Context. X-ray surveys facilitate investigations of the environment of AGNs. Deep Chandra observations revealed that the AGNs source surface density rises near clusters of galaxies. The natural extension of these works is the measurement of spatial clustering of AGNs around clusters and the investigation of relative biasing between active galactic nuclei and galaxies near clusters. Aims. The ma...

Semi-supervised clustering aims to improve clustering performance by considering user-provided side information in the form of pairwise constraints. We study the active learning problem of selecting must-link and cannot-link pairwise constraints for semi-supervised clustering. We consider active learning in an iterative framework; each iteration queries are selected based on the current cluster...

We present a simple framework for the growth and evolution of supermassive black holes (SMBHs) in the hierarchical structure formation paradigm, adopting the general idea that quasar activity is triggered in major mergers. In our model, black hole accretion is triggered during major mergers (mass ratio & 0.3) between host dark matter halos. The successive evolution of quasar luminosities follow...

We present the result of projected cross correlation analysis of AGNs and galaxies at redshifts from 0.3 to 3.0. We used the Japanese Virtual Observatory (JVO) to obtain the Subaru Suprime-Cam images and UKIDSS catalog data around known AGNs. We investigated ∼1,000 AGNs, which is about ten times larger samples than previous studies covering the redshifts larger than 0.6. We found significant ex...

The spatial clustering amplitude (B gq) is determined for a sample of 44 powerful AGN at z ≃ 0.2. No significant difference is detected in the richness of the cluster environments of the radio-loud and radio-quiet sub-samples, both of which typically inhabit environments as rich as Abell Class ≃ 0. Comparison with radio luminosity-matched samples from Hill & Lilly (1991) and Wold et al. (2000a)...

We present the two-point correlation function (2PCF) of narrow-line active galactic nuclei (AGNs) selected within the First Data Release of the Sloan Digital Sky Survey. Using a sample of 13,605 AGNs in the redshift range , we find that the AGN autocorrelation function is consistent with the observed galaxy 0.055 ! z ! 0.2 autocorrelation function on scales from 0.2 to greater than 100 h 1 Mpc....

The observed number counts of quasars may be explained either by long-lived activity within rare massive hosts, or by short-lived activity within smaller, more common hosts. It has been argued that quasar lifetimes may therefore be inferred from their clustering length, which determines the typical mass of the quasar host. Here we point out that the relationship between the mass of the black-ho...

Using XMM-Newton EPIC imaging data, we have detected 50 low-luminosity X-ray sources in the field of view of M 22, where 5±3 of these sources are likely to be related to the cluster. Using differential optical photometry, we have identified probable counterparts to those sources belonging to the cluster. Using X-ray spectroscopic and timing studies, supported by the optical colours, we propose ...

The multiple active contours (snakes) are widely used in image processing to extract objects of interest. However, initialization of the active contours is still an open problem. This paper proposes a new completely automatic initialization of snakes based on a combination of Phrase Portrait Analysis (PPA) image intensity clustering and multi-stage evolution of the active contours. The proposed...

In this paper, we have proposed an algorithm to detect and locate the nuclei from cell masses and then segmentation ofoverlapped cervical in MRI images. Detection of cancerous area with fine boundaries in overlapped cell clusters is an important butchallenging task.In this proposed approach, multiple cell masses are detected from MRI images of overlapped cervical cells by generating superpixels...