SILVERRUSH. XI. Constraints on the Lyα Luminosity Function and Cosmic Reionization at z = 7.3 with Subaru/Hyper Suprime-Cam

The Lyα luminosity function (LF) of Lyα emitters (LAEs) has been used to constrain the neutral hydrogen fraction in the intergalactic medium (IGM) and thus the timeline of cosmic reionization. Here we present the results of a new narrowband imaging survey for z = 7.3 LAEs in a large area of ∼3 deg2 with Subaru/Hyper Suprime-Cam. No LAEs are detected down to L Lyα ≃ 1043.2 erg s−1 in an effective cosmic volume of ∼2 × 106 Mpc3, placing an upper limit on the bright part of the z = 7.3 Lyα LF for the first time and confirming a decrease in bright LAEs from z = 7.0. By comparing this upper limit with the Lyα LF in the case of fully ionized IGM, which is predicted using an observed z = 5.7 Lyα LF on the assumption that the intrinsic Lyα LF evolves in the same way as the UV LF, we obtain the relative IGM transmission T Ly α IGM ( 7.3 ) / T Ly α IGM ( 5.7 ) < 0.77 and then the volume-averaged neutral fraction x H I(7.3) > 0.28. Cosmic reionization is thus still ongoing at z = 7.3, consistent with results from other x H I estimation methods. A similar analysis using literature Lyα LFs finds that at z = 6.6 and 7.0, the observed Lyα LF agrees with the predicted one, consistent with full ionization.

Crucial Factors for Lyα Transmission in the Reionizing Intergalactic Medium: Infall Motion, H ii Bubble Size, and Self-shielded Systems

Using the CoDa II simulation, we study the Lyα transmissivity of the intergalactic medium (IGM) during reionization. At z > 6, a typical galaxy without an active galactic nucleus fails to form a proximity zone around itself due to the overdensity of the surrounding IGM. The gravitational infall motion in the IGM makes the resonance absorption extend to the red side of Lyα, suppressing the transmission up to roughly the circular velocity of the galaxy. In some sight lines, an optically thin blob generated by a supernova in a neighboring galaxy results in a peak feature, which can be mistaken for a blue peak. Redward of the resonance absorption, the damping-wing opacity correlates with the global IGM neutral fraction and the UV magnitude of the source galaxy. Brighter galaxies tend to suffer lower opacity because they tend to reside in larger H ii regions, and the surrounding IGM transmits redder photons, which are less susceptible to attenuation, owing to stronger infall velocity. The H ii regions are highly nonspherical, causing both sight-line-to-sight-line and galaxy-to-galaxy variation in opacity. Also, self-shielded systems within H ii regions strongly attenuate the emission for certain sight lines. All these factors add to the transmissivity variation, requiring a large sample size to constrain the average transmission. The variation is largest for fainter galaxies at higher redshift. The 68% range of the transmissivity is similar to or greater than the median for galaxies with M UV ≥ −21 at z ≥ 7, implying that more than a hundred galaxies would be needed to measure the transmission to 10% accuracy.

FATTY ACID COMPOSITION OF ENDOPHYTIC MICROALGAE LAMINARIOCOLAX AECIDIOIDES, STREBLONEMA CORYMBIFERUM AND STREBLONEMA SP. (ECTOCARPALES, PHAEOPHYCEAE)

Впервые исследован жирнокислотный состав полярных и нейтральных липидов бурых эндофитных микроводорослей Laminariocolax aecidioides, Streblonema corymbiferum и Streblonema sp. Показано, что в состав полярных липидов входят главным образом полиненасыщенные жирные кислоты, такие как 18:3ω-3, 18:4ω-3 и 20:5ω-3. Во фракциях нейтральных липидов всех образцов доминировали насыщенные жирные кислоты 14:0 и 16:0, мононенасыщенная 18:1ω-9 и полиненасыщенная 18:2ω6. Отмечена высокая концентрация 16:1ω-7 в нейтральной фракции Streblonema sp. Во всех липидных фракциях эндофитов, кроме нейтральных липидов S. corymbiferum, обнаружены гидроксилированные жирные кислоты 22:0Δ2-OH и 24:0Δ2-OH. The fatty acid composition of polar and neutral lipids of brown endophytic microalgae Laminariocolax aecidioides , Streblonema corymbiferum and Streblonema sp. was investigated for the first time. It was shown that the composition of polar lipids of endophytes includes mainly polyunsaturated fatty acids, such as 18:3ω-3, 18:4ω-3 and 20: 5ω-3. Saturated 14:0 and 16:0, monounsaturated 18:1ω-9 and polyunsaturated 18:2ω6 dominated the neutral lipids of all samples. A high concentration of 16:1ω-7 was observed in the neutral fraction of Streblonema sp. Hydroxylated fatty acids 22:0Δ2-OH and 24:0Δ2-OH were found in all lipid fractions, except for neutral lipids of S. corymbiferum .

Constraining Reionization in Progress at z = 5.7 with Lyman-α Emitters: Voids, Peaks, and Cosmic Variance

A number of independent observations suggest that the intergalactic medium was significantly neutral at z = 7 and that reionization was, perhaps, still in progress at z = 5.7. The narrowband survey, SILVERRUSH, has mapped over 2,000 Lyman-α emitters (LAEs) at these redshifts. Previous analyses have assumed that reionization was over by z = 5.7, but this data may actually sample the final stages of reionization when the last neutral islands were relegated to the cosmic voids. Motivated by these developments, we reexamine LAE void and peak statistics and their ability to constrain reionization. We construct models of the LAE distribution in (1 Gpc/h)3 volumes, spanning a range of neutral fractions at z = 5.7 and 6.6. Models with a higher neutral fraction show an enhanced probability of finding holes in the LAE distribution. When comparing models at fixed mean surface density, however, LAEs obscured by neutral gas in the voids must be compensated by visible LAEs elsewhere. Hence, in these models the likelihood of finding an over-dense peak is also enhanced in the latter half of reionization. Compared to the widely used angular two-point correlation function (2PCF), we find that the void probability function (VPF) provides a more sensitive test of models during the latter half of reionization. By comparison, at neutral fractions $\sim 50\%$, the VPF and a simple peak thresholding statistic are both similar to the 2PCF in constraining power. Lastly, we find that the cosmic variance and large-scale asymmetries observed in the SILVERRUSH fields are consistent with large-scale structure in a ΛCDM universe.

Interpreting LOFAR 21-cm signal upper limits at z ≈ 9.1 in the context of high-z galaxy and reionization observations

ABSTRACT Using the latest upper limits on the 21-cm power spectrum at z ≈ 9.1 from the Low Frequency Array (LOFAR), we explore the regions of parameter space which are inconsistent with the data. We use 21cmmc, a Monte Carlo Markov chain sampler of 21cmfast which directly forward models the three dimensional (3D) cosmic 21-cm signal in a fully Bayesian framework. We use the astrophysical parametrization from 21cmfast, which includes mass-dependent star formation rates and ionizing escape fractions as well as soft-band X-ray luminosities to place limits on the properties of the high-z galaxies. Further, we connect the disfavoured regions of parameter space with existing observational constraints on the Epoch of Reionization such as ultra-violet (UV) luminosity functions, background UV photoionization rate, intergalactic medium (IGM) neutral fraction, and the electron scattering optical depth. We find that all models exceeding the 21-cm signal limits set by LOFAR at z ≈ 9.1 are excluded at ≳2σ by other probes. Finally, we place limits on the IGM spin temperature from LOFAR, disfavouring at 95 per cent confidence spin temperatures below ∼2.6 K across an IGM neutral fraction range of $0.15 \lesssim \bar{x}_{\rm H\, \rm {\small I}} \lesssim 0.6$. Note, these limits are only obtained from 141 h of data in a single redshift bin. With tighter upper limits, across multiple redshift bins expected in the near future from LOFAR, more viable models will be ruled out. Our approach demonstrates the potential of forward modelling tools such as 21cmmc in combining 21-cm observations with other high-z probes to constrain the astrophysics of galaxies.

Stacking redshifted 21 cm images of H ii regions around high-redshift galaxies as a probe of early reionization

ABSTRACT A number of current and future experiments aim to detect the reionization of neutral hydrogen by the first stars and galaxies in the Universe via the redshifted 21 cm line. Using the bluetides simulation, we investigate the measurement of an average ionized region towards the beginning of reionization by stacking redshifted 21 cm images around optically identified bright galaxies using mock observations. We find that with an SKA 1000 h observation, assuming perfect foreground subtraction, a 5σ detection of a stacked H ii region can be made with 30 images around some of the brightest galaxies in bluetides (brighter than MUV &lt; −22.75) at z = 9 (corresponding to a neutral fraction of 90.1 per cent in our model). We present simulated relationships between the UV magnitude of galaxies, the sizes of the ionized regions they reside in, and the shape of the stacked profiles. These mock observations can also distinguish between scenarios where the intergalactic medium is in net emission or absorption of 21 cm photons. Once 21 cm foreground contamination is included, we find that even with up to 200 images around these rare, bright galaxies, only a tentative &gt;1σ detection will be possible. However, partial foreground subtraction substantially improves signal to noise. For example, we predict that reducing the area of Fourier space dominated by foregrounds by 50 (80) per cent will allow &gt;3σ (&gt;5σ) detections of ionized regions at z = 9.

Exploring reionization and high-z galaxy observables with recent multiredshift MWA upper limits on the 21-cm signal

ABSTRACT We use the latest multiredshift (z = 6.5−8.7) upper limits on the 21-cm signal from the Murchison Widefield Array (MWA) to explore astrophysical models which are inconsistent with the data. We explore these limits in the context of reionization astrophysics by using 21CMMC to connect the disfavoured regions of parameter space to existing observational constraints on reionization such as high-z galaxy ultraviolet (UV) luminosity functions, the background UV photoionization rate, the intergalactic medium (IGM) neutral fraction, the electron scattering optical depth and the soft-band X-ray emissivity. We find the vast majority of disfavoured models to already be inconsistent with existing observational constraints. These can be broadly classified into two types of models: (i) ‘cold’ reionization and (ii) pure matter density fluctuations in a cold, neutral IGM (i.e. no reionization). Interestingly, a small subsample of models inconsistent with the MWA is consistent with the aforementioned constraints (excluding the X-ray emissivity). This implies that the current MWA limits are already providing unique information to disfavour models of reionization, albeit extremely weakly. We also provide the first limits on the soft-band X-ray emissivity from galaxies at high redshifts, finding 1σ lower limits of ϵX, 0.5−2 keV ≳ 1034.5 erg s−1 Mpc−3. Finally, we recover 95 per cent disfavoured limits on the IGM spin temperature of $\bar{T}_{\rm S}\lesssim$ 1.3, 1.4, 1.5, 1.8, 2.1, and 2.4 K at z = 6.5, 6.8, 7.1, 7.8, 8.2, and 8.7. With this, we infer the IGM must have undergone, at the very least, a small amount of X-ray heating. Note, the limits on ϵX, 0.5–2 keV and $\bar{T}_{\rm S}$ are conditional on the IGM neutral fraction.

Anti-malarial activity and toxicity of Aspidosperma nitidum Benth: a plant used in traditional medicine in the Brazilian Amazon

The objective of this work was to evaluate the antiplasmodial activity and toxicity of the extract and fractions obtained from the bark of Aspidosperma nitidum. The ethanol extract obtained from the powdered bark of plants was acid-base partitioned and phytochemically analyzed. The antiplasmodial activity, in vivo antimalarial activity and in vitro cytotoxicity were acessed. The selectivity index (SI) was calculated. The acute oral toxicity and pathological effects, of the ethanol extract was evaluated in mice. The major constituent of the ethanol extract was suggestive of a β-carboline chromophore. The alkaloid and neutral fractions contained compounds with an aspidospermine core as the major constituent. The ethanol extract (IC50 = 3.60 µg/mL), neutral fraction (IC50 = 3.34 µg/mL) and alkaloid fraction (IC50= 2.32 µg/mL) showed high activity against P. falciparum (W2 strain). The ethanol extract and the alkaloid fraction reduced 80% of the parasitemia of P. berghei (ANKA)-infected mice (dose of 500 mg/kg) in the 5th day, which was not sustainable at the 8th day. A similar result was obtained for chloroquine. The ethanol extract (CC50 = 410.65 µg/mL; SI = 114.07), neutral fraction (CC50 = 452.53 µg/mL; SI = 135.49), and alkaloid fraction (CC50 =346.73 µg/mL; SI 149.45) demonstrated low cytotoxicity and high SI. The ethanol extract (5000 mg/kg; gavage) presented low acute oral toxicity, with no clinical or anatomopathological modifications being observed (in comparison to the control group). In vitro studies with a chloroquine-resistant clone of P. falciparum confirmed the antiplasmodial activity of the A. nitidum ethanol extract, and its fractions had low cytotoxicity for HepG2 cells. In vivo studies with P. berghei–infected mice and acute toxicity studies corroborated these results.

Measuring the properties of reionized bubbles with resolved Lyα spectra

ABSTRACT Identifying and characterizing reionized bubbles enables us to track both their size distribution, which depends on the primary ionizing sources, and the relationship between reionization and galaxy evolution. We demonstrate that spectrally resolved z ≳ 6 Lyman-alpha (Lyα) emission can constrain properties of reionized regions. Specifically, the distance from a source to a neutral region sets the minimum observable Lyα velocity offset from systemic. Detection of flux on the blue side of the Lyα resonance implies the source resides in a large, sufficiently ionized region that photons can escape without significant resonant absorption, and thus constrains both the sizes of and the residual neutral fractions within ionized bubbles. We estimate the extent of the region around galaxies which is optically thin to blue Lyα photons, analogous to quasar proximity zones, as a function of the source’s ionizing photon output and surrounding gas density. This optically thin region is typically ≲ 0.3 pMpc in radius (allowing transmission of flux ≳ −250 km s−1), ≲ 20 per cent of the distance to the neutral region. In a proof-of-concept, we demonstrate the z ≈ 6.6 galaxy COLA1 – with a blue Lyα peak – likely resides in an ionized region &gt;0.7 pMpc, with residual neutral fraction &lt;10−5.5. To ionize its own proximity zone we infer COLA1 has a high ionizing photon escape fraction (fesc &gt; 0.50), relatively steep UV slope (β &lt; −1.79), and low line-of-sight gas density (∼0.5 times the cosmic mean), suggesting it is a rare, underdense line-of-sight.

Characterization of extracellular polysaccharides from suspension cultures of apple (Malus domestica)

The polymers secreted by suspension-cultured apple cells were composed of 85% carbohydrate (76% neutral sugar and 9% uronic acid) and 15% w/w protein. The extracellular polysaccharides (ECPs) contain 23% XG and 59% AGPs. The monosaccharide composition of the ECPs consisted of Gal, Ara, Glc and Xyl, with smaller amounts of Rha, Fuc and Man. Fractionation of the ECPs by anion-exchange chromatography yielded an unbound neutral fraction and a bound acidic fraction. Monosaccharide and linkage compositions of each fraction were determined. The neutral fraction (48% recovered carbohydrate) was composed of xyloglucan (XG;>90 mol%) which was purified by selective precipitation with Fehling's solution to yield pure XG. The purified XG had a Glc:Xyl:Gal:Fuc ratio of 4.0:2.5:0.8:0.5; the XG was not O-acetylated. The structure of the secreted XG was similar to that extracted from apple-pomace. The acidic fraction (52% recovered carbohydrate) was composed primarily of arabinogalactan-proteins (AGPs) as detected by the β-glucosyl Yariv diffusion test. The AGP had a Gal:Ara ratio of 1.3: 1.0. Minor amounts of arabinan, xylan and mannan were also detected in the ECPs. This study is the first examination of the polysaccharides secreted by apple cells grown in suspension culture.