A Chemical Composition Survey of the Iron-Complex Globular Cluster NGC 6273 (M 19)

Recent observations have shown that a growing number of the most massive Galactic globular clusters contain multiple populations of stars with different [Fe/H] and neutron-capture element abundances. NGC 6273 has only recently been recognized as a member of this "iron-complex" cluster class, and we provide here a chemical and kinematic analysis of > 300 red giant branch (RGB) and asymptotic giant branch (AGB) member stars using high resolution spectra obtained with the Magellan-M2FS and VLT-FLAMES instruments. Multiple lines of evidence indicate that NGC 6273 possesses an intrinsic metallicity spread that ranges from about [Fe/H] = -2 to -1 dex, and may include at least three populations with different [Fe/H] values. The three populations identified here contain separate first (Na/Al-poor) and second (Na/Al-rich) generation stars, but a Mg-Al anti-correlation may only be present in stars with [Fe/H] > -1.65. The strong correlation between [La/Eu] and [Fe/H] suggests that the s-process must have dominated the heavy element enrichment at higher metallicities. A small group of stars with low [alpha/Fe] is identified and may have been accreted from a former surrounding field star population. The cluster's large abundance variations are coupled with a complex, extended, and multimodal blue horizontal branch (HB). The HB morphology and chemical abundances suggest that NGC 6273 may have an origin that is similar to omega Cen and M 54.Comment: Accepted for Publication in The Astrophysical Journal; 50 pages; 18 figures; 8 tables; higher resolution figures are available upon request or in the published journal articl

Exploring the Chemical Composition and Double Horizontal Branch of the Bulge Globular Cluster NGC 6569

Photometric and spectroscopic analyses have shown that the Galactic bulge cluster Terzan 5 hosts several populations with different metallicities and ages that manifest as a double red horizontal branch (HB). A recent investigation of the massive bulge cluster NGC 6569 revealed a similar, though less extended, HB luminosity split, but little is known about the cluster's detailed chemical composition. Therefore, we have used high-resolution spectra from the Magellan-M2FS and VLT-FLAMES spectrographs to investigate the chemical compositions and radial velocity distributions of red giant branch and HB stars in NGC 6569. We found the cluster to have a mean heliocentric radial velocity of -48.8 km/s (sigma = 5.3 km/s; 148 stars) and a mean [Fe/H] =-0.87 dex (19 stars), but the cluster's 0.05 dex [Fe/H] dispersion precludes a significant metallicity spread. NGC 6569 exhibits light- and heavy-element distributions that are common among old bulge/inner Galaxy globular clusters, including clear (anti)correlations between [O/Fe], [Na/Fe], and [Al/Fe]. The light-element data suggest that NGC 6569 may be composed of at least two distinct populations, and the cluster's low mean [La/Eu] = -0.11 dex indicates significant pollution with r-process material. We confirm that both HBs contain cluster members, but metallicity and light-element variations are largely ruled out as sources for the luminosity difference. However, He mass fraction differences as small as delta Y ~ 0.02 cannot be ruled out and may be sufficient to reproduce the double HB.Comment: 72 pages, 14 figures, 8 tables; published in The Astronomical Journal; electronic versions of all tables are available in the published versio

Identification of sex hormone-binding globulin in the human hypothalamus

Gonadal steroids are known to influence hypothalamic functions through both genomic and non-genomic pathways. Sex hormone-binding globulin ( SHBG) may act by a non-genomic mechanism independent of classical steroid receptors. Here we describe the immunocytochemical mapping of SHBG-containing neurons and nerve fibers in the human hypothalamus and infundibulum. Mass spectrometry and Western blot analysis were also used to characterize the biochemical characteristics of SHBG in the hypothalamus and cerebrospinal fluid (CSF) of humans. SHBG-immunoreactive neurons were observed in the supraoptic nucleus, the suprachiasmatic nucleus, the bed nucleus of the stria terminalis, paraventricular nucleus, arcuate nucleus, the perifornical region and the medial preoptic area in human brains. There were SHBG-immunoreactive axons in the median eminence and the infundibulum. A partial colocalization with oxytocin could be observed in the posterior pituitary lobe in consecutive semithin sections. We also found strong immunoreactivity for SHBG in epithelial cells of the choroid plexus and in a portion of the ependymal cells lining the third ventricle. Mass spectrometry showed that affinity-purified SHBG from the hypothalamus and choroid plexus is structurally similar to the SHBG identified in the CSF. The multiple localizations of SHBG suggest neurohypophyseal and neuroendocrine functions. The biochemical data suggest that CSF SHBG is of brain rather than blood origin. Copyright (c) 2005 S. Karger AG, Base

Quantum evolution of Schwarzschild-de Sitter (Nariai) black holes

We calculate the one-loop effective action for conformal matter (scalars, spinors and vectors) on spherically symmetric background. Such effective action (in large $N$ approximation and expansion on curvature) is used to study quantum aspects of Schwarzschild-de Sitter black holes (SdS BHs) in nearly degenerated limit (Nariai BH). We show that for all types of above matter SdS BHs may evaporate or anti-evaporate in accordance with recent observation by Bousso and Hawking for minimal scalars. Some remarks about energy flow for SdS BHs in regime of evaporation or anti-evaporation are also done. Study of no boundary condition shows that this condition supports anti-evaporation for nucleated BHs (at least in frames of our approximation). That indicates to the possibility that some pair created cosmological BHs may not only evaporate but also anti-evaporate. Hence, cosmological primordial BHs may survive much longer than it is expected.Comment: Latex file, 20 pages, shortened versio

Large Extra Dimensions, Sterile neutrinos and Solar Neutrino Data

Solar, atmospheric and LSND neutrino oscillation results require a light sterile neutrino, $\nu_B$, which can exist in the bulk of extra dimensions. Solar $\nu_e$, confined to the brane, can oscillate in the vacuum to the zero mode of $\nu_B$ and via successive MSW transitions to Kaluza-Klein states of $\nu_B$. This new way to fit solar data is provided by both low and intermediate string scale models. From average rates seen in the three types of solar experiments, the Super-Kamiokande spectrum is predicted with 73% probability, but dips characteristic of the 0.06 mm extra dimension should be seen in the SNO spectrum.Comment: 4 pages, 2 figure

Vacuum defects without a vacuum

Topological defects can arise in symmetry breaking models where the scalar field potential $V(\phi)$ has no minima and is a monotonically decreasing function of $|\phi|$. The properties of such vacuumless defects are quite different from those of the ``usual'' strings and monopoles. In some models such defects can serve as seeds for structure formation, or produce an appreciable density of mini-black holes.Comment: 11 pages, REVTeX, 1 Postscript figure. Minor changes. Final version, to appear in Phys. Rev.

The Shape and Scale of Galactic Rotation from Cepheid Kinematics

A catalog of Cepheid variables is used to probe the kinematics of the Galactic disk. Radial velocities are measured for eight distant Cepheids toward l = 300; these new Cepheids provide a particularly good constraint on the distance to the Galactic center, R_0. We model the disk with both an axisymmetric rotation curve and one with a weak elliptical component, and find evidence for an ellipticity of 0.043 +/- 0.016 near the Sun. Using these models, we derive R_0 = 7.66 +/- 0.32 kpc and v_circ = 237 +/- 12 km/s. The distance to the Galactic center agrees well with recent determinations from the distribution of RR Lyrae variables, and disfavors most models with large ellipticities at the solar orbit.Comment: 36 pages, LaTeX, 10 figure

Casimir Effects Near the Big Rip Singularity in Viscous Cosmology

Analytical properties of the scalar expansion in the cosmic fluid are investigated, especially near the future singularity, when the fluid possesses a constant bulk viscosity \zeta. In addition, we assume that there is a Casimir-induced term in the fluid's energy-momentum tensor, in such a way that the Casimir contributions to the energy density and pressure are both proportional to 1/a^4, 'a' being the scale factor. A series expansion is worked out for the scalar expansion under the condition that the Casimir influence is small. Close to the Big Rip singularity the Casimir term has however to fade away and we obtain the same singular behavior for the scalar expansion, the scale factor, and the energy density, as in the Casimir-free viscous case.Comment: 7 pages RevTeX, no figures. Minor changes in discussion, some references added. To appear in Gen. Rel. Gra

Gravitational field of vacuumless defects

It has been recently shown that topological defects can arise in symmetry breaking models where the scalar field potential $V(\phi)$ has no minima and is a monotonically decreasing function of $|\phi|$. Here we study the gravitational fields produced by such vacuumless defects in the cases of both global and gauge symmetry breaking. We find that a global monopole has a strongly repulsive gravitational field, and its spacetime has an event horizon similar to that in de Sitter space. A gauge monopole spacetime is essentially that of a magnetically charged black hole. The gravitational field of a global string is repulsive and that of a gauge string is attractive at small distances and repulsive at large distances. Both gauge and global string spacetimes have singularities at a finite distance from the string core.Comment: 19 pages, REVTeX, 6 Postscript figure