906 research outputs found

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

    Full text link
    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

    A Corona Australis cloud filament seen in NIR scattered light. III. Modelling and comparison with Herschel sub-millimetre data

    Get PDF
    With recent Herschel observations, the northern filament of the Corona Australis cloud has now been mapped in a number of bands from 1.2um to 870um. The data set provides a good starting point for the study of the cloud over several orders of magnitude in density. We wish to examine the differences of the column density distributions derived from dust extinction, scattering, and emission, and to determine to what extent the observations are consistent with the standard dust models. From Herschel data, we calculate the column density distribution that is compared to the corresponding data derived in the near-infrared regime from the reddening of the background stars, and from the surface brightness attributed to light scattering. We construct three-dimensional radiative transfer models to describe the emission and the scattering. The scattered light traces low column densities of A_V~1mag better than the dust emission, remaining useful to A_V ~ 10-15 mag. Based on the models, the extinction and the level of dust emission are surprisingly consistent with a sub-millimetre dust emissivity typical of diffuse medium. However, the intensity of the scattered light is very low at the centre of the densest clump and this cannot be explained without a very low grain albedo. Both the scattered light and dust emission indicate an anisotropic radiation field. The modelling of the dust emission suggests that the radiation field intensity is at least three times the value of the normal interstellar radiation field. The inter-comparison between the extinction, light scattering, and dust emission provides very stringent constraints on the cloud structure, the illuminating radiation field, and the grain properties.Comment: 13 pages, 16 figures, accepted to A&

    Multiwavelength study of the high-latitude cloud L1642: chain of star formation

    Get PDF
    L1642 is one of the two high galactic latitude (|b| > 30deg) clouds confirmed to have active star formation. We examine the properties of this cloud, especially the large-scale structure, dust properties, and compact sources in different stages of star formation. We present high-resolution far-infrared and submm observations with the Herschel and AKARI satellites and mm observations with the AzTEC/ASTE telescope, which we combined with archive data from near- and mid-infrared (2MASS, WISE) to mm observations (Planck). The Herschel observations, combined with other data, show a sequence of objects from a cold clump to young stellar objects at different evolutionary stages. Source B-3 (2MASS J04351455-1414468) appears to be a YSO forming inside the L1642 cloud, instead of a foreground brown dwarf, as previously classified. Herschel data reveal striation in the diffuse dust emission around L1642. The western region shows striation towards NE and has a steeper column density gradient on its southern side. The densest central region has a bow-shock like structure showing compression from the west and a filamentary tail extending towards east. The differences suggest that these may be spatially distinct structures, aligned only in projection. We derive values of the dust emission cross-section per H nucleon for different regions of the cloud. Modified black-body fits to the spectral energy distribution of Herschel and Planck data give emissivity spectral index beta values 1.8-2.0 for the different regions. The compact sources have lower beta values and show an anticorrelation between T and beta. Markov chain Monte Carlo calculations demonstrate the strong anticorrelation between beta and T errors and the importance of mm Planck data in constraining the estimates. L1642 reveals a more complex structure and sequence of star formation than previously known.Comment: 22 pages, 18 figures, accepted to Astronomy & Astrophysics; abstract shortened and figures reduced for astrop

    Jälkitavujen A-loppuisten vokaaliyhtymien variaatio kinnulalaisten puhekielessä

    Get PDF
    Tiivistelmä. Tutkin kandidaatintutkielmassani jälkitavujen A-loppuisten vokaaliyhtymien variaatiota kinnulalaisten puhekielessä. Lisäksi tutkin, millaisia muotoryhmittäisiä eroja esiintyy jälkitavujen A-loppuisten vokaaliyhtymien variaatiossa. Aineistoni olen kerännyt nauhoittamalla viiden eri-ikäisen informantin keskusteluja. Aineistoa kertyi yhteensä vajaat kolme tuntia. Tutkimukseni edustaa sekä dialektologiaa että sosiolingvististä variaationtutkimusta. Tutkimustulokseni osoittavat, että kinnulalaisten puhekielessä kaikissa tutkimissani vokaaliyhtymissä esiintyy useimmin yleiskielinen variantti. Puhekielessä yleistyvää assimiloitunutta muotoa esiintyy jälkitavujen eA-, OA- ja iA-yhtymissä, mutta huomattavasti vähemmän kuin yleiskielistä varianttia. Lisäksi kinnulalaisten puhekielessä esiintyy eA- ja OA-yhtymissä diftongiutunutta varianttia, jossa on geminaatta. Koska informanttien määrä on melko vähäinen, ja he ovat eri-ikäisiä, tutkimustuloksia voidaan pitää suuntaa antavina

    Grain size limits derived from 3.6 {\mu}m and 4.5 {\mu}m coreshine

    Get PDF
    Recently discovered scattered light from molecular cloud cores in the wavelength range 3-5 {\mu}m (called "coreshine") seems to indicate the presence of grains with sizes above 0.5 {\mu}m. We aim to analyze 3.6 and 4.5 {\mu}m coreshine from molecular cloud cores to probe the largest grains in the size distribution. We analyzed dedicated deep Cycle 9 Spitzer IRAC observations in the 3.6 and 4.5 {\mu}m bands for a sample of 10 low-mass cores. We used a new modeling approach based on a combination of ratios of the two background- and foreground-subtracted surface brightnesses and observed limits of the optical depth. The dust grains were modeled as ice-coated silicate and carbonaceous spheres. We discuss the impact of local radiation fields with a spectral slope differing from what is seen in the DIRBE allsky maps. For the cores L260, ecc806, L1262, L1517A, L1512, and L1544, the model reproduces the data with maximum grain sizes around 0.9, 0.5, 0.65, 1.5, 0.6, and > 1.5 {\mu}m, respectively. The maximum coreshine intensities of L1506C, L1439, and L1498 in the individual bands require smaller maximum grain sizes than derived from the observed distribution of band ratios. Additional isotropic local radiation fields with a spectral shape differing from the DIRBE map shape do not remove this discrepancy. In the case of Rho Oph 9, we were unable to reliably disentangle the coreshine emission from background variations and the strong local PAH emission. Considering surface brightness ratios in the 3.6 and 4.5 {\mu}m bands across a molecular cloud core is an effective method of disentangling the complex interplay of structure and opacities when used in combination with observed limits of the optical depth.Comment: 23 pages, 18 figures, accepted for publication in A&

    Safety of tacrolimus 0.03% and 0.1% ointments in young children with atopic dermatitis: a 36-month follow-up study

    Get PDF
    Summary Background Topical tacrolimus is used off-label in young children, but data are limited on its use in children under 2?years of age and for long-term treatment. Aim To compare safety differences between topical tacrolimus (0.03% and 0.1% ointments) and topical corticosteroids (mild and moderate potency) in young children with atopic dermatitis (AD). Methods We conducted a 36-month follow-up study with 152 young children aged 1?3?years with moderate to severe AD. The children were followed up prospectively, and data were collected on infections, disease severity, growth parameters, vaccination responses and other relevant laboratory tests were gathered. Results There were no significant differences between the treatment groups for skin-related infections (SRIs) (P?=?0.20), non-SRIs (P?=?0.20), growth parameters height (P?=?0.60), body weight (P?=?0.81), Eczema Area and Severity Index (EASI) (P?=?0.19), vaccination responses (P?=?0.62), serum cortisone levels (P?=?0.23) or serum levels of interleukin (IL)-4, IL-10, IL-12, IL-31 and interferon-?. EASI decreased significantly in both groups (P?Peer reviewe

    A History of Cow's Milk Allergy Is Associated with Lower Vitamin D Status in Schoolchildren

    Get PDF
    Background/Aims: Vitamin D insufficiency is common in children. We aimed to evaluate the main determinants of vitamin D status in Finnish school-aged children, including the history of allergic diseases. Methods: We conducted a cross-sectional study on 171 ten-year-olds where serum 25-hydroxyvitamin D (25[OH] D) levels were measured, and data on food consumption and use of vitamin D supplements were collected. The history of allergic diseases was evaluated with a validated questionnaire. Results: Vitamin D insufficiency (Peer reviewe

    Airway hyperresponsiveness in young children with respiratory symptoms A five-year follow-up

    Get PDF
    Background: Recurrent wheezing in early life is transient in most children. The significance of airway hyper-responsiveness (AHR) in persistence of respiratory symptoms from infancy to early childhood is controversial. Objective: We evaluated whether AHR in wheezy infants predicts doctor-diagnosed asthma (DDA) or AHR at the age of 6 years. Methods: Sixty-one wheezy infants (age 6-24 months) were followed up to the median age of 6 years. Lung function and AHR with methacholine challenge test were assessed at infancy and 6 years. The exercise challenge test was performed at the age of 6 years. Atopy was assessed with skin prick tests. Results: At 6 years, 21 (34%) of the children had DDA. Children with DDA had higher logarithmic transformed dose-response slope (LOGDRS) to methacholine in infancy than children without DDA (0.047 vs 0.025; P = .033). Furthermore, AHR to methacholine in infancy and at 6 years were associated with each other (r = 0.324, P = .011). Children with exercise-induced bronchoconstriction (EIB) at 6 years were more reactive to methacholine in infancy than those without EIB (P = .019). Conclusion: Increased AHR in symptomatic infants was associated with increased AHR, DDA, and EIB at median the age of 6 years, suggesting early establishment of AHR. (C) 2019 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.Peer reviewe

    Dust properties inside molecular clouds from coreshine modeling and observations

    Get PDF
    Context. Using observations to deduce dust properties, grain size distribution, and physical conditions in molecular clouds is a highly degenerate problem. Aims. The coreshine phenomenon, a scattering process at 3.6 and 4.5 μ\mum that dominates absorption, has revealed its ability to explore the densest parts of clouds. We want to use this effect to constrain the dust parameters. The goal is to investigate to what extent grain growth (at constant dust mass) inside molecular clouds is able to explain the coreshine observations. We aim to find dust models that can explain a sample of Spitzer coreshine data. We also look at the consistency with near-infrared data we obtained for a few clouds. Methods. We selected four regions with a very high occurrence of coreshine cases: Taurus-Perseus, Cepheus, Chameleon and L183/L134. We built a grid of dust models and investigated the key parameters to reproduce the general trend of surface bright- nesses and intensity ratios of both coreshine and near-infrared observations with the help of a 3D Monte-Carlo radiative transfer code. The grid parameters allow to investigate the effect of coagulation upon spherical grains up to 5 μ\mum in size derived from the DustEm diffuse interstellar medium grains. Fluffiness (porosity or fractal degree), ices, and a handful of classical grain size distributions were also tested. We used the near- and mostly mid-infrared intensity ratios as strong discriminants between dust models. Results. The determination of the background field intensity at each wavelength is a key issue. In particular, an especially strong background field explains why we do not see coreshine in the Galactic plane at 3.6 and 4.5 μ\mum. For starless cores, where detected, the observed 4.5 μ\mum / 3.6 μ\mum coreshine intensity ratio is always lower than \sim0.5 which is also what we find in the models for the Taurus-Perseus and L183 directions. Embedded sources can lead to higher fluxes (up to four times greater than the strongest starless core fluxes) and higher coreshine ratios (from 0.5 to 1.1 in our selected sample). Normal interstellar radiation field conditions are sufficient to find suitable grain models at all wavelengths for starless cores. The standard interstellar grains are not able to reproduce observations and, due to the multi-wavelength approach, only a few grain types meet the criteria set by the data. Porosity does not affect the flux ratios while the fractal dimension helps to explain coreshine ratios but does not seem able to reproduce near-infrared observations without a mix of other grain types. Conclusions. Combined near- and mid-infrared wavelengths confirm the potential to reveal the nature and size distribution of dust grains. Careful assessment of the environmental parameters (interstellar and background fields, embedded or nearby reddened sources) is required to validate this new diagnostic
    corecore