X-ray background and its correlation with the 21 cm signal

We use high resolution hydrodynamical simulations to study the contribution to the X-ray background from high-$z$ energetic sources, such as X-ray binaries, accreting nuclear black holes and shock heated interstellar medium. Adopting the model discussed in Eide et al. (2018), we find that these X-ray sources during the Epoch of Reionization (EoR) contribute less than a few percent of the unresolved X-ray background. The same sources contribute to less than $\sim$2\% of the measured angular power spectrum of the fluctuations of the X-ray background. The outputs of radiative transfer simulations modeling the EoR are used to evaluate the cross-correlations of X-ray background with the 21~cm signal from neutral hydrogen. Such correlation could be used to confirm the origin of the 21 cm signal, as well as give information on the properties of the X-ray sources during the EoR. We find that the correlations are positive during the early stages of reionization when most of the hydrogen is neutral, while they become negative when the intergalactic medium gets highly ionized, with the transition from positive to negative depending on both the X-ray model and the scale under consideration. With {\tt SKA} as the reference instrument for the 21~cm experiment, the predicted S/N for such correlations is $<1$ if the corresponding X-ray survey is only able to resolve and remove X-ray sources with observed flux $>10^{-15}\,\rm erg\, cm^{-2} \, s^{-1}$, while the cumulative S/N from $l=1000$ to $10^{4}$ at $x_{\rm HI}=0.5$ is $\sim 5$ if sources with observed flux $>10^{-17}\,\rm erg\, cm^{-2} \, s^{-1}$ are detected.Comment: 9 pages, 8 figure

Opening Reionization: Quantitative Morphology of the Epoch of Reionization and Its Connection to the Cosmic Density Field

We introduce a versatile and spatially resolved morphological characterisation of binary fields, rooted in the opening transform of mathematical morphology. We subsequently apply it to the thresholded ionization field in simulations of cosmic reionization and study the morphology of ionized regions. We find that an ionized volume element typically resides in an ionized region with radius $\sim8\,h^{-1}\mathrm{cMpc}$ at the midpoint of reionization ($z\approx7.5$) and follow the bubble size distribution even beyond the overlap phase. We find that percolation of the fully ionized component sets in when 25% of the universe is ionized and that the resulting infinite cluster incorporates all ionized regions above $\sim8\,h^{-1}\mathrm{cMpc}$. We also quantify the clustering of ionized regions of varying radius with respect to matter and on small scales detect the formation of superbubbles in the overlap phase. On large scales we quantify the bias values of the centres of ionized and neutral regions of different sizes and not only show that the largest ones at the high-point of reionization can reach $b\approx 30$, but also that early small ionized regions are positively correlated with matter and large neutral regions and late small ionized regions are heavily anti-biased with respect to matter, down to $b\lesssim-20$.Comment: 18 pages, 15 figure, as accepted for publication by MNRA

Cross-correlation between the 21-cm signal and [OIII] emitters during early cosmic reionization

We study statistics of the 21-cm signal from the epoch of reionization. We propose to use [OIII] line emitting galaxies to cross-correlate with the 21-cm signal from $z = 7 - 10$. To this aim, we employ simulations of reionization obtained post-processing the high-resolution cosmological hydrodynamic simulation Massive Black-II with the three-dimensional (3D) radiative transfer code CRASH to follow the propagation of ionizing photons from a variety of sources. We show that, during the early phases of reionization, the 21-cm signal is positively correlated with the spatial distribution of the [OIII] emitters on large scales $(k < 1h~\rm cMpc^{-1})$. This positive correlation is generated by the temperature-galaxy correlation and it is a few times larger than when we assume that the heating is saturated. As the reionized regions expand, the correlation changes its sign to negative from $z = 10$ to 8. The signals at this epoch can be detected by combining the Square Kilometre Array (SKA) and a wide-field [OIII] emitter survey. We also calculate the cross-power spectrum with a 3D [OIII] intensity field, aiming at exploiting future intensity mapping observations. We conclude that high-redshift [OIII] line emitters can be used to probe the reionization process when the intergalactic medium is largely neutral.Comment: 7 pages, 5 figures, published in MNRA

Unlocking the Full Potential of Extragalactic Lyα\alpha through Its Polarization Properties

Lyman-$\alpha$ (Ly$\alpha$) is a powerful astrophysical probe. Not only is it ubiquitous at high redshifts, it is also a resonant line, making Ly$\alpha$ photons scatter. This scattering process depends on the physical conditions of the gas through which Ly$\alpha$ propagates, and these conditions are imprinted on observables such as the Ly$\alpha$ spectrum and its surface brightness profile. In this work, we focus on a less-used observable capable of probing any scattering process: polarization. We implement the density matrix formalism of polarization into the Monte Carlo radiative transfer code tlac. This allows us to treat it as a quantum mechanical process where single photons develop and lose polarization from scatterings in arbitrary gas geometries. We explore static and expanding ellipsoids, biconical outflows, and clumpy multiphase media. We find that photons become increasingly polarized as they scatter and diffuse into the wings of the line profiles, making scattered Ly$\alpha$ polarized in general. The degree and orientation of Ly$\alpha$ polarization depends on the kinematics and distribution of the scattering HI gas. We find that it generally probes spatial or velocity space asymmetries and aligns itself tangentially to the emission source. We show that the mentioned observables, when studied separately, can leave similar signatures for different source models. We conclude by revealing how a joint analysis of the Ly$\alpha$ spectra, surface brightness profiles, and polarization can break these degeneracies and help us extract unique physical information on galaxies and their environments from their strongest, most prominent emission line.Comment: 26 pages, 12 figures. Figure 2 and 3 reordered, Figure 11 updated. Accepted for publication in Ap

The NOMA track module on nutrition, human rights and governance: Part 2. A transnational curriculum using a human rights-based approach to foster key competencies in nutrition professionals

Background. In response to the challenge of the global health needs of the 21st century, four academic institutions in Norway, South Africa and Uganda,each offering a Master’s degree in nutrition, collaboratively developed the NOrwegian MAsters (NOMA) track module on nutrition, human rights andgovernance, integrating a human rights-based approach into graduate education in nutrition.Objective. To capture students’ perceptions about the NOMA track module, focusing on the development of key competencies.Methods. Employing a qualitative approach, 20 (91% response rate) in-depth telephonic interviews were conducted with participating students, voicerecorded and transcribed. Through an inductive process, emerging themes were used to compile a code list for content analysis of the transcribed text. Relevant themes were reported according to the professionals’ roles described by the CanMEDS competency framework.Results. Participation in the module enhanced key competencies in the students, e.g. communication skills and the adoption of a holistic approach tointeraction with people or communities. Their role as collaborator was enhanced by their learning to embrace diversity and cultural differences and similarities. Students had to adapt to different cultures and educational systems. They were inspired to contribute in diverse contexts and act as agents for change in the organisations in which they may work or act as leaders or co-ordinators during interaction with community groups and policy makers. Higher education institutions offering transnational modules should support lecturers to manage the inherent diversity in the classroom as a way of enhancing student performance.Conclusion. The development of future transprofessional modules will benefit from the inclusion of desirable key competencies as part of the moduleoutcomes by following a competency by design process

Large-scale simulations of H and He reionization and heating driven by stars and more energetic sources

We present simulations of cosmic reionization and reheating from z = 18 to z = 5, investigating the role of stars (emitting soft UV-photons), nuclear black holes (BHs, with power-law spectra), X-ray binaries (XRBs, with hard X-ray dominated spectra), and the supernova-associated thermal bremsstrahlung of the diffuse interstellar medium (ISM, with soft X-ray spectra). We post-process the hydrodynamical simulation MassiveBlack-II (MBII) with multifrequency ionizing radiative transfer. The source properties are directly derived from the physical environment of MBII, and our only real free parameter is the ionizing escape fraction fesc. We find that, among the models explored here, the one with an escape fraction that decreases with decreasing redshift yields results most in line with observations, such as of the neutral hydrogen fraction and the Thomson scattering optical depth. Stars are the main driver of hydrogen reionization and consequently of the thermal history of the intergalactic medium (IGM). We obtain = 0.99998 at z = 6 for all source types, with volume-averaged temperatures &lt; T &gt; ∼ 20 000 K. BHs are rare and negligible to hydrogen reionization, but conversely they are the only sources that can fully ionize helium, increasing local temperatures by ∼104 K. The thermal and ionization state of the neutral and lowly ionized hydrogen differs significantly with different source combinations, with ISM and (to a lesser extent) XRBs, playing a significant role and, as a consequence, determining the transition from absorption to emission of the 21-cm signal from neutral hydrogen

New Pulsating White Dwarfs in Cataclysmic Variables

The number of discovered non-radially pulsating white dwarfs (WDs) in cataclysmic variables (CVs) is increasing rapidly by the aid of the Sloan Digital Sky Survey (SDSS). We performed photometric observations of two additional objects, SDSS J133941.11+484727.5 (SDSS 1339), independently discovered as a pulsator by Gansicke et al., and SDSS J151413.72+454911.9, which we identified as a CV/ZZ Ceti hybrid. In this Letter we present the results of the remote observations of these targets performed with the Nordic Optical Telescope (NOT) during the Nordic-Baltic Research School at Moletai Observatory, and follow-up observations executed by NOT in service mode. We also present 3 candidates we found to be non-pulsating. The results of our observations show that the main pulsation frequencies agree with those found in previous CV/ZZ Ceti hybrids, but specifically for SDSS 1339 the principal period differs slightly between individual observations and also from the recent independent observation by Gansicke et al. Analysis of SDSS colour data for the small sample of pulsating and non-pulsating CV/ZZ Ceti hybrids found so far, seems to indicate that the r-i colour could be a good marker for the instability strip of this class of pulsating WDs.Comment: 5 pages, 6 figures, 2 tables, accepted for publication in MNRAS Letter

A CRASH simulation of the contribution of binary stars to the epoch of reionization

We use a set of 3D radiative transfer simulations to study the effect that a large fraction of binary stars in galaxies during the epoch of reionization has on the physical properties of the intergalactic medium (i.e. the gas temperature and the ionization state of hydrogen and helium), on the topology of the ionized bubbles and on the 21 cm power spectra. Consistently to previous literature, we find that the inclusion of binary stars can speed up the reionization process of HI and HeI, while HeII reionization is still dominated by more energetic sources, especially accreting black holes. The earlier ionization attained with binary stars allows for more time for cooling and recombination, so that gas fully ionized by binary stars is typically colder than that ionized by single stars at any given redshift. With the same volume averaged ionization fraction, the inclusion of binary stars results in fewer small ionized bubbles and more large ones, with visible effects also on the large scales of the 21 cm power spectrum.Comment: 14 pages, 11 figures, MNRAS accepte

Marine n-3 fatty acid consumption in a Norwegian renal transplant cohort:Comparison of a food frequency questionnaire with plasma phospholipid marine n-3 levels

BackgroundHigh levels of plasma marine n-3 fatty acids (n-3FAs) are associated with improved patient and graft survival in renal transplant recipients (RTRs). The aim of this study was to evaluate the utility of a new food frequency questionnaire (FFQ) to estimate marine n-3FA consumption in future epidemiological research.MethodsWe developed an FFQ with a simple design of 10 questions to assess intake of marine sources of n-3FAs. RTRs included in the recent ORENTRA trial (n = 132) completed the study FFQ at the baseline visit eight weeks after engraftment and at the end of study visit one year post-transplant. We measured the reference biomarker plasma phospholipid (PL) marine n-3FA levels by gas chromatography at the same time points to evaluate association and degree of agreement between FFQ based marine n-3FA consumption estimates and the biomarker.ResultsThe median plasma PL marine n-3FA level was 6.0 weight percentage (wt)% (interquartile range [IQR] 4.7 to 7.3) at baseline and 6.3 wt% (IQR 4.8 to 7.4) at end of study. Median FFQ based marine n-3FA consumption estimates were 22.8 g/month (IQR 13.0 to 34.0) at baseline and 20.3 g/month (IQR 14.5 to 32.3) at end of study. FFQ based marine n-3FA consumption estimates showed a moderate correlation with plasma PL marine n-3FA levels at baseline (Spearman's correlation coefficient rs = 0.43, pConclusionsMarine n-3FA consumption estimates based on the FFQ showed a moderate correlation with the reference biomarker plasma PL marine n-3FA levels. The FFQ might be useful in epidemiological studies where resources are limited

Indigenous knowledge of rural communities in Malawi on socio-economic use, propagation, biology, biodiversity and ecology of Uapaca kirkiana Muell. Arg

Uapaca kirkiana Muell Arg. is one of the most popular indigenous fruit trees in the Miombo woodlands of southern Africa. An investigation into existing indigenous knowledge and socio- economic use ofthis fruit tree was conducted in Malawi. The survey revealed that U. kirkiana fruits contribute considerably to livelihood as a food supplement and for income generation among local communities.However, U. kirkiana trees are not widely cultivated due to lack of improved planting materials and difficulties in establishment outside their natural habitats. The results from the survey indicate thatfruits are the main non-timber products that contribute to demand for domestication and the attributes preferred by the rural communities for improvement are mainly related to fruit taste and yield. Poormanagement and anthropogenic activities have resulted in the destruction of forest reserves and the local people do not have maximum stewardship of U. kirkiana trees in the forest reserve. Theindigenous knowledge on U. kirkiana trees provides a valuable basis for domestication, propagation and improvement of fruit and tree attributes, and management issues on both co-managed and government forest reserve