Predicting the Clustering of X-Ray Selected Galaxy Clusters in Flux-Limited Surveys

(abridged) We present a model to predict the clustering properties of X-ray clusters in flux-limited surveys. Our technique correctly accounts for past light-cone effects on the observed clustering and follows the non-linear evolution in redshift of the underlying DM correlation function and cluster bias factor. The conversion of the limiting flux of a survey into the corresponding minimum mass of the hosting DM haloes is obtained by using theoretical and empirical relations between mass, temperature and X-ray luminosity of clusters. Finally, our model is calibrated to reproduce the observed cluster counts adopting a temperature-luminosity relation moderately evolving with redshift. We apply our technique to three existing catalogues: BCS, XBACs and REFLEX samples. Moreover, we consider an example of possible future space missions with fainter limiting flux. In general, we find that the amplitude of the spatial correlation function is a decreasing function of the limiting flux and that the EdS models always give smaller correlation amplitudes than open or flat models with low matter density parameter. In the case of XBACs, the comparison with previous estimates of the observational spatial correlation shows that only the predictions of models with Omega_0m=0.3 are in good agreement with the data, while the EdS models have too low a correlation strength. Finally, we use our technique to discuss the best strategy for future surveys. Our results show that the choice of a wide area catalogue, even with a brighter limiting flux, is preferable to a deeper, but with smaller area, survey.Comment: 20 pages, Latex using MN style, 11 figures enclosed. Version accepted for publication in MNRA

Gravitational Quenching in Massive Galaxies and Clusters by Clumpy Accretion

We consider a simple gravitational-heating mechanism for the long-term quenching of cooling flows and star formation in massive dark-matter haloes hosting ellipticals and clusters. The virial shock heating in haloes >10^12 Mo triggers quenching in 10^12-13 Mo haloes (Birnboim, Dekel & Neistein 2007). We show that the long-term quenching in haloes >Mmin~7x10^12 Mo could be due to the gravitational energy of cosmological accretion delivered to the inner-halo hot gas by cold flows via ram-pressure drag and local shocks. Mmin is obtained by comparing the gravitational power of infall into the potential well with the overall radiative cooling rate. The heating wins if the gas inner density cusp is not steeper than r^-0.5 and if the masses in the cold and hot phases are comparable. The effect is stronger at higher redshifts, making the maintenance easier also at later times. Clumps >10^5 Mo penetrate to the inner halo with sufficient kinetic energy before they disintegrate, but they have to be <10^8 Mo for the drag to do enough work in a Hubble time. Pressure confined ~10^4K clumps are stable against their own gravity and remain gaseous once below the Bonnor-Ebert mass ~10^8 Mo. They are also immune to tidal disruption. Clumps in the desired mass range could emerge by thermal instability in the outer halo if the conductivity is not too high. Alternatively, such clumps may be embedded in dark-matter subhaloes if the ionizing flux is ineffective, but they separate from their subhaloes by ram pressure before entering the inner halo. Heating by dynamical friction becomes dominant for massive satellites, which can contribute up to one third of the total gravitational heating. We conclude that gravitational heating by cosmological accretion is a viable alternative to AGN feedback as a long-term quenching mechanism.Comment: 24 pages, 20 figures, some improvements, MNRAS accepted versio

Tracing cosmic evolution with clusters of galaxies

The most successful cosmological models to date envision structure formation as a hierarchical process in which gravity is constantly drawing lumps of matter together to form increasingly larger structures. Clusters of galaxies currently sit atop this hierarchy as the largest objects that have had time to collapse under the influence of their own gravity. Thus, their appearance on the cosmic scene is also relatively recent. Two features of clusters make them uniquely useful tracers of cosmic evolution. First, clusters are the biggest things whose masses we can reliably measure because they are the largest objects to have undergone gravitational relaxation and entered into virial equilibrium. Mass measurements of nearby clusters can therefore be used to determine the amount of structure in the universe on scales of 10^14 to 10^15 solar masses, and comparisons of the present-day cluster mass distribution with the mass distribution at earlier times can be used to measure the rate of structure formation, placing important constraints on cosmological models. Second, clusters are essentially ``closed boxes'' that retain all their gaseous matter, despite the enormous energy input associated with supernovae and active galactic nuclei, because the gravitational potential wells of clusters are so deep. The baryonic component of clusters therefore contains a wealth of information about the processes associated with galaxy formation, including the efficiency with which baryons are converted into stars and the effects of the resulting feedback processes on galaxy formation. This article reviews our theoretical understanding of both the dark-matter component and the baryonic component of clusters. (Abridged)Comment: 54 pages, 15 figures, Rev. Mod. Phys. (in press

Gene Expression Patterns in Peripheral Blood Correlate with the Extent of Coronary Artery Disease

Systemic and local inflammation plays a prominent role in the pathogenesis of atherosclerotic coronary artery disease, but the relationship of whole blood gene expression changes with coronary disease remains unclear. We have investigated whether gene expression patterns in peripheral blood correlate with the severity of coronary disease and whether these patterns correlate with the extent of atherosclerosis in the vascular wall

Effects of AGN feedback on LCDM galaxies

We study the effects of Active Galactic Nuclei (AGN) feedback on the formation and evolution of galaxies in a semi-analytic model of galaxy formation. This model is an improved version of the one described by Cora (2006), which now considers the growth of black holes (BHs) as driven by (i) gas accretion during merger-driven starbursts and mergers with other BHs, (ii) accretion during starbursts triggered by disc instabilities, and (iii) accretion of gas cooled from quasi-hydrostatic hot gas haloes. It is assumed that feedback from AGN operates in the later case. The model has been calibrated in order to reproduce observational correlations between BH mass and mass, velocity dispersion, and absolute magnitudes of the galaxy bulge. AGN feedback has a strong impact on reducing or even suppressing gas cooling, an effect that becomes important at lower redshifts. This phenomenon helps to reproduce the observed galaxy luminosity function (LF) in the optical and near IR bands at z=0, and the cosmic star formation rate and stellar mass functions over a wide redshift range (0<z<5). It also allows to have a population of massive galaxies already in place at z>1, which are mostly early-type and have older and redder stellar populations than lower mass galaxies, reproducing the observed bimodality in the galaxy colour distribution, and the morphological fractions. The evolution of the optical QSO LF is also reproduced, provided that the presence of a significant fraction of obscured QSOs is assumed. We explore the effects of AGN feedback during starbursts and new recent prescriptions for dynamical friction time-scales. (ABRIDGED)Comment: 18 pages, 15 figures. Accepted for publication in MNRAS. High resolution figures available at: http://www.astro.puc.cl/~clagos/AGNOnLCDMGals.pd

Differential expression of anterior gradient gene AGR2 in prostate cancer

<p>Abstract</p> <p>Background</p> <p>The protein AGR2 is a putative member of the protein disulfide isomerase family and was first identified as a homolog of the <it>Xenopus laevis </it>gene XAG-2. AGR2 has been implicated in a number of human cancers. In particular, AGR2 has previously been found to be one of several genes that encode secreted proteins showing increased expression in prostate cancer cells compared to normal prostatic epithelium.</p> <p>Methods</p> <p>Gene expression levels of AGR2 were examined in prostate cancer cells by microarray analysis. We further examined the relationship of AGR2 protein expression to histopathology and prostate cancer outcome on a population basis using tissue microarray technology.</p> <p>Results</p> <p>At the RNA and protein level, there was an increase in AGR2 expression in adenocarcinoma of the prostate compared to morphologically normal prostatic glandular epithelium. Using a tissue microarray, this enhanced AGR2 expression was seen as early as premalignant PIN lesions. Interestingly, within adenocarcinoma samples, there was a slight trend toward lower levels of AGR2 with increasing Gleason score. Consistent with this, relatively lower levels of AGR2 were highly predictive of disease recurrence in patients who had originally presented with high-stage primary prostate cancer (P = 0.009).</p> <p>Conclusions</p> <p>We have shown for the first time that despite an increase in AGR2 expression in prostate cancer compared to non-malignant cells, relatively lower levels of AGR2 are highly predictive of disease recurrence following radical prostatectomy.</p

Identification of Methylated Genes Associated with Aggressive Bladder Cancer

Approximately 500,000 individuals diagnosed with bladder cancer in the U.S. require routine cystoscopic follow-up to monitor for disease recurrences or progression, resulting in over $2 billion in annual expenditures. Identification of new diagnostic and monitoring strategies are clearly needed, and markers related to DNA methylation alterations hold great promise due to their stability, objective measurement, and known associations with the disease and with its clinical features. To identify novel epigenetic markers of aggressive bladder cancer, we utilized a high-throughput DNA methylation bead-array in two distinct population-based series of incident bladder cancer (n = 73 and n = 264, respectively). We then validated the association between methylation of these candidate loci with tumor grade in a third population (n = 245) through bisulfite pyrosequencing of candidate loci. Array based analyses identified 5 loci for further confirmation with bisulfite pyrosequencing. We identified and confirmed that increased promoter methylation of HOXB2 is significantly and independently associated with invasive bladder cancer and methylation of HOXB2, KRT13 and FRZB together significantly predict high-grade non-invasive disease. Methylation of these genes may be useful as clinical markers of the disease and may point to genes and pathways worthy of additional examination as novel targets for therapeutic treatment