Cosmological Implications of the Fundamental Relations of X-ray Clusters

Based on the two-parameter family nature of X-ray clusters of galaxies obtained in a separate paper, we discuss the formation history of clusters and cosmological parameters of the universe. Utilizing the spherical collapse model of cluster formation, and assuming that the cluster X-ray core radius is proportional to the virial radius at the time of the cluster collapse, the observed relations among the density, radius, and temperature of clusters imply that cluster formation occurs in a wide range of redshift. The observed relations favor the low-density universe. Moreover, we find that the model of $n\sim -1$ is preferable.Comment: 7 pages, 4 figures. To be published in ApJ Letter

Merging history as a function of halo environment

According to the hierarchical scenario, galaxies form via merging and accretion of small objects. Using N-body simulations, we study the frequency of merging events in the history of the halos. We find that at z<~2 the merging rate of the overall halo population can be described by a simple power law (1+z)^3. The main emphasis of the paper is on the effects of environment of halos at the present epoch (z=0). We find that the halos located inside clusters have formed earlier (dz \approx 1) than isolated halos of the same mass. At low redshifts (z<1), the merger rate of cluster halos is 3 times lower than that of isolated halos and 2 times lower than merger rate of halos that end up in groups by z=0. At higher redshifts (z~1-4), progenitors of cluster and group halos have 3--5 times higher merger rates than isolated halos. We briefly discuss implications of our results for galaxy evolution in different environments.Comment: submitted to the Astrophys. Journal; 11 pages, 9 figs., LaTeX (uses emulateapj.sty

Normalizing the Temperature Function of Clusters of Galaxies

We re-examine the constraints which can be robustly obtained from the observed temperature function of X-ray cluster of galaxies. The cluster mass function has been thoroughly studied in simulations and analytically, but a direct simulation of the temperature function is presented here for the first time. Adaptive hydrodynamic simulations using the cosmological Moving Mesh Hydro code of Pen (1997a) are used to calibrate the temperature function for different popular cosmologies. Applying the new normalizations to the present-day cluster abundances, we find $\sigma_8=0.53\pm 0.05 \Omega_0^{-0.45}$ for a hyperbolic universe, and $\sigma_8=0.53\pm 0.05 \Omega_0^{-0.53}$ for a spatially flat universe with a cosmological constant. The simulations followed the gravitational shock heating of the gas and dark matter, and used a crude model for potential energy injection by supernova heating. The error bars are dominated by uncertainties in the heating/cooling models. We present fitting formulae for the mass-temperature conversions and cluster abundances based on these simulations.Comment: 20 pages incl 5 figures, final version for ApJ, corrected open universe \gamma relation, results unchange

Interação irrigação-clone-adubação na antracnose do cajueiro.

bitstream/item/45553/1/BPD11005.pd

Do the words matter? An analysis of the linguistic sentiment of earnings conference calls and abnormal stock returns in brazilian companies

In finance and accounting literature, different aspects are presented as possible factors related to stock returns. More recently, studies have been dedicated to analyzing the potential influence of the tone and sentiment of corporate reports, newspaper articles, press releases, and investor message boards on stock prices. Thus, based on assumptions of Legitimacy Theory, we investigate whether cumulative abnormal returns (CAR) on the stocks of Brazilian listed companies are associated with the linguistic sentiment of quarterly earnings conference calls. Using a sample of 78 observations related to the conference calls of 24 companies listed in the Novo Mercado segment in 2016-2017, we measured CAR using the market model and the linguistic sentiment of earnings conference calls using IBM’s Watson Natural Language Understanding platform. An analysis of the results of statistical tests such as descriptive results, correlation matrix, and correspondence analysis enables it to be inferred that, in general, there is a positive association between cumulative abnormal returns and the optimism sentiment of quarterly conference calls. Thus, it is conjectured the possibility that the speeches made by managers in conference calls legitimize company performance in the market, by altering the perception of investors in the stock market and leading to implications for the value of the stocks traded.info:eu-repo/semantics/publishedVersio

Constraining the Matter Power Spectrum Normalization using the SDSS/RASS and REFLEX Cluster surveys

We describe a new approach to constrain the amplitude of the power spectrum of matter perturbations in the Universe, parametrized by sigma_8 as a function of the matter density Omega_0. We compare the galaxy cluster X-ray luminosity function of the REFLEX survey with the theoretical mass function of Jenkins et al. (2001), using the mass-luminosity relationship obtained from weak lensing data for a sample of galaxy clusters identified in Sloan Digital Sky Survey commissioning data and confirmed through cross-correlation with the ROSAT all-sky survey. We find sigma_8 = 0.38 Omega_0^(-0.48+0.27 Omega_ 0), which is significantly different from most previous results derived from comparable calculations that used the X-ray temperature function. We discuss possible sources of systematic error that may cause such a discrepancy, and in the process uncover a possible inconsistency between the REFLEX luminosity function and the relation between cluster X-ray luminosity and mass obtained by Reiprich & Bohringer (2001).Comment: Accepted to ApJ Letters. 4 pages using emulateapj.st