1,361 results on '"Persson, Magnus"'
Search Results
2. The first interferometric measurements of NH$_2$D/NH$_3$ ratio in hot corinos
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Yamato, Yoshihide, Furuya, Kenji, Aikawa, Yuri, Persson, Magnus V., Tobin, John J., Jørgensen, Jes K., and Kama, Mihkel
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Solar and Stellar Astrophysics - Abstract
The nitrogen chemical evolution during star and planet formation is still not fully understood. Ammonia (NH$_3$) is a key specie in the understanding of the molecular evolution in star-forming clouds and nitrogen isotope fractionation. In this paper, we present high spatial resolution observations of multiple emission lines of NH$_3$ toward the protobinary system NGC1333 IRAS4A with Karl G. Jansky Very Large Array (VLA). We spatially resolved the binary (hereafter 4A1 and 4A2) and detected compact emission of NH$_3$ transitions with high excitation energies ($\gtrsim$100 K) from the vicinity of the protostars, indicating the NH$_3$ ice has sublimated at the inner hot region. The NH$_3$ column density is estimated to be $\sim 10^{17}-10^{18}$ cm$^{-2}$. We also detected two NH$_2$D transitions, allowing us to constrain the deuterium fractionation of ammonia. The NH$_2$D/NH$_3$ ratios are as high as $\sim 0.3-1$ in both 4A1 and 4A2. From the comparisons with the astrochemical models in the literature, the high NH$_2$D/NH$_3$ ratios suggest that the formation of NH$_3$ ices mainly started in the prestellar phase after the formation of bulk water ice finished, and that the primary nitrogen reservoir in the star-forming cloud could be atomic nitrogen (or N atoms) rather than nitrogen-bearing species such as N$_2$ and NH$_3$. The implications on the physical properties of IRAS4A cores are discussed as well., Comment: 20 pages, 7 figures, accepted for publication in ApJ
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- 2022
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3. The Immobility of the Mobile Teacher: How Teachers Change Jobs in a Segregated Local School-Market
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Dannefjord, Per, Persson, Magnus, and Bertilsson, Emil
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This study examines job-changing patterns of secondary school teachers in a segregated local school market in Sweden. In an initial step, we use information on pupils' resources to hierarchically group schools in four groups, where schools with similar pupil bases are sorted together. By interviewing 29 teachers, the conclusion is that when teachers change employer, they navigate or are recruited to schools that are similar to schools where their professional approach was formed (formative school). The significance of the formative school is important since the teacher synchronises subjective professional beliefs with the institutional conditions and logics that produce the local working conditions. This process means that the mobility of teachers is limited to schools within the same or adjacent school groups. This indicates that teachers might be locked in to limited sectors of the labour market by the same market forces that segregate pupils on the school market.
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- 2023
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4. Exploring the interplay between within-stand variation and thinning practices in southern Sweden
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Persson, Magnus, Bader, Martin Karl-Friedrich, and Holmström, Emma
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- 2024
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5. Transport and retention of functionalized graphene oxide nanoparticles in saturated/unsaturated porous media: Effects of flow velocity, ionic strength and initial particle concentration
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Shahi, Mahsa, Alavi Moghaddam, Mohammad Reza, Hosseini, Seiyed Mossa, Hashemi, Hossein, Persson, Magnus, and Kowsari, Elaheh
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- 2024
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6. Deuterium-enriched water ties planet-forming disks to comets and protostars
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Tobin, John J., van ’t Hoff, Merel L. R., Leemker, Margot, van Dishoeck, Ewine F., Paneque-Carreño, Teresa, Furuya, Kenji, Harsono, Daniel, Persson, Magnus V., Cleeves, L. Ilsedore, Sheehan, Patrick D., and Cieza, Lucas
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- 2023
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7. Feedback of molecular outflows from protostars in NGC 1333, revealed by Herschel and Spitzer spectro-imaging observations
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Dionatos, Odysseas, Kristensen, Lars. E., Tafalla, Mario, Güdel, Manuel, and Persson, Magnus
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
Large scale spectral maps of star forming regions enable the comparative study of the gas excitation around an ensemble of sources at a common frame of reference, providing direct insights in the multitude of processes involved. In this paper we employ spectral-line maps to decipher the excitation, the kinematical and dynamical processes in NGC 1333 as revealed by a number of different emission lines, aiming to set a reference for the applicability of tracers in constraining diverse physical processes. We reconstruct line maps for H$_2$ , CO, H$_2$O and C$^+$ using data obtained with the Spitzer-IRS and Herschel HIFI-SPIRE. We compare the morphological features of the maps and derive the gas excitation for regions of interest employing LTE and non-LTE methods. We also calculate the kinematical and dynamical properties for each outflow tracer consistently for all outflows in NGC 1333. We finally measure the water abundance in outflows with respect to carbon monoxide and molecular hydrogen. CO and H$_2$ are highly excited around B-stars and at lower levels trace protostellar outflows. H$_2$O emission is dominated by a moderately fast component associated with outflows. Intermediate J CO lines appear brightest at the locations traced by a narrow H$_2$O component, indicating that beyond the dominating collisional processes, a secondary, radiative excitation component can also be active. The morphology, kinematics, excitation and abundance variations of water are consistent with its excitation and partial dissociation in shocks. Water abundance ranges between 5 x 10$^{-7}$ and 10$^{-5}$, with the lower values being more representative. Water is brightest and most abundant around IRAS 4A which is consistent with the latter hosting a hot corino source. Finally, the outflow mass flux is found highest for CO and decreases by one and two orders of magnitude for H$_2$ and H$_2$O, respectively., Comment: 19 pages, 14 figures, 5 tables, A&A accepted
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- 2020
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8. Missing water in Class I protostellar disks
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Harsono, Daniel, Persson, Magnus, Ramos, Alyssa, Murillo, Nadia, Maud, Luke, Hogerheijde, Michiel, Bosman, Arthur, Kristensen, Lars, Jorgensen, Jes, Bergin, Ted, Visser, Ruud, Mottram, Joe, and van Dishoeck, Ewine
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
Water is a key volatile that provides insights into the initial stages of planet formation. The low water abundances inferred from water observations toward low-mass protostellar objects may point to a rapid locking of water as ice by large dust grains during star and planet formation. However, little is known about the water vapor abundance in newly formed planet-forming disks. We aim to determine the water abundance in embedded Keplerian disks through spatially-resolved observations of H$_2^{18}$O lines to understand the evolution of water during star and planet formation. We present H$_2^{18}$O line observations with ALMA and NOEMA millimeter interferometers toward five young stellar objects. NOEMA observed the 3$_{1,3}$ - $2_{2,0}$ line (E$_{\rm up}$ = 203.7 K) while ALMA targeted the $4_{1,4}$ - $3_{2,1}$ line (E$_{\rm up}$ = 322.0 K). Water column densities are derived considering optically thin and thermalized emission. Our observations are sensitive to the emission from the known Keplerian disks around three out of the five Class I objects in the sample. No H$_2^{18}$O emission is detected toward any of our five Class I disks. We report upper limits to the integrated line intensities. The inferred water column densities in Class I disks are N < 10$^{15}$ cm$^{-2}$ on 100 au scales which include both disk and envelope. The upper limits imply a disk-averaged water abundance of $\lesssim 10^{-6}$ with respect to H$_2$ for Class I objects. After taking into account the physical structure of the disk, the upper limit to the water abundance averaged over the inner warm disk with $T>$ 100 K is between 10$^{-7}$ up to 10$^{-5}$. Water vapor is not abundant in warm protostellar envelopes around Class I protostars. Upper limits to the water vapor column densities in Class I disks are at least two orders magnitude lower than values found in Class 0 disk-like structures., Comment: 13 pages + 6 pages appendix, 7 figures, accepted for publication in aanda
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- 2020
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9. Seeds of Life in Space (SOLIS). VI. Chemical evolution of sulfuretted species along the outflows driven by the low-mass protostellar binary NGC1333-IRAS4A
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Taquet, Vianney, Codella, Claudio, de Simone, Marta, López-Sepulcre, Ana, Pineda, Jaime E., Segura-Cox, Dominique, Ceccarelli, Cecilia, Caselli, Paola, Gusdorf, Antoine, Persson, Magnus V., and team, the SOLIS
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Astrophysics - Astrophysics of Galaxies - Abstract
Context. Low-mass protostars drive powerful molecular outflows that can be observed with mm and sub-mm telescopes. Various sulfuretted species are known to be bright in shocks and could be used to infer the physical and chemical conditions throughout the observed outflows. Aims. The evolution of sulfur chemistry is studied along the outflows driven by the NGC1333-IRAS4A protobinary system located in the Perseus cloud to constrain the physical and chemical processes at work in shocks. Methods. We observed various transitions from OCS, CS, SO, and SO$_2$ towards NGC1333-IRAS4A in the 1.3, 2, and 3mm bands using the IRAM NOEMA array and we interpreted the observations through the use of the Paris-Durham shock model. Results. The targeted species clearly show different spatial emission along the two outflows driven by IRAS4A. OCS is brighter on small and large scales along the south outflow driven by IRAS4A1, whereas SO$_2$ is detected rather along the outflow driven by IRAS4A2 that is extended along the north east - south west (NE-SW) direction. Column density ratio maps estimated from a rotational diagram analysis allowed us to confirm a clear gradient of the OCS/SO$_2$ column density ratio between the IRAS4A1 and IRAS4A2 outflows. SO is detected at extremely high radial velocity up to 25 km/s relative to the source velocity, clearly allowing us to distinguish the two outflows on small scales. Conclusions. The observed chemical differentiation between the two outflows of the IRAS4A system could be explained by a different chemical history. The outflow driven by IRAS4A1 is likely younger and more enriched in species initially formed in interstellar ices, such as OCS, and recently sputtered into the shock gas. In contrast, the longer and likely older outflow triggered by IRAS4A2 is more enriched in species that have a gas phase origin, such as SO$_2$., Comment: Accepted for publication in A&A
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- 2020
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10. The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. A Statistical Characterization of Class 0 and I Protostellar Disks
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Tobin, John J., Sheehan, Patrick, Megeath, S. Thomas, Diaz-Rodriguez, Ana Karla, Offner, Stella S. R., Murillo, Nadia M., Hoff, Merel van 't, van Dishoeck, Ewine F., Osorio, Mayra, Anglada, Guillem, Furlan, Elise, Stutz, Amelia M., Reynolds, Nickalas, Karnath, Nicole, Fischer, William J., Persson, Magnus, Looney, Leslie W., Li, Zhi-Yun, Stephens, Ian, Chandler, Claire J., Cox, Erin, Dunham, Michael M., Tychoniec, Lukasz, Kama, Mihkel, Kratter, Kaitlin, Kounkel, Marina, Mazur, Brian, Maud, Luke, Patel, Lisa, Perez, Laura, Sadavoy, Sarah I., Segura-Cox, Dominique, Sharma, Rajeeb, Stephenson, Brian, Watson, Dan M., and Wyrowski, Friedrich
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Astrophysics - Astrophysics of Galaxies - Abstract
We have conducted a survey of 328 protostars in the Orion molecular clouds with ALMA at 0.87 mm at a resolution of $\sim$0.1" (40 au), including observations with the VLA at 9 mm toward 148 protostars at a resolution of $\sim$0.08" (32 au). This is the largest multi-wavelength survey of protostars at this resolution by an order of magnitude. We use the dust continuum emission at 0.87 mm and 9 mm to measure the dust disk radii and masses toward the Class 0, Class I, and Flat Spectrum protostars, characterizing the evolution of these disk properties in the protostellar phase. The mean dust disk radii for the Class 0, Class I, and Flat Spectrum protostars are 44.9$^{+5.8}_{-3.4}$, 37.0$^{+4.9}_{-3.0}$, and 28.5$^{+3.7}_{-2.3}$ au, respectively, and the mean protostellar dust disk masses are 25.9$^{+7.7}_{-4.0}$, 14.9$^{+3.8}_{-2.2}$, 11.6$^{+3.5}_{-1.9}$ Earth masses, respectively. The decrease in dust disk masses is expected from disk evolution and accretion, but the decrease in disk radii may point to the initial conditions of star formation not leading to the systematic growth of disk radii or that radial drift is keeping the dust disk sizes small. At least 146 protostellar disks (35% out of 379 detected 0.87 mm continuum sources plus 42 non-detections) have disk radii greater than 50 au in our sample. These properties are not found to vary significantly between different regions within Orion. The protostellar dust disk mass distributions are systematically larger than that of Class II disks by a factor of $>$4, providing evidence that the cores of giant planets may need to at least begin their formation during the protostellar phase., Comment: 107 pages, 21 Figures, 11 Tables, accepted to ApJ. Version with all source figures: https://www.cv.nrao.edu/~jtobin/Orion-disks-fullfigs.pdf Reduced data available from https://dataverse.harvard.edu/dataverse/VANDAMOrion
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- 2020
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11. The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars I. Identifying and Characterizing the Protostellar Content of the OMC2-FIR4 and OMC2-FIR3 Regions
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Tobin, John J., Megeath, S. Thomas, Hoff, Merel van 't, Diaz-Rodriguez, Ana Karla, Reynolds, Nickalas, Osorio, Mayra, Anglada, Guillem, Furlan, Elise, Karnath, Nicole, Offner, Stella S. R., Sheehan, Patrick, Sadavoy, Sarah I., Stutz, Amelia M., Fischer, William J., Kama, Mihkel, Persson, Magnus, Di Francesco, James, Looney, Leslie W., Watson, Dan M., Li, Zhi-Yun, Stephens, Ian, Chandler, Claire J., Cox, Erin, Dunham, Michael M., Kratter, Kaitlin, Kounkel, Marina, Mazur, Brian, Murillo, Nadia M., Patel, Lisa, Perez, Laura, Segura-Cox, Dominique, Sharma, Rajeeb, Tychoniec, Lukasz, and Wyrowski, Friedrich
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
We present ALMA (0.87~mm) and VLA (9~mm) observations toward OMC2-FIR4 and OMC2-FIR3 within the Orion integral-shaped filament that are thought to be the nearest regions of intermediate mass star formation. We characterize the continuum sources within these regions on $\sim$40~AU (0\farcs1) scales and associated molecular line emission at a factor of $\sim$30 better resolution than previous observations at similar wavelengths. We identify six compact continuum sources within OMC2-FIR4, four in OMC2-FIR3, and one additional source just outside OMC2-FIR4. This continuum emission is tracing the inner envelope and/or disk emission on less than 100~AU scales. HOPS-108 is the only protostar in OMC2-FIR4 that exhibits emission from high-excitation transitions of complex organic molecules (e.g., methanol and other lines) coincident with the continuum emission. HOPS-370 in OMC2-FIR3 with L~$\sim$~360~\lsun, also exhibits emission from high-excitation methanol and other lines. The methanol emission toward these two protostars is indicative of temperatures high enough to thermally evaporate methanol from icy dust grains; overall these protostars have characteristics similar to hot corinos. We do not identify a clear outflow from HOPS-108 in \twco, but find evidence of interaction between the outflow/jet from HOPS-370 and the OMC2-FIR4 region. The multitude of observational constraints indicate that HOPS-108 is likely a low to intermediate-mass protostar in its main mass accretion phase and it is the most luminous protostar in OMC2-FIR4. The high resolution data presented here are essential for disentangling the embedded protostars from their surrounding dusty environments and characterizing them., Comment: 32 Pages, 10 Figures, 5 Tables, accepted to ApJ
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- 2019
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12. Interferometric observations of warm deuterated methanol in the inner regions of low-mass protostars
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Taquet, Vianney, Bianchi, Eleonora, Codella, Claudio, Persson, Magnus V., Ceccarelli, Cecilia, Cabrit, Sylvie, Jørgensen, Jes K., Kahane, Claudine, López-Sepulcre, Ana, and Neri, Roberto
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Solar and Stellar Astrophysics - Abstract
Methanol is a key species in astrochemistry since it is the most abundant organic molecule in the ISM and is thought to be the mother molecule of many complex organic species. Estimating the deuteration of methanol around young protostars is of crucial importance because it highly depends on its formation mechanisms and the physical conditions during its moment of formation. We analyse dozens of transitions from deuterated methanol isotopologues coming from various existing observational datasets from the IRAM-PdBI and ALMA sub-mm interferometers to estimate the methanol deuteration surrounding three low-mass protostars on Solar System scales. A population diagram analysis allows us to derive a [CH$_2$DOH]/[CH$_3$OH] abundance ratio of 3-6 % and a [CH$_3$OD]/[CH$_3$OH] ratio of 0.4-1.6 % in the warm inner protostellar regions. These values are ten times lower than those derived with previous single-dish observations towards these sources but they are 10-100 times higher than the methanol deuteration measured in massive hot cores. Dust temperature maps obtained from Herschel and Planck observations show that massive hot cores are located in warmer molecular clouds than low-mass sources, with temperature differences of $\sim$10 K. Comparison with the predictions of the gas-grain astrochemical model GRAINOBLE shows that such a temperature difference is sufficient to explain the different deuteration observed in low- to high-mass sources, suggesting that the physical conditions of the molecular cloud at the origin of the protostars mostly govern the present observed deuteration of methanol. The methanol deuteration measured in this work is higher by a factor of 5 than the upper limit in methanol deuteration estimated in comet Hale-Bopp, implying that an important reprocessing of the organic material would have occurred in the solar nebula during the formation of the Solar System., Comment: 16 pages, 10 figures, accepted for publication in Astronomy & Astrophysics
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- 2019
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13. Kinematics around the B335 protostar down to au scales
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Bjerkeli, Per, Ramsey, Jon P., Harsono, Daniel, Calcutt, Hannah, Kristensen, Lars E., van der Wiel, Matthijs H. D., Jørgensen, Jes K., Muller, Sébastien, and Persson, Magnus V.
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
Context. The relationship between outflow launching and formation of accretion disks around young stellar objects is still not entirely understood, which is why spectrally and spatially resolved observations are needed. Recently, the Atacama Large Millimetre/sub-millimetre Array (ALMA) has carried out long-baseline observations towards a handful of sources, revealing connections between outflows and the inner regions of disks. Aims. Here we aim to determine the small-scale kinematic and morphological properties of the outflow from the isolated protostar B335 for which no Keplerian disk has, so far, been observed on scales down to 10 au. Methods. We use ALMA in its longest-baseline configuration to observe emission from CO isotopologs, SiO, SO$_2$ and CH$_3$OH. The proximity of B335 provides a resolution of ~3 au (0.03''). We also combine our long-baseline data with archival data to produce a high-fidelity image covering scales up to 700 au (7''). Results. $^{12}$CO has a X-shaped morphology with arms ~50 au in width that we associate with the walls of an outflow cavity, similar to what is observed on larger scales. Long-baseline continuum emission is confined to <7 au of the protostar, while short-baseline continuum emission follows the $^{12}$CO outflow and cavity walls. Methanol is detected within ~30 au of the protostar. SiO is also detected in the vicinity of the protostar, but extended along the outflow. Conclusions. The $^{12}$CO outflow shows no clear signs of rotation at distances $\gtrsim$30 au from the protostar. SiO traces the protostellar jet on small scales, but without obvious rotation. CH$_3$OH and SO$_2$ trace a region <16 au in diameter, centred on the continuum peak, which is clearly rotating. Using episodic, high-velocity, $^{12}$CO features, we estimate the launching radius of the outflow to be <0.1 au and dynamical timescales on the order of a few years., Comment: Abstract very slightly abridged. 15 pages, 13 figures, accepted for publication in A&A
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- 2019
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14. Molecular complexity on disk-scales uncovered by ALMA: The chemical composition of the high-mass protostar AFGL 4176
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Bøgelund, Eva G., Barr, Andrew G., Taquet, Vianney, Ligterink, Niels F. W., Persson, Magnus V., Hogerheijde, Michiel R., and van Dishoeck, Ewine F.
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
The chemical composition of high-mass protostars reflects the physical evolution associated with different stages of star formation. In this study, the molecular inventory of the forming high-mass star AFGL 4176 is studied in detail at high angular resolution (~0.35 arcsec) using ALMA. This high resolution makes it possible to separate the emission associated with the inner hot envelope and disk around the forming star from that of its cool outer envelope. In addition, the high sensitivity of ALMA makes it possible to identify weak and optically thin lines and allows for many isotopologues to be detected, providing a more complete and accurate inventory of the source. A total of 23 different molecular species and their isotopologues are detected in the spectrum towards AFGL 4176. The most abundant species is methanol (CH3OH), remaining species are present at levels between 0.003 % and 15 % with respect to CH3OH. Hints that N-bearing species peak slightly closer to the location of the peak continuum emission than the O-bearing species are seen. AFGL 4176 comprises a rich chemical inventory including many complex species present on disk-scales. On average, the derived column density ratios with respect to methanol of O-bearing species are higher than those derived for N-bearing species by a factor of three. This may indicate that AFGL 4176 is a relatively young source since nitrogen chemistry generally takes longer to evolve in the gas-phase. Taking methanol as a reference, the composition of AFGL 4176 more closely resembles that of the low-mass protostar IRAS 16293-2422B than that of high-mass star-forming regions located near the Galactic centre. This similarity hints that the chemical composition of complex species is already set in the cold cloud stage and implies that AFGL 4176 is a young source whose chemical composition has not yet been strongly processed by the central protostar., Comment: Accepted for publication in Astronomy & Astrophysics
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- 2019
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15. astroquery: An Astronomical Web-Querying Package in Python
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Ginsburg, Adam, Sipőcz, Brigitta M., Brasseur, C. E., Cowperthwaite, Philip S., Craig, Matthew W., Deil, Christoph, Guillochon, James, Guzman, Giannina, Liedtke, Simon, Lim, Pey Lian, Lockhart, Kelly E., Mommert, Michael, Morris, Brett M., Norman, Henrik, Parikh, Madhura, Persson, Magnus V., Robitaille, Thomas P., Segovia, Juan-Carlos, Singer, Leo P., Tollerud, Erik J., de Val-Borro, Miguel, Valtchanov, Ivan, Woillez, Julien, and collaboration, the Astroquery
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Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
astroquery is a collection of tools for requesting data from databases hosted on remote servers with interfaces exposed on the internet, including those with web pages but without formal application program interfaces (APIs). These tools are built on the Python requests package, which is used to make HTTP requests, and astropy, which provides most of the data parsing functionality. astroquery modules generally attempt to replicate the web page interface provided by a given service as closely as possible, making the transition from browser-based to command-line interaction easy. astroquery has received significant contributions from throughout the astronomical community, including several significant contributions from telescope archives. astroquery enables the creation of fully reproducible workflows from data acquisition through publication. This paper describes the philosophy, basic structure, and development model of the astroquery package. The complete documentation for astroquery can be found at http://astroquery.readthedocs.io/., Comment: Accepted to AJ. The documentation is at http://astroquery.readthedocs.io/ and the repository is at https://github.com/astropy/astroquery/
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- 2019
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16. Sensor Technologies for Optimized Tapping Procedures
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Wenzl, Christine, Persson, Magnus, Koncik, Ladislav, Steenkamp, Joalet D., editor, Gregurek, Dean, editor, Reynolds, Quinn G., editor, Alvear Flores, Gerardo, editor, Joubert, Hugo, editor, and Mackey, Phillip J., editor
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- 2022
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17. Benefits of Modularity Strategies - Implications of Decisions and Timing
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Hansen, Poul Kyvsgaard, Persson, Magnus, Hsuan, Juliana, Cavas-Martínez, Francisco, Series Editor, Chaari, Fakher, Series Editor, di Mare, Francesca, Series Editor, Gherardini, Francesco, Series Editor, Haddar, Mohamed, Series Editor, Ivanov, Vitalii, Series Editor, Kwon, Young W., Series Editor, Trojanowska, Justyna, Series Editor, Andersen, Ann-Louise, editor, Andersen, Rasmus, editor, Brunoe, Thomas Ditlev, editor, Larsen, Maria Stoettrup Schioenning, editor, Nielsen, Kjeld, editor, Napoleone, Alessia, editor, and Kjeldgaard, Stefan, editor
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- 2022
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18. Linking interstellar and cometary O$_2$: a deep search for $^{16}$O$^{18}$O in the solar-type protostar IRAS 16293--2422
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Taquet, Vianney, van Dishoeck, Ewine F., Swayne, Matthew, Harsono, Daniel, Jørgensen, Jes K., Maud, Luke, Ligterink, Niels F. W., Müller, Holger S. P., Codella, Claudio, Altwegg, Kathrin, Bieler, Andre, Coutens, Audrey, Drozdovskaya, Maria N., Furuya, Kenji, Persson, Magnus V., Hoff, Merel L. R. van 't, Walsh, Catherine, and Wampfler, Suzanne F.
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Astrophysics - Astrophysics of Galaxies - Abstract
Recent measurements carried out at comet 67P/C-G with the ${\it Rosetta}$ probe revealed that molecular oxygen, O$_2$, is the fourth most abundant molecule in comets. Models show that O$_2$ is likely of primordial nature, coming from the interstellar cloud from which our Solar System was formed. However, gaseous O$_2$ is an elusive molecule in the interstellar medium with only one detection towards quiescent molecular clouds, in the $\rho$ Oph A core. We perform a deep search for molecular oxygen, through the $2_1 - 0_1$ rotational transition at 234 GHz of its $^{16}$O$^{18}$O isotopologue, towards the warm compact gas surrounding the nearby Class 0 protostar IRAS 16293--2422 B with the ALMA interferometer. The targeted $^{16}$O$^{18}$O transition is surrounded by two brighter transitions at $\pm 1$ km s$^{-1}$ relative to the expected $^{16}$O$^{18}$O transition frequency. After subtraction of these two transitions, residual emission at a 3$\sigma$ level remains, but with a velocity offset of $0.3 - 0.5$ km s$^{-1}$ relative to the source velocity, rendering the detection "tentative". We derive the O$_2$ column density for two excitation temperatures $T_{\rm ex}$ of 125 and 300 K, as indicated by other molecules, in order to compare the O$_2$ abundance between IRAS16293 and comet 67P/C-G. Assuming that $^{16}$O$^{18}$O is not detected and using methanol CH$_3$OH as a reference species, we obtain a [O$_2$]/[CH$_3$OH] abundance ratio lower than $2-5$, depending on the assumed $T_{\rm ex}$, a three to four times lower abundance than the [O$_2$]/[CH$_3$OH] ratio of $5-15$ found in comet 67P/C-G. Such a low O$_2$ abundance could be explained by the lower temperature of the dense cloud precursor of IRAS16293 with respect to the one at the origin of our Solar System that prevented an efficient formation of O$_2$ in interstellar ices., Comment: 12 pages, 3 figures, accepted for publication in Astronomy & Astrophysics
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- 2018
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19. Tracing the atomic nitrogen abundance in star-forming regions with ammonia deuteration
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Furuya, Kenji and Persson, Magnus V.
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Astrophysics - Astrophysics of Galaxies - Abstract
Partitioning of elemental nitrogen in star-forming regions is not well constrained. Most nitrogen is expected to be partitioned among atomic nitrogen, molecular nitrogen (N2), and icy N-bearing molecules, such as ammonia (NH3) and N2. Atomic nitrogen is not directly observable in the cold gas. In this paper, we propose an indirect way to constrain the amount of atomic nitrogen in the cold gas of star-forming clouds, via deuteration in ammonia ice, the [ND2H/NH2D]/[NH2D/NH3] ratio. Using gas-ice astrochemical simulations, we show that if atomic nitrogen remains as the primary reservoir of nitrogen during cold ice formation stages, the [ND2H/NH2D]/[NH2D/NH3] ratio is close to the statistical value of 1/3 and lower than unity, whereas if atomic nitrogen is largely converted into N-bearing molecules, the ratio should be larger than unity. Observability of ammonia isotopologues in the inner hot regions around low-mass protostars, where ammonia ice has sublimated, is also discussed. We conclude that the [ND2H/NH2D]/[NH2D/NH3] ratio can be quantified using a combination of VLA and ALMA observations with reasonable integration times, at least toward IRAS 16293-2422 where high molecular column densities are expected., Comment: Accepted for publication in MNRAS, 12 pages, 9 figures, 1 Table
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- 2018
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20. The ALMA-PILS survey: The sulphur connection between protostars and comets: IRAS 16293-2422 B and 67P/Churyumov-Gerasimenko
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Drozdovskaya, Maria N., van Dishoeck, Ewine F., Jørgensen, Jes K., Calmonte, Ursina, van der Wiel, Matthijs H. D., Coutens, Audrey, Calcutt, Hannah, Müller, Holger S. P., Bjerkeli, Per, Persson, Magnus V., Wampfler, Susanne F., and Altwegg, Kathrin
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
The evolutionary past of our Solar System can be pieced together by comparing analogous low-mass protostars with remnants of our Protosolar Nebula - comets. Sulphur-bearing molecules may be unique tracers of the joint evolution of the volatile and refractory components. ALMA Band 7 data from the large unbiased Protostellar Interferometric Line Survey (PILS) are used to search for S-bearing molecules in the outer disc-like structure, 60 au from IRAS 16293-2422 B, and are compared with data on 67P/C-G stemming from the ROSINA instrument aboard Rosetta. Species such as SO$_{2}$, SO, OCS, CS, H$_{2}$CS, H$_{2}$S and CH$_{3}$SH are detected via at least one of their isotopologues towards IRAS 16293-2422 B. The search reveals a first-time detection of OC$^{33}$S towards this source and a tentative first-time detection of C$^{36}$S towards a low-mass protostar. The data show that IRAS 16293-2422 B contains much more OCS than H$_{2}$S in comparison to 67P/C-G; meanwhile, the SO/SO$_{2}$ ratio is in close agreement between the two targets. IRAS 16293-2422 B has a CH$_{3}$SH/H$_{2}$CS ratio in range of that of our Solar System (differences by a factor of 0.7-5.3). It is suggested that the levels of UV radiation during the initial collapse of the systems may have varied and have potentially been higher for IRAS 16293-2422 B due to its binary nature; thereby, converting more H$_{2}$S into OCS. It remains to be conclusively tested if this also promotes the formation of S-bearing complex organics. Elevated UV levels of IRAS 16293-2422 B and a warmer birth cloud of our Solar System may jointly explain the variations between the two low-mass systems., Comment: Accepted for publication in MNRAS; 47 pages, 43 figures, 6 tables
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- 2018
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21. Imaging the water snowline in a protostellar envelope with H$^{13}$CO$^+$
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Hoff, Merel L. R. van 't, Persson, Magnus V., Harsono, Daniel, Taquet, Vianney, Jørgensen, Jes K., Visser, Ruud, Bergin, Edwin A., and van Dishoeck, Ewine F.
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
Snowlines are key ingredients for planet formation. Providing observational constraints on the locations of the major snowlines is therefore crucial for fully connecting planet compositions to their formation mechanism. Unfortunately, the most important snowline, that of water, is very difficult to observe directly in protoplanetary disks due to its close proximity to the central star. Based on chemical considerations, HCO$^+$ is predicted to be a good chemical tracer of the water snowline, because it is particularly abundant in dense clouds when water is frozen out. This work maps the optically thin isotopologue H$^{13}$CO$^+$ ($J=3-2$) toward the envelope of the low-mass protostar NGC1333-IRAS2A (observed with NOEMA at ~0.9" resolution), where the snowline is at larger distance from the star than in disks. The H$^{13}$CO$^+$ emission peaks ~2" northeast of the continuum peak, whereas the previously observed H$_2^{18}$O shows compact emission on source. Quantitative modeling shows that a decrease in H$^{13}$CO$^+$ abundance by at least a factor of six is needed in the inner ~360 AU to reproduce the observed emission profile. Chemical modeling predicts indeed a steep increase in HCO$^+$ just outside the water snowline; the 50% decrease in gaseous H$_2$O at the snowline is not enough to allow HCO$^+$ to be abundant. This places the water snowline at 225 AU, further away from the star than expected based on the 1D envelope temperature structure for NGC1333-IRAS2A. In contrast, DCO$^+$ observations show that the CO snowline is at the expected location, making an outburst scenario unlikely. The spatial anticorrelation of the H$^{13}$CO$^+$ and H$_2^{18}$O emission provide a proof of concept that H$^{13}$CO$^+$ can be used as a tracer of the water snowline., Comment: 10 pages, 8 figures, 3 tables. Accepted for publication in A&A
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- 2018
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22. 'I Have Neither His Voice nor Body': Upper Secondary Schoolteacher Students Experiencing Gendered Division of Labor
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Persson, Magnus
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For this study, Swedish upper secondary schoolteacher students were interviewed about their experiences and perceptions of teacher work in light of the traditional gendered division of labor in teaching. While female teaching has been signified by caring work, male teaching has been signified by distant teacher-pupil relations and the use of bodily resources to discipline pupils. In this study, both genders expressed feeling comforted when teacher practice corresponded to the traditional gendered division of labor and experiencing unease when it did not. Women expressed shortcomings in their ability to perform authoritative work because of their lack of male bodily resources. This subordination has been understood as symbolic violence, processed by a gendered habitus that structures women to prefer a special type of teacher work. Despite a small female majority in the profession and in teacher education, male domination still permeates the professional properties of the upper secondary schoolteacher work.
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- 2021
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23. Effects of customization and product modularization on financial performance
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Persson, Magnus and Lantz, Björn
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- 2022
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24. Similarities and differences between China and Sweden regarding the core features of palliative care for people aged 60 or older: a systematic scoping review
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Ahlström, Gerd, Huang, Hongli, Luo, Yu, Bökberg, Christina, Rasmussen, Birgit H., Persson, Eva I., Xue, Lian, Cai, Le, Tang, Pingfen, Persson, Magnus, and Huang, Jingjing
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- 2022
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25. Teachers' professional dispositions: Foundations for the immobile mobility in the diversified Swedish school market
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Persson, Magnus and Dannefjord, Per
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- 2022
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26. Culture on the move
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Lindberg, Ylva, primary, Wärnsby, Anna, additional, Nordenstam, Anna, additional, and Persson, Magnus, additional
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- 2024
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27. A Triple Protostar System Formed via Fragmentation of a Gravitationally Unstable Disk
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Tobin, John, Kratter, Kaitlin, Persson, Magnus, Looney, Leslie, Dunham, Michael, Segura-Cox, Dominique, Li, Zhi-Yun, Chandler, Claire, Sadavoy, Sarah, Harris, Robert, Melis, Carl, and Perez, Laura
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
Binary and multiple star systems are a frequent outcome of the star formation process, and as a result, almost half of all sun-like stars have at least one companion star. Theoretical studies indicate that there are two main pathways that can operate concurrently to form binary/multiple star systems: large scale fragmentation of turbulent gas cores and filaments or smaller scale fragmentation of a massive protostellar disk due to gravitational instability. Observational evidence for turbulent fragmentation on scales of $>$1000~AU has recently emerged. Previous evidence for disk fragmentation was limited to inferences based on the separations of more-evolved pre-main sequence and protostellar multiple systems. The triple protostar system L1448 IRS3B is an ideal candidate to search for evidence of disk fragmentation. L1448 IRS3B is in an early phase of the star formation process, likely less than 150,000 years in age, and all protostars in the system are separated by $<$200~AU. Here we report observations of dust and molecular gas emission that reveal a disk with spiral structure surrounding the three protostars. Two protostars near the center of the disk are separated by 61 AU, and a tertiary protostar is coincident with a spiral arm in the outer disk at a 183 AU separation. The inferred mass of the central pair of protostellar objects is $\sim$1 M$_{sun}$, while the disk surrounding the three protostars has a total mass of $\sim$0.30 M$_{\sun}$. The tertiary protostar itself has a minimum mass of $\sim$0.085 M$_{sun}$. We demonstrate that the disk around L1448 IRS3B appears susceptible to disk fragmentation at radii between 150~AU and 320~AU, overlapping with the location of the tertiary protostar. This is consistent with models for a protostellar disk that has recently undergone gravitational instability, spawning one or two companion stars., Comment: Published in Nature on Oct. 27th. 24 pages, 8 figures
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- 2016
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28. Servitization, Modularity, and Innovation in Supply Chain Management
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Hsuan, Juliana, primary and Persson, Magnus, additional
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- 2022
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29. Sensor Technologies for Optimized Tapping Procedures
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Wenzl, Christine, primary, Persson, Magnus, additional, and Koncik, Ladislav, additional
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- 2022
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30. Benefits of Modularity Strategies - Implications of Decisions and Timing
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Hansen, Poul Kyvsgaard, primary, Persson, Magnus, additional, and Hsuan, Juliana, additional
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- 2021
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31. Evaluation of modified Hilhorst models for pore electrical conductivity estimation using a low-cost dielectric sensor
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Zemni, Nessrine, Bouksila, Fethi, Slama, Fairouz, Persson, Magnus, Berndtsson, Ronny, and Bouhlila, Rachida
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- 2022
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32. Modelling forest road trafficability with satellite-based soil moisture variables
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Fjeld, Dag, Persson, Magnus, Fransson, Johan, Bjerketvedt, Jan, Brathen, Martin, Fjeld, Dag, Persson, Magnus, Fransson, Johan, Bjerketvedt, Jan, and Brathen, Martin
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Recent decades have seen increased temperatures and precipitation in the Nordic countries with long-term projections for reduced frost duration and depth. The consequence of these trends has been a gradual shift of delivery volumes to the frost-free season, requiring more agile management to exploit suitable weather conditions. Bearing capacity and trafficability are dependent on soil moisture state and in this context two satellite missions offer potenially useful information on soil moisture levels; NASA's SMAP (Soil Moisture Active Passive) and ESA's Sentinel-1. The goal of this pilot study was to quantify the performance of such satellite-based soil moisture variables for modeling forest road bearing capacity (e-module) during the frost-free season. The study was based on post-transport registrations of 103 forest road segments on the coastal and interior side of the Scandinavian mountain range. The analysis focused on roads of three types of surface deposits. Weekly SMAP soil moisture values better explained the variation in road e-module than soil water index (SWI) derived from Sentinel-1. Soil Water Index (SWI), however, reflected the weather conditions typical for operations on the respective surface deposit types. Regression analysis using (i) SMAP-based soil dryness index and (ii) its interaction with surface deposit types, together with (iii) the ratio between a combined SMAP_SWI dryness index and segment-specific depth to water (DTW) explained over 70% of the variation in road e-module. The results indicate a future potential to monitor road trafficability over large supply areas on a weekly level, given further refinement of study methods and variables for improved prediction.
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- 2024
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33. Historically restricted or historically empowered? : Differences in access to historical content knowledge between low- and high-SES pupils
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Rosenlund, David, Persson, Magnus, Rosenlund, David, and Persson, Magnus
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In the study presented in this article, the aim is to further the understanding regarding the differences between pupils (aged 15–16) from schools with low or high socio-economic status (SES), regarding the amount and diversity of content knowledge in history that they have acquired by the end of compulsory schooling. Following a definition of historical content knowledge, we situate the concept in relation to other aspects of the history school subject. This is done to visualize historical content knowledge's central role in more complex aspects of the subject. The empiri-cal material used in the study is pupils' responses on both selected and constructed response items on the Swedish national test in history. In the study, a com-bination of qualitative and quantitative approaches is used. The results show not only that pupils in low- SES schools provide fewer examples of historical content knowledge. We can also establish that the historical content knowledge of pupils from high-SES schools represents several perspectives while there are few perspectives present in the responses from pupils in low-SES schools. The results are used to discuss how the differences between pupils in low- and high-SES schools may affect their possibilities for educational success and active participation in society.
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- 2024
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34. Crossing a social demarcation line : Students experience friction in the transformed Swedish higher education system
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Persson, Magnus and Persson, Magnus
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One consequence of the widened participation in higher education (HE) is that the social demarcation line that once existed at the entrance to HE has moved inside the HE system. This study investigates how students experience social friction when demarcation lines are crossed and how such friction develops over time. This was achieved by repeated interviews with the same 10 HE students during their time at university. The study deploys habitus and hysteresis to explain how social dispositions from social origins are challenged but able to change when they are exposed to unfamiliar social situations. The study reveals how social friction in relation to both social background and to the HE system, progresses in terms of either fading or amplifying. These findings are concluded in a model that offers a systematic way of investigating how students experience HE over time in relation to social background.
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- 2024
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35. Culture on the move : Language and literature as vectors for cultural empowerment in Swedish education
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Lindberg, Ylva, Wärnsby, Anna, Nordenstam, Anna, Persson, Magnus, Lindberg, Ylva, Wärnsby, Anna, Nordenstam, Anna, and Persson, Magnus
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This special issue consists of five position papers, four articles and two essays covering diverse aspects of the theme Culture on the Move that foregrounds language and literature both as pedagogical tools and disciplinary fields necessary for learning to live and work in a culturally diverse world. The contributions stem from the initial activities within the graduate school “Culturally Empowering Education through Language and Literature” (CuEEd-LL). Centre-staging teaching and learning in Swedish education, the texts in this issue present a range of inroads into how language and literature can be used to support cultural diversity among pupils, students and teachers since cultural diversity is steadily gaining attention both as a resource and a challenge in education and society., Position paper.
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- 2024
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36. Special issue: Culture on the move (Educare, 2024:1)
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Lindberg, Ylva, Wärnsby, Anna, Nordenstam, Anna, Persson, Magnus, Lindberg, Ylva, Wärnsby, Anna, Nordenstam, Anna, and Persson, Magnus
- Abstract
This special issue consists of five position papers, four articles and two essays covering diverse aspects of the theme Culture on the Move that foregrounds language and literature both as pedagogical tools and disciplinary fields necessary for learning to live and work in a culturally diverse world. The contributions stem from the initial activities within the graduate school “Culturally Empowering Education through Language and Literature” (CuEEd-LL). Centre-staging teaching and learning in Swedish education, the texts in this issue present a range of inroads into how language and literature can be used to support cultural diversity among pupils, students and teachers since cultural diversity is steadily gaining attention both as a resource and a challenge in education and society.
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- 2024
37. Läsning, ekologi och siffror : Sanningspraktiker hos en läsfrämjande aktör
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Sundström Sjödin, Elin, Persson, Magnus, Pettersson, Daniel, Sundström Sjödin, Elin, Persson, Magnus, and Pettersson, Daniel
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I denna artikel redogör vi för en mindre delstudie i det pågående, och av Vetenskapsrådet finansierade, projektet Från ord till siffror. Hur läsning blir ett samhälleligt och didaktiskt problem. Med hjälp av teoretiska och metodologiska perspektiv från Science- and Technology Studies (STS) undersöker vi i projektet hur forskning, läsfrämjande aktörer och skolans svenskundervisning deltar i och konstruerar diskurser om läsningens nödvändighet. I den delstudie som är aktuell här fokuserar vi på Sveriges Författarförbund (SFF) och deras lansering av ett litteraturpolitiskt program under våren 2022. Vi undersöker på vilka sätt SFF använder exempelvis metaforen om litteraturens ekosystem och siffror som sanningsskapande praktiker. Det empiriska materialet består av SFF:s tryckta litteraturpolitiska program från 2022, en intervju med förbundets vice ordförande, samt fältanteckningar från en heldagskonferens om litteraturpolitik arrangerad av SFF. Analysen visar att ekologi och siffror är kraftfulla tekniker som skapar en berättelse om läsningens nödvändighet och utsatthet, samtidigt som dessa sanningspraktiker också genererar motsägelser och motsättningar. Läsning etableras här såväl som oumbärligt för samhället och individen, och som under hot från en mängd aktörer och processer, däribland marknadifieringen och digitaliseringen.
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- 2024
38. How do socio-economic differences affect pupils' access to historical content knowledge
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Persson, Magnus, Rosenlund, David, Persson, Magnus, and Rosenlund, David
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- 2024
39. Social Frictions at University : Swedish Students Experience Hysteresis-effects in a Transformed Higher Education System
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Persson, Magnus and Persson, Magnus
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Despite that higher education (HE) has been accessible to most social classes in society, HE continues to be a propellor for reproduction of social inequality. Numerous studies have demonstrated how social differentiation, whose previous demarcation line was whether to pursue HE or not, has penetrated into the HE system (Bathmaker et al., 2016; Ingram, 2023; Persson, 2022). This study (Persson, 2022) explored how a group of novice students navigated through an academic professional program positioned in the social mid-level of the Swedish HE hierarchy at one of the post99 universities. The students had different class backgrounds and different acquired educational capital (grades, SweSAT-results), which reflected the fragility of their positions as university students. In empirical terms, this meant that the students experienced social frictions both in relation to the HE field they entered and in relation to their social background. Four different combinations of frictions crystallized. Firstly, students who didn’t experienced any social frictions (Fish in Water), secondly, students who experienced social frictions both in relation to HE and social background (Two-Front Battle), thirdly, students who experienced social friction regarding their social background but not in relation to HE (Voluntary Exile), and fourthly, students who experienced social friction in relation to HE but not in relation to their social background (Behind Enemy Lines). The study demonstrates how social frictions can be traced back to the chosen educational program and university’s social position in the Swedish HE field, a field that is not as overtly hierarchically organized as, for example, the British (Bathmaker et al., 2016) or French (Winkler & Sackmann). The results of the study show how social class differences are reproduced through the HE, even when formal barriers of a social nature have been eliminated. The study’s panel design further illustrates how class-related frictions
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- 2024
40. Att formas till lärare på den svenska skolmarknaden
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Persson, Magnus, Dannefjord, Per, Persson, Magnus, and Dannefjord, Per
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Tidigare forskning har visat att den innehållsligt diversifierade och socialt segregerade skolmarknaden försvårat rörligheten av lärare mellan olika typer av skolor. Fenomenet har beskrivits som en inlåsning av lärare både till skolmarknadens olika sociala skikt och innehållsliga profiler. Inlåsningen förefaller ha föregåtts av en social formningsprocess där lärarens yrkesmässiga disposition formas för att passa den anställande skolans strukturella position och innehållsliga profil. Resultatet av formningen bidrar till hur läraren navigerar på skolmarknaden och strukturen på deras yrkeskarriärer. I denna studie undersöks hur denna formning går till. Genom återkommande intervjuer med nio ämneslärarstudenter från examen, vidare under lärarkarriärens tre första år fångas kontinuitet och förändring i hur lärarna beskriver sitt professionella lärarskap. Preliminära resultat visar att de är kritiska mot lärarutbildningens oförmåga att förbereda för viktiga delar av yrket. De pekar på avsaknaden av tekniker för klassrummet, bedömning, föräldrakontakt och planering. I intervjuer med erfarna lärare framgår det att just dessa aspekter av yrket varierar mellan olika skolor och måste därför i stor utsträckning läras in i den kontext där de ska utföras. Kritiken finns redan i samband med examen, men blir starkare och mer konkret efter ett år i yrket. Efter två år i yrket uttrycker de hur de synkroniseras med sin arbetsplats. Den lokala skolkulturen internaliseras i deras individuella lärarskap vilket gör dem mer benägna att stanna kvar, även om skolan inte motsvarar den skoltyp de initialt hade önskat sig.
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- 2024
41. Detection of glycolaldehyde towards the solar-type protostar NGC1333 IRAS2A
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Coutens, Audrey, Persson, Magnus V., Jørgensen, Jes K., Wampfler, Susanne F., and Lykke, Julie M.
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Astrophysics - Solar and Stellar Astrophysics - Abstract
Glycolaldehyde is a key molecule in the formation of biologically relevant molecules such as ribose. We report its detection with the Plateau de Bure interferometer towards the Class 0 young stellar object NGC1333 IRAS2A, which is only the second solar-type protostar for which this prebiotic molecule is detected. Local thermodynamic equilibrium analyses of glycolaldehyde, ethylene glycol (the reduced alcohol of glycolaldehyde) and methyl formate (the most abundant isomer of glycolaldehyde) were carried out. The relative abundance of ethylene glycol to glycolaldehyde is found to be ~5 -higher than in the Class 0 source IRAS 16293-2422 (~1), but comparable to the lower limits derived in comets ($\geq$3-6). The different ethylene glycol-to-glycolaldehyde ratios in the two protostars could be related to different CH3OH:CO compositions of the icy grain mantles. In particular, a more efficient hydrogenation on the grains in NGC 1333 IRAS2A would favor the formation of both methanol and ethylene glycol. In conclusion, it is possible that, like NGC 1333 IRAS2A, other low-mass protostars show high ethylene glycol-to-glycolaldehyde abundance ratios. The cometary ratios could consequently be inherited from earlier stages of star formation, if the young Sun experienced conditions similar to NGC1333 IRAS2A., Comment: 11 pages, 5 figures, accepted in A&A
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- 2015
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42. Assessment of groundwater safety surrounding contaminated water storage sites using multivariate statistical analysis and Heckman selection model: a case study of Kazakhstan
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Radelyuk, Ivan, Tussupova, Kamshat, Persson, Magnus, Zhapargazinova, Kulshat, and Yelubay, Madeniyet
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- 2021
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43. Drivers of regional crop variability in Chad
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Nilsson, Erik, Uvo, Cintia Bertacchi, Becker, Per, and Persson, Magnus
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- 2020
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44. Practice-Performance Relationships in Product Development – Towards a More Granular View
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Persson, Magnus, primary, Lantz, Björn, additional, and Magnusson, Mats, additional
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- 2024
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45. Modelling forest road trafficability with satellite-based soil moisture variables
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Fjeld, Dag, primary, Persson, Magnus, additional, Fransson, Johan E.S., additional, Bjerketvedt, Jan, additional, and Bråthen, Martin, additional
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- 2023
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46. High D$_2$O/HDO ratio in the inner regions of the low-mass protostar NGC1333 IRAS2A
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Coutens, Audrey, Jørgensen, Jes, Persson, Magnus, van Dishoeck, Ewine, Vastel, Charlotte, and Taquet, Vianney
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Astrophysics - Solar and Stellar Astrophysics - Abstract
Water plays a crucial role both in the interstellar medium and on Earth. To constrain its formation mechanisms and its evolution through the star formation process, the determination of the water deuterium fractionation ratios is particularly suitable. Previous studies derived HDO/H$_2$O ratios in the warm inner regions of low-mass protostars. We here report a detection of the D$_2$O 1$_{1,0}$-1$_{0,1}$ transition toward the low-mass protostar NGC1333 IRAS2A with the Plateau de Bure interferometer: this represents the first interferometric detection of D$_2$O - and only the second solar-type protostar for which this isotopologue is detected. Using the observations of the HDO 5$_{4,2}$-6$_{3,3}$ transition simultaneously detected and three other HDO lines previously observed, we show that the HDO line fluxes are well reproduced with a single excitation temperature of 218$\pm$21 K and a source size of $\sim$0.5 arcsec. The D$_2$O/HDO ratio is $\sim$(1.2$\pm$0.5) $\times$ 10$^{-2}$, while the use of previous H$_2^{18}$O observations give an HDO/H$_2$O ratio of $\sim$(1.7$\pm$0.8) $\times$ 10$^{-3}$, i.e. a factor of 7 lower than the D$_2$O/HDO ratio. These results contradict the predictions of current grain surface chemical models and indicate that either the surface deuteration processes are poorly understood or that both sublimation of grain mantles and water formation at high temperatures ($\gtrsim$230 K) take place in the inner regions of this source. In the second scenario, the thermal desorption of the grain mantles would explain the high D$_2$O/HDO ratio, while water formation at high temperature would explain significant extra production of H$_2$O leading to a decrease of the HDO/H$_2$O ratio., Comment: Accepted for publication in ApJ Letters; 12 pages, 2 figures
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- 2014
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47. ALMA observations of the kinematics and chemistry of disc formation
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Lindberg, Johan E., Jørgensen, Jes K., Brinch, Christian, Haugbølle, Troels, Bergin, Edwin A., Harsono, Daniel, Persson, Magnus V., Visser, Ruud, and Yamamoto, Satoshi
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
Context: The R CrA cloud hosts a handful of Class 0/I low-mass young stellar objects. The chemistry and physics at scales $>500$ AU in this cloud are dominated by the irradiation from the nearby Herbig Be star R CrA. The luminous large-scale emission makes it necessary to use high-resolution spectral imaging to study the chemistry and dynamics of the inner envelopes and discs of the protostars. Aims: We aim to better understand the structure of the inner regions of these protostars and, in particular, the interplay between the chemistry and the presence of discs. Methods: Using Atacama Large Millimeter/submillimeter Array (ALMA) high-resolution spectral imaging interferometry observations, we study the molecular line and dust continuum emission at submillimetre wavelengths. Results: We detect dust continuum emission from four circumstellar discs around Class 0/I objects within the R CrA cloud. Towards IRS7B we detect C$^{17}$O emission showing a rotation curve consistent with a Keplerian disc with a well-defined edge that gives a good estimate for the disc radius at 50 AU. We derive the central object mass to $2.3M_{\odot}$ and the disc mass to $0.024M_{\odot}$. The observations are also consistent with a model of material infalling under conservation of angular momentum; however, this model provides a worse fit to the data. We also report a likely detection of faint CH$_3$OH emission towards this point source, as well as more luminous CH$_3$OH emission in an outflow orthogonal to the major axis of the C$^{17}$O emission. Conclusions: The faint CH$_3$OH emission seen towards IRS7B can be explained by a flat density profile of the inner envelope caused by the disc with a radius $\lesssim50$ AU. We propose that the regions of the envelopes where complex organic molecules are present in Class 0/I young stellar objects can become quenched as the disc grows., Comment: Accepted for publication in A&A; 11 pages, 9 figures
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- 2014
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48. Rotationally-supported disks around Class I sources in Taurus: disk formation constraints
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Harsono, Daniel, Jorgensen, Jes K., van Dishoeck, Ewine F., Hogerheijde, Michiel R., Bruderer, Simon, Persson, Magnus V., and Mottram, Joseph C.
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Astrophysics - Astrophysics of Galaxies - Abstract
(Abridged) Disks are observed around pre-main sequence stars, but how and when they form is still heavily debated. While disks around young stellar objects have been identified through thermal dust emission, spatially and spectrally resolved molecular line observations are needed to determine their nature. We present subarcsecond observations of dust and gas toward four Class I low-mass young stellar objects in Taurus. The 13CO and C18O J=2-1 transitions at 220 GHz were observed with the Plateau de Bure Interferometer at a spatial resolution of ~0.8'' and analyzed using uv-space position velocity diagrams to determine the nature of their observed velocity radient. Rotationally supported disks (RSDs) are detected around 3 of the 4 Class I sources studied. The derived masses identify them as Stage I objects; i.e., their stellar mass is higher than their envelope and disk masses. The outer radii of the Keplerian disks toward our sample of Class I sources are <~ 100 AU. The lack of on-source C18O emission for TMR1 puts an upper limit of 50 AU on its size. Flattened structures at radii > 100 AU around these sources are dominated by infalling motion (v propto r^-1). A large-scale envelope model is required to estimate the basic parameters of the flattened structure from spatially resolved continuum data. Similarities and differences between the gas and dust disk are discussed. Combined with literature data, the sizes of the RSDs around Class I objects are best described with evolutionary models with an initial rotation of 10^-14 Hz and slow sound speeds. Based on the comparison of gas and dust disk masses, little CO is frozen out within 100 AU in these disks. RSDs with radii up to 100 AU are present around Class I embedded objects. Larger surveys of both Class 0 and I objects are needed to determine whether most disks form late or early in the embedded phase., Comment: Accepted for publication in A&A, 22 pages with appendix; 13 figures
- Published
- 2013
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49. A recent accretion burst in the low-mass protostar IRAS 15398-3359: ALMA imaging of its related chemistry
- Author
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Jorgensen, Jes K., Visser, Ruud, Sakai, Nami, Bergin, Edwin A., Brinch, Christian, Harsono, Daniel, Lindberg, Johan E., van Dishoeck, Ewine F., Yamamoto, Satoshi, Bisschop, Suzanne E., and Persson, Magnus V.
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
Low-mass protostars have been suggested to show highly variable accretion rates through-out their evolution. Such changes in accretion, and related heating of their ambient envelopes, may trigger significant chemical variations on different spatial scales and from source-to-source. We present images of emission from C17O, H13CO+, CH3OH, C34S and C2H toward the low-mass protostar IRAS 15398-3359 on 0.5" (75 AU diameter) scales with the Atacama Large Millimeter/submillimeter Array (ALMA) at 340 GHz. The resolved images show that the emission from H13CO+ is only present in a ring-like structure with a radius of about 1-1.5" (150-200 AU) whereas the CO and other high dipole moment molecules are centrally condensed toward the location of the central protostar. We propose that HCO+ is destroyed by water vapor present on small scales. The origin of this water vapor is likely an accretion burst during the last 100-1000 years increasing the luminosity of IRAS 15398-3359 by a factor of 100 above its current luminosity. Such a burst in luminosity can also explain the centrally condensed CH3OH and extended warm carbon-chain chemistry observed in this source and furthermore be reflected in the relative faintness of its compact continuum emission compared to other protostars., Comment: Accepted for publication in ApJ Letters; 14 pages, 5 figures
- Published
- 2013
- Full Text
- View/download PDF
50. Spatiotemporal variation of nitrate concentrations in soil and groundwater of an intensely polluted agricultural area
- Author
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Nakagawa, Kei, Amano, Hiroki, Persson, Magnus, and Berndtsson, Ronny
- Published
- 2021
- Full Text
- View/download PDF
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