High-resolution interstellar spectroscopy and star formation

1981 ◽  
Vol 303 (1480) ◽  
pp. 565-579 ◽  
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Molecular Spectroscopy ◽  
Active Regions ◽  
Infrared Source ◽  
Very Large Array ◽  
Dark Clouds ◽  
The Past ◽  
Different Types ◽  
Interstellar Molecular Clouds

During the past several years, high spatial and spectral resolution molecular spectroscopy has greatly contributed to our knowledge of the physics, dynamics and chemistry of interstellar molecular clouds and thus has led to a better understanding of the conditions that lead to star formation. According to their physical properties, molecular clouds can be grouped into four different types: (i) the dark clouds, (ii) the molecular clouds associated with H+ regions, (iii) the ‘protostellar’ (or maser) environment, and (iv) the molecular envelopes of late-type stars. The first three types of cloud contain generally active regions of star formation. As typical examples the properties are discussed of individual clouds such as TMC 1 and L 183 for the cold clouds, S 140 and S 106 for the warm dark clouds with embedded infrared source, and Orion A for a region with associated H+ region. In S 140, NH 3 is clumped on a scale of not more than 20", whereas recent observations towards Orion A with the Very Large Array show that NH 3 clumps on a scale smaller than 5".

scholarly journals Kinematics and Dynamics of Dense Clouds

1977 ◽  
Vol 75 ◽  
pp. 69-94
Author(s):  
James Lequeux
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Molecular Clouds ◽  
Kinematics And Dynamics ◽  
Interstellar Molecular Clouds ◽  
Maser Sources

Star formation is widely considered as resulting from the collapse of interstellar molecular clouds. The purpose of this paper is to review the observational evidences for collapse in dense clouds, and also for the factors which can play against collapse (turbulence, rotation, magnetic field). We shall also examine to which extent the maser sources (OH, H2O, SiO) can be related to star formation. An overlap with the review papers given by P. Thaddeus, P.G. Mezger, and to some extent by C.G. Wynn-Williams and L. Mestel appears unavoidable.

scholarly journals A Historical Review of Star Formation: Observation and Theory

1987 ◽  
Vol 115 ◽  
pp. 57-57
Author(s):  
Kenneth R. Lang
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Interstellar Dust ◽  
Historical Context ◽  
Historical Review ◽  
Interstellar Space ◽  
Giant Molecular Clouds ◽  
Dark Clouds ◽  
T Tauri ◽  
Infrared Stars

We present a historical review of evidence for ongoing star formation in our Galaxy beginning with the discovery that interstellar space is not empty. The discoveries of interstellar dust, interstellar hydrogen and molecular clouds are reviewed. Observational investigations of dark clouds are then traced from the photographs of Edward Emerson Barnard to contemporary studies of their molecular constituents. A historical overview of observational evidence for new-born stars includes T-Tauri stars, young stellar clusters, sequential star birth and infrared stars beginning with Alfred Joy, Merle Walker, Becklin, and Neugebauer, and Adrian Blaauw and continuing to giant molecular clouds and IRAS. Theoretical studies of gravitational collapse and the early stages of stellar evolution are also placed within a historical context.

Fossil magnetic fields and rotation of early-type stars

1994 ◽  
Vol 162 ◽  
pp. 184-185
Author(s):  
A.E. Dudorov
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Magnetic Fields ◽  
Molecular Clouds ◽  
Main Sequence ◽  
Early Type ◽  
Main Sequence Stars ◽  
Early Type Stars ◽  
Quadrupole Magnetic Field ◽  
Interstellar Molecular Clouds

Observational data of the last 10 years allow two main conclusions:a) Main sequence stars can be separated in two classes: - magnetic (Bp) stars with surface strengths of a dipole or quadrupole magnetic field of Bs ≈ n · (102 − 103) G, n = 2,3,4…7, and - normal main sequence stars (F-O) with magnetic fields Bs ≈ 1 − 100 G (< 300 G);b) Typical star formation takes place in interstellar molecular clouds with magnetic field strengths B ≈ 10-5 G (See Dudorov 1990).

scholarly journals The irreplaceable role of ubiquitous cosmic rays in the space chemistry: from the origin of complex species in interstellar molecular clouds to the ozone depletion in the atmospheres of Earth-like planets

2020 ◽  
pp. 37-54
Author(s):  
Ararat Yeghikyan
Keyword(s):  
Star Formation ◽  
Cosmic Rays ◽  
Atmospheric Chemistry ◽  
Ozone Depletion ◽  
Molecular Clouds ◽  
Complex Species ◽  
The Galaxy ◽  
Earth Like Planets ◽  
Interstellar Molecular Clouds

A review is given of low-energy cosmic rays (1 MeV-10 GeV), which play an important role in the physics and chemistry of interstellar medium of our Galaxy. According to the generally accepted theory of star formation, cosmic rays penetrate into molecular clouds and ionize the dense gaseous medium of star formation centers besides due to a process of ambipolar diffusion they establish a star formation time scale of about 100-1000 thousand years. The source of cosmic rays in the Galaxy are supernovae remnants where diffusion acceleration at the shock front accelerates particles up to energies of 1015 eV. Being the main source of ionization in the inner regions of molecular clouds, cosmic rays play a fundamental role in the global chemistry of clouds, triggering the entire chain of ion-molecular reactions that make it possible to obtain basic molecules. The review also noted the importance of cosmic rays in atmospheric chemistry: playing a significant role in the formation of nitric oxide, especially with an increase in the flux, they cause a decrease in the concentration of ozone in the atmosphere with all climatic consequences.

scholarly journals Magnetic Fields in Molecular Clouds—Observation and Interpretation

Galaxies ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 41
Author(s):  
Hua-Bai Li
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Molecular Clouds ◽  
Zeeman Effect ◽  
Ambipolar Diffusion ◽  
Grain Alignment ◽  
The Past ◽  
Turbulence Velocity ◽  
Cloud Cores ◽  
Dust Grain

The Zeeman effect and dust grain alignment are two major methods for probing magnetic fields (B-fields) in molecular clouds, largely motivated by the study of star formation, as the B-field may regulate gravitational contraction and channel turbulence velocity. This review summarizes our observations of B-fields over the past decade, along with our interpretation. Galactic B-fields anchor molecular clouds down to cloud cores with scales around 0.1 pc and densities of 104–5 H2/cc. Within the cores, turbulence can be slightly super-Alfvénic, while the bulk volumes of parental clouds are sub-Alfvénic. The consequences of these largely ordered cloud B-fields on fragmentation and star formation are observed. The above paradigm is very different from the generally accepted theory during the first decade of the century, when cloud turbulence was assumed to be highly super-Alfvénic. Thus, turbulence anisotropy and turbulence-induced ambipolar diffusion are also revisited.

scholarly journals The Scaling of Star Formation: from Molecular Clouds to Galaxies

2014 ◽  
Vol 10 (S309) ◽  
pp. 121-128
Author(s):  
Daniela Calzetti
Keyword(s):  
Star Formation ◽  
Recent Work ◽  
Molecular Clouds ◽  
Gas Content ◽  
Scaling Relations ◽  
Scaling Relation ◽  
The Past ◽  
Tremendous Progress ◽  
Observing Techniques

AbstractThis is a review of the extant literature and recent work on the scaling relation(s) that link the gas content of galaxies to the measured star formation rates. A diverse array of observing techniques and underlying physical assumptions characterize the determination of these relations at different scales, that range from the tens of parsec sizes of molecular clouds to the tens of kpc sizes of whole galaxies. Different techniques and measurements, and a variety of strategies, have been used by many authors to compare the scaling relations, both within and across galaxies. Although the picture is far from final, the past decade has seen tremendous progress in this field, and more progress is expected over the next several years.

scholarly journals Sgr A West in the light of molecules: cold and dense gas east of the circumnuclear disk

2013 ◽  
Vol 9 (S303) ◽  
pp. 86-88 ◽  
Author(s):  
Lydia Moser ◽  
A. Eckart ◽  
A. Borkar ◽  
M. García-Marin ◽  
D. Kunneriath ◽  
...  
Keyword(s):  
Black Hole ◽  
Star Formation ◽  
Molecular Clouds ◽  
Near Infrared ◽  
Line Emission ◽  
Dense Gas ◽  
Dark Clouds ◽  
Supermassive Black Hole ◽  
Circumnuclear Disk ◽  
Sgr A

AbstractWe present the very first detection of N2H+J = (1 – 0) and CH3OH(2k−1k) line emission on 5″ scales in the circumnuclear disk (CND) around Sgr A*. The emission matches the position and shape of the dark clouds in the near-infrared. Our findings suggest that these molecular clouds in the eastern CND are significantly colder and denser than the rest of the CND, and partially shocked. The research on these dark clouds will contribute to understanding the processes of star formation close to a supermassive black hole.

scholarly journals Infrared Dark Clouds and High-mass Star Formation Activity in Galactic Molecular Clouds

2020 ◽  
Vol 897 (1) ◽  
pp. 53 ◽  
Author(s):  
R. Retes-Romero ◽  
Y. D. Mayya ◽  
A. Luna ◽  
L. Carrasco
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
High Mass ◽  
Mass Star ◽  
Dark Clouds ◽  
Star Formation Activity ◽  
Infrared Dark Clouds

scholarly journals Molecular spectral line surveys and the organic molecules in the interstellar molecular clouds

2008 ◽  
Vol 4 (S251) ◽  
pp. 17-26 ◽  
Author(s):  
Masatoshi Ohishi
Keyword(s):  
Molecular Clouds ◽  
Organic Molecules ◽  
Spectral Lines ◽  
Giant Molecular Clouds ◽  
Dark Clouds ◽  
Organic Species ◽  
Independent Observations ◽  
Grain Surface ◽  
Interstellar Molecular Clouds ◽  
Recent Claim

AbstractIt is known that more than 140 interstellar and circumstellar molecules have so far been detected, mainly by means of the radio astronomy observations. Many organic molecules are also detected, including alcohols, ketons, ethers, aldehydes, and others, that are distributed from dark clouds and hot cores in the giant molecular clouds. It is believed that most of the organic molecules in space are synthesized through the grain surface reactions, and are evaporated from the grain surface when they are heated up by the UV radiation from adjacent stars.On the other hand the recent claim on the detection of glycine have raised an important issue how difficult it is to confirm secure detection of weak spectra from less abundant organic molecules in the interstellar molecular cloud.I will review recent survey observations of organic molecules in the interstellar molecular clouds, including independent observations of glycine by the 45 m radio telescope in Japan, and will discuss the procedure to securely identify weak spectral lines from organic molecules and the importance of laboratory measurement of organic species.

Geometry of Hα Active Region Loops Observed on the Solar Disk

1983 ◽  
Vol 5 (2) ◽  
pp. 204-208 ◽  
Author(s):  
Chen Chuan-le ◽  
R. E. Loughhead
Keyword(s):  
Active Regions ◽  
Ground Level ◽  
Optical Observations ◽  
Large Array ◽  
Very Large Array ◽  
X Ray ◽  
The Past ◽  
Geometrical Shapes ◽  
Microwave Sources ◽  
Made In

Plasma loops are the dominant structures, in the higher levels of the Sun’s atmosphere above active regions. Much of our knowledge of their properties has come from space observations made over the past decade or so in the EUV and X-ray regions of the spectrum and, more recently, from high-resolution, two-dimensional images of microwave sources obtained with the Very Large Array radio interferometer (VLA). On the other hand, the spatial resolution of rocket and satellite observations has so far generally failed to match that of ground-level optical observations made in Hα and other strong chromospheric lines. The latter permit one to study in much greater detail the morphology of individual loops, as illustrated for example in the recent work of Loughhead, Wang and Blows (1983). These authors addressed themselves to the task of determining the true geometrical shapes of individual loops, a problem which had hitherto received little attention.

Sign in / Sign up

Export Citation Format

Share Document