A star-forming galaxy at z= 5.78 in the Chandra Deep Field South

We report the discovery of a luminous z = 5.78 star-forming galaxy in the Chandra Deep Field South. This galaxy was selected as an ‘i-drop’ from the GOODS public survey imaging with the Hubble Space Telescope/Advanced Camera for Surveys (object 3 in the work of Stanway, Bunker & McMahon 2003). The large colour of (i′−z′)AB = 1.6 indicated a spectral break consistent with the Lyman α forest absorption shortward of Lyman α at z≈ 6. The galaxy is very compact (marginally resolved with ACS with a half-light radius of 0.08 arcsec, so rhl 5. Our spectroscopic redshift for this object confirms the validity of the i′-drop technique of Stanway et al. to select star-forming galaxies atz≈ 6

Spitzer Imaging of i'-drop Galaxies: Old Stars at z~6

We present new evidence for mature stellar populations with ages >100Myr in massive galaxies (M_stellar>10^10M_sun) seen at a time when the Universe was less than 1Gyr old. We analyse the prominent detections of two z~6 star-forming galaxies (SBM03#1 & #3) made at wavelengths corresponding to the rest-frame optical using the IRAC camera onboard the Spitzer Space Telescope. We had previously identified these galaxies in HST/ACS GOODS images of Chandra Deep Field South through the "i-drop" Lyman break technique, and subsequently confirmed spectroscopically with the Keck telescope. The new Spitzer photometry reveals significant Balmer/4000Ang discontinuities, indicative of dominant stellar populations with ages >100Myr. Fitting a range of population synthesis models (for normal initial mass functions) to the HST/Spitzer photometry yields ages of 250-650Myr and implied formation redshifts z~7.5-13.5 in presently-accepted world models. Remarkably, our sources have best-fit stellar masses of 1.3-3.8x10^10M_sun (95% confidence) assuming a Salpeter initial mass function. This indicates that at least some galaxies with stellar masses >20% of those of a present-day L* galaxy had already assembled within the first Gyr after the Big Bang. We also deduce that the past average star formation rate must be comparable to the current observed rate (SFR_UV~5-30M_sun/yr), suggesting that there may have been more vigorous episodes of star formation in such systems at higher redshifts. Although a small sample, limited primarily by Spitzer's detection efficiency, our result lends support to the hypothesis advocated in our earlier analyses of the Ultra Deep Field and GOODS HST/ACS data. The presence of established systems at z~6 suggests long-lived sources at earlier epochs (z>7) played a key role in reionizing the Universe.Comment: Accepted for publication in MNRAS (minor corrections made

Swift J1112.2-8238: A Candidate Relativistic Tidal Disruption Flare

We present observations of Swift J1112.2-8238, and identify it as a candidate relativistic tidal disruption flare (rTDF). The outburst was first detected by Swift/BAT in June 2011 as an unknown, long-lived (order of days) $\gamma$-ray transient source. We show that its position is consistent with the nucleus of a faint galaxy for which we establish a likely redshift of $z=0.89$ based on a single emission line that we interpret as the blended [OII]$\lambda3727$ doublet. At this redshift, the peak X/$\gamma$-ray luminosity exceeded $10^{47}$ ergs s$^{-1}$, while a spatially coincident optical transient source had $i^{\prime} \sim 22$ (M$_g \sim -21.4$ at $z=0.89$) during early observations, $\sim 20$ days after the Swift trigger. These properties place Swift J1112.2-8238 in a very similar region of parameter space to the two previously identified members of this class, Swift J1644+57 and Swift J2058+0516. As with those events the high-energy emission shows evidence for variability over the first few days, while late time observations, almost 3 years post-outburst, demonstrate that it has now switched off. Swift J1112.2-8238 brings the total number of such events observed by Swift to three, interestingly all detected by Swift over a $\sim$3 month period ($<3\%$ of its total lifetime as of March 2015). While this suggests the possibility that further examples may be uncovered by detailed searches of the BAT archives, the lack of any prime candidates in the years since 2011 means these events are undoubtedly rare.Comment: 11 pages, 5 figures, accepted for publication by MNRA

Comparison of Theoretical Starburst Photoionisation Models for Optical Diagnostics

We study and compare different examples of stellar evolutionary synthesis input parameters used to produce photoionisation model grids using the MAPPINGS V modelling code. The aim of this study is to (a) explore the systematic effects of various stellar evolutionary synthesis model parameters on the interpretation of emission lines in optical strong-line diagnostic diagrams, (b) characterise the combination of parameters able to reproduce the spread of local galaxies located in the star-forming region in the Sloan Digital Sky Survey, and (c) investigate the emission from extremely metal-poor galaxies using photoionisation models. We explore and compare the stellar input ionising spectrum (stellar population synthesis code [Starburst99, SLUG, BPASS], stellar evolutionary tracks, stellar atmospheres, star-formation history, sampling of the initial mass function) as well as parameters intrinsic to the H II region (metallicity, ionisation parameter, pressure, H II region boundedness). We also perform a comparison of the photoionisation codes MAPPINGS and CLOUDY. On the variations in the ionising spectrum model parameters, we find that the differences in strong emission-line ratios between varying models for a given input model parameter are small, on average ~0.1 dex. An average difference of ~0.1 dex in emission-line ratio is also found between models produced with MAPPINGS and CLOUDY. Large differences between the emission-line ratios are found when comparing intrinsic H II region parameters. We find that low-metallicity galaxies are better explained by a density-bounded H II region and higher pressures better encompass the spread of galaxies at high redshift.Comment: 33 pages, 26 figures, accepted for publication in Ap

Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results

The Binary Population and Spectral Synthesis (BPASS) suite of binary stellar evolution models and synthetic stellar populations provides a framework for the physically motivated analysis of both the integrated light from distant stellar populations and the detailed properties of those nearby. We present a new version 2.1 data release of these models, detailing the methodology by which BPASS incorporates binary mass transfer and its effect on stellar evolution pathways, as well as the construction of simple stellar populations. We demonstrate key tests of the latest BPASS model suite demonstrating its ability to reproduce the colours and derived properties of resolved stellar populations, including well- constrained eclipsing binaries. We consider observational constraints on the ratio of massive star types and the distribution of stellar remnant masses. We describe the identification of supernova progenitors in our models, and demonstrate a good agreement to the properties of observed progenitors. We also test our models against photometric and spectroscopic observations of unresolved stellar populations, both in the local and distant Universe, finding that binary models provide a self-consistent explanation for observed galaxy properties across a broad redshift range. Finally, we carefully describe the limitations of our models, and areas where we expect to see significant improvement in future versions.Comment: 69 pages, 45 figures. Accepted for publication in PASA. Accompanied by a full, documented data release at http://bpass.auckland.ac.nz and http://warwick.ac.uk/bpas

Molecular analysis of an echovirus 3 strain isolated from an individual concurrently with appearance of islet cell and IA-2 autoantibodies

Growing evidence has implicated members of the genus Enterovirus of the family Picornaviridae in the etiology of some cases of type I diabetes (T1D). To contribute to an understanding of the molecular determinants underlying this association, we determined the complete nucleotide sequence of a strain of echovirus 3 (E3), Human enterovirus B (HEV-B) species, isolated from an individual who soon after virus isolation developed autoantibodies characteristic of T1D. The individual has remained positive for over 6 years for tyrosine phosphatase-related IA-2 protein autoantibodies and islet cell autoantibodies, indicating an ongoing autoimmune process, although he has not yet developed clinical T1D. The sequence obtained adds weight to the observation that recent enterovirus isolates differ significantly from prototype strains and provides further evidence of a role for recombination in enterovirus evolution. In common with most HEV-B species members, the isolate exhibits 2C and VP1 sequences suggested as triggers of autoimmunity through molecular mimicry. However, comparisons with the E3 prototype strain and previously reported diabetogenic and nondiabetogenic HEV-B strains do not reveal clear candidates for sequence features of PicoBank/DM1/E3 that could be associated with autoantibody appearance. This is the first time a virus strain isolated at the time of commencement of beta-cell damage has been analyzed and is an invaluable addition to enterovirus strains isolated previously at the onset of T1D in the search for specific molecular features which could be associated with diabetes induction

Exploring the Cosmic Evolution of Habitability with Galaxy Merger Trees

We combine inferred galaxy properties from a semi-analytic galaxy evolution model incorporating dark matter halo merger trees with new estimates of supernova and gamma ray burst rates as a function of metallicity from stellar population synthesis models incorporating binary interactions. We use these to explore the stellar mass fraction of galaxies irradiated by energetic astrophysical transients and its evolution over cosmic time, and thus the fraction which is potentially habitable by life like our own. We find that 18 per cent of the stellar mass in the Universe is likely to have been irradiated within the last 260 Myr, with GRBs dominating that fraction. We do not see a strong dependence of irradiated stellar mass fraction on stellar mass or richness of the galaxy environment. We consider a representative merger tree as a Local Group analogue, and find that there are galaxies at all masses which have retained a high habitable fraction (>40 per cent) over the last 6 Gyr, but also that there are galaxies at all masses where the merger history and associated star formation have rendered galaxies effectively uninhabitable. This illustrates the need to consider detailed merger trees when evaluating the cosmic evolution of habitability.Comment: 11 page, 10 figures. MNRAS accepted 13th Dec 2017. Updated to match accepted version, with additional discussion of metallicity effect

Keck Spectroscopy of Faint 3<z<7 Lyman Break Galaxies: - I. New constraints on cosmic reionisation from the luminosity and redshift-dependent fraction of Lyman-alpha emission

We present results from a new Keck spectroscopic survey of UV-faint LBGs in the redshift range 3<z<7. Combined with earlier Keck and published ESO VLT data, our sample contains more than 600 dropouts, offering new insight into the nature of sub-L* sources typical of those likely to dominate the cosmic reionisation process. Here we use this sample to characterise the fraction of strong Lya emitters within the continuum-selected dropouts. By quantifying how the "Lya fraction" varies with redshift, we seek to constrain changes in Lya transmission associated with reionisation. In order to distinguish the effects of reionisation from other factors which affect the Lya fraction (e.g. dust, ISM kinematics), we study the luminosity and redshift-dependence of the Lya fraction over 3<z<6, when the IGM is known to be ionised. These results reveal that low luminosity galaxies show strong Lya emission much more frequently than luminous systems, and that at fixed luminosity, the prevalence of strong Lya emission increases moderately with redshift over 3 < z < 6. Based on the correlation between blue UV slopes and strong Lya emitting galaxies in our dataset, we argue that the Lya fraction trends are governed by redshift and luminosity-dependent variations in the dust obscuration, with likely additional contributions from trends in the kinematics and covering fraction of neutral hydrogen. We find a tentative decrease in the Lya fraction at z~7 based on the limited IR spectra for candidate z~7 lensed LBGs, a result which, if confirmed with future surveys, would suggest an increase in the neutral fraction by this epoch. Given the supply of z and Y-drops now available from Hubble WFC3/IR surveys, we show it will soon be possible to significantly improve estimates of the Lya fraction using optical and near-IR spectrographs, thereby extending the study conducted in this paper to 7<z<8.Comment: 23 pages, 15 figures, submitted to MNRA

Large Scale Structure traced by Molecular Gas at High Redshift

We present observations of redshifted CO(1-0) and CO(2-1) in a field containing an overdensity of Lyman break galaxies (LBGs) at z=5.12. Our Australia Telescope Compact Array observations were centered between two spectroscopically-confirmed z=5.12 galaxies. We place upper limits on the molecular gas masses in these two galaxies of M(H_2) <1.7 x 10^10 M_sun and <2.9 x 10^9 M_sun (2 sigma), comparable to their stellar masses. We detect an optically-faint line emitter situated between the two LBGs which we identify as warm molecular gas at z=5.1245 +/- 0.0001. This source, detected in the CO(2-1) transition but undetected in CO(1-0), has an integrated line flux of 0.106 +/- 0.012 Jy km/s, yielding an inferred gas mass M(H_2)=(1.9 +/- 0.2) x 10^10 M_sun. Molecular line emitters without detectable counterparts at optical and infrared wavelengths may be crucial tracers of structure and mass at high redshift.Comment: 4 pages, accepted for publication in ApJ Letter

Long term adjuvant endocrine therapy and risk of cardiovascular disease in female breast cancer survivors: systematic review

OBJECTIVE: To investigate the effect of endocrine therapies on a wide range of specific clinical cardiovascular disease outcomes in women with a history of non-metastatic breast cancer. DESIGN: Systematic review and meta-analysis of randomised controlled trials and observational studies. DATA SOURCES: Medline and Embase up until June 2018. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Studies were included if they investigated the risk of a specific cardiovascular disease outcome associated with use of either tamoxifen or an aromatase inhibitor, or compared the two treatments, in women with a history of non-metastatic breast cancer. APPRAISAL AND DATA EXTRACTION: Relevant studies were originally identified and results extracted by one researcher, with a full replication of the study identification process by a combination of two other researchers. The Cochrane Collaboration's tool for assessing risk of bias was used to assess risk of bias in randomised controlled trials, and this tool was adapted to assess risk of bias in observational studies. RESULTS: 26 studies were identified, with results for seven specific cardiovascular disease outcomes (venous thromboembolism, myocardial infarction, stroke, angina, heart failure, arrhythmia, and peripheral vascular disease). Results suggested an increased risk of venous thromboembolism in tamoxifen users compared with both non-users and aromatase inhibitor users. Results were also consistent with a higher risk of the vascular diseases myocardial infarction and angina in aromatase inhibitor users compared with tamoxifen users, but there was also a suggestion that this may be partly driven by a protective effect of tamoxifen on these outcomes. Data were limited, and evidence was generally inconsistent for all other cardiovascular disease outcomes. CONCLUSION: This review has collated substantial randomised controlled trial and observational evidence on the effect of endocrine therapies on several specific cardiovascular disease outcomes including venous thromboembolism and myocardial infarction, progressing knowledge. Although the choice of aromatase inhibitor or tamoxifen will primarily be based on the effectiveness against the recurrence of breast cancer, this review shows that the individual patient's risk of venous or arterial vascular disease should be an important secondary consideration. SYSTEMATIC REVIEW REGISTRATION: Prospero CRD42017065944