The Evolution of the Lyman-Alpha Luminosity Function During Reionization

The time frame in which hydrogen reionization occurred is highly uncertain, but can be constrained by observations of Lyman-alpha (Ly$\alpha$) emission from distant sources. Neutral hydrogen in the intergalactic medium (IGM) attenuates Ly$\alpha$~photons emitted by galaxies. As reionization progressed the IGM opacity decreased, increasing Ly$\alpha$~visibility. The galaxy Ly$\alpha$~luminosity function (LF) is thus a useful tool to constrain the timeline of reionization. In this work, we model the Ly$\alpha$~LF as a function of redshift, $z=5-10$, and average IGM neutral hydrogen fraction, \overline{x}_\textsc{hi}. We combine the Ly$\alpha$~luminosity probability distribution obtained from inhomogeneous reionization simulations with a model for the UV LF to model the Ly$\alpha$~LF. As the neutral fraction increases, the average number density of Ly$\alpha$~emitting galaxies decreases, and are less luminous, though for \overline{x}_\textsc{hi} \lesssim 0.4 there is only a small decrease of the Ly$\alpha$~LF. We use our model to infer the IGM neutral fraction at $z=6.6, 7.0, 7.3$ from observed Ly$\alpha$~LFs. We conclude that there is a significant increase in the neutral fraction with increasing redshift: \overline{x}_\textsc{hi}(z=6.6)=0.08^{+ 0.08}_{- 0.05}, \, \overline{x}_\textsc{hi}(z=7.0)=0.28 \pm 0.05 and \overline{x}_\textsc{hi}(z=7.3)=0.83^{+ 0.06}_{- 0.07}. We predict trends in the Ly$\alpha$~luminosity density and Schechter parameters as a function of redshift and the neutral fraction. We find that the Ly$\alpha$~luminosity density decreases as the universe becomes more neutral. Furthermore, as the neutral fraction increases, the faint-end slope of the Ly$\alpha$~LF steepens, and the characteristic Ly$\alpha$~luminosity shifts to lower values, concluding that the evolving shape of the Ly$\alpha$~LF -- not just its integral -- is an important tool to study reionization.Comment: 20 pages, 10 figures, submitted to Ap

The Evolution of the Lyman-alpha Luminosity Function during Reionization

The time frame in which hydrogen reionization occurred is highly uncertain, but can be constrained by observations of Lyman-alpha (Lya) emission from distant sources. Neutral hydrogen in the intergalactic medium (IGM) attenuates Lya photons emitted by galaxies. As reionization progressed the IGM opacity decreased, increasing Lya visibility. The galaxy Lya luminosity function (LF) is thus a useful tool to constrain the timeline of reionization. In this work, we model the Lya LF as a function of redshift, z = 5 10, and average IGM neutral hydrogen fraction, xH?. We combine the Lya luminosity probability distribution obtained from inhomogeneous reionization simulations with a model for the UV LF to model the Lya LF. As the neutral fraction increases, the average number density of Lya emitting galaxies decreases, and are less luminous, though for xH? ? 0.4 there is only a small decrease in the Lya LF. We use our model to infer the IGM neutral fraction at z = 6.6, 7.0, and 7.3 from observed Lya LFs. We conclude that there is a significant increase in the neutral fraction with increasing redshift: = = - = = ? x z 6.6 0.08+ , x z 7.0 0.28 0.05 H 0.05 0.08 ? ( ) H? ( ) and = = - x z 7.3 0.83+ H 0.07 0.06 ? ( ) . We predict trends in the Lya luminosity density and Schechter parameters as a function of redshift and the neutral fraction. We find that the Lya luminosity density decreases as the universe becomes more neutral. Furthermore, as the neutral fraction increases, the faint-end slope of the Lya LF steepens, and the characteristic Lya luminosity shifts to lower values; hence, we conclude that the evolving shape of the Lya LF not just its integral is an important tool to study reionization

The Impact of Cosmic Variance on Inferences of Global Neutral Fraction Derived from Lyα\alpha Luminosity Functions During Reionization

We investigate the impact of field-to-field variation, deriving from cosmic variance, in measured Lyman-$\alpha$ emitter (LAE) luminosity functions (LFs) and this variation's impact on inferences of the neutral fraction of the intergalactic medium (IGM) during reionization. We post-process a z=7 IGM simulation to populate the dark matter halos with LAEs. These LAEs have realistic UV magnitudes, Ly$\alpha$ fluxes, and Ly$\alpha$ line profiles. We calculate the attenuation of Ly$\alpha$ emission in universes with varying IGM neutral fraction, $\bar{\rm{x}}_{\rm{HI}}$. In a $\bar{\rm{x}}_{\rm{HI}}=0.3$ simulation, we perform 100 realizations of a mock 2 square degree survey with a redshift window $\Delta z = 0.5$ and flux limit $\rm{f}_{Ly\alpha}>1\times10^{-17}\:\rm{ergs}\:\: \rm{s}^{-1} \: \rm{cm}^{-2}$; such a survey is typical in depth and volume of the largest LAE surveys conducted today. For each realization, we compute the LAE LF and use it to recover the input $\bar{\rm{x}}_{\rm{HI}}$. Comparing the inferred values of $\bar{\rm{x}}_{\rm{HI}}$ across the ensemble of the surveys, we find that cosmic variance, deriving from large-scale structure and variation in the neutral gas along the sightline, imposes a floor in the uncertainty of $\Delta \bar{\rm{x}}_{\rm{HI}} \sim 0.2$ when $\bar{\rm{x}}_{\rm{HI}}$ $=0.3$. We explore mitigation strategies to decrease this uncertainty, such as increasing the volume, decreasing the flux limit, or probing the volume with many independent fields. Increasing the area and/or depth of the survey does not mitigate the uncertainty, but composing a survey with many independent fields is effective. This finding highlights the best strategy for LAE surveys aiming at constraining $\bar{\rm{x}}_{\rm{HI}}$ of the universe during reionization.Comment: 17 pages, 13 figure

Live imaging of the immune response to heart injury in larval zebrafish reveals a multi-stage model of neutrophil and macrophage migration

Neutrophils and macrophages are crucial effectors and modulators of repair and regeneration following myocardial infarction, but they cannot be easily observed in vivo in mammalian models. Hence many studies have utilized larval zebrafish injury models to examine neutrophils and macrophages in their tissue of interest. However, to date the migratory patterns and ontogeny of these recruited cells is unknown. In this study, we address this need by comparing our larval zebrafish model of cardiac injury to the archetypal tail fin injury model. Our in vivo imaging allowed comprehensive mapping of neutrophil and macrophage migration from primary hematopoietic sites, to the wound. Early following injury there is an acute phase of neutrophil recruitment that is followed by sustained macrophage recruitment. Both cell types are initially recruited locally and subsequently from distal sites, primarily the caudal hematopoietic tissue (CHT). Once liberated from the CHT, some neutrophils and macrophages enter circulation, but most use abluminal vascular endothelium to crawl through the larva. In both injury models the innate immune response resolves by reverse migration, with very little apoptosis or efferocytosis of neutrophils. Furthermore, our in vivo imaging led to the finding of a novel wound responsive mpeg1+ neutrophil subset, highlighting previously unrecognized heterogeneity in neutrophils. Our study provides a detailed analysis of the modes of immune cell migration in larval zebrafish, paving the way for future studies examining tissue injury and inflammation

Variety.

The inaugural exhibition, Variety, references the venue's past as a seaside centre for entertainment, and examines its future as a centre for contemporary arts in the 21st century. Pantomime, slapstick, burlesque, illusion, song and dance, and spectacle all feature in the exhibition

Personalising Clinical Pathways in a London Breast Cancer Service

Using interview and observational data from a busy and research-intensive breast cancer service in the United Kingdom, we discuss recent developments in Personalised Medicine. Specifically, we show how clinical and research practices meet in clinical pathways that are reconfigured in response to changing approaches of diagnosing, monitoring, treating and understanding cancers. Clinical pathways are increasingly sensitive to changes in evidence deduced through new technologies and therapies as well as decisions based on intensive, iterative analysis of data collected across a range of platforms. We contribute to existing research by showing how the organisation of on clinical pathways both maintains established clinical practices and responds to new research evidence, managing a threshold between evidence-based and experimental medicine. Finally, we invite comparisons with other forms of personalisation to understand how they depend on the ‘real time’ collection, analysis and application of data

A review of progress made with growing energy crops in EU economic appraisal of wheat and miscanthus in selected member states

vKV

Aristocracy in Early T'ang Period.

An amendment to this paper has been published and can be accessed via a link at the top of the paper

Enzymatically dissociated muscle fibers display rapid dedifferentiation and impaired mitochondrial calcium control

Cells rapidly lose their physiological phenotype upon disruption of their extracellular matrix (ECM)-intracellular cytoskeleton interactions. By comparing adult mouse skeletal muscle fibers, isolated either by mechanical dissection or by collagenase-induced ECM digestion, we investigated acute effects of ECM disruption on cellular and mitochondrial morphology, transcriptomic signatures, and Ca2+ handling. RNA-sequencing showed striking differences in gene expression patterns between the two isolation methods with enzymatically dissociated fibers resembling myopathic phenotypes. Mitochondrial appearance was grossly similar in the two groups, but 3D electron microscopy revealed shorter and less branched mitochondria following enzymatic dissociation. Repeated contractions resulted in a prolonged mitochondrial Ca2+ accumulation in enzymatically dissociated fibers, which was partially prevented by cyclophilin inhibitors. Of importance, muscle fibers of mice with severe mitochondrial myopathy show pathognomonic mitochondrial Ca2+ accumulation during repeated contractions and this accumulation was concealed with enzymatic dissociation, making this an ambiguous method in studies of native intracellular Ca2+ fluxes

Scientific Basis for Managing PFAS as a Chemical Class

This commentary presents a scientific basis for managing as one chemical class the thousands of chemicals known as PFAS (per- and polyfluoroalkyl substances). The class includes perfluoroalkyl acids, perfluoroalkylether acids, and their precursors; fluoropolymers and perfluoropolyethers; and other PFAS. The basis for the class approach is presented in relation to their physicochemical, environmental, and toxicological properties. Specifically, the high persistence, accumulation potential, and/or hazards (known and potential) of PFAS studied to date warrant treating all PFAS as a single class. Examples are provided of how some PFAS are being regulated and how some businesses are avoiding all PFAS in their products and purchasing decisions. We conclude with options for how governments and industry can apply the class-based approach, emphasizing the importance of eliminating non-essential uses of PFAS, and further developing safer alternatives and methods to remove existing PFAS from the environment.ISSN:2328-893