemente Island, California

Zusammenfassung. Eine Abfolge quartarer Strandterrassen auf ~an Clemente Island, Kalifornien, liefert einen Rahmen fur die quantitative Analyse der Anderungen an vom Meer verlassenen Kustenkliffen als Funktion der Zeit. Es wurde eine Abschatzung der Anwendbarkeit von BUCKNAM & ANDERSON (1979) log-lin~arer Beziehung zwischen Wandhohe und Hangwinkel durchgefuhrt, indem Brandungskliffhohe und maximale Hangwinkel verwendet wurden. Die Ergebnisse zeigen eine regelhafte Zunahme des Hangwinkels mit dem Logarithmus der Kliffhohe, und Kliffe einer bestimmten Hohe zeigen m,it der Zeit eine Abnahmedes maximalen Hangwinkels. 1m ganzen waren die Relationen schwacher als fur FluBterrassen und Bruchstufen in unverfestigten Materialen, aber die Methode kann wahrscheinlich verwendet werden, urn fruhe, mittlere und junge quartare Bruchstufen und Kustenkliffe in verfestigtem Material erfolgreich zu unterscheiden. Summary. A flight of Quaternary marine terraces on San Clemente Island, California, provides a framework for quantitative analysis of abandoned sea cliff modification as a function of time. An assessment was made of the applicability of BUCKNAM & ANDERSON\u27S (1979) log-linear relationship between scarp height and slope angle using sea cliff height and maximum slope angle. Results indicate a regular increase in slope angle with the logarithm of the cliff height and cliffs of a given height show a decline in maximum slope angle with time. Overall, the relationships are weaker than for stream terraces and fault scarps in unconsolidated materials, but the method can probably be used successfully to distinguish early, middle and late Quaternary fault scarps or sea cliffs in consolidated materials. Resume. Une serie de terrasses marines quaternaires sur l\u27ile de San Clemente (Californie) fournit un cadre pour l\u27analyse quantitative de l\u27evolution de falaises marines mortes. Une hypothese a ete avancee concernant l\u27application de la relation log-normale de BUCKNAM & ANDERSON (1979) entre la hauteur de l\u27escarpement et l\u27angle de la pente appliquee ici a la hauteur de la falaise marine et l\u27angle maximum de la pente. Les resultats indiquent un accroissement regulier de la pente avec Ie logarithme de la hauteur de la falaise et les falaises d\u27une hauteur determinee montrent un abaissement de l\u27angle de pente maximum en fonction du temps. Partout, les relations sont moins bonnes que pour les terrasses de rivieres et des escarpements de failles dans des materiaux meubles. Toutefois, la methode peut probablerment etre utilisee avec succes pour donner un age quaternaire recent moyen ou ancien aux escarpements de failles ou aux falaises marines dans des materiaux c;onsolides. Text in English: The rate of alteration of slopes, particularly those derived from fault scarps, has received increasing attention in recent years because of the need for accurate assessment\u27 of potential fault hazards (WALLACE 1977; BUCKNAM & ANDERSON, 1979; NASH 1980a, 1980b, 1984; MACHETTE 1982; COLMAN 1983; COLMAN & WATSON 1983; HANKS et al. 1984; MAYER 1984; STERR 1985). Often there is a need for age determination of a fault scarp, but little or no material available for radiometric dates. Hence, many investigators have utilized morphometric parameters in order to establish relative and in some cases absolute ages. BUCKNAM & ANDERSON (1979) were perhaps the first to quantify changes in fault scarp slope angles through time. They examined the relationship between scarp height and slope angle in Quaternary deposits in the Great Basin of western Utah and quantified earlier observations of WALLACE (1977). Their results indicated that for small scarps less than 10 m high, slope angle increases with the logarithm of scarp height and decreases through time for a scarp of a given height. This relationship has been confirmed for fault scarps in other locations in the southwestern U. S. A. (MACHETTE 1982; MAYER 1984; HANKS et al. 1984) and has been, extended to other landforms such as stream terrace scarps (COLMAN 1983) and lake cliffs (NASH 1980b). Several studies have gone beyond the relative dating method proposed by BUCKNAM & ANDERSON (1979) and models for determination of absolute age have been generated (NASH 1980b, 1984; COLMAN & WATSON 1983; HANKS et al. 1984; HANKS & WALLACE 1985; STERR 1985). MAYER (1984) recently discussed the complicating effects of measurement error, lithology, particle size, and composite scarps