Effects of magnetic field orientations in dense cores on gas kinematics in protostellar envelopes

Theoretically, misalignment between the magnetic field and rotational axis in a dense core is considered to be dynamically important in the star formation process, however, extent of this influence remains observationally unclear. For a sample of 32 Class 0 and I protostars in the Perseus Molecular Cloud, we analyzed gas motions using C18O data from the SMA MASSES survey and the magnetic field structures using 850 μm polarimetric data from the JCMT BISTRO-1 survey and archive. We do not find any significant correlation between the velocity gradients in the C18O emission in the protostellar envelopes at a 1,000 au scale and the misalignment between the outflows and magnetic field orientations in the dense cores at a 4,000 au scale, and there is also no correlation between the velocity gradients and the angular dispersions of the magnetic fields. However, a significant dependence on the misalignment angles emerges after we normalize the rotational motion by the infalling motion, where the ratios increase from ≲1 to ≳1 with increasing misalignment angles. This suggests that the misalignment could prompt angular momentum transportation to the envelope scale but is not a dominant factor in determining the envelope rotation, and other parameters, like mass accretion in protostellar sources, also play an important role. These results remain valid after taking into account projection effects. The comparison between our estimated angular momentum in the protostellar envelopes and the sizes of the known protostellar disks suggests that significant angular momentum is likely lost between radii of ∼1,000-100 au in protostellar envelopes

Magnetic Field Structure in Spheroidal Star-forming Clouds. II. Estimating Field Structure from Observed Maps

This paper presents models to estimate the structure of density and magnetic field strength in spheroidal condensations from maps of their column density and their polarization of magnetically aligned dust grains. The density model is obtained by fitting a column density map with an embedded p = 2 Plummer spheroid of any aspect ratio and inclination. The magnetic properties are based on the density model, the Davis-Chandrasekhar-Fermi (DCF) model of Alfvénic fluctuations, and the spheroid flux freezing (SFF) model of mass and flux conservation in Paper I. The field strength model has the resolution of the column density map, which is finer than the resolution of the DCF estimate of field strength. The models are applied to ALMA observations of the envelope of the protostar BHR 71 IRS1. Column density fits give the density model from (2.0 ± 0.4) × 105 to (7 ± 1) × 107 cm-3. The density model predicts the field directions map, which fits the polarization map best within 1100 au, with standard deviation of angle differences of 17°. In this region, the DCF mean field strength is 0.7 ± 0.2 mG, and the envelope mass is supercritical, with a ratio of mass to magnetic critical mass of 1.5 ± 0.4. The SFF field strength profile scales with the DCF field strength from 60 ± 10 μG to 3 ± 1 mG. The spatial resolution of the SFF field strength estimate is finer than the DCF resolution by a factor of ∼7, and the peak SFF field strength exceeds the DCF field strength by a factor of ∼4

Microdata protection

The increased power and interconnectivity of computer systems available today provide the ability of storing and processing large amounts of data, resulting in networked information accessible from anywhere at any time. This information sharing and dissemination process is clearly selective. Indeed, if on the one hand there is a need to disseminate some data, there is on the other hand an equally strong need to protect those data that, for various reasons, should not be disclosed. Consider, for example, the case of a private organization making available various data regarding its business (products, sales, and so on), but at the same time wanting to protect more sensitive information, such as the identity of its customers or plans for future products. As another example, government agencies, when releasing historical data, may require a sanitization process to \u201cblank out\u201d information considered sensitive, either directly or because of the sensitive information it would allow the recipient to infer. Effective information sharing and dissemination can take place only if the data holder has some assurance that, while releasing information, disclosure of sensitive information is not a risk

Effects of rolling on wind-induced detachment thresholds of volcanic glass on Mars

Dunes in the northern lowlands on planet Mars are composed of volcanic sands with high contents of volcanic glass and these deposits are mobilised and transported by winds in the present-day surface environment. In this experimental study we measured fluid thresholds for detachment of Mars-analogue volcanic glass particles using a low-fluid density wind tunnel under wind shear stresses in the range of 0.1-0.6 N m−2. Measured thresholds for larger particle diameters (>150 µm) were best-explained using a semi-empirical model of detachment which incorporates the effects of drag-induced rolling. Fitting of this semi-empirical model to obtained experimental data, combined with a residual analysis of the model fit with quantified particle properties made it possible to assess the sensitivity and validity of the model for predicting this type of particle detachment. This new model was used to predict the threshold shear stress for detachment of particles on Mars and indicated that larger particle diameters can detach by drag-induced rolling when subjected to present-day surface wind shears. A large morphological and granulometric variety of particles is therefore susceptible to this form of detachment, which provides a possible mechanism for the initial mobilisation of particles at lower wind speeds than required for detachment by saltation. Recent sand mobility may therefore have benefited from rolling as a contributing or as a saltation triggering process