Ambipolar diffusion, cloud cores, and star formation: Two-dimensional, cylindrically symmetric contraction. III. A further parameter study and magnetically controlled accretion rate

Telemachos Ch Mouschovias, Scott A. Morton

Research output: Contribution to journalArticle

Abstract

The self-initiated formation and contraction of protostellar cores (due to ambipolar diffusion) and its dependence on the three dimensionless free parameters present in the two-fluid magnetohydrodynamic equations are investigated further. We follow the evolution of four thermally supercritical, primarily magnetically supported model clouds up to a central density enhancement of 106 (e.g., from 3 × 103 to 3 × 109 cm-3). Together with the 10 models studied in Paper II, they reveal and quantify the crucial and unavoidable role of ambipolar diffusion in the formation of stars in otherwise quiescent molecular clouds. The physical origin of two breaks in the slope of the log ρ-log r neutral density profile, one in the envelope and one just outside the shrinking, nearly uniform-density core, is discussed. The ambipolar-diffusion limited mass infall (or accretion) rate is both qualitatively and quantitatively very different from that of nonmagnetic calculations and their extrapolations to magnetic clouds. The dependence on the free parameters of the exponent k in the relation Bc ∝ ρck between the magnetic field strength and the gas density in contracting cores is studied thoroughly in this (cylindrical) geometry. For completeness, the evolution of a thermally subcritical (but still initially primarily magnetically supported) model cloud is also followed until a final equilibrium state is reached.

Original languageEnglish (US)
Pages (from-to)166-180
Number of pages15
JournalAstrophysical Journal
Volume390
Issue number1
DOIs
StatePublished - Jan 1 1992

Fingerprint

ambipolar diffusion
contraction
star formation
accretion
magnetic clouds
gas density
completeness
molecular clouds
magnetohydrodynamics
extrapolation
field strength
envelopes
exponents
slopes
stars
augmentation
fluids
profiles
geometry
magnetic field

Keywords

  • Accretion, accretion disks
  • Diffusion
  • ISM: magnetic fields
  • MHD
  • Plasmas
  • Stars : formation
  • Stars: pre-main-sequence

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

@article{f2211298e4a940c1b70f3a549b05ab50,
title = "Ambipolar diffusion, cloud cores, and star formation: Two-dimensional, cylindrically symmetric contraction. III. A further parameter study and magnetically controlled accretion rate",
abstract = "The self-initiated formation and contraction of protostellar cores (due to ambipolar diffusion) and its dependence on the three dimensionless free parameters present in the two-fluid magnetohydrodynamic equations are investigated further. We follow the evolution of four thermally supercritical, primarily magnetically supported model clouds up to a central density enhancement of 106 (e.g., from 3 × 103 to 3 × 109 cm-3). Together with the 10 models studied in Paper II, they reveal and quantify the crucial and unavoidable role of ambipolar diffusion in the formation of stars in otherwise quiescent molecular clouds. The physical origin of two breaks in the slope of the log ρ-log r neutral density profile, one in the envelope and one just outside the shrinking, nearly uniform-density core, is discussed. The ambipolar-diffusion limited mass infall (or accretion) rate is both qualitatively and quantitatively very different from that of nonmagnetic calculations and their extrapolations to magnetic clouds. The dependence on the free parameters of the exponent k in the relation Bc ∝ ρck between the magnetic field strength and the gas density in contracting cores is studied thoroughly in this (cylindrical) geometry. For completeness, the evolution of a thermally subcritical (but still initially primarily magnetically supported) model cloud is also followed until a final equilibrium state is reached.",
keywords = "Accretion, accretion disks, Diffusion, ISM: magnetic fields, MHD, Plasmas, Stars : formation, Stars: pre-main-sequence",
author = "Mouschovias, {Telemachos Ch} and Morton, {Scott A.}",
year = "1992",
month = "1",
day = "1",
doi = "10.1086/171268",
language = "English (US)",
volume = "390",
pages = "166--180",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1",

}

TY - JOUR

T1 - Ambipolar diffusion, cloud cores, and star formation

T2 - Two-dimensional, cylindrically symmetric contraction. III. A further parameter study and magnetically controlled accretion rate

AU - Mouschovias, Telemachos Ch

AU - Morton, Scott A.

PY - 1992/1/1

Y1 - 1992/1/1

N2 - The self-initiated formation and contraction of protostellar cores (due to ambipolar diffusion) and its dependence on the three dimensionless free parameters present in the two-fluid magnetohydrodynamic equations are investigated further. We follow the evolution of four thermally supercritical, primarily magnetically supported model clouds up to a central density enhancement of 106 (e.g., from 3 × 103 to 3 × 109 cm-3). Together with the 10 models studied in Paper II, they reveal and quantify the crucial and unavoidable role of ambipolar diffusion in the formation of stars in otherwise quiescent molecular clouds. The physical origin of two breaks in the slope of the log ρ-log r neutral density profile, one in the envelope and one just outside the shrinking, nearly uniform-density core, is discussed. The ambipolar-diffusion limited mass infall (or accretion) rate is both qualitatively and quantitatively very different from that of nonmagnetic calculations and their extrapolations to magnetic clouds. The dependence on the free parameters of the exponent k in the relation Bc ∝ ρck between the magnetic field strength and the gas density in contracting cores is studied thoroughly in this (cylindrical) geometry. For completeness, the evolution of a thermally subcritical (but still initially primarily magnetically supported) model cloud is also followed until a final equilibrium state is reached.

AB - The self-initiated formation and contraction of protostellar cores (due to ambipolar diffusion) and its dependence on the three dimensionless free parameters present in the two-fluid magnetohydrodynamic equations are investigated further. We follow the evolution of four thermally supercritical, primarily magnetically supported model clouds up to a central density enhancement of 106 (e.g., from 3 × 103 to 3 × 109 cm-3). Together with the 10 models studied in Paper II, they reveal and quantify the crucial and unavoidable role of ambipolar diffusion in the formation of stars in otherwise quiescent molecular clouds. The physical origin of two breaks in the slope of the log ρ-log r neutral density profile, one in the envelope and one just outside the shrinking, nearly uniform-density core, is discussed. The ambipolar-diffusion limited mass infall (or accretion) rate is both qualitatively and quantitatively very different from that of nonmagnetic calculations and their extrapolations to magnetic clouds. The dependence on the free parameters of the exponent k in the relation Bc ∝ ρck between the magnetic field strength and the gas density in contracting cores is studied thoroughly in this (cylindrical) geometry. For completeness, the evolution of a thermally subcritical (but still initially primarily magnetically supported) model cloud is also followed until a final equilibrium state is reached.

KW - Accretion, accretion disks

KW - Diffusion

KW - ISM: magnetic fields

KW - MHD

KW - Plasmas

KW - Stars : formation

KW - Stars: pre-main-sequence

UR - http://www.scopus.com/inward/record.url?scp=0041078946&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0041078946&partnerID=8YFLogxK

U2 - 10.1086/171268

DO - 10.1086/171268

M3 - Article

AN - SCOPUS:0041078946

VL - 390

SP - 166

EP - 180

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1

ER -