Spectroscopy of luminous z>7 galaxy candidates and sources of contamination in z>7 galaxy searches

We present three bright z+ dropout candidates selected from deep Near-Infrared (NIR) imaging of the COSMOS 2 square degree field. All three objects match the 0.8-8um colors of other published z>7 candidates but are three magnitudes brighter, facilitating further study. Deep spectroscopy of two of the candidates covering 0.64-1.02um with Keck-DEIMOS and all three covering 0.94-1.10um and 1.52-1.80um with Keck-NIRSPEC detects weak spectral features tentatively identified as Ly-alpha at z=6.95 and z=7.69 in two of the objects. The third object is placed at z~1.6 based on a 24um and weak optical detection. A comparison with the spectral energy distributions of known z<7 galaxies, including objects with strong spectral lines, large extinction, and large systematic uncertainties in the photometry yields no objects with similar colors. However, the lambda>1um properties of all three objects can be matched to optically detected sources with photometric redshifts at z~1.8, so the non-detection in the i+ and z+ bands are the primary factors which favors a z>7 solution. If any of these objects are at z~7 the bright end of the luminosity function is significantly higher at z>7 than suggested by previous studies, but consistent within the statistical uncertainty and the dark matter halo distribution. If these objects are at low redshift, the Lyman-Break selection must be contaminated by a previously unknown population of low redshift objects with very strong breaks in their broad band spectral energy distributions and blue NIR colors. The implications of this result on luminosity function evolution at high redshift is discussed. We show that the primary limitation of z>7 galaxy searches with broad filters is the depth of the available optical data.Comment: 15 Pages, 15 figures, accepted to Ap

A spectroscopic measurement of galaxy formation time-scales with the Redshift One LDSS3 Emission line Survey

Publisher's version/PDFWe present measurements of the specific star formation rate (SSFR)–stellar mass relation for star-forming galaxies. Our deep spectroscopic samples are based on the Redshift One LDSS3 Emission line Survey (ROLES) and European Southern Observatory (ESO) public spectroscopy at z = 1, and on the Sloan Digital Sky Survey (SDSS) at z = 0.1. These data sets cover an equally deep mass range of 8.5 [less than or similar to] log(M[subscript ∗]/M[subscript circled dot]) [less than or similar to] 11 at both epochs. We find that the SSFR–mass relation evolves in a way which is remarkably independent of stellar mass, as we previously found for the SFR density (SFRD)–mass relation. However, we see a subtle upturn in SSFR–mass for the lowest mass galaxies (which may at least partly be driven by mass-incompleteness in the K-selected sample). This upturn is suggestive of greater evolution for lower mass galaxies, which may be explained by less massive galaxies forming their stars later and on longer time-scales than higher mass galaxies, as implied by the ‘cosmic downsizing’ scenario. Parametrizing the e-folding time-scale and formation redshift as simple functions of baryonic mass gives best-fitting parametrizations of [tau] (M[subscript b]) [alpha] M[superscript −1.01][subscript b] and 1 + z[subscript f](M[subscript b]) [alpha] M[superscript 0.30][subscript b]. This subtle upturn is also seen in the SFRD as a function of stellar mass. At higher masses, such as those probed by previous surveys, the evolution in SSFR–mass is almost independent of stellar mass. At higher masses [log(M[subscript ∗]/M[subscript circled dot]) [greater than] 10] the shapes of the cumulative cosmic SFRDs are very similar at both z = 0.1 and 1.0, both showing 70 per cent of the total SFRD above a mass of log(M[subscript *]/M[subscript circled dot]) [greater than] 10. Mass functions are constructed for star-forming galaxies and found to evolve by only [less than]35 per cent between z = 1 and 0.1 over the whole mass range. The evolution is such that the mass function decreases with increasing cosmic time, confirming that galaxies are leaving the star-forming sequence/blue cloud. The observational results are extended to z ∼ 2 by adding two recent Lyman break galaxy samples, and data at these three epochs (z = 0.1, 1, 2) are compared with the GALFORM semi-analytic model of galaxy formation. GALFORM predicts an overall SFRD as a function of stellar mass in reasonable agreement with the observations. The star formation time-scales inferred from 1/SSFR also give reasonable overall agreement, with the agreement becoming worse at the lowest and highest masses. The models do not reproduce the SSFR upturn seen in our data at low masses, where the effects of extinction and active galactic nuclei feedback should be minimal and the comparison should be most robust

A randomized controlled trial to assess the clinical and cost effectiveness of a nurse-led Antenatal Asthma Management Service in South Australia (AAMS study)

Background: Pregnancy presents a unique situation for the management of asthma as it can alter the course of asthma severity and its treatment, which in turn can affect pregnancy outcomes. Despite awareness of the substantial adverse effects associated with asthma during pregnancy, little has been done to improve its management and reduce associated perinatal morbidity and mortality. The aim of this randomized controlled trial is to evaluate the clinical and cost effectiveness of an Antenatal Asthma Management Service. Methods/design: Design: Multicentre, randomized controlled trial. Inclusion criteria: Women with physician diagnosed asthma, which is not currently in remission, who are less than 20 weeks gestation with a singleton pregnancy and do not have a chronic medical condition. Trial entry and randomization: Eligible women with asthma, stratified by treatment site, disease severity and parity, will be randomized into either the ‘Standard Care Group’ or the ‘Intervention Group’. Study groups: Both groups will be followed prospectively throughout pregnancy. Women in the ‘Standard Care Group’ will receive routine obstetric care reflecting current clinical practice in Australian hospitals. Women in the ‘Intervention Group’ will receive additional care through the nurse-led Antenatal Asthma Management Service, based in the antenatal outpatient clinic. Women will receive asthma education with a full assessment of their asthma at 18, 24, 30 and 36 weeks gestation. Each antenatal visit will include a 60 min session where asthma management skills are assessed including: medication adherence and knowledge, inhaler device technique, recognition of asthma deterioration and possession of a written asthma action plan. Furthermore, subjects will receive education about asthma control and management skills including trigger avoidance and smoking cessation counseling when appropriate. Primary study outcome: Asthma exacerbations during pregnancy. Sample size: A sample size of 378 women will be sufficient to show an absolute reduction in asthma exacerbations during pregnancy of 20% (alpha 0.05 two-tailed, 90% power, 5% loss to follow-up). Discussion: The integration of an asthma education program within the antenatal clinic setting has the significant potential to improve the participation of pregnant women in the self-management of their asthma, reduce asthma exacerbations and improve perinatal health outcomes.Luke E Grzeskowiak, Gustaaf Dekker, Karen Rivers, Kate Roberts-Thomson, Anil Roy, Brian Smith, Jeffery Bowden, Robert Bryce, Michael Davies, Justin Beilby, Anne Wilson, Philippa Middleton, Richard Ruffin, Jonathan Karnon, Vicki L Clifton and for the AAMS study grou

The UDF05 Follow-up of the HUDF: II. Constraints on Reionization from z-dropout Galaxies

[Abridged] We detect three (plus one less certain) z-dropout sources in two separate fields of our UDF05 HST NICMOS images. These z~7 Lyman-Break Galaxy (LBG) candidates allow us to constrain the Luminosity Function (LF) of the star forming galaxy population at those epochs. By assuming a change in only M* and adopting a linear evolution in redshift, anchored to the measured values at z~6, the best fit evolution coefficient is found to be 0.43+-0.19 mag per unit redshift (0.36+-0.18, if including all four candidates), which provides a value of M*(z=7.2)=-19.7+-0.3. This implies a steady evolution for the LBG LF out to z~7, at the same rate that is observed throughout the z~3 to 6 period. This puts a strong constraint on the star-formation histories of z~6 galaxies, whose ensemble star-formation rate density must be lower by a factor 2 at ~170 Myr before the epoch at which they are observed. In particular, a large fraction of stars in the z~6 LBG population must form at redshifts well above z~7. Extrapolating this steady evolution of the LF out to higher redshifts, we estimate that galaxies would be able to reionize the universe by z~6, provided that the faint-end slope of the z>7 LF steepens to alpha~-1.9, and that faint galaxies, with luminosities below the current detection limits, contribute a substantial fraction of the required ionizing photons. This scenario gives however an integrated optical depth to electron scattering that is ~2sigma below the WMAP-5 measurement. Therefore, altogether, our results indicate that, should galaxies be the primary contributors to reionization, either the currently detected evolution of the galaxy population slows down at z>7, or the LF evolution must be compensated by a decrease in metallicity and a corresponding increase in ionization efficiency at these early epochs.Comment: Accepted for publication in ApJ, 7 pages, 4 figures; minor revisions to match accepted versio