The Anisotropy in the Galaxy Velocity Field Originated from the Gravitational Pancaking Effect

We analyze the Millennium run semi-analytic galaxy catalog to explore quantitatively the gravitational pancaking effect on the orientation of galaxy velocity field. We first calculate the probability density distribution of the cosine of the angle between the velocity of a field galaxy and the direction normal to a local pancake plane which is determined using two nearest neighbor field galaxies. A clear signal of alignment is detected for the case that the pancake scale is in the range of $5-8h^{-1}$ Mpc. The tendency of the velocity-pancake alignment is found to still exist when the pancakes are determined using three neighbor galaxies, indicating that it has a spatial coherence. The degree of the velocity-pancake alignment is shown to increase with the velocity magnitude and the local density, while it decreases with the separation distance from the galaxy to the pancake and disappears when the pancake has a filamentary shape. A final conclusion is that our work may provide another clue to understanding the large-scale structure in the universe.Comment: accepted by ApJL, new analyses included, discussions improve

Intrinsic Inclination of Galaxies embedded in Cosmic Sheets and its Cosmological Implications: An Analytic Calculation

We investigate analytically a large-scale coherence in the orientation of galaxies embedded in two-dimensional sheet-like structures in the frame of the tidal torque theory. Assuming that the galaxy spin and the surrounding matter fields are intrinsically aligned in accordance with the tidal torque model, we first derive analytically the probability distribution of the galaxy position angles, and evaluate the degree of their inclinations relative to the plane of the sheet. Then, we apply our analytic approach to the nearby spirals in the Local Super Cluster, and provide theoretical explanations about why and to what degree the nearby spirals are inclined relative to the supergalatic plane. Finally, we conclude that the observed large-scale coherence in the orientation of nearby spirals relative to the supergalactic plane can be quantitatively understood in terms of galaxy intrinsic alignment predicted by the tidal torque theory, and that the spins of luminous galaxies might be more strongly aligned with the surrounding matter than the underlying dark halos. If applied to large scale surveys like Sloan Digital Sky Survey (SDSS), our analytic approach will allow us to measure accurately the strength of galaxy intrinsic alignment which plays a role of statistical error in weak lensing searches and can be used as a fossil record to reconstruct cosmology.Comment: accepted by the ApJ Letters, revised version, typos and mistakes corrected,12 pages, 3 figure

Constraining Disk Parameters of Be Stars using Narrowband H-alpha Interferometry with the NPOI

Interferometric observations of two well-known Be stars, gamma Cas and phi Per, were collected and analyzed to determine the spatial characteristics of their circumstellar regions. The observations were obtained using the Navy Prototype Optical Interferometer equipped with custom-made narrowband filters. The filters isolate the H-alpha emission line from the nearby continuum radiation, which results in an increased contrast between the interferometric signature due to the H-alpha-emitting circumstellar region and the central star. Because the narrowband filters do not significantly attenuate the continuum radiation at wavelengths 50 nm or more away from the line, the interferometric signal in the H-alpha channel is calibrated with respect to the continuum channels. The observations used in this study represent the highest spatial resolution measurements of the H-alpha-emitting regions of Be stars obtained to date. These observations allow us to demonstrate for the first time that the intensity distribution in the circumstellar region of a Be star cannot be represented by uniform disk or ring-like structures, whereas a Gaussian intensity distribution appears to be fully consistent with our observations.Comment: 23 pages, 14 figures, accepted for publication in A

ISO observations of the Galactic center Interstellar Medium: neutral gas and dust

The 500 central pc of the Galaxy (hereafter GC) exhibit a widespread gas component with a kinetic temperature of 100-200 K. The bulk of this gas is not associated to the well-known thermal radio continuum or far infrared sources like Sgr A or Sgr B. How this gas is heated has been a longstanding problem. With the aim of studying the thermal balance of the neutral gas and dust in the GC, we have observed 18 molecular clouds located at projected distances far from thermal continuum sources with the Infrared Space Observatory (ISO). In this paper we present observations of several fine structure lines and the full continuum spectra of the dust between 40 and 190 microns. A warm dust component with a temperature between 27 and 42 K is needed to fit the spectra. We have compared the gas and the dust emission with the predictions from J-type and C-type shocks and photodissociation region (PDRs) models. We conclude that the dust and the fine structure lines observations are best explained by a PDR with a density of 10$^3$ cm^-3 and an incident far-ultraviolet field 10$^3$ times higher than the local interstellar radiation field. PDRs can naturally explain the discrepancy between the gas and the dust temperatures. However, these PDRs can only account for 10-30% of the total H2 column density with a temperature of ~ 150 K. We discuss other possible heating mechanisms (short version).Comment: Accepted for publication by A&

Disentangling the Cosmic Web I: Morphology of Isodensity Contours

We apply Minkowski functionals and various derived measures to decipher the morphological properties of large-scale structure seen in simulations of gravitational evolution. Minkowski functionals of isodensity contours serve as tools to test global properties of the density field. Furthermore, we identify coherent objects at various threshold levels and calculate their partial Minkowski functionals. We propose a set of two derived dimensionless quantities, planarity and filamentarity, which reduce the morphological information in a simple and intuitive way. Several simulations of the gravitational evolution of initial power-law spectra provide a framework for systematic tests of our method.Comment: 26 pages including 12 figures. Accepted for publication in Ap

Tidal disruption of NEAs - a case of P\v{r}\'ibram

This work studies the dynamical evolution of a possible meteor stream along the orbit of the P\v{r}\'{i}bram meteorite, which originated in the tidal disruption of the putative rubble-pile-like parent body during a close approach to the Earth. We assumed the disruption at the time when the ascending or descending node of the parent orbit was close to the Earth's orbit. In the last 5000 years, the P\v{r}\'{i}bram orbit has crossed the Earth orbit twice. It happened about 4200 years and 3300 years ago. In both cases, we modeled the release of particles from the simplified model of rotating asteroid, and traced their individual orbital evolution to the current date. It takes several hundred years to spread released meteoroids along the entire orbit of the parent body. Even today, the stream would be relatively narrow. Considering a model parent body with physical parameters of the asteroid Itokawa, the complete disintegration of the object produced 3.8$\times10^{11}$ meteoroid particles with diameter $\geq$ 1\,cm. The meteor activity observed from the Earth is revealed and justification of follow-up observation during suggested activity of the shower in the first two weeks of April is discussed. The Earth's tidal forces would disintegrate a fraction of NEA population into smaller objects. We evaluate the upper limit of mass of disintegrated asteroids within the mean NEA lifetime and the contribution of disrupted matter to the size distribution of the NEA.Comment: 8 pages, 10 figure

Steps toward the power spectrum of matter. II. The biasing correction with sigma_8 normalization

A new method to determine the bias parameter of galaxies relative to matter is suggested. The method is based on the assumption that gravity is the dominating force which determines the formation of the structure in the Universe. Due to gravitational instability the galaxy formation is a threshold process: in low-density environments galaxies do not form and matter remains in primordial form. We investigate the influence of the presence of void and clustered populations to the power spectrum of matter and galaxies. The power spectrum of galaxies is similar to the power spectrum of matter; the fraction of total matter in the clustered population determines the difference between amplitudes of fluctuations of matter and galaxies, i.e. the bias factor. To determine the fraction of matter in voids and clustered population we perform numerical simulations. The fraction of matter in galaxies at the present epoch is found using a calibration through the sigma_8 parameter.Comment: LaTex (sty files added), 31 pages, 4 PostScript figures embedded, Astrophysical Journal (accepted

Cross-Disorder Genome-Wide Analyses Suggest a Complex Genetic Relationship Between Tourette\u27s Syndrome and OCD

OBJECTIVE: Obsessive-compulsive disorder (OCD) and Tourette\u27s syndrome are highly heritable neurodevelopmental disorders that are thought to share genetic risk factors. However, the identification of definitive susceptibility genes for these etiologically complex disorders remains elusive. The authors report a combined genome-wide association study (GWAS) of Tourette\u27s syndrome and OCD. METHOD: The authors conducted a GWAS in 2,723 cases (1,310 with OCD, 834 with Tourette\u27s syndrome, 579 with OCD plus Tourette\u27s syndrome/chronic tics), 5,667 ancestry-matched controls, and 290 OCD parent-child trios. GWAS summary statistics were examined for enrichment of functional variants associated with gene expression levels in brain regions. Polygenic score analyses were conducted to investigate the genetic architecture within and across the two disorders. RESULTS: Although no individual single-nucleotide polymorphisms (SNPs) achieved genome-wide significance, the GWAS signals were enriched for SNPs strongly associated with variations in brain gene expression levels (expression quantitative loci, or eQTLs), suggesting the presence of true functional variants that contribute to risk of these disorders. Polygenic score analyses identified a significant polygenic component for OCD (p=2x10(-4)), predicting 3.2% of the phenotypic variance in an independent data set. In contrast, Tourette\u27s syndrome had a smaller, nonsignificant polygenic component, predicting only 0.6% of the phenotypic variance (p=0.06). No significant polygenic signal was detected across the two disorders, although the sample is likely underpowered to detect a modest shared signal. Furthermore, the OCD polygenic signal was significantly attenuated when cases with both OCD and co-occurring Tourette\u27s syndrome/chronic tics were included in the analysis (p=0.01). CONCLUSIONS: Previous work has shown that Tourette\u27s syndrome and OCD have some degree of shared genetic variation. However, the data from this study suggest that there are also distinct components to the genetic architectures of these two disorders. Furthermore, OCD with co-occurring Tourette\u27s syndrome/chronic tics may have different underlying genetic susceptibility compared with OCD alone