The intrinsic three-dimensional shape of galactic bars

We present the first statistical study on the intrinsic three-dimensional (3D) shape of a sample of 83 galactic bars extracted from the CALIFA survey. We use the galaXYZ code to derive the bar intrinsic shape with a statistical approach. The method uses only the geometric information (ellipticities and position angles) of bars and discs obtained from a multi-component photometric decomposition of the galaxy surface-brightness distributions. We find that bars are predominantly prolate-triaxial ellipsoids (68%), with a small fraction of oblate-triaxial ellipsoids (32%). The typical flattening (intrinsic C/A semiaxis ratio) of the bars in our sample is 0.34, which matches well the typical intrinsic flattening of stellar discs at these galaxy masses. We demonstrate that, for prolate-triaxial bars, the intrinsic shape of bars depends on the galaxy Hubble type and stellar mass (bars in massive S0 galaxies are thicker and more circular than those in less massive spirals). The bar intrinsic shape correlates with bulge, disc, and bar parameters. In particular with the bulge-to-total (B/T) luminosity ratio, disc g-r color, and central surface brightness of the bar, confirming the tight link between bars and their host galaxies. Combining the probability distributions of the intrinsic shape of bulges and bars in our sample we show that 52% (16%) of bulges are thicker (flatter) than the surrounding bar at 1$\sigma$ level. We suggest that these percentages might be representative of the fraction of classical and disc-like bulges in our sample, respectively.Comment: 18 pages, 11 figures, accepted for publication in MNRA

Ultrastructure of multicellular dwarf males with external gametangium in Oedogonium macrandrium (Oedogoniales, Chlorophyta).

This is the first comprehensive ultrastructural study on dwarf males with external gametangia in the genus Oedogonium, from androspore germination to the liberation of mature male gametes. The ultrastructure of the process in O. macrandrium Wittrok is similar to that of Bulbochaete hiloensis (Nordstedt) Tiffany, but with two remarkable differences. In O. macrandrium: 1) instead of a true transverse wall, only condensed mucilage appears between the gametes of each antheridial cell, and 2) the cell wall between the basal cell and the basal most antheridial cell has simple plasmodesmata similar to those present in the transverse walls of vegetative cells, which are absent in B. hiloensis.Fil: D'Amico, Silvana L.. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ficología y Micología; Argentina;Fil: Leonardi, Patricia Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentina; Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ficología y Micología; Argentina;Fil: Caceres, Eduardo Jorge. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; Argentina; Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ficología y Micología; Argentina

The inner environment of Z~CMa: High-Contrast Imaging Polarimetry with NaCo

Context. Z\,CMa is a binary composed of an embedded Herbig Be and an FU Ori class star separated by $\sim100$ au. Observational evidence indicate a complex environment in which each star has a circumstellar disk and drives a jet, and the whole system is embedded in a large dusty envelope. Aims. We aim to probe the circumbinary environment of Z\,CMa in the inner 400 au in scattered light. Methods. We use high contrast imaging polarimetry with VLT/NaCo at $H$ and $K_s$ bands. Results. The central binary is resolved in both bands. The polarized images show three bright and complex structures: a common dust envelope, a sharp extended feature previously reported in direct light, and an intriguing bright clump located 0\farcs3 south of the binary, which appears spatially connected to the sharp extended feature. Conclusions.We detect orbital motion when compared to previous observations, and report a new outburst driven by the Herbig star. Our observations reveal the complex inner environment of Z\,CMa with unprecedented detail and contrast.Comment: Accepted for publication in A&A Letter

Horta conduzida em escola municipal melhora rendimento dos alunos.

bitstream/item/77702/1/ADM155.pd

Perfil de materia oscura de grupos y cúmulos de galaxias: una aplicación del efecto lente gravitacional galaxia-galaxia

La cosmología se encuentra en una de sus más importantes épocas de desarrollo; los avances teóricos y, más aún, el crecimiento de pruebas cosmológicas de alta precisión (satélites como WMAP y Planck) han impulsado y seguirán impulsando en la cosmología un período de avance sin precedentes en la historia de la física. El paradigma actual del llamado (ΛCDM) es soportado hasta la fecha, no sin problemas, por la teoría general de la relatividad. Sin embargo, dos componentes exóticas son dominantes del modelo cosmológico actual: la materia y la energía oscuras. Nosotros presentamos una de las pruebas más directas y con menos restricciones al estudio de parámetros fundamentales cosmológicos (Ωm, Ωλ, σ8) y estudiamos el uso de la esquila cosmológica en el estudio de la función de correlación de dos puntos. Se discute brevemente el problema del sesgo entre materia luminosa  y materia oscura.      Cosmology is in one of its most important periods of development. Theorical progress, and even more, growth in high-precision cosmological tests (satellites as WMAP and Planck) have given and will continue giving cosmology a period of unprecedented progress in the history of physics. The current paradigm of the so-called (ΛCDM) is supported so far, not without problems, by the general theory of relativity. However, two exotic components are dominant in current cosmological model: the dark matter and energy. We present one of the most direct and with fewer restrictions evidence on the study of fundamental cosmological parameters (Ωm, Ωλ, σ8 ) and analyze the use of shear in the cosmological study of the correlation function of two points. It is also briefly discussed the problem of bias among luminous matter and dark matter.   Keywords:lentes gravitacionales, dark matter profiles, cosmology, power-spectrum

The Energy of a Moving Quark-Antiquark Pair in an N=4 SYM Plasma

We make use of the AdS/CFT correspondence to determine the energy of an external quark-antiquark pair that moves through strongly-coupled thermal N=4 super-Yang-Mills plasma, both in the rest frame of the plasma and in the rest frame of the pair. It is found that the pair feels no drag force, has an energy that reproduces the expected 1/L (or gamma/L) behavior at small quark-antiquark separations, and becomes unbound beyond a certain screening length whose velocity-dependence we determine. We discuss the relation between the high-velocity limit of our results and the lightlike Wilson loop proposed recently as a definition of the jet-quenching parameter.Comment: LaTeX 2e, 27 pages, 8 eps figures; v2: added computation of the pair energy in the plasma rest frame, clarified the comparison with hep-ph/0607062, corrected typos, added reference

Shells and Shapes in the N=28 isotones

International audienceNew experimental results on 43S and 44S reveal that these nuclei are located in a transitional region of shape coexistence between the spherical 48Ca and the oblate 42Si. The origin of the deformation is discussed in terms of the evolution of the single particle energy levels leading to the compression of the energy difference of the orbitals in the sd and pf shells for protons and neutrons, respectively. Therefore, due to quadrupole excitations across the Z = 14 and N = 28 gaps, the intruder configuration in the neutron rich S isotopes became the ground state

Indirect Collider Signals for Extra Dimensions

A recent suggestion that quantum gravity may become strong near the weak scale has several testable consequences. In addition to probing for the new large (submillimeter) extra dimensions associated with these theories via gravitational experiments, one could search for the Kaluza Klein towers of massive gravitons which are predicted in these models and which can interact with the fields of the Standard Model. Here we examine the indirect effects of these massive gravitons being exchanged in fermion pair production in \epem annihilation and Drell-Yan production at hadron colliders. In the latter case, we examine a novel feature of this theory, which is the contribution of gluon gluon initiated processes to lepton pair production. We find that these processes provide strong bounds, up to several TeV, on the string scale which are essentially independent of the number of extra dimensions. In addition, we analyze the angular distributions for fermion pair production with spin-2 graviton exchanges and demonstrate that they provide a smoking gun signal for low-scale quantum gravity which cannot be mimicked by other new physics scenarios.Comment: Corrected typos, added table and reference