Abstract
We present a study of the relative orientation between the magnetic field projected onto the plane of sky (B⊥) on scales down to 0.4 pc, inferred from the polarized thermal emission of Galactic dust observed by Planck at 353 GHz, and the distribution of gas column density (NH) structures on scales down to 0.026 pc, derived from the observations by Herschel in submillimeter wavelengths, toward ten nearby (d < 450 pc) molecular clouds. Using the histogram of relative orientation technique in combination with tools from circular statistics, we found that the mean relative orientation between NH and B⊥ toward these regions increases progressively from 0°, where the NH structures lie mostly parallel to B⊥, with increasing NH, in many cases reaching 90°, where the NH structures lie mostly perpendicular to B⊥. We also compared the relative orientation between NH and B⊥ and the distribution of NH, which is characterized by the slope of the tail of the NH probability density functions (PDFs). We found that the slopes of the NH PDF tail are steepest in regions where NH and B⊥ are close to perpendicular. This coupling between the NH distribution and the magnetic field suggests that the magnetic fields play a significant role in structuring the interstellar medium in and around molecular clouds. However, we found no evident correlation between the star formation rates, estimated from the counts of young stellar objects, and the relative orientation between NH and B⊥ in these regions.
Highlights
The physical processes that regulate the formation of stars are one of the main open subjects of research in contemporary astrophysics
We present a study of the relative orientation between the magnetic field projected onto the plane of sky (B⊥) on scales down to 0.4 pc, inferred from the polarized thermal emission of Galactic dust observed by Planck at 353 GHz, and the distribution of gas column density (NH) structures on scales down to 0.026 pc, derived from the observations by Herschel in submillimeter wavelengths, toward ten nearby (d < 450 pc) molecular clouds
Further information on the magnetic fields in molecular clouds (MCs) is provided by observations of the linear polarization, in extinction from background stars and in emission from interstellar dust grains, reveal the orientation of the interstellar magnetic field averaged along the line of sight (LOS) and projected onto the plane of the sky, B⊥, (Hiltner 1949; Davis & Greenstein 1951; Hildebrand 1988; Pattle & Fissel 2019)
Summary
The physical processes that regulate the formation of stars are one of the main open subjects of research in contemporary astrophysics (for a review see McKee & Ostriker 2007; Dobbs et al 2014; Molinari et al 2014). Observations of the Zeeman splitting in emission and absorption by species such as neutral hydrogen (H) and the hydroxyl (OH) and cyanide (CN) radicals provide the only direct detections of the magnetic field strength in the stellar medium (see Crutcher 2012, for a review). The requirements of both high sensitivity and control of systematic effects considerably limit the coverage of the observations of the Zeeman splitting in MCs, (Bourke et al 2001; Troland & Crutcher 2008). Further information on the magnetic fields in MCs is provided by observations of the linear polarization, in extinction from background stars and in emission from interstellar dust grains, reveal the orientation of the interstellar magnetic field averaged along the line of sight (LOS) and projected onto the plane of the sky, B⊥, (Hiltner 1949; Davis & Greenstein 1951; Hildebrand 1988; Pattle & Fissel 2019)
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