Ages and metallicities of faint red galaxies in the Shapley Supercluster

We present results on the stellar populations of 232 quiescent galaxies in the Shapley Supercluster, based on spectroscopy from the AAOmega spectrograph at the AAT. The key characteristic of this survey is its coverage of many low-luminosity objects (sigma ~ 50 km/s), with high signal-to-noise (~45 per Angstrom). Balmer-line age estimates are recovered with ~25% precision even for the faintest sample members. We summarize the observations and absorption line data, and present correlations of derived ages and metallicities with mass and luminosity. We highlight the strong correlation between age and alpha-element abundance ratio, and the anti-correlation of age and metallicity at fixed mass, which is shown to extend into the low-luminosity regime.Comment: Four pages, three figures; To appear in Proceedings of IAU Symp. 245 "Formation and Evolution of Galaxy Bulges", (Oxford, July 16-20 2007), Eds. Martin Bureau, Lia Athanassoula, and Beatriz Barbu

Effect of plyometric training on swimming block start performance in adolescents

This study aimed to identify the effect of plyometric training (PT), when added to habitual training (HT) regimes, on swim start performance. After the completion of a baseline competitive swim start, 22 adolescent swimmers were randomly assigned to either a PT (n = 11, age: 13.1 ± 1.4 yr, mass: 50.6 ± 12.3 kg, stature: 162.9 ± 11.9 cm) or an HT group (n = 11, age: 12.6 ± 1.9 yr, mass: 43.3 ± 11.6 kg, stature: 157.6 ± 11.9 cm). Over an 8-week preseason period, the HT group continued with their normal training program, whereas the PT group added 2 additional 1-hour plyometric-specific sessions, incorporating prescribed exercises relating to the swimming block start (SBS). After completion of the training intervention, post-training swim start performance was reassessed. For both baseline and post-trials, swim performance was recorded using videography (50Hz Canon MVX460) in the sagital plane of motion. Through the use of Silicon Coach Pro analysis package, data revealed significantly greater change between baseline and post-trials for PT when compared with the HT group for swim performance time to 5.5 m (−0.59 s vs. −0.21 s; p < 0.01) and velocity of take-off to contact (0.19 ms−1 vs. −0.07 ms−1; p < 0.01). Considering the practical importance of a successful swim start to overall performance outcome, the current study has found that inclusion of suitable and safely implemented PT to adolescent performers, in addition to HT routines, can have a positive impact on swim start performance

Synthesis of H-alpha absorption in old stellar systems: Formation of the cluster red sequence by "Downsizing"

We compute population synthesis models for the variation of H-alpha absorption indices (HaA and HaF), as a function of age and metallicity in old stellar systems. The models are based on the STELIB spectral library, and defined at resolution of 3 Angstrom FWHM. The indices are found to be highly sensitive to age variation, with only moderate response to metallicity. For galaxies uncontaminated by nebular emission, our HaA index is more powerful in breaking the age/metallicity degeneracy than H-beta or H-gamma_F. Using a sample of red cluster galaxies carefully selected to exclude objects with emission, we find a steep decline of HaA with velocity dispersion (slope -0.75 +/- 0.07 Angstrom/dex). The slope can be translated to constraints on age and metallicity scaling relations, incorporating measurement and model errors. If the HaA-sigma slope is due only to age, we obtain Age proportional to sigma^{0.95 +/- 0.12}. Because HaA depends quite weakly on [Fe/H], a metallicity interpretation would require Fe/H proportional to sigma^1.2 or steeper. The HaA-sigma slope is consistent with the combined age and metallicity scaling relations reported by Nelan et al. from classical Lick indices. The relations obtained by Thomas et al. significantly under-predict the observed slope. The discrepancy could arise from differences in the sample compositions.We discuss in detail the effects of emission contamination on the results, and conclude that these are unlikely to yield the observed behaviour in the Ha-sigma relations. The steep age--mass relation supports a "downsizing" formation scenario: fainter red-sequence galaxies became quiescent at lower redshifts, z < 0.5. This picture accords with recent observations of truncated red sequences in clusters at z ~ 0.7.Comment: 11 pages, 9 figures, accepted by MNRA

Discovering novae in early-type galaxies with MUSE: A chance find in NGC 1404, and 12 more candidates from an archival search

I report the discovery of a transient broad-Hα point source in the outskirts of the giant elliptical galaxy NGC 1404, discovered in archival observations taken with the Multi-Unit Spectroscopic Explorer (MUSE) integral field spectrograph. The Hα line width of 1950 km s−1 full width at half-maximum, and luminosity of (4.1 ± 0.1) × 1036 erg s−1, are consistent with a nova outburst, and the source is not visible in MUSE data obtained 9 months later. A transient soft X-ray source was detected at the same position (within <1 arcsec), 14 yr before the Hα transient. If the X-ray and Hα emission are from the same object, the source may be a short-time-scale recurrent nova with a massive white dwarf accretor, and hence a possible Type-Ia supernova progenitor. Selecting broad-Hα point sources in MUSE archival observations for a set of nearby early-type galaxies, I discovered 12 more nova candidates with similar properties to the NGC 1404 source, including five in NGC 1380 and four in NGC 4365. Multi-epoch data are available for four of these twelve sources; all four are confirmed to be transient on ∼1 yr time-scales, supporting their identification as novae

Stuffed MO layer as a diffusion barrier in metallizations for high temperature electronics

Auger electron spectroscopy was employed to characterize the diffusion barrier properties of molybdenum in the CrSi2/Mo/Au metallization system. The barrier action of Mo was demonstrated to persist even after 2000 hours annealing time at 300 C in a nitrogen ambient. At 340 C annealing temperature, however, rapid interdiffusion was observed to have occurred between the various metal layers after only 261 hours. The presence of controlled amounts of oxygen in the Mo layer is believed to be responsible for suppressing the short circuit interdiffusion between the thin film layers. Above 340 C, its is believed that the increase in the oxygen mobility led to deterioration of its stuffing action, resulting in the rapid interdiffusion of the thin film layers along grain boundaries