Physical Properties of Prestellar Cores

The Origin of Stars and Planets: The VLT View - ESO ASTROPHYSICS SYMPOSIA ◽

10.1007/10856518_3 ◽

2006 ◽

pp. 29-36

Author(s):

Malcolm Walmsley ◽

Paola Caselli ◽

Antonio Zucconi ◽

Daniele Galli

Keyword(s):

Physical Properties ◽

Prestellar Cores

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Investigating the Physical Properties and Fragmentation of the AFGL 333-Ridge

The Astronomical Journal ◽

10.3847/1538-3881/ac2aa5 ◽

2021 ◽

Vol 162 (6) ◽

pp. 239

Author(s):

Xiaolian Liang ◽

Jin-Long Xu ◽

Jun-Jie Wang

Keyword(s):

Physical Properties ◽

Velocity Dispersion ◽

Massive Stars ◽

Mass Density ◽

Critical Value ◽

Mass Relation ◽

Linear Mass ◽

Thermal Pressure ◽

Prestellar Cores ◽

Spacing Length

Abstract We present multiwavelength data to investigate the physical properties and fragmentation of AFGL 333-Ridge. A statistical analysis of velocity dispersion indicates that turbulence is the dominant motion in the ridge. However, the linear mass density (1124.0 M ⊙/pc) of AFGL 333-Ridge far exceeds its critical value of 406.5 M ⊙/pc, suggesting that additional motions are required to prevent the filament radial collapse. Using the getsources algorithm, we identified 14 cores from the Herschel maps, including two protostellar cores and 12 starless cores. All of these starless cores are gravitationally bound, and are therefore considered to be prestellar cores. Based on their radius-mass relation, 11 of 14 cores have the potential to form massive stars. Moreover, the seven cores in two subfilaments of AFGL 333-Ridge seem to constitute two necklace-like chains with a spacing length of 0.51 and 0.45 pc, respectively. Compared the spacing length with theoretical prediction lengths by Jeans and cylindrical fragmentations, we argued that the combination of turbulence and thermal pressure may lead to the fragmentation of the two subfilaments into the cores.

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Physical Properties of Prestellar Cores

Astrophysics and Space Science Library - Cores to Clusters ◽

10.1007/0-387-26357-8_1 ◽

2008 ◽

pp. 3-14

Author(s):

Malcolm Walmsley

Keyword(s):

Physical Properties ◽

Prestellar Cores

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Physical properties and chemical composition of the cores in the California molecular cloud

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833622 ◽

2018 ◽

Vol 620 ◽

pp. A163 ◽

Cited By ~ 5

Author(s):

Guo-Yin Zhang ◽

Jin-Long Xu ◽

A. I. Vasyunin ◽

D. A. Semenov ◽

Jun-Jie Wang ◽

...

Keyword(s):

Star Formation ◽

Chemical Composition ◽

Physical Properties ◽

Molecular Cloud ◽

Initial Conditions ◽

Mass Function ◽

High Mass ◽

Core Mass ◽

Prestellar Cores ◽

Formation Efficiency

Aims. We aim to reveal the physical properties and chemical composition of the cores in the California molecular cloud (CMC), so as to better understand the initial conditions of star formation. Methods. We made a high-resolution column density map (18.2′′) with Herschel data, and extracted a complete sample of the cores in the CMC with the fellwalker algorithm. We performed new single-pointing observations of molecular lines near 90 GHz with the IRAM 30m telescope along the main filament of the CMC. In addition, we also performed a numerical modeling of chemical evolution for the cores under the physical conditions. Results. We extracted 300 cores, of which 33 are protostellar and 267 are starless cores. About 51% (137 of 267) of the starless cores are prestellar cores. Three cores have the potential to evolve into high-mass stars. The prestellar core mass function (CMF) can be well fit by a log-normal form. The high-mass end of the prestellar CMF shows a power-law form with an index α = −0.9 ± 0.1 that is shallower than that of the Galactic field stellar mass function. Combining the mass transformation efficiency (ε) from the prestellar core to the star of 15 ± 1% and the core formation efficiency (CFE) of 5.5%, we suggest an overall star formation efficiency of about 1% in the CMC. In the single-pointing observations with the IRAM 30m telescope, we find that 6 cores show blue-skewed profile, while 4 cores show red-skewed profile. [HCO+]/[HNC] and [HCO+]/[N2H+] in protostellar cores are higher than those in prestellar cores; this can be used as chemical clocks. The best-fit chemical age of the cores with line observations is ~5 × 104 yr.

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The Photometric Properties of the Ap Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100080684 ◽

1976 ◽

Vol 32 ◽

pp. 365-377 ◽

Cited By ~ 2

Author(s):

B. Hauck

Keyword(s):

Physical Properties ◽

Ap Stars

The Ap stars are numerous - the photometric systems tool It would be very tedious to review in detail all that which is in the literature concerning the photometry of the Ap stars. In my opinion it is necessary to examine the problem of the photometric properties of the Ap stars by considering first of all the possibility of deriving some physical properties for the Ap stars, or of detecting new ones. My talk today is prepared in this spirit. The classification by means of photoelectric photometric systems is at the present time very well established for many systems, such as UBV, uvbyβ, Vilnius, Geneva and DDO systems. Details and methods of classification can be found in Golay (1974) or in the proceedings of the Albany Colloquium edited by Philip and Hayes (1975).

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The Infection of Cells by Bullet-Shaped Viruses

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100063779 ◽

1969 ◽

Vol 27 ◽

pp. 372-373

Author(s):

Frederick A. Murphy ◽

Alyne K. Harrison ◽

Sylvia G. Whitfield

Keyword(s):

Electron Microscopy ◽

Physical Properties ◽

Host Cell ◽

Thin Section ◽

Cultured Cells ◽

Cell Infection ◽

Thin Section Electron Microscopy ◽

Section Electron ◽

Section Electron Microscopy

The bullet-shaped viruses are currently classified together on the basis of similarities in virion morphology and physical properties. Biologically and ecologically the member viruses are extremely diverse. In searching for further bases for making comparisons of these agents, the nature of host cell infection, both in vivo and in cultured cells, has been explored by thin-section electron microscopy.

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Transmission electron microscopy of composite materials

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100107125 ◽

1988 ◽

Vol 46 ◽

pp. 1012-1015

Author(s):

K.P.D. Lagerlof

Keyword(s):

Composite Materials ◽

Physical Properties ◽

Structural Defects ◽

Structural Composites ◽

Multiphase Materials ◽

Structural Reinforcement ◽

Transmission Electron ◽

Reinforced Fiber ◽

Particulate Reinforced Composites ◽

Definition Of

Although most materials contain more than one phase, and thus are multiphase materials, the definition of composite materials is commonly used to describe those materials containing more than one phase deliberately added to obtain certain desired physical properties. Composite materials are often classified according to their application, i.e. structural composites and electronic composites, but may also be classified according to the type of compounds making up the composite, i.e. metal/ceramic, ceramic/ceramie and metal/semiconductor composites. For structural composites it is also common to refer to the type of structural reinforcement; whisker-reinforced, fiber-reinforced, or particulate reinforced composites [1-4].For all types of composite materials, it is of fundamental importance to understand the relationship between the microstructure and the observed physical properties, and it is therefore vital to properly characterize the microstructure. The interfaces separating the different phases comprising the composite are of particular interest to understand. In structural composites the interface is often the weakest part, where fracture will nucleate, and in electronic composites structural defects at or near the interface will affect the critical electronic properties.

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