The Recent Star Formation in NGC 6822: an Ultraviolet Study

We characterize the star formation in the low-metallicity galaxy NGC 6822 over the past few hundred million years, using GALEX far-UV (FUV, 1344-1786 A) and near-UV (NUV, 1771-2831 A) imaging, and ground-based Ha imaging. From GALEX FUV image, we define 77 star-forming (SF) regions with area >860 pc^2, and surface brightness <=26.8 mag(AB)arcsec^-2, within 0.2deg (1.7kpc) of the center of the galaxy. We estimate the extinction by interstellar dust in each SF region from resolved photometry of the hot stars it contains: E(B-V) ranges from the minimum foreground value of 0.22mag up to 0.66+-0.21mag. The integrated FUV and NUV photometry, compared with stellar population models, yields ages of the SF complexes up to a few hundred Myr, and masses from 2x10^2 Msun to 1.5x10^6 Msun. The derived ages and masses strongly depend on the assumed type of interstellar selective extinction, which we find to vary across the galaxy. The total mass of the FUV-defined SF regions translates into an average star formation rate (SFR) of 1.4x10^-2 Msun/yr over the past 100 Myr, and SFR=1.0x10^-2 Msun/yr in the most recent 10 Myr. The latter is in agreement with the value that we derive from the Ha luminosity, SFR=0.008 Msun/yr. The SFR in the most recent epoch becomes higher if we add the SFR=0.02 Msun/yr inferred from far-IR measurements, which trace star formation still embedded in dust (age <= a few Myr).Comment: Accepted for publication in ApJ, 21 pages, 6 figures, 3 table

IR and UV Galaxies at z=0.6 -- Evolution of Dust Attenuation and Stellar Mass as Revealed by SWIRE and GALEX

We study dust attenuation and stellar mass of $\rm z\sim 0.6$ star-forming galaxies using new SWIRE observations in IR and GALEX observations in UV. Two samples are selected from the SWIRE and GALEX source catalogs in the SWIRE/GALEX field ELAIS-N1-00 ($\Omega = 0.8$ deg$^2$). The UV selected sample has 600 galaxies with photometric redshift (hereafter photo-z) $0.5 \leq z \leq 0.7$ and NUV$\leq 23.5$ (corresponding to \rm L_{FUV} \geq 10^{9.6} L_\sun). The IR selected sample contains 430 galaxies with $f_{24\mu m} \geq 0.2$ mJy (\rm L_{dust} \geq 10^{10.8} L_\sun) in the same photo-z range. It is found that the mean $\rm L_{dust}/L_{FUV}$ ratios of the z=0.6 UV galaxies are consistent with that of their z=0 counterparts of the same $\rm L_{FUV}$. For IR galaxies, the mean $\rm L_{dust}/L_{FUV}$ ratios of the z=0.6 LIRGs (\rm L_{dust} \sim 10^{11} L_\sun) are about a factor of 2 lower than local LIRGs, whereas z=0.6 ULIRGs (\rm L_{dust} \sim 10^{12} L_\sun) have the same mean $\rm L_{dust}/L_{FUV}$ ratios as their local counterparts. This is consistent with the hypothesis that the dominant component of LIRG population has changed from large, gas rich spirals at z$>0.5$ to major-mergers at z=0. The stellar mass of z=0.6 UV galaxies of \rm L_{FUV} \leq 10^{10.2} L_\sun is about a factor 2 less than their local counterparts of the same luminosity, indicating growth of these galaxies. The mass of z=0.6 UV lunmous galaxies (UVLGs: \rm L_{FUV} > 10^{10.2} L_\sun) and IR selected galaxies, which are nearly exclusively LIRGs and ULIRGs, is the same as their local counterparts.Comment: 27 pages, 8 figures, to be published in the Astrophysical Journal Supplement series dedicated to GALEX result

Extinction Corrected Star Formation Rates Empirically Derived from Ultraviolet-Optical Colors

Using a sample of galaxies from the Sloan Digital Sky Survey spectroscopic catalog with measured star-formation rates (SFRs) and ultraviolet (UV) photometry from the GALEX Medium Imaging Survey, we derived empirical linear correlations between the SFR to UV luminosity ratio and the UV-optical colors of blue sequence galaxies. The relations provide a simple prescription to correct UV data for dust attenuation that best reconciles the SFRs derived from UV and emission line data. The method breaks down for the red sequence population as well as for very blue galaxies such as the local ``supercompact'' UV luminous galaxies and the majority of high redshift Lyman Break Galaxies which form a low attenuation sequence of their own.Comment: 20 pages, 11 figures, accepted for publication in the ApJS GALEX special issu

Ultraviolet through Infrared Spectral Energy Distributions from 1000 SDSS Galaxies: Dust Attenuation

The meaningful comparison of models of galaxy evolution to observations is critically dependent on the accurate treatment of dust attenuation. To investigate dust absorption and emission in galaxies we have assembled a sample of ~1000 galaxies with ultraviolet (UV) through infrared (IR) photometry from GALEX, SDSS, and Spitzer and optical spectroscopy from SDSS. The ratio of IR to UV emission (IRX) is used to constrain the dust attenuation in galaxies. We use the 4000A break as a robust and useful, although coarse, indicator of star formation history (SFH). We examine the relationship between IRX and the UV spectral slope (a common attenuation indicator at high-redshift) and find little dependence of the scatter on 4000A break strength. We construct average UV through far-IR spectral energy distributions (SEDs) for different ranges of IRX, 4000A break strength, and stellar mass (M_*) to show the variation of the entire SED with these parameters. When binned simultaneously by IRX, 4000A break strength, and M_* these SEDs allow us to determine a low resolution average attenuation curve for different ranges of M_*. The attenuation curves thus derived are consistent with a lambda^{-0.7} attenuation law, and we find no significant variations with M_*. Finally, we show the relationship between IRX and the global stellar mass surface density and gas-phase-metallicity. Among star forming galaxies we find a strong correlation between IRX and stellar mass surface density, even at constant metallicity, a result that is closely linked to the well-known correlation between IRX and star-formation rate.Comment: 12 pages, 8 figures, 2 tables, appearing in the Dec 2007 GALEX special issue of ApJ Supp (29 papers

Which treatments are most effective for common tendinopathies? A systematic review and network meta-analysis protocol.

This is a preprint for a protocol. The purpose of the study described by the protocol was to compare the effectiveness of different treatment classes across a range of tendinopathies and outcomes, to better establish a treatment hierarchy. Where sufficient data were obtained, the potential for covariates - including patient demographics and condition specifics (e.g. symptom severity) - to explain statistical heterogeneity was explored

Comparison of exercise therapies across multiple tendinopathies: a systematic review and network meta-analysis protocol.

This is a preprint for a protocol. The study described by the protocol aimed to use network structures to compare exercise treatments and treatment classes in attempts to identify a treatment hierarchy. Additionally, the large amount of data synthesised was used to explore relevant factors that may explain statistical heterogeneity

The effect of dose on resistance exercise therapies for tendinopathy: a systematic review and meta-analysis protocol.

This is a preprint for a protocol. The purpose of the study described by the protocol was to investigate the effect of resistance exercise dose across multiple common tendinopathies (rotator cuff, lateral elbow, patellar or Achilles), where the frequency, volume and intensity can be accurately quantified. By combining a large data set with contemporary meta-analysis and meta-regression approaches (including relevant covariates within models), the systematic review attempted to explore statistical heterogeneity and better assess potential dose-response relationships that may exist. Where placebo and no-treatment arms were included, these studies were used to reduce heterogeneity and provide sensitivity analyses to support or refute analyses with larger, but more complex data

The effect of dose components on resistance exercise therapies for tendinopathy management: a systematic review and meta-analysis.

The purpose of this study was to investigate potential moderating effects of resistance exercise dose components including intensity, volume and frequency, for the management of common tendinopathies. The research was undertaken through a systematic review and meta-analysis, comprising an extensive search of databases and trial registries. Eligibility criteria for selecting studies included randomised and non-randomised controlled trials investigating resistance exercise as the dominant treatment class and reporting sufficient information regarding at least two components of exercise dose (intensity, frequency, volume). Non-controlled standardised mean difference effect sizes were calculated across a range out outcome domains and combined with Bayesian hierarchical meta-analysis models for domains generating large (disability; function; pain) and small (range of motion; physical function capacity; and quality of life) effect size values. Meta-regressions were used to estimate differences in pooled mean values across categorical variables quantifying intensity, frequency and volume. Ninety-one studies presented sufficient data to be included in meta-analyses, comprising 126 treatment arms (TAs) and 2965 participants. Studies reported on five tendinopathy locations (Achilles: 39 TAs, 31.0%; rotator cuff: 39 TAs, 31.0%; lateral elbow: 25 TAs, 19.8%; patellar: 19 TAs, 15.1%; and gluteal: 4 TAs, 3.2%). Meta-regressions provided consistent evidence of greater pooled mean effect sizes for higher intensity therapies comprising additional external resistance compared to body mass only (large effect size domains: 0.39 [95% CrI: 0.00 to 0.82; p = 0.976]; small effect size domains (0.09 [95% CrI: -0.20 to 0.37; p = 0.723]) when data were combined across tendinopathy locations or analysed separately. Consistent evidence of greater pooled mean effect sizes was also identified for the lowest frequency (less than daily) compared with mid (daily) and high frequencies (more than daily) for both large effect size domain ( -0.66 [95% CrI: -1.2 to -0.19; p >0.999]; -0.54 [95% CrI:-0.99 to -0.10; p >0.999]) and small effect size domains ( -0.51 [95% CrI: -0.78 to -0.24; p >0.999]; -0.34 [95% CrI: -0.60 to -0.06; p = 0.992]) when data were combined across tendinopathy locations or analysed separately. Minimal and inconsistent evidence was obtained for differences for a moderating effect of training volume. The study concluded that resistance exercise dose is poorly reported within the tendinopathy management literature. However, this large meta-analysis identified some consistent patterns indicating greater efficacy on average with therapies prescribing higher intensities (through the inclusion of additional external loads) and lower frequencies, potentially creating stronger stimuli and facilitating adequate recovery

Empirically derived guidelines for interpreting the effectiveness of exercise therapy for tendinopathies: a protocol.

This is a preprint for a protocol. The aim of the study described by the protocol was to perform a large synthesis of the available research investigating exercise therapy for tendinopathies, creating empirically derived thresholds to benchmark interventions and explore potential differences across tendinopathy types and outcome domains