A New Measurement of the Stellar Mass Density at z~5: Implications for the Sources of Cosmic Reionization

We present a new measurement of the integrated stellar mass per comoving volume at redshift 5 determined via spectral energy fitting drawn from a sample of 214 photometrically-selected galaxies with z'<26.5 in the southern GOODS field. Following procedures introduced by Eyles et al. (2005), we estimate stellar masses for various sub-samples for which reliable and unconfused Spitzer IRAC detections are available. A spectroscopic sample of 14 of the most luminous sources with =4.92 provides a firm lower limit to the stellar mass density of 1e6 Msun/Mpc^3. Several galaxies in this sub-sample have masses of order 10^11 Msun implying significant earlier activity occurred in massive systems. We then consider a larger sample whose photometric redshifts in the publicly-available GOODS-MUSIC catalog lie in the range 4.4 <z 5.6. Before adopting the GOODS-MUSIC photometric redshifts, we check the accuracy of their photometry and explore the possibility of contamination by low-z galaxies and low-mass stars. After excising probable stellar contaminants and using the z'-J color to exclude any remaining foreground red galaxies, we conclude that 196 sources are likely to be at z~5. The implied mass density from the unconfused IRAC fraction of this sample, scaled to the total available, is 6e6 Msun/Mpc^3. We discuss the uncertainties as well as the likelihood that we have underestimated the true mass density. Including fainter and quiescent sources the total integrated density could be as high as 1e7 Msun/Mpc^3. Using the currently available (but highly uncertain) rate of decline in the star formationhistory over 5 <z< 10, a better fit is obtained for the assembled mass at z~5 if we admit significant dust extinction at early times or extend the luminosity function to very faint limits. [abridged]Comment: Accepted for Publication in ApJ, 39 page

The Stellar Initial Mass Function at the Epoch of Reionization

I provide estimates of the ultraviolet and visible light luminosity density at z~6 after accounting for the contribution from faint galaxies below the detection limit of deep Hubble and Spitzer surveys. I find the rest-frame V-band luminosity density is a factor of ~2-3 below the ultraviolet luminosity density at z~6. This implies that the maximal age of the stellar population at z~6, for a Salpeter initial mass function, and a single, passively evolving burst, must be <100 Myr. If the stars in z~6 galaxies are remnants of the star-formation that was responsible for ionizing the intergalactic medium, reionization must have been a brief process that was completed at z<7. This assumes the most current estimates of the clumping factor and escape fraction and a Salpeter slope extending up to 200 M_{\sun} for the stellar initial mass function (IMF; dN/dM \propto M^{\alpha}, \alpha=-2.3). Unless the ratio of the clumping factor to escape fraction is less than 60, a Salpeter slope for the stellar IMF and reionization redshift higher than 7 is ruled out. In order to maintain an ionized intergalactic medium from redshift 9 onwards, the stellar IMF must have a slope of \alpha=-1.65 even if stars as massive as ~200 M_{\sun} are formed. Correspondingly, if the intergalactic medium was ionized from redshift 11 onwards, the IMF must have \alpha~-1.5. The range of stellar mass densities at z~6 straddled by IMFs which result in reionization at z>7 is 1.3+/-0.4\times10^{7} Msun/Mpc^3.Comment: 25 pages, 2 tables, 6 figures, ApJ, in press, v680 n

A synoptic view of solar transient evolution in the inner heliosphere using the Heliospheric Imagers on STEREO

By exploiting data from the STEREO/heliospheric imagers (HI) we extend a well-established technique developed for coronal analysis by producing time-elongation plots that reveal the nature of solar transient activity over a far more extensive region of the heliosphere than previously possible from coronagraph images. Despite the simplicity of these plots, their power in demonstrating how the plethora of ascending coronal features observed near the Sun evolve as they move antisunward is obvious. The time-elongation profile of a transient tracked by HI can, moreover, be used to establish its angle out of the plane-of-the-sky; an illustration of such analysis reveals coronal mass ejection material that can be clearly observed propagating out to distances beyond 1AU. This work confirms the value of the time-elongation format in identifying/characterising transient activity in the inner heliosphere, whilst also validating the ability of HI to continuously monitor solar ejecta out to and beyond 1A

Finding LoTSS of hosts for GRBs: a search for galaxy - gamma-ray burst coincidences at low frequencies with LOFAR

The LOFAR Two-Metre Sky Survey (LoTSS) is an invaluable new tool for investigating the properties of sources at low frequencies and has helped to open up the study of galaxy populations in this regime. In this work, we perform a search for host galaxies of gamma-ray bursts (GRBs). We use the relative density of sources in Data Release 2 of LoTSS to define the probability of a chance alignment, $P_{\rm chance}$, and find 18 sources corresponding to 17 GRBs which meet a $P_{\rm chance}$<1% criterion. We examine the nature and properties of these radio sources using both LOFAR data and broadband information, including their radio spectral index, star formation rate estimates and any contributions from active galactic nucleus emission. Assuming the radio emission is dominated by star formation, we find that our sources show high star formation rates ($10^1$-$10^3$ $M_{\odot}$ yr$^{-1}$) compared with both a field galaxy sample and a sample of core-collapse supernova hosts, and the majority of putative hosts are consistent with ultraluminous infrared galaxy (ULIRG) classifications. As a result of our analyses, we define a final sample of eight likely GRB host candidates in the LoTSS DR2 survey.Comment: 15 pages, 9 figures and 6 tables. Accepted by MNRA

'Targeting care: tailoring non-surgical management according to clinical presentation'

International evidence-based guidelines recommend a multitude of nonsurgical treatment options for the management of osteoarthritis. This article summarizes the evidence available for patient characteristics that have been analyzed as potential predictors of response to nonsurgical interventions for patients with hip and knee osteoarthritis. The specific variables targeted for this review include body mass index, psychological factors, muscle strength, tibiofemoral alignment, radiographic changes, and signs of inflammation. Several studies provide moderate to good evidence of potential predictors of response to nonsurgical treatments, and areas for future research are illuminated. Copyright 2013 Elsevier Inc. All rights reserved

'Targeting care: tailoring non-surgical management according to clinical presentation'

International evidence-based guidelines recommend a multitude of nonsurgical treatment options for the management of osteoarthritis. This article summarizes the evidence available for patient characteristics that have been analyzed as potential predictors of response to nonsurgical interventions for patients with hip and knee osteoarthritis. The specific variables targeted for this review include body mass index, psychological factors, muscle strength, tibiofemoral alignment, radiographic changes, and signs of inflammation. Several studies provide moderate to good evidence of potential predictors of response to nonsurgical treatments, and areas for future research are illuminated. Copyright 2013 Elsevier Inc. All rights reserved

A salt-reduction smartphone app supports lower-salt food purchases for people with cardiovascular disease: Findings from the SaltSwitch randomised controlled trial

Background SaltSwitch is an innovative smartphone application (app) that enables shoppers to scan the barcode of a packaged food and receive an immediate, interpretive, traffic light nutrition label on the screen, along with suggestions for lower salt alternatives. Our aim was to determine the effectiveness of SaltSwitch to support people with cardiovascular disease to make lower salt food choices. Design Six-week, two-arm, parallel, randomised controlled trial in Auckland, New Zealand (2 weeks baseline and 4 weeks intervention). Methods Sixty-six adults with diagnosed cardiovascular disease (mean (SD) age 64 (7) years) were randomly assigned in a 1:1 ratio to either the SaltSwitch smartphone app or control (usual care). The primary outcome was the salt content of household packaged food purchases during the 4-week intervention (g/MJ). Secondary outcomes were the saturated fat content (g/MJ), energy content (kJ/kg) and expenditure (NZ$) of household food purchases; systolic blood pressure (mmHg), urinary sodium (mg) and use and acceptability of the SaltSwitch app. Results Thirty-three participants with cardiovascular disease were allocated to the SaltSwitch intervention, and 33 to the control group. A significant reduction in mean household purchases of salt was observed (mean difference (95% confidence interval), -0.30 (-0.58 to -0.03) g/MJ), equating to a reduction of ∼0.7 g of salt per person per day during the 4-week intervention phase. There were no significant between-group differences in any secondary outcomes (all P > 0.05). Conclusions The SaltSwitch smartphone app is effective in supporting people with cardiovascular disease to make lower salt food purchases. A larger trial with longer follow-up is warranted to determine the effects on blood pressure. Trial registration Australian New Zealand Clinical Trials Registry https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=365784&isReview=true ACTRN12614000206628

Interpreting high [O III]/H β ratios with maturing starbursts

Star-forming galaxies at high redshift show ubiquitously high-ionization parameters, as measured by the ratio of optical emission lines. We demonstrate that local (z < 0.2) sources selected as Lyman break analogues also manifest high line ratios with a typical [O III]/Hβ=3.36+0.14−0.04 – comparable to all but the highest ratios seen in star-forming galaxies at z ∼ 2–4. We argue that the stellar population synthesis code BPASS can explain the high-ionization parameters required through the ageing of rapidly formed star populations, without invoking any AGN contribution. Binary stellar evolution pathways prolong the age interval over which a starburst is likely to show elevated line ratios, relative to those predicted by single stellar evolution codes. As a result, model galaxies at near-solar metallicities and with ages of up to ∼100 Myr after a starburst typically have a line ratio [O III]/Hβ ∼ 3, consistent with those seen in Lyman break galaxies and local sources with similar star formation densities. This emphasises the importance of including binary evolution pathways when simulating the nebular line emission of young or bursty stellar populations

First imaging of corotating interaction regions using the STEREO spacecraft

Plasma parcels are observed propagating from the Sun out to the large coronal heights monitored by the Heliospheric Imagers (HI) instruments onboard the NASA STEREO spacecraft during September 2007. The source region of these out-flowing parcels is found to corotate with the Sun and to be rooted near the western boundary of an equatorial coronal hole. These plasma enhancements evolve during their propagation through the HI cameras’ fields of view and only becoming fully developed in the outer camera field of view. We provide evidence that HI is observing the formation of a Corotating Interaction Region(CIR) where fast solar wind from the equatorial coronal hole is interacting with the slow solar wind of the streamer belt located on the western edge of that coronal hole. A dense plasma parcel is also observed near the footpoint of the observed CIR at a distance less than 0.1AU from the Sun where fast wind would have not had time to catch up slow wind. We suggest that this low-lying plasma enhancement is a plasma parcel which has been disconnected from a helmet streamer and subsequently becomes embedded inside the corotating interaction region