The polar ring galaxy AM1934-563 revisited

We report long-slit spectroscopic observations of the dust-lane polar-ring galaxy AM1934-563 obtained with the Southern African Large Telescope (SALT) during its performance-verification phase. The observations target the spectral region of the Ha, [NII] and [SII] emission-lines, but show also deep NaI stellar absorption lines that we interpret as produced by stars in the galaxy. We derive rotation curves along the major axis of the galaxy that extend out to about 8 kpc from the center for both the gaseous and the stellar components, using the emission and absorption lines. We derive similar rotation curves along the major axis of the polar ring and point out differences between these and the ones of the main galaxy. We identify a small diffuse object visible only in Ha emission and with a low velocity dispersion as a dwarf HII galaxy and argue that it is probably metal-poor. Its velocity indicates that it is a fourth member of the galaxy group in which AM1934-563 belongs. We discuss the observations in the context of the proposal that the object is the result of a major merger and point out some observational discrepancies from this explanation. We argue that an alternative scenario that could better fit the observations may be the slow accretion of cold intergalactic gas, focused by a dense filament of galaxies in which this object is embedded (abridged).Comment: 19 pages, 13 figures, submitted to MNRAS. Some figures were bitmapped to reduce the size. Full resolution version is available from http://www.saao.ac.za/~akniazev/pub/AM1934_563.pd

A deep Giant Metre-wave Radio Telescope 610-MHz survey of the 1^HXMM–Newton/Chandra survey field

We present the results of a deep 610-MHz survey of the 1^HXMM–Newton/Chandra survey area with the Giant Metre-wave Radio Telescope. The resulting maps have a resolution of ~7 arcsec and an rms noise limit of 60 μJy. To a 5σ detection limit of 300 μJy, we detect 223 sources within a survey area of 64 arcmin in diameter. We compute the 610-MHz source counts and compare them to those measured at other radio wavelengths. The well-known flattening of the Euclidean-normalized 1.4-GHz source counts below ~2 mJy, usually explained by a population of starburst galaxies undergoing luminosity evolution, is seen at 610 MHz. The 610-MHz source counts can be modelled by the same populations that explain the 1.4-GHz source counts, assuming a spectral index of −0.7 for the starburst galaxies and the steep spectrum active galactic nucleus (AGN) population. We find a similar dependence of luminosity evolution on redshift for the starburst galaxies at 610 MHz as is found at 1.4 GHz (i.e. 'Q'= 2.45^(+0.3)_(−0.4))

Constraints on the distribution of absorption in the X-ray selected AGN population found in the 13H XMM-Newton/Chandra deep field

We present an analysis of the X-ray properties of sources detected in the 13H XMM-Newton deep (200ks) field. In order to constrain the absorbed AGN population, we use extensive Monte Carlo simulations to directly compare the X-ray colours of observed sources with those predicted by several model distributions. We have tested the simplest form of the AGN unified scheme, whereby the intrinsic XLF of absorbed AGN is set to be the same as that of their unabsorbed brethren, coupled with various model distributions of absorption. The best fitting of these models sets the fraction of AGN with absorbing column NH, proportional to (logNH)^8. We have also tested two extensions to the unified scheme: an evolving absorption scenario, and a luminosity dependent model distribution. Both of these provide poorer matches to the observed X-ray colour distributions than the best fitting simple unified model. We find that a luminosity dependent density evolution XLF reproduces poorly the 0.5-2 keV source counts seen in the 13H field. Field to field variations could be the cause of this disparity. Computing the simulated X-ray colours with a simple absorbed power-law + reflection spectral model is found to over-predict, by a factor of two, the fraction of hard sources that are completely absorbed below 0.5 keV, implying that an additional source of soft-band flux must be present for a number of the absorbed sources. Finally, we show that around 40% of the 13H sample are expected to be AGN with NH>10^22 cm^-2.Comment: 13 pages, 9 figures, Accepted for publication in MNRA

The metallicity extremes of the Sagittarius dSph using SALT spectroscopy of PNe

In this work we present the first spectroscopic results obtained with the Southern African Large Telescope (SALT) telescope during its perfomance-verification phase. We find that the Sagittarius dwarf spheroidal galaxy (Sgr) Sgr contains a youngest stellar population with [O/H] -0.2 and age t>1 Gyr, and an oldest population with [O/H]=-2.0. The values are based on spectra of two planetary nebulae (PNe), using empirical abundance determinations. We calculated abundances for O, N, Ne, Ar, S, Cl, Fe, C and He. We confirm the high abundances of PN StWr2-21 with 12+log(O/H) = 8.57+/-0.02 dex. The other PN studied, BoBn1, is an extraordinary object in that the neon abundance exceeds that of oxygen. The abundances of S, Ar and Cl in BoBn1 yield the original stellar metallicity, corresponding to 12+log(O/H) = 6.72+/-0.16 dex which is 1/110 of the solar value. The actual [O/H] is much higher: third dredge-up enriched the material by a factor of ~12 in oxygen, ~240 in nitrogen and ~70 in neon. Neon as well as nitrogen and oxygen content may have been produced in the intershell of low-mass AGB stars. Well defined broad WR lines are present in the spectrum of StWr2-21 and absent in the spectrum of BoBn1. This puts the fraction of [WR]-type central PNe stars to 67% for dSph galaxies.Comment: 14 pages, 4 figures, accepted to MNRA

The Star-formation History of the Universe as Revealed from Deep Radio Observations of the 13^H XMM-Newton/Chandra Deep Field

Discerning the exact nature of the faint (sub-mJy) radio population has been historically difficult due to the low luminosity of these sources at most wavelengths. Using deep observations from Chandra/XMM-Newton/Spitzer and ground based follow up we are able to disentangle the AGN and star- forming populations for the first time in a deep multi-frequency GMRT/VLA/MERLIN Survey. The many diagnostics include radio luminosity, morphology, radio to mid-IR flux density ratios, radio to optical flux density ratios and radio spectral indices. Further diagnostics, e.g. optical spectra, X-ray spectra/hardness ratios, IR colours indicate the presence of the AGN independent of whether the radio emission is powered by AGN or star-formation. We are able to examine the star-formation history of the universe up to z = 2.5 in a unique way based on an unbiased star-formation rate indicator, radio luminosity. This work provides an alternative perspective on the distribution of star-formation by mass, “downsizing” and allows us to examine the prevalence of AGN in star-bursts

Categorising the sub-mJy population: Star-forming galaxies from deep radio surveys

Models predict that starforming galaxies make up the majority of the source population detected in the very deepest radio surveys. Radio selected samples of starforming galaxies are therefore a potentially excellent method to chart e.g. the cosmic history of star-formation. However, a significant minority of the faintest radio sources are AGN powered ‘contaminants’, and must be removed from any solely star-formation powered sample. Here we describe a multi-pronged method for spearating star-forming and AGN powered sources in a deep 1.4 GHz radio survey. We utilise a wealth of multi-wavelength information, including radio spectral and morphological information and radio to mid-IR SED modelling, to select a clean sample of star-formation powered sources. We then derive the 1.4 GHz source counts separately for AGN and SFGs, calculate an independent measure of the evolving star-formation rate density to z∼2, and compare our results to the star-formation rate density determined at other wavelengths

XMM-Newton 13H Deep field - I. X-ray sources

We present the results of a deep X-ray survey conducted with XMM-Newton, centred on the UK ROSAT 13H deep field area. This region covers 0.18 deg^2 and is the first of two areas covered with XMM-Newton as part of an extensive multi-wavelength survey designed to study the nature and evolution of the faint X-ray source population. We have produced detailed Monte-Carlo simulations to obtain a quantitative characterisation of the source detection procedure and to assess the reliability of the resultant sourcelist. We use the simulations to establish a likelihood threshold above which we expect less than 7 (3%) of our sources to be spurious. We present the final catalogue of 225 sources. Within the central 9 arcmin, 68 per cent of source positions are accurate to 2 arcsec, making optical follow-up relatively straightforward. We construct the N(>S) relation in four energy bands: 0.2-0.5 keV, 0.5-2 keV, 2-5 keV and 5-10 keV. In all but our highest energy band we find that the source counts can be represented by a double powerlaw with a bright end slope consistent with the Euclidean case and a break around 10^-14 cgs. Below this flux the counts exhibit a flattening. Our source counts reach densities of 700, 1300, 900 and 300 deg^-2 at fluxes of 4.1x10^-16, 4.5x10^-16, 1.1x10^-15 and 5.3x10^-15 cgs in the 0.2-0.5, 0.5-2, 2-5 and 5-10 keV energy bands respectively. We have compared our source counts with those in the two Chandra deep fields and Lockman hole and find our source counts to be amongst the highest of these fields in all energy bands. We resolve >51% (>50%) of the X-ray background emission in the 1-2 keV (2-5 keV) energy bands.Comment: 27 pages, 18 figures, MNRAS accepte

Exercise-based injury prevention for community-level adolescent pace bowlers

Sporting injuries are on the rise and wide-scale injury prevention strategies are needed in community-level sport. Research indicates that community-level adolescent pace bowlers could benefit from exercise-based injury prevention programs (IPPs), however, a specific program for this group has not been developed. The primary aim of this thesis was to therefore develop a specific IPP for community-level adolescent pace bowlers and investigate if this program could modify risk factors for injury in this population. The Translating Research into Injury Prevention Practice (TRIPP) framework guided the progression of studies in this thesis. In Chapter 2, risk factors for injury in adolescent pace bowlers were systematically reviewed. The review included all experimental and observational studies that reported risk factors for non-contact injuries in pace bowlers aged 12-19 years. The Newcastle-Ottawa Quality Assessment Scale was used to assess risk of bias. In Chapter 3 the various barriers and facilitators to program implementation at the community-level were identified and used to guide the development of an IPP that was appropriate for community-level adolescent pace bowlers. In Chapters 4 and 5 a cluster-randomised controlled trial was employed to examine the efficacy of this IPP to modify neuromuscular risk factors and alter bowling kinematics. Eligible pace bowlers from eight cricket organisations (clusters) were recruited and then randomised into either an intervention group or control group. The intervention group completed an eight-week IPP while the control continued their normal cricket activity. Either side of the eight-week intervention period all participants attend a baseline and follow-up session where measures of muscle strength, muscle endurance, dynamic neuromuscular control and bowling kinematics were assessed. The treatment effect of the IPP was estimated with linear mixed models. Chapter 2 identified several potentially modifiable risk factors for injury in adolescent pace bowlers and these included; excessive lateral trunk flexion while bowling, kinematics of pelvis and hip while bowling, reduced trunk endurance, and poor lumbo-pelvic-hip movement control. There were conflicting results amongst the studies which investigated the mixed technique, bowling workload, and quadratus lumborum asymmetry. Among the five cross-sectional studies, risk of bias was high and very high. Of the 11 cohort studies, three were rated as low risk of bias and eight as high risk of bias. With the information gathered in Chapter 2, an exercise program to modify risk factors was developed in Chapter 3. The program included exercises to improve; eccentric strength of the external shoulder rotators, hip adductor strength, eccentric hamstring strength, dynamic neuromuscular control of the lumbo-pelvic region and lower-limbs, and trunk extensor endurance. Chapter 3 also considered the various facilitators to program implementation at the community-level, and therefore included exercises that were; simple to learn, non-reliant on expensive equipment, and time-efficient. In Chapter 4 the efficacy of this newly developed IPP to modify neuromuscular risk factors was assessed. There were significant treatment effects (estimated marginal mean with 95% confidence intervals) favouring the intervention group for; isokinetic shoulder strength (90°/s) (0.05 Newton meters per kilogram (N.m/kg); 0.02 to 0.09), isokinetic hamstring strength (60°/s) (0.32 N.m/kg; 0.13 to 0.50), hip adductor strength dominant side (0.40 N.m/kg; 0.26 to 0.55) and non-dominant side (0.33 N.m/kg; 0.20 to 0.47), Star Excursion Balance Test reach distance dominant side (3.80 percent of leg length (%LL); 1.63 to 6.04) and non-dominant side (3.60 %LL; 1.43 to 5.78), and back endurance (20.4 seconds; 4.80 to 36.0). No differences were observed for isokinetic shoulder strength (180°/s) (p=0.09), isokinetic hamstring strength (180°/s) (p=0.07), lumbo-pelvic stability (p=0.90), and single leg squat knee valgus angle (dominant p=0.06, non-dominant p=0.15). In Chapter 5 there were significant treatment effects favouring the intervention group for shoulder counter-rotation (-3.75°; -7.19 to -0.32) and lateral trunk flexion relative to pelvis (-2.24°; -3.97 to -0.52). There were however, no significant between-group differences for; global angles of lateral trunk flexion at front foot contact (FFC) (1.2°; -2.5 to 4.8), global angles of lateral trunk flexion ball release (BR) (-0.5°; -3.0 to 2.0), pelvis rotation FFC (0.9°; -4.0 to 2.2), pelvis rotation BR (-1.1°; -5.7 to 3.6), front hip angle FFC (1.6°; -3.6 to 6.7), front hip angle BR (-1.6°; -5.0 to 1.9), front knee angle FFC (-1.1°; -4.5 to 2.3), front knee angle BR (1.7°; -5.6 to 9.1), or ball velocity (1.1 km/h; -7.5 to 9.7). This thesis demonstrates that the TRIPP framework can used to successfully guide the process of injury prevention in community-level adolescent pace bowlers. The IPP in this thesis was also able to modify several neuromuscular and biomechanical risk factors, however a number of measures were not altered. Future research is needed to refine the current IPP and investigate if it can reduce injury risk in a real-world setting

BeppoSAX/PDS serendipitous detections at high galactic latitudes

At a flux limit of ~10^(-11) erg/cm2/s in the 20-100 keV band, the PDS instrument on-board BeppoSAX offers the opportunity to study the extragalactic sky with an unprecedented sensitivity. In this work we report on the results of a search in the BeppoSAX archive for serendipitous high energy sources at high galactic latitudes (|b| > 13 deg). We have defined a set of twelve regions in which the PDS/MECS cross-calibration constant is higher than the nominal value. We attribute this mismatch to the presence of a serendipitous source in the PDS field of view.In four cases the likely high energy emitter is also present in the MECS field of view. In these cases, we have performed a broad band spectral analysis (1.5-100 keV) so as to understand the source spectral behaviour and compare it with previous BeppoSAX observations when available. In eight cases the identification of the source likely to provide the PDS spectrum is based on indirect evidence (extrapolation to lower energies and/or comparison to previous observations). This approach leads to the discovery of six new hard X-ray emitting objects (PKS 2356-611, 2MASX J14585116-1652223, NGC 1566, NGC 7319, PKS 0101-649 and ESO 025-G002) and to the presentation the PDS spectrum of NGC 3227 for the first time. In the remaining five cases we provide extra BeppoSAX observations that can be compared with measurements which are already published and/or in the archive.Comment: 16 pages, 9 figures, accepted for publication in A&A, main journa