UV penetrated clumpy molecular cloud cores

Recent observations of sub-mm and far-IR atomic fine structure and molecular rotational lines give evidence that due to the clumpiness of the molecular cloud cores the UV radiation from newly formed stars affects a very large fraction of the cloud material. Direct observations of the clumpy structure in M17 SW allow to derive several parameters of the clump distribution, in particular the clump mass spectrum and the volume filling factor. Implications of these results in regard to star formation are shortly discussed.

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Triggered formation and collapse of molecular cloud cores

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307001561 ◽

2006 ◽

Vol 2 (S237) ◽

pp. 251-257

Author(s):

Anthony P. Whitworth

Keyword(s):

Mass Spectrum ◽

Star Formation ◽

Turbulent Flows ◽

Molecular Cloud ◽

External Pressure ◽

Minimum Mass ◽

Core Formation ◽

Core Mass ◽

The Core ◽

Cloud Cores

AbstractFirst I discuss the dynamics of core formation in two scenarios relevant to triggered star formation, namely the fragmentation of shock-compressed layers created by colliding turbulent flows and the fragmentation of shells swept up by expanding nebulae. Second I discuss the influence of thermodynamics on the core mass spectrum, on determining which cores are ‘pre-stellar’ (i.e. destined to spawn stars) and on the minimum mass for a pre-stellar core. Third, I discuss the properties of pre-existing cores whose collapse has been triggered by an increase in external pressure, and compare the results with observations of collapsing pre-stellar cores and evaporating gaseous globules (EGGs).

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Aperture synthesis CS and 98 GHz continuum observations of protostellar IRAS sources in Taurus

Symposium - International Astronomical Union ◽

10.1017/s0074180900239673 ◽

1991 ◽

Vol 147 ◽

pp. 353-356

Author(s):

N. Ohashi ◽

R. Kawabe ◽

M. Hayashi ◽

M. Ishiguro

Keyword(s):

Molecular Cloud ◽

Total Mass ◽

T Tauri Stars ◽

Continuum Emission ◽

Beam Size ◽

Dust Grains ◽

Dynamical Mass ◽

T Tauri ◽

Cloud Cores ◽

The Continuum

The CS (J = 2 — 1) line and 98 GHz continuum emission have been observed for 11 protostellar IRAS sources in the Taurus molecular cloud with resolutions of 2.6″−8.8″ (360 AU—1200 AU) using the Nobeyama Millimeter Array (NMA). The CS emission is detected only toward embedded sources, while the continuum emission from dust grains is detected only toward visible T Tauri stars except for one embedded source, L1551-IRS5. This suggests that the dust grains around the embedded sources do not centrally concentrate enough to be detected with our sensitivity (∼4 m Jy r.m.s), while dust grains in disks around the T Tauri stars have enough total mass to be detected with the NMA. The molecular cloud cores around the embedded sources are moderately extended and dense enough to be detected in CS, while gas disks around the T Tauri are not detected because the radius of such gas disks may be smaller than 70 (50 K/Tex) AU. These results imply that the total amount of matter within the NMA beam size must increase when the central objects evolve into T Tauri stars from embedded sources, suggesting that the compact and highly dense disks around T Tauri stars are formed by the dynamical mass accretion during the embedded protostar phase.

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Chemical variation in molecular cloud cores in the Orion A Cloud. III

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psu116 ◽

2014 ◽

Vol 66 (6) ◽

pp. 119 ◽

Cited By ~ 10

Author(s):

Satoshi Ohashi ◽

Ken'ichi Tatematsu ◽

Minho Choi ◽

Miju Kang ◽

Tomofumi Umemoto ◽

...

Keyword(s):

Molecular Cloud ◽

Chemical Variation ◽

Cloud Cores

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Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1518183113 ◽

2016 ◽

Vol 113 (8) ◽

pp. 2011-2016 ◽

Cited By ~ 84

Author(s):

Elishevah M. M. E. Van Kooten ◽

Daniel Wielandt ◽

Martin Schiller ◽

Kazuhide Nagashima ◽

Aurélien Thomen ◽

...

Keyword(s):

Solar System ◽

Thermal Processing ◽

Molecular Cloud ◽

Decay Product ◽

Isotopic Signature ◽

Carbonaceous Chondrites ◽

Outer Solar System ◽

Precursor Material ◽

System Composition ◽

Cloud Material

The short-lived 26Al radionuclide is thought to have been admixed into the initially 26Al-poor protosolar molecular cloud before or contemporaneously with its collapse. Bulk inner Solar System reservoirs record positively correlated variability in mass-independent 54Cr and 26Mg*, the decay product of 26Al. This correlation is interpreted as reflecting progressive thermal processing of in-falling 26Al-rich molecular cloud material in the inner Solar System. The thermally unprocessed molecular cloud matter reflecting the nucleosynthetic makeup of the molecular cloud before the last addition of stellar-derived 26Al has not been identified yet but may be preserved in planetesimals that accreted in the outer Solar System. We show that metal-rich carbonaceous chondrites and their components have a unique isotopic signature extending from an inner Solar System composition toward a 26Mg*-depleted and 54Cr-enriched component. This composition is consistent with that expected for thermally unprocessed primordial molecular cloud material before its pollution by stellar-derived 26Al. The 26Mg* and 54Cr compositions of bulk metal-rich chondrites require significant amounts (25–50%) of primordial molecular cloud matter in their precursor material. Given that such high fractions of primordial molecular cloud material are expected to survive only in the outer Solar System, we infer that, similarly to cometary bodies, metal-rich carbonaceous chondrites are samples of planetesimals that accreted beyond the orbits of the gas giants. The lack of evidence for this material in other chondrite groups requires isolation from the outer Solar System, possibly by the opening of disk gaps from the early formation of gas giants.

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