Higher-order generalized uncertainty principle corrections to the Jeans mass

The Jeans instability is regarded as an important tool for analyzing the dynamics of a self-gravitating system. However, this theory is challenging since astronomical observation data show some Bok globules, whose masses are less than the Jeans mass and still have stars or at least undergo the star formation process. To explain this problem, we investigate the effects of the higher-order generalized uncertainty principle on the Jeans mass of the collapsing molecular cloud. The results in this paper show that the higher order generalized uncertainty principle has a very significant effect on the canonical energy and gravitational potential of idea gas, and finally leads to a modified Jeans mass lower than the original case, which is conducive to the generation of stars in small mass Bok globules. Furthermore, we estimate the new generalized uncertainty principle parameter $$\gamma _0$$ γ 0 by applying various data of Bok globules, and find that the range of magnitude of $$\gamma _0$$ γ 0 is $${10^{11}} {-} {10^{12}}$$ 10 11 - 10 12 .

Magnetic fields in Bok globules: multi-wavelength polarimetry as tracer across large spatial scales

Context. The role of magnetic fields in the process of star formation is a matter of continuous debate. Clear observational proof of the general influence of magnetic fields on the early phase of cloud collapse is still pending. In an earlier study on Bok globules with simple structures, we find strong indications of dominant magnetic fields across large spatial scales. Aims. The aim of this study is to test the magnetic field influence across Bok globules with more complex density structures. Methods. We apply near-infrared polarimetry to trace the magnetic field structure on scales of 104–105 au (~0.05–0.5pc) in selected Bok globules. The combination of these measurements with archival data in the optical and sub-mm wavelength range allows us to characterize the magnetic field on scales of 103–106 au (~0.005–5pc). Results. We present polarimetric data in the near-infrared wavelength range for the three Bok globules CB34, CB56, and [OMK2002]18, combined with archival polarimetric data in the optical wavelength range for CB34 and CB56, and in the submillimeter wavelength range for CB34 and [OMK2002]18. We find a strong polarization signal (P ≥ 2%) in the near-infrared for all three globules. For CB34, we detect a connection between the structure on scales of 104–105 au (~0.05–0.5pc) to 105–106 au (~0.5–5pc). For CB56, we trace aligned polarization segments in both the near-infrared and optical data, suggesting a connection of the magnetic field structure across the whole globule. In the case of [OMK2002]18, we find ordered polarization structures on scales of 104–105 au (~0.05–0.5pc). Conclusions. We find strongly aligned polarization segments on large scales which indicate dominant magnetic fields across Bok globules with complex density structures. To reconcile our findings in globules, the lowest mass clouds known, and the results on intermediate (e.g. Taurus) and more massive (e.g. Orion) clouds, we postulate a mass-dependent role of magnetic fields, whereby magnetic fields appear to be dominant on low and high mass but rather subdominant on intermediate mass clouds.

Magnetic field dispersion in the neighbourhood of Bok Globules

We performed an observational study of the relation between the interstellar magnetic field alignment and star formation in twenty (20) sky regions containing Bok Globules. The presence of young stellar objects in the globules is verified by a search of infrared sources with spectral energy distribution compatible with a pre main-sequence star. The interstellar magnetic field direction is mapped using optical polarimetry. These maps are used to estimate the dispersion of the interstellar magnetic field direction in each region from a Gaussian fit, σB. In addition to the Gaussian dispersion, we propose a new parameter, η, to measure the magnetic field alignment that does not rely on any function fitting. Statistical tests show that the dispersion of the magnetic field direction is different in star forming globules relative to quiescent globules. Specifically, the less organised magnetic fields occur in regions having young stellar objects.