The X-ray Luminosity Function of Nearby Rich and Poor Clusters of Galaxies: A Cosmological Probe

In this letter, we present a new determination of the local (z<0.09) X-ray luminosity function (XLF) using a large, statistical sample of 294 Abell clusters and the ROSAT All-Sky-Survey. Given our large sample size, we have reduced errors by a factor of two for L(X)(0.5-2keV)>10^43 ergs/sec. We combine our data with previous work in order to explore possible constraints imposed by the shape of the XLF on cosmological models. A set of currently viable cosmologies is used to construct theoretical XLFs assuming Lx is proportional to M^p and a sigma_8-Omega_0 constraint (from Viana & Liddle 1996) based on the local X-ray temperature function. We fit these models to our observed XLF and verify that the simplest adiabatic, analytic scaling relation (e.g. Kaiser 1986) disagrees strongly with observations. If we assume that clusters can be described by the pre-heated, constant core-entropy models of Evrard & Henry (1991) then the observed XLF is consistent only with 0.1 < Omega_0 < 0.4 if the energy per unit mass in galaxies is roughly equal to the gas energy (ie if beta=1). (abridged)Comment: 4 pages, 2 figures, accepted for publication in ApJ Letters. uses emulateapj.st

Early childhood adversity and adolescent depression: the mediating role of continued stress

Background. While various conceptualizations of the link between childhood adversity and later depression have been offered, most have not accounted for the possibility that early adversity predicts continuing stress proximal to depression onset. Thus, the present study tested the possible mediating role of recent stress in the association between early adversity and depression in late adolescence

Evidence of Substructure in the Cluster of Galaxies A3558

We investigate the dynamical properties of the cluster of galaxies A3558 (Shapley 8). Studying a region of one square degree ($\sim$ 3 Mpc$^2$) centered on the cluster cD galaxy, we have obtained a statistically complete photometric catalog with positions and magnitudes of 1421 galaxies (down to a limiting magnitude of $B \sim 21$). This catalog has been matched to the recent velocity data obtained by Mazure et al. (1997) and from the literature, yielding a radial velocity catalog containing 322 galaxies. Our analysis shows that the position/velocity space distribution of galaxies shows significant substructure. A central bimodal core detected previously in preliminary studies is confirmed by using the Adaptive Kernel Technique and Wavelet Analysis. We show that this central bimodal subtructure is nevertheless composed of a projected feature, kinematically unrelated to the cluster, plus a group of galaxies probably in its initial merging phase into a relaxed core. The cD velocity offset with respect to the average cluster redshift, reported earlier by several authors, is completely eliminated as a result of our dynamical analysis. The untangling of the relaxed core component also allows a better, more reliable determination of the central velocity dispersion, which in turn eliminates the ``$\beta$-problem'' for A3558. The cluster also shows a ``preferential'' distribution of subclumps coinciding with the direction of the major axis position angle of the cD galaxy and of the central X-ray emission ellipsoidal distribution, in agreement with an anisotropic merger scenario.Comment: 35 pages in latex, 17 figures in Postscript, accepted for publication in the Astrophysical Journa

Investigating Veterans’ Pre-, Peri-, and Post-Deployment Experiences as Potential Risk Factors for Problem Gambling

Background and aims Gambling disorder and its comorbid diagnoses are observed at higher rates in military veterans than in the general population. A significant research gap exists regarding the relationships of veterans’ life and service experiences to problematic gambling. The present study explored pre-, peri-, and post-deployment factors associated with problem gambling in veterans. Methods Veterans of Operation Iraqi Freedom, Operation Enduring Freedom, and Operation New Dawn (n = 738; 463 males, and 275 females) completed questionnaires via structured telephone interview. We conducted bivariate and multinomial logistic regression analyses exploring associations among problem-gambling severity and socio-demographic variables, psychiatric comorbidities, and 10 scales of the Deployment Risk and Resilience Inventory measuring experiences pre-, peri-, and post-deployment. Results Approximately 4.2% of veterans indicated at-risk or probable pathological gambling (ARPG) post-deployment (two or more DSM-IV criteria for pathological gambling). Bivariate analyses found more severe gambling in males, higher frequencies of post-traumatic stress disorder, substance dependence, traumatic brain injury, panic disorder, and depression in veterans with ARPG, and higher general harassment during deployment, and lower social support and more stressful life events post-deployment in those with ARPG. In multivariable models, both post-deployment factors remained significantly associated with ARPG. Discussion The study suggests that problem gambling among veterans is related to service experiences, and particularly to life experiences post-deployment. Conclusions Adverse service and life experiences and lack of social support may contribute to the risk of problem gambling in military veterans. Investigation of how Veterans Affairs clinical settings may serve veterans following deployment to prevent behavioral addictions is warranted

Projection, Spatial Correlations, and Anisotropies in a Large and Complete Sample of Abell Clusters

An analysis of R >= 1 Abell clusters is presented for samples containing recent redshifts from the MX Northern Abell Cluster Survey. The newly obtained redshifts from the MX Survey as well as those from the ESO Nearby Abell Cluster Survey (ENACS) provide the necessary data for the largest magnitude-limited correlation analysis of rich clusters in the entire sky (excluding the galactic plane) to date. We find 19.4 <= r_0 <= 23.3 h^-1Mpc, -1.92 <= gamma <= -1.83 for four different subsets of Abell/ACO clusters, including a large sample (N=104) of cD clusters. We have used this dataset to look for line-of-sight anisotropies within the Abell/ACO catalogs. We show that the strong anisotropies present in previously studied Abell cluster datasets are not present in our R >= 1 samples. There are, however, indications of residual anisotropies which we show are the result of two elongated superclusters, Ursa Majoris and Corona Borealis, whose axes lie near the line-of-sight. After rotating these superclusters so that their semi-major axes are prependicular to the line-of-sight, we find no anisotropies as indicated by the correlation function. The amplitude and slope of the two-point correlation function remain the same before and after these rotations. We also remove a subset of R = 1 Abell/ACO clusters that show sizable foreground/background galaxy contamination and again find no change in the amplitude or slope of the correlation function. We conclude that the correlation length of R >= 1 Abell clusters is not artificially enhanced by line-of-sight anisotropies.Comment: 37 pages, 8 figures, AASTeX Accepted for publication in Ap

The Aquarius Superclusters - I. Identification of Clusters and Superclusters

We study the distribution of galaxies and galaxy clusters in a 10^deg x 6^deg field in the Aquarius region. In addition to 63 clusters in the literature, we have found 39 new candidate clusters using a matched-filter technique and a counts-in-cells analysis. From redshift measurements of galaxies in the direction of these cluster candidates, we present new mean redshifts for 31 previously unobserved clusters, while improved mean redshifts are presented for 35 other systems. About 45% of the projected density enhancements are due to the superposition of clusters and/or groups of galaxies along the line of sight, but we could confirm for 72% of the cases that the candidates are real physical associations similar to the ones classified as rich galaxy clusters. On the other hand, the contamination due to galaxies not belonging to any concentration or located only in small groups along the line of sight is ~ 10%. Using a percolation radius of 10 h^{-1} Mpc (spatial density contrast of about 10), we detect two superclusters of galaxies in Aquarius, at z = 0.086 and at z = 0.112, respectively with 5 and 14 clusters. The latter supercluster may represent a space overdensity of about 160 times the average cluster density as measured from the Abell et al. (1989) cluster catalog, and is possibly connected to a 40 h^{-1} Mpc filament from z ~ 0.11 to 0.14.Comment: LateX text (21 pages) and 12 (ps/eps/gif) figures; figures 5a, 5b and 6 are not included in the main LateX text; to be published in the Astronomical Journal, March issu

Boosting local search thanks to {CDCL}

International audienceIn this paper, a novel hybrid and complete approach for propositional satisfiability, called SAT HYS (Sat Hybrid Solver), is introduced. It efficiently combines the strength of both local search and CDCL based SAT solvers. Considering the consistent partial assignment under construction by the CDCL SAT solver, local search is used to extend it to a model of the Boolean formula, while the CDCL component is used by the local search one as a strategy to escape from a local minimum. Additionally, both solvers heavily cooperate thanks to relevant information gathered during search. Experimentations on SAT instances taken from the last competitions demonstrate the efficiency and the robustness of our hybrid solver with respect to the state-of-the-art CDCL based, local search and hybrid SAT solvers

The ROSAT All-Sky Survey: a Catalog of Clusters of Galaxies in a Region of 1 Ster around the South Galactic Pole

A field of 1.013 ster in the ROSAT all-sky survey (RASS), centered on the south galactic pole (SGP), has been searched in a systematic, objective manner for clusters of galaxies. The procedure relied on a correlation of the X-ray positions and properties of ROSAT sources with the distribution of galaxies in the COSMOS digitised data base, which was obtained by scanning the plates of the UK Schmidt IIIa-J optical southern sky survey. The study used the second ROSAT survey data base (RASS-2) and included several optical observing campaigns to measure redshifts. The search, a precursor to the larger REFLEX survey of the whole southern sky, reached the detection limits of the RASS and the COSMOS data, and yielded a catalog of 186 clusters in which the lowest flux is 1.5e-12 erg/cm2/s in the 0.1-2.4 keV band. Of these 157 have measured redshifts. Using a limit of 3.0e-12 erg/cm2/s a complete subset of 112 clusters was obtained, of which 110 have measured redshifts. The spatial distribution of the X-ray clusters out to z = 0.15 shows an extension of the Local Supercluster to the Pisces-Cetus supercluster (z<~0.07), and a more distant orthogonal structure at 0.07<z<0.15.Comment: To be published in ApJ Supplements in February 2002: 53 pages: 18 figure

A Flux-limited Sample of Bright Clusters of Galaxies from the Southern Part of the ROSAT All-Sky Survey: the Catalog and the LogN-LogS

We describe the selection of an X-ray flux-limited sample of bright clusters of galaxies in the southern hemisphere, based on the first analysis of the ROSAT All-Sky Survey data (RASS1). The sample is constructed starting from an identification of candidate clusters in RASS1, and their X-ray fluxes are remeasured using the Steepness Ratio Technique. This method is better suited than the RASS1 standard algorithm for measuring flux from extended sources. The final sample is count-rate-limited in the ROSAT hard band (0.5-2.0 keV), so that due to the distribution of NH, its effective flux limit varies between about 3-4 x 10**-12 ergs cm**-2 s**-1 over the selected area. This covers the Decl<2.5 deg part of the south Galactic cap region (b<-20 deg) - with the exclusion of patches of low RASS1 exposure time and of the Magellanic Clouds area - for a total of 8235 deg**2. 130 candidate sources fulfill our selection criteria for bonafide clusters of galaxies in this area. Of these, 101 are Abell/ACO clusters, while 29 do not have a counterpart in these catalogs. Of these clusters, 126 (97%) clusters have a redshift and for these we compute an X-ray luminosity. 20% of the cluster redshifts come from new observations, as part of the ESO Key Program REFLEX Cluster Survey that is under completion. Considering the intrinsic biases and incompletenesses introduced by the flux selection and source identification processes, we estimate the overall completeness to be better than 90%. The observed number count distribution, LogN-LogS, is well fitted by a power law with slope alpha = 1.34 +/- 0.15 and normalization A = 11.87 +/- 1.04 sr**-1 (10**-11 ergs cm**-2 s**-1)**alpha, in good agreement with other measurements.Comment: 27 pages, 8 figures and 3 tables included, LaTex, emulateapj.sty and epsf.sty, accepted for publication in ApJ: scheduled for the March 20, 1999, Vol.514. The cluster catalog is available at http://www.merate.mi.astro.it/~degrand