Problems of Gravitational Stability in the Presence of a Magnetic Field.

Chandrasekhar, S.; Fermi, E.

doi:10.1086/145732

Cited by 708 publications

(518 citation statements)

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“…Both the gravitational and magnetic forces obey inverse-square power-law behaviour, and so in both cases, n = −2. This result was shown by Chandrasekhar & Fermi (1953b).…”

Section: The Virial Theoremsupporting

confidence: 60%

“…The three forces, other than the internal energy, which we consider to be significant to the virial balance of starless cores are the gravitational force (Clausius 1870), the electro-magnetic force (Chandrasekhar & Fermi 1953b), and the force due to external pressure on the core (Spitzer 1978). The first two of these are conservative forces, and can hence be described by the gradient of a potential, V , i.e.…”

Section: The Virial Theoremmentioning

confidence: 99%

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Submillimetre Studies of Prestellar and Starless Cores in the Ophiuchus, Taurus and Cepheus Molecular Clouds

Pattle¹

2017

Springer Theses

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“…Both the gravitational and magnetic forces obey inverse-square power-law behaviour, and so in both cases, n = −2. This result was shown by Chandrasekhar & Fermi (1953b).…”

Section: The Virial Theoremsupporting

confidence: 60%

Section: The Virial Theoremmentioning

confidence: 99%

Submillimetre Studies of Prestellar and Starless Cores in the Ophiuchus, Taurus and Cepheus Molecular Clouds

Pattle¹

2017

Springer Theses

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“…The Herschel Space Observatory HiGal survey has confirmed the near-ubiquity of filamentary structures in the Galactic plane, often associated with regions of active, massive star formation (Molinari et al 2010). These observations have renewed interest in cylindrical accretion geometries (Chandrasekhar & Fermi 1953)-"sausage" instabilities that form clusters with regular spacings along filaments (Nagasawa 1987;Jackson et al 2010)-and hybrid scenarios involving accretion via cylindrical filaments onto dense, spherical molecular cloud cores, often observed at the nodal points where filaments intersect (Myers 2009;Hennemann et al 2012;Palmeirim et al 2013). …”

Section: Introductionmentioning

confidence: 99%

RAPID CIRCUMSTELLAR DISK EVOLUTION AND AN ACCELERATING STAR FORMATION RATE IN THE INFRARED DARK CLOUD M17 SWex

Povich

Townsley

Robitaille

et al. 2016

ApJ

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We present a catalog of 840 X-ray sources and first results from a 100 ks Chandra X-ray Observatory imaging study of the filamentary infrared (IR) dark cloud G014.225-00.506, which forms the central regions of a larger cloud complex known as the M17 southwest extension (M17 SWex). In addition to the rich population of protostars and young stellar objects with dusty circumstellar disks revealed by archival data from the Spitzer Space Telescope, we discover a population of X-ray-emitting, intermediate-mass pre-main-sequence stars that lack IR excess emission from circumstellar disks. We model the IR spectral energy distributions of this source population to measure its mass function and place new constraints on the destruction timescales for the inner dust disk for 2-8 M ☉ stars. We also place a lower limit on the star formation rate (SFR) and find that it is quite high (  M 0.007 M ☉ yr −1 ), equivalent to several Orion Nebula Clusters in G14.225-0.506 alone, and likely accelerating. The cloud complex has not produced a population of massive, O-type stars commensurate with its SFR. This absence of very massive (20 M ☉ ) stars suggests that either (1) M17 SWex is an example of a distributed mode of star formation that will produce a large OB association dominated by intermediate-mass stars but relatively few massive clusters, or (2) the massive cores are still in the process of accreting sufficient mass to form massive clusters hosting O stars.

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“…Other authors(e.g. Ebert 1964;Cameron 1972) assume that the cloud flattens into a disk-like structure, without much angular momentum redistribution. The mass is concentrated towards the centre via the same gross gravitational instability that yields the flat rotation curve in disk-like galaxies (Mestel 1963;Hunter 1963).…”

Section: Weakly Magnetic Rotating Systemsmentioning

confidence: 99%

“…A cool, dense, roughly spherical cloud at temperature T, with mean density ρ and mean molecular weight y, immersed in a hot, low-density intercloud medium will collapse if its mass M exceeds a critical mass M -2[(^T/y) 3 /G 3 p]i (Ebert 1955;Bonnor 1956;McCrea 1957). This "Jeans mass" is close to that of a sphere of density ρ and radius equal to the "Jeans length" that emerges from the classical but non-rigorous treatment of gravitational instability.…”

mentioning

confidence: 99%

Theoretical Processes in Star Formation

Mestel

1977

Symp. - Int. Astron. Union

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To bring out the basic problem of star formation, consider a non-rotating cosmical gas cloud which is free to contract and so to convert most of its gravitational energy into kinetic energy of mass motion. Fluid dynamical systems in general tend to dissipate their kinetic energy, and a diffuse gas cloud easily radiates excess heat. If the cloud did not break up into fragments, then the steady conversion of gravitational energy into radiation would lead ultimately into the formation of a compact massive body - perhaps a quasar - but not of a star cluster, which is maintained at a comparatively low mean density by random stellar kinetic energy. Thus the transition from a gravitationally-bound cloud of gas and dust into a bound star cluster - or a fortiori into an expanding O-B association - requires that gravitational energy released during collapse be conserved as the random macroscopic kinetic energy. It is very likely that star formation is often triggered by processes that are essentially dissipative, such as shocks following passage of the spiral wave, or cloud-cloud collisions; however, it is equally important to emphasise that we require at some stage a cut-off in kinetic energy dissipation. And indeed, once a cloud has been able to fragment into a group of self-gravitating blobs, each of small geometrical cross-section, the chance of inelastic collisions between blobs is sharply reduced.

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Problems of Gravitational Stability in the Presence of a Magnetic Field.

Cited by 708 publications

References 0 publications

Submillimetre Studies of Prestellar and Starless Cores in the Ophiuchus, Taurus and Cepheus Molecular Clouds

Submillimetre Studies of Prestellar and Starless Cores in the Ophiuchus, Taurus and Cepheus Molecular Clouds

RAPID CIRCUMSTELLAR DISK EVOLUTION AND AN ACCELERATING STAR FORMATION RATE IN THE INFRARED DARK CLOUD M17 SWex

Theoretical Processes in Star Formation

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