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Title: RADIATIVE INTERACTION OF SHOCKS WITH SMALL INTERSTELLAR CLOUDS AS A PRE-STAGE TO STAR FORMATION

Abstract

Cloud compression by external shocks is believed to be an important triggering mechanism for gravitational collapse and star formation in the interstellar medium. We have performed MHD simulations to investigate whether the radiative interaction between a shock wave and a small interstellar cloud can induce the conditions for Jeans instability and how the interaction is influenced by magnetic fields of different strengths and orientation. The simulations use the NIRVANA code in three dimensions with anisotropic heat conduction and radiative heating/cooling at an effective resolution of 100 cells per cloud radius. Our cloud has radius 1.5 pc, has density 17 cm{sup -3}, is embedded in a medium of density 0.17 cm{sup -3}, and is struck by a planar Mach 30 shock wave. The simulations produce dense, cold fragments similar to those of Mellema et al. and Fragile et al. We do not find any regions that are Jeans unstable but do record transient cloud density enhancements of factors {approx}10{sup 3}-10{sup 5} for the bulk of the cloud mass, which then decline and converge toward seemingly stable net density enhancement factors {approx}10{sup 2}-10{sup 4}. Our run with a weak, initial magnetic field ({beta} = 10{sup 3}) perpendicular to the shock normal standsmore » out as producing the most lasting density enhancements. We interpret this field strength as being the compromise between weak internal magnetic pressure preventing compression and sufficiently strong magnetic field to thermally insulate the condensations, thus helping them cool radiatively.« less

Authors:
;  [1]
  1. Leibniz Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)
Publication Date:
OSTI Identifier:
22167550
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 766; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANISOTROPY; COMPUTERIZED SIMULATION; COOLING; DENSITY; GRAVITATIONAL COLLAPSE; HEATING; INTERSTELLAR SPACE; MAGELLANIC CLOUDS; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; MASS; RESOLUTION; SHOCK WAVES; SUPERNOVA REMNANTS; THERMAL CONDUCTION

Citation Formats

Johansson, Erik P. G., and Ziegler, Udo. RADIATIVE INTERACTION OF SHOCKS WITH SMALL INTERSTELLAR CLOUDS AS A PRE-STAGE TO STAR FORMATION. United States: N. p., 2013. Web. doi:10.1088/0004-637X/766/1/45.
Johansson, Erik P. G., & Ziegler, Udo. RADIATIVE INTERACTION OF SHOCKS WITH SMALL INTERSTELLAR CLOUDS AS A PRE-STAGE TO STAR FORMATION. United States. https://doi.org/10.1088/0004-637X/766/1/45
Johansson, Erik P. G., and Ziegler, Udo. 2013. "RADIATIVE INTERACTION OF SHOCKS WITH SMALL INTERSTELLAR CLOUDS AS A PRE-STAGE TO STAR FORMATION". United States. https://doi.org/10.1088/0004-637X/766/1/45.
@article{osti_22167550,
title = {RADIATIVE INTERACTION OF SHOCKS WITH SMALL INTERSTELLAR CLOUDS AS A PRE-STAGE TO STAR FORMATION},
author = {Johansson, Erik P. G. and Ziegler, Udo},
abstractNote = {Cloud compression by external shocks is believed to be an important triggering mechanism for gravitational collapse and star formation in the interstellar medium. We have performed MHD simulations to investigate whether the radiative interaction between a shock wave and a small interstellar cloud can induce the conditions for Jeans instability and how the interaction is influenced by magnetic fields of different strengths and orientation. The simulations use the NIRVANA code in three dimensions with anisotropic heat conduction and radiative heating/cooling at an effective resolution of 100 cells per cloud radius. Our cloud has radius 1.5 pc, has density 17 cm{sup -3}, is embedded in a medium of density 0.17 cm{sup -3}, and is struck by a planar Mach 30 shock wave. The simulations produce dense, cold fragments similar to those of Mellema et al. and Fragile et al. We do not find any regions that are Jeans unstable but do record transient cloud density enhancements of factors {approx}10{sup 3}-10{sup 5} for the bulk of the cloud mass, which then decline and converge toward seemingly stable net density enhancement factors {approx}10{sup 2}-10{sup 4}. Our run with a weak, initial magnetic field ({beta} = 10{sup 3}) perpendicular to the shock normal stands out as producing the most lasting density enhancements. We interpret this field strength as being the compromise between weak internal magnetic pressure preventing compression and sufficiently strong magnetic field to thermally insulate the condensations, thus helping them cool radiatively.},
doi = {10.1088/0004-637X/766/1/45},
url = {https://www.osti.gov/biblio/22167550}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 766,
place = {United States},
year = {Wed Mar 20 00:00:00 EDT 2013},
month = {Wed Mar 20 00:00:00 EDT 2013}
}