Axisymmetric gravitational collapse of rotating interstellar gas clouds

1981 ◽  
Vol 79 (1) ◽  
pp. 129-144 ◽  
Author(s):  
N. Virgopia ◽  
F. Ferraioli
Keyword(s):  
Gravitational Collapse ◽  
Interstellar Gas

The Main Sequence Evolution of Inhomogeneous Stars

1982 ◽  
Vol 4 (4) ◽  
pp. 396-400 ◽  
Author(s):  
J. Lattanzio
Keyword(s):  
Gravitational Collapse ◽  
Heavy Element ◽  
Main Sequence ◽  
Element Abundance ◽  
Sequence Evolution ◽  
Interstellar Gas ◽  
Convective Mixing ◽  
The Core ◽  
Gas Cloud

Duley (1974) has shown that, at the temperatures usually associated with interstellar gas clouds, we would expect CNO grains to be present. During gravitational collapse these grains migrate to the centre of the gas cloud, leading to an enhancement of the heavy-element abundance in the core (Prentice 1976, 1978). It was Krautschneider (1977) who verified such a scenario, by considering the dynamical collapse of gas and grain clouds. If such an initial radial abundance inhomogeneity existed, Prentice (1976a) showed that this configuration may well survive the later convective mixing phase and thus approach the zero-age main-sequence (ZAMS) with a small (-v 3% by mass) metal enhanced core.

Problems on gravitational collapse of interstellar gas clouds

1978 ◽  
Vol 56 (2) ◽  
pp. 303-321 ◽  
Author(s):  
F. Ferraioli ◽  
T. Ruggeri ◽  
N. Virgopia
Keyword(s):  
Gravitational Collapse ◽  
Interstellar Gas

scholarly journals Star formation in molecular clouds

1985 ◽  
Vol 106 ◽  
pp. 561-566
Author(s):  
Frank H. Shu
Keyword(s):  
Star Formation ◽  
Gravitational Collapse ◽  
Molecular Gas ◽  
Interstellar Gas ◽  
Low Mass Stars ◽  
Neutral Gas ◽  
Ultimate Source ◽  
The Galaxy ◽  
Low Mass ◽  
Cloud Cores

We examine how star formation occurs in the Galaxy and come to the following conclusions. (1) The distribution of newly-born stars in the Galaxy depends on the origin of giant-molecular-cloud complexes. For individual complexes, we favor the mechanism of Parker's instability behind galactic shocks. The production of “supercomplexes” may require the mediation of Jeans instability in the interstellar gas. (2) Magnetic fields help to support the clumps of molecular gas making up a complex against gravitational collapse. On a timescale of 107 years, these fields slip by ambipolar diffusion relative to the neutral gas, leading to the formation of dense cloud cores. This timescale is the expected spread in ages of stars born in any clump. (3) When the cores undergo gravitational collapse, they usually give rise to low-mass stars on a timescale of 105 years. (4) What shuts off the accretion flow and determines the mass of a new star is the onset of a powerful stellar wind. The ultimate source of energy for driving this wind in low-mass stars is the release of the energy of differential rotation acquired during the protostellar phase of evolution. The release is triggered by the entire protostar being driven convectively unstable when deuterium burning turns on.

Interstellar gas in the central region of the Galaxy

1967 ◽  
Vol 31 ◽  
pp. 239-251 ◽  
Author(s):  
F. J. Kerr
Keyword(s):  
Central Region ◽  
Galactic Plane ◽  
Neutral Hydrogen ◽  
Continuum Emission ◽  
Galactic Centre ◽  
Interstellar Gas ◽  
Hydrogen Recombination ◽  
The Galaxy ◽  
Centre Region ◽  
The Relationship

A review is given of information on the galactic-centre region obtained from recent observations of the 21-cm line from neutral hydrogen, the 18-cm group of OH lines, a hydrogen recombination line at 6 cm wavelength, and the continuum emission from ionized hydrogen.Both inward and outward motions are important in this region, in addition to rotation. Several types of observation indicate the presence of material in features inclined to the galactic plane. The relationship between the H and OH concentrations is not yet clear, but a rough picture of the central region can be proposed.

Supernovae and interstellar gas dynamics

1967 ◽  
Vol 31 ◽  
pp. 117-119
Author(s):  
F. D. Kahn ◽  
L. Woltjer
Keyword(s):  
Lower Limit ◽  
High Velocity ◽  
Gas Dynamics ◽  
Interstellar Cloud ◽  
Interstellar Gas ◽  
Random Motions ◽  
Relativistic Particles

The efficiency of the transfer of energy from supernovae into interstellar cloud motions is investigated. A lower limit of about 0·002 is obtained, but values near 0·01 are more likely. Taking all uncertainties in the theory and observations into account, the energy per supernova, in the form of relativistic particles or high-velocity matter, needed to maintain the random motions in the interstellar gas is estimated as 1051·4±1ergs.

Remarks on the diffuse interstellar lines

1967 ◽  
Vol 31 ◽  
pp. 91-93 ◽  
Author(s):  
G. Herzberg
Keyword(s):  
Hydrogen Atoms ◽  
Interstellar Gas

It is suggested that the diffuse interstellar lines are produced in the interstellar gas by molecules consisting of a few hydrogen atoms and one other atom, such as CH4+ or NH4. Diffuseness of the lines is assumed to result from predissociation of these molecules.

NEW BACKGROUND INFRARED SOURCES FOR STUDYING THE GALACTIC CENTER'S INTERSTELLAR GAS

2015 ◽  
Author(s):  
Thomas Geballe ◽  
C Westrick ◽  
Miwa Goto ◽  
B. Schlegelmilch ◽  
S. Yeh ◽  
...  
Keyword(s):  
Interstellar Gas ◽  
Infrared Sources

Introduction

2018 ◽  
Author(s):  
Flavio Mercati
Keyword(s):  
Field Theory ◽  
General Relativity ◽  
Gravitational Collapse ◽  
Present State ◽  
Strong Gravity ◽  
Shape Dynamics

Shape Dynamics (SD) is a field theory that describes gravity in a different way than General Relativity (GR): it assumes a preferred notion of simultaneity, and the dynamical content of the theory consists of conformal 3- geometries. SD coincides with (GR) in most situations, in particular in the experimentally well-tested regimes, but it departs from it in some strong-gravity situations, for example at cosmological singularities or upon gravitational collapse. This chapter provides a quick introduction to the theory and a brief description of its present state.

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