Do environmental conditions affect the dust-induced fragmentation in low-metallicity clouds? Effect of pre-ionization and far-ultraviolet/cosmic-ray fields

Research output: Contribution to journalArticle

Abstract

We study the effects of the fully ionized initial state, or pre-ionization, on the subsequent thermal evolution of low-metallicity clouds under various intensities of external far-ultraviolet (FUV) and cosmic-ray (CR) fields. Preionization significantly affects the thermal and dynamical evolution of metal-free clouds without FUV/CRs by way of efficient HD formation. On the other hand, the pre-ionization effect on thermal evolution is limited in the very low-density regime for more metal-enriched clouds ([Z=H] ≳ -4), or those under a modest FUV (≳ 10-3) field or CR field (≳ 0.1) of the present-day galactic disk levels. In any case, for ≳ 10 8cm-3, neither the initial ionization state nor the irradiating FUV strength affect the thermal evolution. The dust cooling is an important mechanism for making sub-solar mass fragments in low-metallicity gas. Since this fragmentation occurs at the temperature minimum by dust cooling at ≳ 1010 cm-3, this process is not vulnerable either to the initial ionization state or external radiation.

Original languageEnglish
JournalPublications of the Astronomical Society of Japan
Volume64
Issue number5
DOIs
Publication statusPublished - 2012 Oct 25
Externally publishedYes

Keywords

  • ISM: molecules
  • Stars: formation
  • Stars: population II

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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