Galaxy Clustering at z ~ 2 and Halo Radii

The amplitude of the angular two-point galaxy correlation function w(\theta) for galaxies at z~2 is estimated for galaxies in the Hubble Deep Field by using a U < 27 complete sub-sample. (i) It is confirmed that the amplitude of the correlation can be corrected for the integral constraint without having to make assumptions about the shape of the correlation function and by avoiding the introduction of linear error terms. The estimate using this technique is w(5'') = 0.10 \pm 0.09. (ii) If the biases introduced in faint galaxy selection due to obscuration by large objects are not corrected for by masking areas around them, then the estimate would be w(5'') =0.16\pm 0.07. (iii) The effective (3-D) galaxy pair separation at 5'' and this redshift range is ~ 25-250 /h kpc, so the correction to the spatial correlation function \xi(r) due to exclusion of overlapping galaxy dark matter haloes should be considered. For clustering stable in proper units in an \Omega=1,\lambda=0 universe, our w(5\arcs) estimate (a) implies a present-day correlation length of r_0 ~ 2.6^{+1.1}_{-1.7}/h Mpc if halo overlapping is ignored, but (b) for a present-day correlation length of r_0=5.5/h Mpc implies that a typical halo exclusion radius is r_halo=70^{+420}_{-30}/h kpc. (iv) The decreasing correlation period (DCP) of a high initial bias in the spatial correlation function is not detected at this redshift. For an \Omega=1,\lambda=0 universe and (proper) stable clustering, possible detections of the DCP in other work would imply that \xi at redshifts greater than z_t = 1.7\pm0.9 would be [(1+z)/(1+z_t)]^{2.1\pm3.6} times higher than at z_t, which is consistent with our lack of a detection at z ~ 2.Comment: 17 pages, 13 figures, accepted for MNRAS, additional FITS files with HDF images available at http://www.iap.fr/users/roukema/xi2

Correlations in the (Sub)millimeter Background from ACT × BLAST

We present measurements of the auto- and cross-frequency correlation power spectra of the cosmic (sub)millimeter background at 250, 350, and 500 μm (1200, 860, and 600 GHz) from observations made with the Balloon-borne Large Aperture Submillimeter Telescope (BLAST); and at 1380 and 2030 μm (218 and 148 GHz) from observations made with the Atacama Cosmology Telescope (ACT). The overlapping observations cover 8.6 deg^2 in an area relatively free of Galactic dust near the south ecliptic pole. The ACT bands are sensitive to radiation from the cosmic microwave background, to the Sunyaev-Zel'dovich effect from galaxy clusters, and to emission by radio and dusty star-forming galaxies (DSFGs), while the dominant contribution to the BLAST bands is from DSFGs. We confirm and extend the BLAST analysis of clustering with an independent pipeline and also detect correlations between the ACT and BLAST maps at over 25σ significance, which we interpret as a detection of the DSFGs in the ACT maps. In addition to a Poisson component in the cross-frequency power spectra, we detect a clustered signal at 4σ, and using a model for the DSFG evolution and number counts, we successfully fit all of our spectra with a linear clustering model and a bias that depends only on redshift and not on scale. Finally, the data are compared to, and generally agree with, phenomenological models for the DSFG population. This study demonstrates the constraining power of the cross-frequency correlation technique to constrain models for the DSFGs. Similar analyses with more data will impose tight constraints on future models

ModuLand plug-in for Cytoscape: determination of hierarchical layers of overlapping network modules and community centrality

Summary: The ModuLand plug-in provides Cytoscape users an algorithm for determining extensively overlapping network modules. Moreover, it identifies several hierarchical layers of modules, where meta-nodes of the higher hierarchical layer represent modules of the lower layer. The tool assigns module cores, which predict the function of the whole module, and determines key nodes bridging two or multiple modules. The plug-in has a detailed JAVA-based graphical interface with various colouring options. The ModuLand tool can run on Windows, Linux, or Mac OS. We demonstrate its use on protein structure and metabolic networks. Availability: The plug-in and its user guide can be downloaded freely from: http://www.linkgroup.hu/modules.php. Contact: [email protected] Supplementary information: Supplementary information is available at Bioinformatics online.Comment: 39 pages, 1 figure and a Supplement with 9 figures and 10 table

Overlapping Community Structure in Co-authorship Networks: a Case Study

Community structure is one of the key properties of real-world complex networks. It plays a crucial role in their behaviors and topology. While an important work has been done on the issue of community detection, very little attention has been devoted to the analysis of the community structure. In this paper, we present an extensive investigation of the overlapping community network deduced from a large-scale co-authorship network. The nodes of the overlapping community network represent the functional communities of the co-authorship network, and the links account for the fact that communities share some nodes in the co-authorship network. The comparative evaluation of the topological properties of these two networks shows that they share similar topological properties. These results are very interesting. Indeed, the network of communities seems to be a good representative of the original co-authorship network. With its smaller size, it may be more practical in order to realize various analyses that cannot be performed easily in large-scale real-world networks.Comment: 2014 7th International Conference on u- and e- Service, Science and Technolog