Details

Autor(en) / Beteiligte

• Inoue, Tsuyoshi
• Inutsuka, Shu-ichiro

Titel

FORMATION OF H i CLOUDS IN SHOCK-COMPRESSED INTERSTELLAR MEDIUM: PHYSICAL ORIGIN OF ANGULAR CORRELATION BETWEEN FILAMENTARY STRUCTURE AND MAGNETIC FIELD

Ist Teil von

• The Astrophysical journal, 2016-12, Vol.833 (1), p.10

Ort / Verlag

Philadelphia: The American Astronomical Society

Erscheinungsjahr

2016

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

• ABSTRACT Recent observations of the neutral Galactic interstellar medium showed that filamentary structures of H i clouds are aligned with the interstellar magnetic field. Many interesting applications are proposed based on the alignment, such as measurement of magnetic field strength through the Chandrasekhar-Fermi method and removal of foreground dust emissions for the detection of inflationary polarized emission in the cosmic microwave background radiation. However, the physical origin of the alignment remains to be explained. To understand the mechanism, we examine the formation of H i clouds triggered by shock compression of the diffuse warm neutral medium using three-dimensional magnetohydrodynamic simulations. We show that the shock-compressed medium of density cm−3 evolves into H i clouds with cm−3 via thermal instability consistent with previous studies. We apply a machine vision transformation developed by Clark et al. to the simulated column density structures to measure angle correlation between filamentary structures of H i clouds and magnetic field. We find that the orientation of H i filaments depends on the environmental turbulent velocity field, particularly on the strength of shear strain in the direction of the magnetic field, which is controlled by the angle between the shock propagation direction and upstream magnetic field. When the strain along the magnetic field is weak, filamentary components of H i clouds lie perpendicular to the magnetic field. However, the filaments have come to align with the magnetic field, if we enhance the turbulent strain along the magnetic field or if we set turbulence in the preshock medium.