Red Giants in the Small Magellanic Cloud. II. Metallicity Gradient and Age-Metallicity Relation

We present results from the largest CaII triplet line metallicity study of Small Magellanic Cloud (SMC) field red giant stars to date, involving 3037 objects spread across approximately 37.5 sq. deg., centred on this galaxy. We find a median metallicity of [Fe/H]=-0.99+/-0.01, with clear evidence for an abundance gradient of -0.075+/-0.011 dex / deg. over the inner 5 deg. We interpret the abundance gradient to be the result of an increasing fraction of young stars with decreasing galacto-centric radius, coupled with a uniform global age-metallicity relation. We also demonstrate that the age-metallicity relation for an intermediate age population located 10kpc in front of the NE of the Cloud is indistinguishable from that of the main body of the galaxy, supporting a prior conjecture that this is a stellar analogue of the Magellanic Bridge. The metal poor and metal rich quartiles of our RGB star sample (with complementary optical photometry from the Magellanic Clouds Photometric Survey) are predominantly older and younger than approximately 6Gyr, respectively. Consequently, we draw a link between a kinematical signature, tentatively associated by us with a disk-like structure, and the upsurges in stellar genesis imprinted on the star formation history of the central regions of the SMC. We conclude that the increase in the star formation rate around 5-6Gyr ago was most likely triggered by an interaction between the SMC and LMC.Comment: To appear in MNRA

Red Giants in the Small Magellanic Cloud. I. Disk and Tidal Stream Kinematics

We present results from an extensive spectroscopic survey of field stars in the Small Magellanic Cloud (SMC). 3037 sources, predominantly first-ascent red giants, spread across roughly 37.5 sq. deg, are analysed. The line of sight velocity field is dominated by the projection of the orbital motion of the SMC around the LMC/Milky Way. The residuals are inconsistent with both a non-rotating spheroid and a nearly face on disk system. The current sample and previous stellar and HI kinematics can be reconciled by rotating disk models with line of nodes position angle, theta, ~ 120-130 deg., moderate inclination (i ~ 25-70 deg.), and rotation curves rising at 20-40 km/s/kpc. The metal-poor stars exhibit a lower velocity gradient and higher velocity dispersion than the metal-rich stars. If our interpretation of the velocity patterns as bulk rotation is appropriate, then some revision to simulations of the SMC orbit is required since these are generally tuned to the SMC disk line-of-nodes lying in a NE-SW direction. Residuals show strong spatial structure indicative of non-circular motions that increase in importance with increasing distance from the SMC centre. Kinematic substructure in the north-west part of our survey area is associated with the tidal tail or Counter-Bridge predicted by simulations. Lower line-of-sight velocities towards the Wing and the larger velocities just beyond the SW end of the SMC Bar are probably associated with stellar components of the Magellanic Bridge and Counter-Bridge, respectively. Our results reinforce the notion that the intermediate-age stellar population of the SMC is subject to substantial stripping by external forces.Comment: To appear in MNRA

Star Clusters in the Magellanic Clouds-1: Parameterisation and Classification of 1072 Clusters in the LMC

We have introduced a semi-automated quantitative method to estimate the age and reddening of 1072 star clusters in the Large Magellanic Cloud (LMC) using the Optical Gravitational Lensing Experiment (OGLE) III survey data. This study brings out 308 newly parameterised clusters. In a first of its kind, the LMC clusters are classified into groups based on richness/mass as very poor, poor, moderate and rich clusters, similar to the classification scheme of open clusters in the Galaxy. A major cluster formation episode is found to happen at 125 +- 25 Myr in the inner LMC. The bar region of the LMC appears prominently in the age range 60 - 250 Myr and is found to have a relatively higher concentration of poor and moderate clusters. The eastern and the western ends of the bar are found to form clusters initially, which later propagates to the central part. We demonstrate that there is a significant difference in the distribution of clusters as a function of mass, using a movie based on the propagation (in space and time) of cluster formation in various groups. The importance of including the low mass clusters in the cluster formation history is demonstrated. The catalog with parameters, classification, and cleaned and isochrone fitted CMDs of 1072 clusters, which are available as online material, can be further used to understand the hierarchical formation of clusters in selected regions of the LMC.Comment: 19 pages, 19figures, published in MNRAS on August 16, 2016 Supplementary material is available in the MNRAS websit

Optical/IR studies of Be stars in NGC 6834 with emphasis on two specific stars

We present optical and infrared photometric and spectroscopic studies of two Be stars in the 70--80-Myr-old open cluster NGC 6834. NGC 6834(1) has been reported as a binary from speckle interferometric studies whereas NGC 6834(2) may possibly be a gamma Cas-like variable. Infrared photometry and spectroscopy from the United Kingdom Infrared Telescope (UKIRT), and optical data from various facilities are combined with archival data to understand the nature of these candidates. High signal-to-noise near-IR spectra obtained from UKIRT have enabled us to study the optical depth effects in the hydrogen emission lines of these stars. We have explored the spectral classification scheme based on the intensity of emission lines in the $H$ and $K$ bands and contrasted it with the conventional classification based on the intensity of hydrogen and helium absorption lines. This work also presents hitherto unavailable UBV CCD photometry of NGC 6834, from which the evolutionary state of the Be stars is identified.Comment: Published in Research in Astronomy and Astrophysics, RAA 14 (2014) 1173-1192, 20 pages, 10 figure

Nurses' knowledge, attitude, practice and barriers towards the use of evidence based nursing practice (EBNP) at government Hospital in Malaysia

In the nursing profession, EBNP makes a positive contribution to healthcare outcomes, care delivery, clinical teaching and research. The research objective was to determine the nurses’ knowledge, attitude, practice of EBNP and barriers to adopt EBNP in four hospitals in Malaysia, Hospital Universiti Sains Malaysia (Hospital USM), Hospital Pulau Pinang (HPP), Hospital Sultan Abdul Halim (HSAH) and Hospital Seberang Jaya (HSJ). A cross-sectional study was conducted from January until December 2012 among nurses working in all disciplines, on shift or day time duties in four selected hospitals. The questionnaire was adapted from a Singapore study. The data were analysed with SPSS version 21.0, using descriptive statistics, Independent T-Test, One- Way ANOVA and Multi-Factorial ANOVA. Results showed that among the nurses working in four different Malaysian hospitals, nearly 50% knew what the evidence based practice meant. The items assessing the attitude showed a large number nurses responding that they did neither agree nor disagree with statements provided. The majority of the remaining nurses tended to show a rather positive attitude except when asked about how the workload interfered with their EBP practice. Most nurses recognized there were many barriers to EBP in their working place. The significant mean differences of practice on EBNP between senior and junior nurses were observed for the statements 1, 2, and 3 (p=<0.001), (p=0.005) and (p=0.028) respectively. Multifactorial ANOVA analysis used to determine the effect of academic qualification, working place, working experience and training on nurses’ knowledge towards EBNP. In conclusion, this study may have helped to increase understanding of knowledge, attitudes, practice and barriers to adopt EBNP to the utilization of research by nurses through an exploration of perceived barriers and facilitators on the part of nurses

Evidence of a counterrotating core in the Large Magellanic Cloud

Stellar radial velocity in the central region of the Large Magellanic Cloud (LMC) is used to estimate the radial velocity curve along various position angles (PA) including the line of nodes (LON). The central part of the radial velocity profile, along the LON, shows a V-shaped profile - a clear indication of counterrotation. The counterrotating region and the secondary bar have similar location and PA. The origin of the counter-rotating core could be internal(secondary bar) or external(accretion). To explain the observed velocity profile, we propose the existence of two disks in the inner LMC, with one counterrotating. This two disk model is found to match the HI velocities as well. Two disks with different LON and velocity profiles can create regions which are kinematically and spatially separated. Predicted such locations are found to match the observed locations where the HI clouds are found to have two velocities.Comment: 12 pages including 3 figures, to appear in ApJ Letter

Entanglement entropy and multifractality at localization transitions

The von Neumann entanglement entropy is a useful measure to characterize a quantum phase transition. We investigate the non-analyticity of this entropy at disorder-dominated quantum phase transitions in non-interacting electronic systems. At these critical points, the von Neumann entropy is determined by the single particle wave function intensity which exhibits complex scale invariant fluctuations. We find that the concept of multifractality is naturally suited for studying von Neumann entropy of the critical wave functions. Our numerical simulations of the three dimensional Anderson localization transition and the integer quantum Hall plateau transition show that the entanglement at these transitions is well described using multifractal analysis.Comment: v3, 5 pages, published versio

Issues in Physics Practicals in an Open and Distance Learning Environment

This paper reviews the objectives of physics practicals in physics education in relation to the hilosophy of open and distance learning programme. The various issues that arise in the implementation of physics experiment based on an existing practical model are presented. Two major concerns are the effectiveness of the practical sessions and sustaining the fundamentals of the open and distance learning programme. A new practical physics model is then proposed, which enables students to experience physics experiments without violating the open and distance learning programme fundamentals. (Authors' abstract