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Matching dust emission structures and magnetic field in high-latitude cloud L1642: comparing Herschel and Planck maps

The nearby cloud L1642 is one of only two known very high latitude (|b| > 30 deg) clouds actively forming stars. It is a rare example of star formation in isolated conditions, and can reveal important details of star formation in general, e.g., of the effect of magnetic fields. We compare Herschel dust emission structures and magnetic field orientation revealed by Planck polarization maps in L1642. The high-resolution ($\sim20"$) Herschel data reveal a complex structure including a dense, compressed central clump, and low density striations. The Planck polarization data (at 10$'$ resolution) reveal an ordered magnetic field pervading the cloud and aligned with the surrounding striations. There is a complex interplay between the cloud structure and large scale magnetic field. This suggests that the magnetic field is closely linked to the formation and evolution of the cloud. CO rotational emission confirms that the striations are connected with the main clumps and likely to contain material either falling into or flowing out of the clumps. There is a clear transition from aligned to perpendicular structures approximately at a column density of $N_{\rm{H}} = 1.6 \times 10^{21}\, {\rm cm}^{-2}$. Comparing the Herschel maps with the Planck polarization maps shows the close connection between the magnetic field and cloud structure even in the finest details of the cloud.