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

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

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&

Evaporation Ages: a New Dating Method for Young Star Clusters

The ages of young star clusters are fundamental clocks to constrain the formation and evolution of pre-main-sequence stars and their protoplanetary disks and exoplanets. However, dating methods for very young clusters often disagree, casting doubts on the accuracy of the derived ages. We propose a new method to derive the kinematic age of star clusters based on the evaporation ages of their stars. The method is validated and calibrated using hundreds of clusters identified in a supernova-driven simulation of the interstellar medium forming stars for approximately 40 Myr within a 250 pc region. We demonstrate that the clusters' evaporation-age uncertainty can be as small as about 10% for clusters with a large enough number of evaporated stars and small but realistic observational errors. We have obtained evaporation ages for a pilot sample of 10 clusters, finding a good agreement with their published isochronal ages. The evaporation ages will provide important constraints for modeling the pre-main-sequence evolution of low-mass stars, as well as to investigate the star-formation and gas-evaporation history of young clusters. These ages can be more accurate than isochronal ages for very young clusters, for which observations and models are more uncertain.Comment: 13 pages, 11 figures, 2 tables, submitted to A&A on Nov 14th, 202

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

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&

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

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

From the CMF to the IMF: Beyond the Core-Collapse Model

Observations have indicated that the prestellar core mass function (CMF) is similar to the stellar initial mass function (IMF), except for an offset towards larger masses. This has led to the idea that there is a one-to-one relation between cores and stars, such that the whole stellar mass reservoir is contained in a gravitationally-bound prestellar core, as postulated by the core-collapse model, and assumed in recent theoretical models of the stellar IMF. We test the validity of this assumption by comparing the final mass of stars with the mass of their progenitor cores in a high-resolution star-formation simulation that generates a realistic IMF under physical conditions characteristic of observed molecular clouds. Using a definition of bound cores similar to previous works we obtain a CMF that converges with increasing numerical resolution. We find that the CMF and the IMF are closely related in a statistical sense only; for any individual star there is only a weak correlation between the progenitor core mass and the final stellar mass. In particular, for high mass stars only a small fraction of the final stellar mass comes from the progenitor core, and even for low mass stars the fraction is highly variable, with a median fraction of only about 50%. We conclude that the core-collapse scenario and related models for the origin of the IMF are incomplete. We also show that competitive accretion is not a viable alternative.Comment: 23 pages, 29 figures. Link to supplementary material and full Table 1: http://www.erda.dk/vgrid/core-mass-function/ . Submitted to MNRA

Health of singletons born after frozen embryo transfer until early adulthood : a Finnish register study

STUDY QUESTION Is the health of singletons born after frozen embryo transfer (FET) comparable to that of singletons born after fresh embryo transfer (ET) until early adulthood? SUMMARY ANSWER The health of singletons born after FET does not differ from that of singletons born after fresh ET. WHAT IS KNOWN ALREADY The differences in perinatal outcomes of children born after FET and fresh ET are well known. FET is associated with an increased risk of large-for-gestational-age but diminished risks of preterm birth (PTB), small-for-gestational-age and decreased perinatal mortality compared to fresh ET. However, knowledge on the long-term health after FET is scarce. STUDY DESIGN, SIZE, DURATION This retrospective register-based cohort study compares singletons born after FET (n = 1825) between the years 1995 and 2006 to those born after fresh ET (n = 2933) and natural conception (NC, n = 31 136) with a mean follow-up time of 18-20 years. PARTICIPANTS/MATERIALS, SETTING, METHODS Singletons born after FET were compared to those born after fresh ET and NC regarding the frequencies of diagnoses in the main ICD-10 chapters (International Statistical Classification of Diseases and Related Health Problems, 10th revision), the number of outpatient visits and hospital admissions, and mortality. Adjustments were made for PTB, maternal age, parity, socioeconomic status based on mother's occupation and offspring sex. The study combines data from the Finnish Medical Birth Register, the Finnish Care Register for Health Care (CRHC) and the Cause-of-Death Register at Statistics Finland. The Student's T-test was used for continuous variables, and the Chi-square test was used for categorical variables. Cox regression was used to estimate crude and adjusted hazard ratios (HRs and aHRs, respectively). A general linear model was used to compare the means of outpatient visits, hospital admissions and lengths of hospital stays per person. MAIN RESULTS AND THE ROLE OF CHANCE No significant differences between the FET and fresh ET groups were found in the frequency of diagnoses in any of the ICD-10 chapters or in the parameters describing the need for hospital care. However, compared to the NC group, higher proportions in the FET group had outpatient visits in the hospital (93.5% vs 92.2%, aHR 1.23, 95% CI 1.17, 1.30) or hospital admissions (48% vs 46.5%, aHR 1.28, 95% CI 1.19, 1.37). Compared to the NC group, the FET group had elevated adjusted risks of diagnoses of infectious and parasitic diseases (aHR 1.24; 95% CI 1.11, 1.38), neoplasms (aHR 1.68; 95% CI 1.48, 1.91), diseases of the eye and adnexa, the ear or mastoid process (aHR 1.11; 95% CI 1.01, 1.21), the respiratory system (aHR 1.15; 95% CI 1.06, 1.23), the digestive system (aHR 1.17; 95% CI 1.05, 1.32), the skin or subcutaneous tissue (aHR 1.28; 95% CI 1.14, 1.43) and the genitourinary system (aHR 1.27; 95% CI 1.11, 1.45), as well as congenital malformations or chromosomal abnormalities (aHR 1.31; 95% CI 1.14, 1.50) and symptoms, signs or abnormal clinical or laboratory findings (aHR 1.25, 95% CI 1.16, 1.34). LIMITATIONS, REASONS FOR CAUTION Only hospital-based inpatient and outpatient care is covered by the CRHC register, excluding milder cases diagnosed elsewhere. We were not able to study the effect of ART treatments and subfertility separately in our setting. In addition, although our cohort is reasonably sized, even larger cohorts would be needed to reliably study rare outcomes, such as cancer. WIDER IMPLICATIONS OF THE FINDINGS For many ICD-10 chapters, we present the first published data on the long-term outcome of singletons born after FET. The results on FET versus fresh ET are reassuring, whereas the results on FET versus NC warrant further investigation. STUDY FUNDING/COMPETING INTEREST(S) Finnish government research funding was obtained for this study. Funding was also obtained from the Finnish Medical Society Duodecim, the Paivikki and Sakari Sohlberg Foundation, Orion Research Foundation, Finnish Society of Obstetrics and Gynaecology (research grants to A.M.T.) and Finnish government research funding. The funding sources were not involved in the planning or execution of the study. The authors have no competing interests to declare.Peer reviewe

Elämänoppia nykyihmiselle:viisauden opettamisen tematiikkaa Michel de Montaignen esseessä ”Koulumestareista”

Tiivistelmä. Tarkastelen tutkielmassani viisauden tematiikkaa Michel de Montaignen teoksessa Esseitä. Päähuomioni kohdistuu esseeseen ”Koulumestareista” (Du pédantisme), jota tutkin viisauden opettamisen näkökulmasta. Toinen tutkimuskysymykseni laajentaa näkökulmaa viisauden opet-tamisesta viisaaksi kasvamiseen. Lähtökohtaoletuksenani on, että ihminen on viisauden saralla oppilas koko elämänsä ajan, joten viisastumista voi tapahtua kaikissa elämänkaaren vaiheissa. Aineistona toisessa tutkimuskysymyksessäni onkin esseitä Montaignen tuotannon eri vaiheilta mukaan lukien hänen laaja esseensä ”Apologia eli Raimond Sebondin puolustus” sekä koko esseekokoelman viimeinen essee ”Kokemuksesta”. Kolmas tutkimuskysymykseni tarkastelee Montaignen käsityksiä viisaudesta nykyajan viisaustutkimuksen valossa. Minulle viisaus näyttäytyy jollakin tapaa ikiaikaisena käsitteenä, joten haluan selvittää, kuinka paljon yhtymäkohtia on 1500-luvulla kirjoitettujen tekstien ja nykyajan tutkimustulosten välillä. Analyysini perustuu tarkkaan lähilukuun, jossa otan huomioon Montaignen esseiden ominaispiirteet: lukuisat filosofiset lainaukset ja viittaukset, arkielämästä ja yhteiskunnasta poimitut esimerkit, pyrrhonistisen epäilyn ja Montaignen omintakeisen tyylin pohdiskella asioita. Esseissä katsotaan yhtä aikaa kauas ja lähelle, ympäröivään yhteiskuntaan ja itseensä, yleisiin totuuksiin ja henkilökohtaisiin mieltymyksiin. Teoriataustassani avaan käsityksiäni siitä, miten Montaignen Esseitä tulisi lukea, esittelen tutkielmani hermeneuttiset lähtökohdat, tarkastelen Montaignen suhdetta pyrrhonismiin ja avaan käsitteen viisaus filosofista taustaa. Lisäksi esittelen Ann Hartlen kehittelemää kehämäisen dialektiikan käsitettä, jota sovellan erityisesti ”Koulumestareista”-esseen analyysissa. Keskeisenä tutkimustuloksena esitän, että viisauden opettamisessa ei pohjimmiltaan ole kyse kirjoista opituista tiedoista ja käytännön taidoista, vaan tärkeintä ovat opetuksen taustalla olevat arvot ja se, miten tiedoista tehdään omakohtaisia ja miten tietoja ja taitoja opitaan käyttämään hyödyksi käytännön tilanteissa. Myös harkinta, itsetuntemus ja omien rajojen tunnistaminen ovat viisauden opettamisessa oleellisia elementtejä. Nämä elementit näyttäytyvät tärkeinä myös viisaaksi kasvamisessa. Viisaaksi kasvamisessa muita keskeisiä tekijöitä ovat omien kokemusten hyödyntäminen elämässä, virheistä oppiminen sekä nöyryys omaa viisautta kohtaan. Erityisesti kokoelman viimeisessä esseessä nousevat esiin myös kestävien arvojen tavoittelu elämässä, oman paikan löytäminen ja aidon elämän eläminen, joiden voidaan ajatella olevan vahvimmin elämänkokemuksen mukanaan tuomaa viisautta. Montaignen ajattelulla osoittautuu olevan varsin paljon yhtymäkohtia nykyaikaisen viisaustutkimuksen kanssa. Ainoa selkeä ero Montaignen ajattelun ja nykyaikaisen viisaustutkimuksen välillä on se, että Montaigne erottaa toisistaan jumalallisen ja inhimillisen viisauden, mutta nykytutkimuksen lähtökohtana on ajatus, että siinä etsitään yksilöllistä ja ihmisen saavutettavissa oleva viisautta. Muut nykyaikaisen viisaustutkimuksen perusperiaatteet — älykkyys ei tee ihmisestä viisasta ja tiedon on tultava näkyväksi viisaan ihmisen elämässä — ovat varsin hyvin linjassa Montaignen ajattelun kanssa. Lisäksi yhtäläinen näkemys on siitä, että nöyryys, itsetuntemus, kokemus ja toisten ymmärtäminen ovat osa viisaan ihmisen elämää. Vaikka Montaignen Esseitä on kirjoitettu viisisataa vuotta sitten, voidaan todeta, että Montaignen ajatukset viisauden opettamisesta ja viisaaksi kasvamisesta ovat varsin relevantteja vieläkin. Viisaus ja viisaat sanat eivät vanhene samalla tavalla kuin tieto saattaa vanhentua

Dust properties inside molecular clouds from coreshine modeling and observations

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 $\mu$m 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 $\mu$m 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 $\mu$m. For starless cores, where detected, the observed 4.5 $\mu$m / 3.6 $\mu$m coreshine intensity ratio is always lower than $\sim$0.5 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