Structure and Mass of a Young Globular Cluster in NGC 6946

Using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope, we have imaged a luminous young star cluster in the nearby spiral galaxy NGC 6946. The cluster has an absolute visual magnitude M(V)=-13.2, comparable to the brightest young `super-star clusters' in the Antennae merger galaxy. UBV colors indicate an age of about 15 Myr. The cluster has a compact core (core radius = 1.3 pc), surrounded by an extended envelope. We estimate that the effective radius (Reff) = 13 pc, but this number is uncertain because the outer parts of the cluster profile gradually merge with the general field. Combined with population synthesis models, the luminosity and age of the cluster imply a mass of 8.2x10^5 Msun for a Salpeter IMF extending down to 0.1 Msun, or 5.5x10^5 Msun if the IMF is log-normal below 0.4 Msun. Depending on model assumptions, the central density of the cluster is between 5300 Msun pc^-3 and 17000 Msun pc^-3, comparable to other high-density star forming regions. We also estimate a dynamical mass for the cluster, using high-dispersion spectra from the HIRES spectrograph on the Keck I telescope. The velocity dispersion is 10.0 +/- 2.7 km/s, implying a total cluster mass within 65 pc of (1.7 +/- 0.9) x 10^6 Msun. Comparing the dynamical mass with the mass estimates based on the photometry and population synthesis models, the mass-to-light ratio is at least as high as for a Salpeter IMF extending down to 0.1 Msun, although a turn-over in the IMF at 0.4 Msun is still possible within the errors. The cluster will presumably remain bound, evolving into a globular cluster-like object.Comment: 33 pages, including 10 figures and 3 tables. Accepted for publication in the Astrophysical Journa

Everything You Wanted to Know About Breast Augmentation Surgery But Were Afraid To Ask: A Medical - Legal Overview

This article will provide a medical/legal perspective to breast augmentation surgery. Written by an attorney who teaches anatomy and a plastic surgeon who routinely performs the procedure, it will initially offer a medical analysis of how the procedure is performed along with its attendant risks. The second part will focus on the court cases and legal theories that have arisen when things go wrong. The article will explain the convoluted litigation history involving breast augmentation when suits were common place and a group of experts linked breast implants to the development of autoimmune disease without any real scientific basis to support their opinions. It will conclude with a discussion of the various legal theories currently being asserted when the surgery does not live up to the patient\u27s expectations

An investigation of the reaction of titanium with hydrogen Summary report

Hydrogen gas reaction with titanium and titanium alloys determined at low temperatures and pressure

New Zealand athletes' attitudes towards seeking sport psychology consultation

The aim of this study was to use the Sport Psychology Attitudes-Revised (SPA-R) questionnaire (Martin, Kellman, Lavallee & Page, 2002) to develop an understanding of the attitudes elite New Zealand athletes (N = 112) hold towards sport psychology so that services can be tailored to accommodate these views. The influence of athlete characteristics such as nationality, gender, age, level of competition achieved, and previous use of sport psychology on attitudes was explored. Further, the SPA-R was used as a measure of attitudes within the Theory of Reasoned Action (TRA; Ajzen & Fishbein, 1980) and Theory Planned Behaviour (TPB; Ajzen, 1985, 1991), and integrated with measures of subjective norm and perceived behavioural control to investigate the influence of these variables on predicting athletes' intention to use sport psychology. Results suggested that New Zealand athletes generally held positive attitudes regarding sport psychology, with gender and previous experience of sport psychology significantly influencing attitudes. Regression analyses indicated that the TPB was a better model than the TRA for predicting intention, and the variables predicted 39.7% of variance in intention to use sport psychology. The only SPA-R subscale that contributed significantly was confidence in sport psychology, and perceived behavioural control and subjective norm also contributed significantly. These findings suggest the SPA-R may have limited value in predicting intentions, although the TPB could provide a useful theoretical framework to direct interventions aimed at increasing athletes' intention to use sport psychology

The Absence of Extra-Tidal Structure in the Sculptor Dwarf Spheroidal Galaxy

The results of a wide-field survey of the Sculptor dwarf spheroidal galaxy are presented. Our aims were to obtain an accurate map of the outer structure of Sculptor, and to determine the level of interaction between this system and the Galaxy. Photometry was obtained in two colours down to the magnitude limits of V=20 and I=19, covering a 3.1 times 3.1 square deg area centred on Sculptor. The resulting colour-magnitude data were used as a mask to select candidate horizontal branch and red giant branch stars for this system. Previous work has shown that the red horizontal branch (HB) stars are more concentrated than the blue HB stars. We have determined the radial distributions of these two populations and show that the overall Sculptor density profile is well described by a two component model based on a combination of these radial distributions. Additionally, spectra of the Ca ii triplet region were obtained for over 700 candidate red giant stars over the 10 square deg region using the 2dF instrument on the Anglo-Australian Telescope. These spectra were used to remove foreground Galactic stars based on radial velocity and Ca ii triplet strength. The final list of Sculptor members contained 148 stars, seven of which are located beyond the nominal tidal radius. Both the photometric and spectroscopic datasets indicate no significant extra-tidal structure. These results support at most a mild level of interaction between this system and the Galaxy, and we have measured an upper mass limit for extra-tidal material to be 2.3 +/- 0.6% of the Sculptor luminous mass. This lack of tidal interaction indicates that previous velocity dispersion measurements (and hence the amount of dark matter detected) in this system are not strongly influenced by the Galactic tidal field.Comment: 53 pages, 23 figures. Accepted for publication in the Astronomical Journal. Some figures are reduced in size, and a full version is available at: ftp://ftp.mso.anu.edu.au/pub/coleman/sculptor.pd

Ca II Triplet Spectroscopy of Giants in SMC Star Clusters: Abundances, Velocities and the Age-Metallicity Relation

We have obtained spectra at the Ca II triplet of individual red giants in seven SMC star clusters whose ages range from ~4 to 12 Gyr. The spectra have been used to determine mean abundances for six of the star clusters to a typical precision of 0.12 dex. When combined with existing data for other objects, the resulting SMC age-metallicity relation is generally consistent with that for a simple model of chemical evolution, scaled to the present-day SMC mean abundance and gas mass fraction. Two of the clusters (Lindsay 113 and NGC 339), however, have abundances that ~0.5 dex lower than that expected from the mean age-metallicity relation. It is suggested that the formation of these clusters, which have ages of ~5 Gyr, may have involved the infall of uneriched gas, perhaps from the Magellanic Stream. The spectra also yield radial velocities for the seven clusters. The resulting velocity dispersion is 16 +/- 4 km/sec, consistent with those of the SMC planetary nebula and carbon star populations.Comment: 28 pages including 4 figure

The Effect of Star Formation History on the Inferred Initial Stellar Mass Function

Peaks and lulls in the star formation rate (SFR) over the history of the Galaxy produce plateaux and declines in the present day mass function (PDMF) where the main-sequence lifetime overlaps the age and duration of the SFR variation. These PDMF features can be misinterpreted as the form of the intrinsic stellar initial mass function (IMF) if the star formation rate is assumed to be constant or slowly varying with time. This effect applies to all regions that have formed stars for longer than the age of the most massive stars, including OB associations, star complexes, and especially galactic field stars. Related problems may apply to embedded clusters. Evidence is summarized for temporal SFR variations from parsec scales to entire galaxies, all of which should contribute to inferred IMF distortions. We give examples of various star formation histories to demonstrate the types of false IMF structures that might be seen. These include short-duration bursts, stochastic histories with log-normal amplitude distributions, and oscillating histories with various periods and phases. The inferred IMF should appear steeper than the intrinsic IMF over mass ranges where the stellar lifetimes correspond to times of decreasing SFRs; shallow portions of the inferred IMF correspond to times of increasing SFRs. If field regions are populated by dispersed clusters and defined by their low current SFRs, then they should have steeper inferred IMFs than the clusters. The SFRs required to give the steep field IMFs in the LMC and SMC are determined. Structure observed in several determinations of the Milky Way field star IMF can be accounted for by a stochastic and bursty star formation history.Comment: accepted by ApJ for 1 Jan 2006, Vol 636, 12 pages + 6 figure

Epidemiology and clinical management of elbow joint disease in dogs under primary veterinary care in the UK

Conditions affecting the elbow joint are a common cause of lameness in dogs. Primary-care veterinary clinical data are now recognised as a valuable research resource. Using data from the VetCompass Programme, this study aimed to report the frequency and risk factors for elbow joint disease in dogs under primary veterinary care in the UK and describe clinical management

A Prediction of Brown Dwarfs in Ultracold Molecular Gas

A recent model for the stellar initial mass function (IMF), in which the stellar masses are randomly sampled down to the thermal Jeans mass from hierarchically structured pre-stellar clouds, predicts that regions of ultra-cold CO gas, such as those recently found in nearby galaxies by Allen and collaborators, should make an abundance of Brown Dwarfs with relatively few normal stars. This result comes from the low value of the thermal Jeans mass, considering that the hierarchical cloud model always gives the Salpeter IMF slope above this lower mass limit. The ultracold CO clouds in the inner disk of M31 have T~3K and pressures that are probably 10 times higher than in the solar neighborhood. This gives a mass at the peak of the IMF equal to 0.01 Msun, well below the Brown Dwarf limit of 0.08 Msun. Using a functional approximation to the IMF, the ultracold clouds would have 50% of the star-like mass and 90% of the objects below the Brown Dwarf limit. The brightest of the Brown Dwarfs in M31 should have an apparent, extinction-corrected K-band magnitude of ~21 mag in their pre-main sequence phase.Comment: 13 pages, 2 figures, to be published in Astrophysical Journal, Vol 522, September 10, 199

Virgo cluster early-type dwarf galaxies with the Sloan Digital Sky Survey. II. Early-type dwarfs with central star formation

Despite the common picture of an early-type dwarf (dE) as a quiescent galaxy with no star formation and little gas, we identify 23 dEs that have blue central colors caused by recent or ongoing star formation in our sample of 476 Virgo cluster dEs. In addition, 14 objects that were mostly classified as (candidate) BCDs have similar properties. Among the certain cluster members, the dEs with blue centers reach a fraction of more than 15% of the dE population at brighter (B<=16) magnitudes. A spectral analysis of the centers of 16 galaxies reveals in all cases an underlying old population that dominates the mass, with M(old)>=90% for all but one object. Therefore the majority of these galaxies will appear like ordinary dEs within ~one Gigayear or less after the last episode of star formation. Their overall gas content is less than that of dwarf irregular galaxies, but higher than that of ordinary dEs. Their flattening distribution suggests the shape of a thick disk, similar to what has been found for dEs with disk features in Paper I of this series. Their projected spatial distribution shows no central clustering, and their distribution with projected local density follows that of irregular galaxies, indicative of an unrelaxed population. This is corroborated by their velocity distribution, which displays two side peaks characteristic of recent infall. We discuss possible formation mechanisms (ram-pressure stripping, tidally induced star formation, harassment) that might be able to explain both the disk shape and the central star formation of the dEs with blue centers.Comment: 16 pages + 15 figures. Accepted for publication in AJ. We recommend downloading the full resolution version from http://www.virgo-cluster.com/lisker2006b.ps.g