The M33 Variable Star Population Revealed by Spitzer

We analyze five epochs of Spitzer Space Telescope/Infrared Array Camera (IRAC) observations of the nearby spiral galaxy M33. Each epoch covered nearly a square degree at 3.6, 4.5, and 8.0 microns. The point source catalog from the full dataset contains 37,650 stars. The stars have luminosities characteristic of the asymptotic giant branch and can be separated into oxygen-rich and carbon-rich populations by their [3.6] - [4.5] colors. The [3.6] - [8.0] colors indicate that over 80% of the stars detected at 8.0 microns have dust shells. Photometric comparison of epochs using conservative criteria yields a catalog of 2,923 variable stars. These variables are most likely long-period variables amidst an evolved stellar population. At least one-third of the identified carbon stars are variable.Comment: Accepted for publication in ApJ. See published article for full resolution figures and electronic table

The effectiveness of the Dutch Meaningful Roles program in children : a study protocol for a cluster randomized controlled study

Background: A positive, prosocial classroom climate is associated with improved social competence and academic achievement, as well as with decreased internalizing problems and antisocial behavior in children. It is expected that motivation to behave prosocially is needed to achieve a prosocial climate in the classroom, and that such motivation can be enhanced through three components of self-determination theory (SDT): competence, relatedness, and autonomy. The goal of this protocol is to describe the design of a study aiming to evaluate the effectiveness of a classroom-based program based on SDT components promoting a prosocial classroom climate. Methods: A cluster randomized controlled trial (RCT) will be conducted to examine the effectiveness of the classroom-based program Meaningful Roles, aiming to improve prosocial classroom climate through increasing children’s intrinsic prosocial motivation, stimulated by increasing social autonomy, social competence, and social relatedness. A multi-informant (i.e., children, teachers, and school leaders) and multi-method (i.e., questionnaires and focus groups) approach will be used to assess primary outcomes (i.e., prosocial behavior, intrinsic (prosocial) motivation, social autonomy, social competence, and social relatedness) and secondary outcomes (i.e., school wellbeing, social position, bullying, victimization, and civic skills), as well as moderators (i.e., working elements, child, teacher, school, and program characteristics, and program integrity). Discussion: The current study will provide information on the effectiveness of a classroom-based program promoting a prosocial classroom climate. It is of crucial importance that the school environment can provide a positive, prosocial classroom climate in which children feel safe and can achieve optimal social and academic competence and wellbeing. Trial registration: ClinicalTrials (NCT05891067)

Stellar Populations and Mass-Loss in M15: A Spitzer Detection of Dust in the Intra-Cluster Medium

We present Spitzer Space Telescope IRAC and MIPS observations of the galactic globular cluster M15 (NGC 7078), one of the most metal-poor clusters with a [Fe/H] = -2.4. Our Spitzer images reveal a population of dusty red giants near the cluster center, a previously detected planetary nebula (PN) designated K648, and a possible detection of the intra-cluster medium (ICM) arising from mass loss episodes from the evolved stellar population. Our analysis suggests 9 (+/-2) x 10^-4 solar masses of dust is present in the core of M15, and this material has accumulated over a period of approximately 10^6 years, a timescale ten times shorter than the last galactic plane crossing event. We also present Spitzer IRS follow up observations of K648, including the detection of the [NeII] 12.81 micron line, and discuss abundances derived from infrared fine structure lines.Comment: Accepted for publication in AJ. 20 pages, 10 figures, 6 tables. Full resolution versions of figures 1, 5, 7, and 8 are available in a PDF version of this manuscript at http://ir.astro.umn.edu/~mboyer/ms_060906.pd

Spitzer Space Telescope spectral observations of AGB stars in the Fornax dwarf spheroidal galaxy

We have observed five carbon-rich AGB stars in the Fornax dwarf spheroidal (dSph) galaxy, using the Infrared Spectrometer on board the Spitzer Space Telescope. The stars were selected from a near-infrared survey of Fornax and include the three reddest stars, with presumably the highest mass-loss rates, in that galaxy. Such carbon stars probably belong to the intermediate-age population (2-8 Gyr old and metallicity of [Fe/H] -1) of Fornax. The primary aim of this paper is to investigate mass-loss rate, as a function of luminosity and metallicity, by comparing AGB stars in several galaxies with different metallicities. The spectra of three stars are fitted with a radiative transfer model. We find that mass-loss rates of these three stars are 4-7x10^-6 Msun yr-1. The other two stars have mass-loss rates below 1.3x10^-6 Msun yr-1. We find no evidence that these rates depend on metallicity, although we do suggest that the gas-to-dust ratio could be higher than at solar metallicity, in the range 240 to 800. The C2H2 bands are stronger at lower metallicity because of the higher C/O ratio. In contrast, the SiC fraction is reduced at low metallicity, due to low silicon abundance. The total mass-loss rate from all known carbon-rich AGB stars into the interstellar medium of this galaxy is of the order of 2x10^-5 Msun yr-1. This is much lower than that of the dwarf irregular galaxy WLM, which has a similar visual luminosity and metallicity. The difference is attributed to the younger stellar population of WLM. The suppressed gas-return rate to the ISM accentuates the difference between the relatively gas-rich dwarf irregular and the gas-poor dwarf spheroidal galaxies. Our study will be useful to constrain gas and dust recycling processes in low metallicity galaxies.Comment: MNRAS accepte

A Spitzer IRS Spectral Atlas of Luminous 8 micron Sources in the Large Magellanic Cloud

We present an atlas of Spitzer Space Telescope Infrared Spectrograph (IRS) spectra of highly luminous, compact mid-infrared sources in the Large Magellanic Cloud. Sources were selected on the basis of infrared colors and 8 micron (MSX) fluxes indicative of highly evolved, intermediate- to high-mass stars with current or recent mass loss at large rates. We determine the chemistry of the circumstellar envelope from the mid-IR continuum and spectral features and classify the spectral types of the stars. In the sample of 60 sources, we find 21 Red Supergiants (RSGs), 16 C-rich Asymptotic Giant Branch (AGB) stars, 11 HII regions, 4 likely O-rich AGB stars, 4 Galactic O-rich AGB stars, 2 OH/IR stars, and 2 B[e] supergiants with peculiar IR spectra. We find that the overwhelming majority of the sample AGB stars (with typical IR luminosities ~1.0E4 L_sun) have C-rich envelopes, while the O-rich objects are predominantly luminous RSGs with L_IR ~ 1.0E5 L_sun. We determine mean bolometric corrections to the stellar K-band flux densities and find that for carbon stars, the bolometric corrections depend on the infrared color, whereas for RSGs, the bolometric correction is independent of IR color. Our results reveal that objects previously classified as PNe on the basis of IR colors are in fact compact HII regions with very red IRS spectra that include strong atomic recombination lines and PAH emission features. We demonstrate that the IRS spectral classes in our sample separate clearly in infrared color-color diagrams that use combinations of 2MASS data and synthetic IRAC/MIPS fluxes derived from the IRS spectra. On this basis, we suggest diagnostics to identify and classify, with high confidence levels, IR-luminous evolved stars and HII regions in nearby galaxies using Spitzer and near-infrared photometry.Comment: 46 pages, 9 figures; accepted for publication in AJ; abstract abridge

Both resistance- and endurance-type exercise reduce the prevalence of hyperglycaemia in individuals with impaired glucose tolerance and in insulin-treated and non-insulin-treated type 2 diabetic patients

Aims/hypothesis The present study compares the impact of endurance- vs resistance-type exercise on subsequent 24 h blood glucose homeostasis in individuals with impaired glucose tolerance (IGT) and type 2 diabetes. Methods Fifteen individuals with IGT, 15 type 2 diabetic patients treated with exogenous insulin (INS), and 15 type 2 diabetic patients treated with oral glucose-lowering medication (OGLM) participated in a randomised crossover experiment. Participants were studied on three occasions for 3 days under strict dietary standardisation, but otherwise free-living conditions. Blood glucose homeostasis was assessed by ambulatory continuous glucose monitoring over the 24 h period following a 45 min session of resistance-type exercise (75% one repetition maximum), endurance-type exercise (50% maximum workload capacity) or no exercise at all. Results Average 24 h blood glucose concentrations were reduced from 7.4±0.2, 9.6±0.5 and 9.2±0.7 mmol/l during the control experiment to 6.9±0.2, 8.6±0.4 and 8.1±0.5 mmol/l (resistance-type exercise) and 6.8±0.2, 8.6±0.5 and 8.5±0.5 mmol/l (endurance-type exercise) over the 24 h period following a single bout of exercise in the IGT, OGLM and INS groups, respectively (p 10 mmol/l) was reduced by 35±7 and 33±11% over the 24 h period following a single session of resistanceand endurance-type exercise, respectively (p< 0.001 for both treatments). Conclusions/interpretation A single session of resistanceor endurance-type exercise substantially reduces the prevalence of hyperglycaemia during the subsequent 24 h period in individuals with IGT, and in insulin-treated and non-insulin-treated type 2 diabetic patients. Both resistance- and endurance-type exercise can be integrated in exercise intervention programmes designed to improve glycaemic control. Trial registration: Clinicaltrials.gov NCT00945165 Funding: The Netherlands Organization for Health Research and Development (ZonMw, the Netherlands). © 2011 The Author(s)