Estimation of high-resolution dust column density maps. Comparison of modified black-body fits and radiative transfer modelling

Sub-millimetre dust emission is often used to derive the column density N of dense interstellar clouds. The observations consist of data at several wavelengths but of variable resolution. We examine two procedures that been proposed for the estimation of high resolution N maps. Method A uses a low-resolution temperature map combined with higher resolution intensity data while Method B combines N estimates from different wavelength ranges. Our aim is to determine the accuracy of the methods relative to the true column densities and the estimates obtainable with radiative transfer modelling. We use magnetohydrodynamical (MHD) simulations and radiative transfer calculations to simulate sub-millimetre observations at the wavelengths of the Herschel Space Observatory. The observations are analysed with the methods and the results compared to the true values and to the results from radiative transfer modelling of observations. Both methods A and B give relatively reliable column density estimates at the resolution of 250um data while also making use of the longer wavelengths. For high signal-to-noise data, the results of Method B are better correlated with the true column density, while Method A is less sensitive to noise. When the cloud has internal heating, results of Method B are consistent with those that would be obtained with high-resolution data. Because of line-of-sight temperature variations, these underestimate the true column density and, because of a favourable cancellation of errors, Method A can sometimes give more correct values. Radiative transfer modelling, even with very simple 3D cloud models, can provide better results. However, the complexity of the models required for improvements increases rapidly with the complexity and opacity of the clouds.Comment: 14 pages, Accepted to A&

Mapping of interstellar clouds with infrared light scattered from dust: TMC-1N

Mapping of near-infrared (NIR) scattered light is a recent method for the study of interstellar clouds, complementing other, more commonly used methods, like dust emission and extinction. Our goal is to study the usability of this method on larger scale, and compare the properties of a filament using NIR scattering and other methods. We also study the radiation field and differences in grain emissivity between diffuse and dense areas. We have used scattered J, H, and K band surface brightness WFCAM-observations to map filament TMC-1N in Taurus, covering an area of 1dx1d corresponding to ~(2.44 pc)^2. We have converted the data into optical depth and compared the results with NIR extinction and Herschel observations of submm dust emission. We see the filament in scattered light in all three NIR bands. We note that our WFCAM observations in TMC-1N show notably lower intensity than previous results in Corona Australis using the same method. We show that 3D radiative transfer simulations predict similar scattered surface brightness levels as seen in the observations. However, changing the assumptions about the background can change the results of simulations notably. We derive emissivity by using optical depth in the J band as an independent tracer of column density. We obtain opacity sigma(250um) values 1.7-2.4x10^-25 cm^2/H, depending on assumptions of the extinction curve, which can change the results by over 40%. These values are twice as high as obtained for diffuse areas, at the lower limit of earlier results for denser areas. We show that NIR scattering can be a valuable tool in making high resolution maps. We conclude, however, that NIR scattering observations can be complicated, as the data can show relatively low-level artefacts. This suggests caution when planning and interpreting the observations.Comment: abstract shortened and figures reduced for astrop

Profiles of interstellar cloud filaments. Observational effects in synthetic sub-millimetre observations

Sub-millimetre observations suggest that the filaments of interstellar clouds have rather uniform widths and can be described with the so-called Plummer profiles. The shapes of the filament profiles are linked to their physical state. Before drawing conclusions on the observed column density profiles, we must evaluate the observational uncertainties. We want to estimate the bias that could result from radiative transfer effects or from variations of submm dust emissivity. We use cloud models obtained with magnetohydrodynamic simulations and carry out radiative transfer calculations to produce maps of sub-millimetre emission. Column densities are estimated based on the synthetic observations. For selected filaments, the estimated profiles are compared to those derived from the original column density. Possible effects from spatial variations of dust properties are examined. With instrumental noise typical of the Herschel observations, the parameters derived for nearby clouds are correct to within a few percent. The radiative transfer effects have only a minor effect on the results. If the signal-to-noise ratio is degraded by a factor of four, the errors become significant and for half of the examined filaments the values cannot be constrained. The errors increase in proportion to the cloud distance. Assuming the resolution of Herschel instruments, the model filaments are barely resolved at a distance of ~400 pc and the errors in the parameters of the Plummer function are several tens of per cent. The Plummer parameters, in particular the power-law exponent p, are sensitive to noise but can be determined with good accuracy using Herschel data. One must be cautious about possible line-of-sight confusion. In our models, a large fraction of the filaments seen in the column density maps are not continuous structures in three dimensions.Comment: 12 pages, 14 figures, accepted to A&

Assessment of the systemic effects of budesonide inhaled from Easyhaler®and from Turbuhaler®in healthy male volunteers

AbstractThe main objective of this study was to show dose-dependent equivalence in the systemic activity of budesonide 800 μ g day−1and 1600 μ g day−1delivered from either Easyhaler®or Turbuhaler®in healthy male subjects.This single-centre study was carried out according to a randomized, double-blind, double-dummy, five-way cross-over design over a 9-week period. All subjects received 1 week of treatment with the following, in randomized order, with a washout week between each treatment: budesonide Easyhaler®800 μ g day−1plus placebo Turbuhaler®; budesonide Easyhaler®1600 μ g day−1plus placebo Turbuhaler®; placebo Easyhaler®plus Pulmicort®Turbuhaler®800 μ g day−1; placebo Easyhaler®plus Pulmicort®Turbuhaler®1600 μ g day−1; placebo Easyhaler®plus placebo Turbuhaler®. The final inhalation of study drug was performed at the study centre, where blood and urine samples were collected.Fifteen subjects were recruited and all completed the study. Mean serum cortisol AUC0–20values (the primary outcome variable) were comparable for each device at the two dose levels, and met the defined criteria for equivalence (90% CI 0·8–1·25 for between-treatment difference). Budesonide 800 μ g day−1caused minimal suppression of serum cortisol AUC0-20values. Budesonide 1600 μ g day−1statistically significantly suppressed serum cortisol AUC0–20values compared with placebo. Mean morning serum cortisol values were within the reference range in all treatment groups. At a budesonide dose of 800 μ g day−1mean urine cortisol/creatinine ratio was statistically significantly higher with Easyhaler®than with Turbuhaler®, but there was no significant difference between the devices at the 1600 μ g day−1dose. Serum budesonide concentrations were equivalent for each device at both dose levels. Adverse drug reactions were infrequent and mild in nature and there were no clinically significant changes in laboratory safety variables.In conclusion, in healthy male volunteers, budesonide 800μ g day−1and 1600 μ g day−1inhaled from Easyhaler®had comparable systemic effects to the same doses inhaled via Turbuhaler®

Viscothermal Losses in Double-Negative Acoustic Metamaterials

[EN] The influence of losses in double-negative metamaterial slabs recently introduced by Graciá-Salgado et al. [Phys. Rev. B 88, 224305 (2013)] is comprehensively studied. Viscous and thermal losses are considered in the linearized Navier-Stokes equations with no flow. Despite the extremely low thicknesses of boundary layers associated with each type of losses, the double-negative behavior is totally suppressed for the rigid structures under analysis. In other words, almost 100% of the energy transmitted into the slab is dissipated by viscothermal effects, in agreement with experimental data. Simulations undertaken for larger structures, using scale factors of up to 20 times, show that double-negative behavior is never recovered. The huge dissipation obtained by these structures leads us to propose them as interesting alternatives to conventional absorbers for specific situations, e.g., when treating low frequencies or when the excitation is narrow banded.V. M. G.-C. and J. S.-D. acknowledge the support from the Spanish Ministerio de Economia y Competitividad (MINECO), and the European Union Fondo Europeo de Desarrollo Regional (FEDER) through Project No. TEC 2014-53088-C3-1-R.Cutanda-Henriquez, V.; Garcia Chocano, VM.; Sánchez-Dehesa Moreno-Cid, J. (2017). Viscothermal Losses in Double-Negative Acoustic Metamaterials. Physical Review Applied. 8(1):014029-1-014029-12. doi:10.1103/PhysRevApplied.8.014029S014029-1014029-128

Profiling filaments: comparing near-infrared extinction and submillimetre data in TMC-1

Interstellar filaments are an important part of star formation. To understand the structure of filaments, cross-section profiles are often fitted with Plummer profiles. This profiling is often done with submm studies, such as Herschel. It would be convenient if filament properties could also be studied using groundbased NIR data. We compare the filament profiles obtained by NIR extinction and submm observations to find out if reliable profiles can be derived using NIR data. We use J-, H-, and K-band data of a filament north of TMC-1 to derive an extinction map from colour excesses of background stars. We compare the Plummer profiles obtained from extinction maps with Herschel dust emission maps. We present 2 methods to estimate profiles from NIR: Plummer profile fits to median Av of stars or directly to the Av of individual stars. We compare the methods by simulations. In simulations extinction maps and the new methods give correct results to within ~10-20 for modest densities. Direct fit to data on individual stars gives more accurate results than extinction map, and can work in higher density. In profile fits to real observations, values of Plummer parameters are generally similar to within a factor of ~2. Although parameter values can vary significantly, estimates of filament mass usually remain accurate to within some tens of per cent. Our results for TMC-1 are in agreement with earlier results. High resolution NIR data give more details, but 2MASS data can be used to estimate profiles. NIR extinction can be used as an alternative to submm observations to profile filaments. Direct fits of stars can also be a valuable tool. Plummer profile parameters are not always well constrained, and caution should be taken when making fits. In the evaluation of Plummer parameters, one can use the independence of dust emission and NIR data and the difference in the shapes of the confidence regions.Comment: accepted to Astronomy & Astrophysics; abstract has been shortened for astrop

New Stone Age Sites to the North of Lake Ladoga in Karelia, Russia

In 2012, the Museum of Lahti and the Museum of Petrozavodsk completed a joint archaeological field project, begun in 2008, in present-day Russian Karelia for the purpose of studying the oldest postglacial settlement of the area between Lake Ladoga and Lake Onega. During the five field seasons, altogether 19 new Stone Age sites were found. Test excavations were carried out at five sites. The finds consisted mostly of burned bone and flakes of quartz and other lithics. The oldest site was found in Harlu at the mouth of the Jänisjoki River, with a dating of ca. 7760 calBC

Ecological speciation in a generalist consumer expands the trophic niche of a dominant predator

Ecological speciation - whereby an ancestral founder species diversifies to fill vacant niches - is a phenomenon characteristic of newly formed ecosystems. Despite such ubiquity, ecosystem-level effects of such divergence remain poorly understood. Here, we compared the trophic niche of European whitefish (Coregonus lavaretus) and their predators in a series of contrasting subarctic lakes where this species had either diversified into four ecomorphologically distinct morphs or instead formed monomorphic populations. We found that the trophic niche of whitefish was almost three times larger in the polymorphic than in the monomorphic lakes, due to an increase in intraspecific specialisation. This trophic niche expansion was mirrored in brown trout (Salmo trutta), a major predator of whitefish. This represents amongst the first evidence for ecological speciation directly altering the trophic niche of a predator. We suggest such mechanisms may be a common and important - though presently overlooked - factor regulating trophic interactions in diverse ecosystems globally.Peer reviewe