A near-infrared and optical photometric study of the Sculptor dwarf spheroidal galaxy: implications for the metallicity spread

We present here a detailed study of the Sculptor dSph galaxy red giant branch (RGB) and horizontal branch (HB) morphology, combining new near-infrared photometry from CIRSI, with optical data from the ESO WFI. For a Sculptor-like old and generally metal-poor system, the position of RGB stars on the colour-magnitude diagram is mainly metallicity dependent. The advantage of using optical-NIR colours is that the position of the RGB locus is much more sensitive to metallicity than with optical colours alone. In contrast the horizontal branch (HB) morphology is strongly dependent on both metallicity and age. Therefore a detailed study of both the RGB in optical-NIR colours and the HB can help break the age-metallicity degeneracy. Our measured photometric width of the Sculptor giant branch corresponds to a range in metallicity of 0.75 dex. We detect the RGB and AGB bumps in both the NIR and optical luminosity functions, and derive from them a mean metallicity of [M/H] = -1.3 +/- 0.1. From isochrone fitting we derive a mean metallicity of [Fe/H] = -1.42 with a dispersion of 0.2 dex. These photometric estimators are for the first time consistent with individual metallicity measurements derived from spectroscopic observations. No spatial gradient is detected in the RGB morphology within a radius of 13 arcmin, twice the core radius. On the other hand, a significant gradient is observed in the HB morphology index, confirming the `second parameter problem' present in this galaxy. These observations are consistent with an early extended period of star formation continuing in time for a few Gyr. (Abridged)Comment: 9 pages, 10 figures. Accepted for publication in MNRA

When are projections also embeddings?

We study an autonomous four-dimensional dynamical system used to model certain geophysical processes.This system generates a chaotic attractor that is strongly contracting, with four Lyapunov exponents $\lambda_i$ that satisfy $\lambda_1+ \lambda_2+\lambda_3<0$, so the Lyapunov dimension is $D_L=2+|\lambda_3|/\lambda_1 < 3$ in the range of coupling parameter values studied. As a result, it should be possible to find three-dimensional spaces in which the attractors can be embedded so that topological analyses can be carried out to determine which stretching and squeezing mechanisms generate chaotic behavior. We study mappings into $R^3$ to determine which can be used as embeddings to reconstruct the dynamics. We find dramatically different behavior in the two simplest mappings: projections from $R^4$ to $R^3$. In one case the one-parameter family of attractors studied remains topologically unchanged for all coupling parameter values. In the other case, during an intermediate range of parameter values the projection undergoes self-intersections, while the embedded attractors at the two ends of this range are topologically mirror images of each other

A Comparison of Tests for Embeddings

It is possible to compare results for the classical tests for embeddings of chaotic data with the results of a recently proposed test. The classical tests, which depend on real numbers (fractal dimensions, Lyapunov exponents) averaged over an attractor, are compared with a topological test that depends on integers. The comparison can only be done for mappings into three dimensions. We find that the classical tests fail to predict when a mapping is an embedding and when it is not. We point out the reasons for this failure, which are not restricted to three dimensions

Regioselective Reactions of Highly Substituted Arynes

The fully regioselective reactivity of four new highly substituted silyl aryl triflate aryne precursors in aryne acyl-alkylation, acyl-alkylation/condensation, and heteroannulation reactions is reported. The application of these more complex arynes provides access to diverse natural product scaffolds and obviates late-stage functionalization of aromatic rings

Generalized coherent states are unique Bell states of quantum systems with Lie group symmetries

We consider quantum systems, whose dynamical symmetry groups are semisimple Lie groups, which can be split or decay into two subsystems of the same symmetry. We prove that the only states of such a system that factorize upon splitting are the generalized coherent states. Since Bell's inequality is never violated by the direct product state, when the system prepared in the generalized coherent state is split, no quantum correlations are created. Therefore, the generalized coherent states are the unique Bell states, i.e., the pure quantum states preserving the fundamental classical property of satisfying Bell's inequality upon splitting.Comment: 4 pages, REVTeX, amssymb style. More information on http://www.technion.ac.il/~brif/science.htm

Deep Luminosity Functions of Old and Intermediate-Age Globular Clusters in NGC 1316: Evidence for Dynamical Evolution of Second-Generation Globular Clusters

The Advanced Camera for Surveys on board the Hubble Space Telescope has been used to obtain deep high-resolution images of the giant early-type galaxy NGC 1316 which is an obvious merger remnant. These observations supersede previous, shallower observations which revealed the presence of a population of metal-rich globular clusters of intermediate age (~ 3 Gyr). We detect a total of 1496 cluster candidates, almost 4 times as many as from the previous WFPC2 images. We confirm the bimodality of the color distribution of clusters, even in V-I, with peak colors 0.93 and 1.06. The large number of detected clusters allows us to evaluate the globular cluster luminosity functions as a function of galactocentric radius. We find that the luminosity function of the inner 50% of the intermediate-age, metal-rich (`red') population of clusters differs markedly from that of the outer 50%. In particular, the luminosity function of the inner 50% of the red clusters shows a clear flattening consistent with a turnover that is about 1.0 mag fainter than the turnover of the blue clusters. This constitutes the first direct evidence that metal-rich cluster populations formed during major mergers of gas-rich galaxies can evolve dynamically (through disruption processes) into the red, metal-rich cluster populations that are ubiquitous in `normal' giant ellipticals.Comment: Accepted for publication in ApJ Letters; 4 pages in emulateapj style. 3 figure

The Analysis of Isochrone Fitting Methods for Red Giant Branch Photometry, and Tip Red Giant Branch Distance Determination

We consider the procedure of isochrone fitting and its application to the study of red giant branch (RGB) photometry in old stellar populations. This is extended to consider the problems introduced by the inclusion of lower-magnitude regions of the Colour Magnitude Diagram (CMD). We refer especially to our previous paper Frayn & Gilmore (2002), where the details of our isochrone interpolation and fitting code are explained. We address the systematic errors inherent in the process of isochrone fitting, and investigate the extent to which simple stellar populations can be recovered from noisy photometric data. We investigate the effects caused by inaccurate distance estimates, isochrone model variation and photometric errors. We present results from two studies of approximately coeval stellar populations, those of the Milky Way Globular Cluster System (MWGCS), and the Ursa Minor dwarf spheroidal galaxy. In addition, we introduce a new method for estimating distances using photometry of the tip of the RGB which is significantly more robust than the standard edge-detection filter.Comment: 11 pages, 17 postscript figure

Paramagnon dispersion in β\beta-FeSe observed by Fe LL-edge resonant inelastic x-ray scattering

We report an Fe $L$-edge resonant inelastic x-ray scattering (RIXS) study of the unusual superconductor $\beta$-FeSe. The high energy resolution of this RIXS experiment ($\approx\,$55$\,$meV FWHM) made it possible to resolve low-energy excitations of the Fe $3d$ manifold. These include a broad peak which shows dispersive trends between 100-200$\,$meV along the $(\pi,0)$ and $(\pi,\pi)$ directions of the one-Fe square reciprocal lattice, and which can be attributed to paramagnon excitations. The multi-band valence state of FeSe is among the most metallic in which such excitations have been discerned by soft x-ray RIXS