Covariance matrices for halo number counts and correlation functions

We study the mean number counts and two-point correlation functions, along with their covariance matrices, of cosmological surveys such as for clusters. In particular, we consider correlation functions averaged over finite redshift intervals, which are well suited to cluster surveys or populations of rare objects, where one needs to integrate over nonzero redshift bins to accumulate enough statistics. We develop an analytical formalism to obtain explicit expressions of all contributions to these means and covariance matrices, taking into account both shot-noise and sample-variance effects. We compute low-order as well as high-order (including non-Gaussian) terms. We derive expressions for the number counts per redshift bins both for the general case and for the small window approximation. We estimate the range of validity of Limber's approximation and the amount of correlation between different redshift bins. We also obtain explicit expressions for the integrated 3D correlation function and the 2D angular correlation. We compare the relative importance of shot-noise and sample-variance contributions, and of low-order and high-order terms. We check the validity of our analytical results through a comparison with the Horizon full-sky numerical simulations, and we obtain forecasts for several future cluster surveys.Comment: 37 page

Evolution of the X-ray Profiles of Poor Clusters from the XMM-LSS Survey

A sample consisting of 27 X-ray selected galaxy clusters from the XMM-LSS survey is used to study the evolution in the X-ray surface brightness profiles of the hot intracluster plasma. These systems are mostly groups and poor clusters, with temperatures 0.6-4.8 keV, spanning the redshift range 0.05 to 1.05. Comparing the profiles with a standard beta-model motivated by studies of low redshift groups, we find 54% of our systems to possess a central excess, which we identify with a cuspy cool core. Fitting beta-model profiles, allowing for blurring by the XMM point spread function, we investigate trends with both temperature and redshift in the outer slope (beta) of the X-ray surface brightness, and in the incidence of cuspy cores. Fits to individual cluster profiles and to profiles stacked in bands of redshift and temperature indicate that the incidence of cuspy cores does not decline at high redshifts, as has been reported in rich clusters. Rather such cores become more prominent with increasing redshift. Beta shows a positive correlation with both redshift and temperature. Given the beta-T trend seen in local systems, we assume that temperature is the primary driver for this trend. Our results then demonstrate that this correlation is still present at z~0.3, where most of our clusters reside.Comment: Accepted for publication in MNRAS. 15 pages, 12 figure

Du modalisateur au marqueur de ponctuation des actions : le cas de bon

Bon, est un mot du discours qui reçoit des interprétations variées suivant le contexte conversationnel. Nous tentons de décrire les propriétés associées aux différents emplois de bon sur les plans syntagmatique, pragmatique et structurel du discours. L’analyse fait ressortir deux fonctions discursives principales : le modalisateur et le marqueur de structuration de la conversation (MSC) (Roulet & al., 1985). L’examen du fonctionnement de ce marqueur discursif révèle qu’il est possible de rassembler autour d’une même valeur sémantico-pragmatique l’ensemble de ces emplois : le marqueur de ponctuation oral qui scande et délimite les activités verbales et non verbales (cognitive, énonciative ou physique) des participants à la conversation.Certains words like bon in French are subject to various interpretations according to context in which they appear. A description of the syntagmatic, pragmatic and discursive properties associated with the different uses of bon is presented. Two values of bon are examined: the modifier and the discourse marker (Roulet & al., 1985). A general semantico-pragmatic value is proposed to account for the various roles associated with bon in conversation: an "action punctuation marker" that scands and delimites the verbal and non verbal (cognitive, utterance or physical) activities of the participants

Structure Detection in Low Intensity X-Ray Images

In the context of assessing and characterizing structures in X-ray images, we compare different approaches. Most often the intensity level is very low and necessitates a special treatment of Poisson statistics. The method based on wavelet function histogram is shown to be the most reliable one. We also present a multi-resolution filtering method based on the wavelet coefficients detection. Comparative results are presented by means of a simulated cluster of galaxies.Comment: 11 pages, 9 figures, to appear in Astronomy & Astrophysic

Fauna africana oligocena y nuevas formas endémicas entre los micromamíferos de Mallorca (Nota preliminar)

Abstract not availabl

The X-CLASS - redMaPPer galaxy cluster comparison: I. Identification procedures

We performed a detailed and, for a large part interactive, analysis of the matching output between the X-CLASS and redMaPPer cluster catalogues. The overlap between the two catalogues has been accurately determined and possible cluster positional errors were manually recovered. The final samples comprise 270 and 355 redMaPPer and X-CLASS clusters respectively. X-ray cluster matching rates were analysed as a function of optical richness. In a second step, the redMaPPer clusters were correlated with the entire X-ray catalogue, containing point and uncharacterised sources (down to a few 10^{-15} erg s^{-1} cm^{-2} in the [0.5-2] keV band). A stacking analysis was performed for the remaining undetected optical clusters. Main results show that neither of the wavebands misses any massive cluster (as coded by X-ray luminosity or optical richness). After correcting for obvious pipeline short-comings (about 10% of the cases both in optical and X-ray), ~50% of the redMaPPer (down to a richness of 20) are found to coincide with an X-CLASS cluster; when considering X-ray sources of any type, this fraction increases to ~ 80%; for the remaining objects, the stacking analysis finds a weak signal within 0.5 Mpc around the cluster optical centers. The fraction of clusters totally dominated by AGN-type emission appears to be of the order of a few percent. Conversely ~ 40% of the X-CLASS clusters are identified with a redMaPPer (down to a richness of 20) - part of the non-matches being due to the fact that the X-CLASS sample extends further out than redMaPPer (z<1 vs z<0.6); extending the correlation down to a richness of 5, raises the matching rate to ~ 65%.Comment: 15 pages, 20 figures, 2 table

Effets de lisière sur les peuplements de chauves-souris frugivores et nectarivores de forêt primaire néotropicale en Guyane française

The impact of a road crossing a continuous Guyana primary forest was studied through the analysis of qualitative and quantitative changes in a frugivorous and nectarivorous bat community at different distances from forest edge. Bats were captured along three 3-km forest transects perpendicular to the edge, and at the Nouragues Station located 150 km in the interior of the primary forest block, in an uninhabited area. Along the 3-km transects, we caught over seven times more individuals than in primary forest, this value decreasing according to the distance from the edge. Moreover, at the very edge, species richness was higher than along transects, probably due to exchanges between primary forest and the open habitats. On the contrary, diversity values at forest edges were lower than in primary forest, with a demographic explosion of a few opportunistic phyllostomid species such as Carollia perspicillata and Artibeus jamaicensis. Species restricted to degraded habitat like Glossophaga soricina and Artibeus cinereus were still present 3 km away from the edge, where the proportion of C. perspicillata was seven times higher than in primary forest at Nouragues. These changes in the community of bats have important consequences on seed and pollen dispersal. So edge effects may signifi cantly affect both faunal and fl oral assemblage. We conclude that changes in bat community occur up to at least 3 km from forest edge, i. e. at a greater distance than that found for all other vertebrates previously studied. By their implications our results should be considered in habitat and species conservation management plansAfin d'étudier l'impact d'une route traversant une forêt primaire guyanaise continue, nous avons étudié les changements quantitatifs et qualitatifs du peuplement de chiroptères frugivores et nectarivores à différentes distances de la lisière. Les captures ont été effectuées le long de trois transects de 3 km chacun, partant de la lisière vers l'intérieur du bloc forestier ainsi qu'à la Station des Nouragues, située 150 km dans l'intérieur du bloc forestier, dans une zone intacte inhabitée. En lisière nous avons capturé sept fois plus d'individus qu'en forêt primaire, le nombre de captures diminuant au fur et à mesure que l'on s'éloigne de la lisière. De plus, les bordures révèlent une plus grande richesse spécifique que le long des transects, sans doute à cause de l'échange de chauves-souris entre forêt primaire et milieu ouvert. En revanche la diversité spécifique sur les 3 km de profondeur de lisière est plus faible qu'en forêt primaire témoin, avec une explosion démographique de quelques frugivores opportunistes comme Carollia perspicillata et Artibeus jamaicensis. A 3 km de la lisière, des espèces inféodées aux milieux ouverts comme Glossophaga soricina et Artiheus cinereus sont encore présentes, et la proportion de C. perspicillata y est sept fois plus grande qu'en forêt primaire des Nouragues. Ces changements dans la communauté de chiroptères ont des conséquences sur la pollinisation et sur la dispersion des graines. La lisière affecte donc les communautés animales et végétales. Nous concluons que les changements dans les communautés de chauves-souris ont lieu au moins jusqu'à 3 km des lisières, ce qui est plus important que ce qui avait été estimé jusqu'alors pour d'autres vertébrés. Ces résultats devraient être pris en compte par les gestionnaires de l'environnement et de la conservation des espèces