scholarly journals Masers in SGR B2: Sites of Star-Forming Regions

1987 ◽  
Vol 115 ◽  
pp. 161-163 ◽  
Author(s):  
J. B. Whiteoak ◽  
F. F. Gardner ◽  
J. R. Forster ◽  
P. Palmer ◽  
V. Pankonin
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Large Scale ◽  
Star Forming ◽  
Star Forming Regions ◽  
H Ii Region ◽  
Cloud Complex

H2CO and OH masers in the H II-region/molecular-cloud complex Sgr B2 have been observed with the VLA and combined with other observations of OH and H2O masers. It is found that groups of the masers and compact continuum components are located along a north-south line extending across the complex. The overall alignment suggests that star formation is being triggered by a single large-scale event such as an interaction between molecular clouds.

scholarly journals CO (J=2-1) Observations of the Molecular Cloud Complex in the Galactic Center

1994 ◽  
Vol 140 ◽  
pp. 168-169
Author(s):  
Tomoharu Oka ◽  
Tetsuo Hasegawa ◽  
Masahiko Hayashi ◽  
Toshihiro Handa ◽  
Sei'ichi Sakamoto
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Large Scale ◽  
Galactic Center ◽  
Molecular Gas ◽  
Star Forming ◽  
Near Future ◽  
Cloud Complex ◽  
Mapping Observation

AbstractWe report a large scale mapping observation of the Galactic center region in the CO (J=2-1) line using the Tokyo-NRO 60cm survey telescope. Distribution of the CO (J=2-1) emission in the I-V plane suggests that molecular clouds forms a huge complex (Nuclear Molecular cloud Complex, NMC). Tracers of star formation activities in the last 106-108 years show that star formation has occured in a ring ~ 100 pc in radius. Relative to this Star Forming Ring, the molecular gas is distributed mainly on the positive longitude side. This may indicate that much of the gas in NMC is in transient orbit to fall into the star forming ring or to the nucleus in the near future.

scholarly journals Objective Prism Study of Star Forming Regions

1994 ◽  
Vol 161 ◽  
pp. 470-472
Author(s):  
M. Kun
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Wavelength Region ◽  
Mass Star ◽  
Star Forming ◽  
Millimeter Wavelength ◽  
Star Forming Regions ◽  
Low Mass ◽  
Objective Prism

Radio molecular observations in the millimeter wavelength region in the last decade have revealed a number of giant molecular cloud complexes at relatively high galactic latitudes. Examples for such cloud complexes are Cepheus Flare (Lebrun 1986), and Ursa Major and Camelopardalis clouds (Heithausen et al. 1993). Because of their high galactic latitudes, these cloud complexes probably belong to the nearest molecular clouds and among them we may find some nearby regions of low-mass star formation.

Large-Scale NH3Observations toward the Galactic Star-Forming Regions I. W 51 Molecular Cloud Complex

2008 ◽  
Vol 60 (6) ◽  
pp. 1285-1296 ◽  
Author(s):  
Kazuo Sorai ◽  
Asao Habe ◽  
Hiroyuki Nishitani ◽  
Keita Hosaka ◽  
Yoshimasa Watanabe ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Large Scale ◽  
Star Forming ◽  
Star Forming Regions ◽  
Cloud Complex

scholarly journals Numerical Simulations of Collapse of a Magnetized Rotating Molecular Cloud

1994 ◽  
Vol 140 ◽  
pp. 280-281
Author(s):  
Kanji Ohta ◽  
Asao Habe
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Numerical Simulations ◽  
Formation Process ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Star Forming ◽  
Star Forming Regions ◽  
The Magnetic Field ◽  
Collapse Process

Recent observations reveal the velocity structure of star forming regions and the magnetic field in molecular clouds. It is known from observations that the molecular clouds rotate. It is suggested that the magnetic field have a important roll of the star formation process (e.g. Myers and Goodman 1988) and rotation of cloud have effects for evolution of molecular cloud. However it is not cleared how the magnetic field plays a roll of the star formation process in a rotating cloud.In the previous theoretical studies, most of simulations are performed for collapse process of a rotating cloud without magnetic field (e.g. Miyama et al. 1984, Boss 1990) or collapse process of a magnetized cloud without rotation (e.g. Scott and Black 1980). Dorfi (1982) studied collapse of a magnetized, rotating cloud. However he did not calculate those with high resolutions, since he performed 3-dimensional calculations of about 6000 grid points.Since observation instruments have been developed, it is possible to observe the star forming regions with good resolution. We study the collapse of the rotating, magnetized, isothermal cloud by mean of the axisymmetric numerical simulations with high resolution.

scholarly journals FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 m telescope (FUGIN). VI. Dense gas and mini-starbursts in the W 43 giant molecular cloud complex

2020 ◽  
Author(s):  
Mikito Kohno ◽  
Kengo Tachihara ◽  
Kazufumi Torii ◽  
Shinji Fujita ◽  
Atsushi Nishimura ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Large Scale ◽  
Galactic Plane ◽  
High Mass ◽  
Mass Star ◽  
Dense Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Giant Molecular Cloud ◽  
Cloud Complex

Abstract We performed new large-scale 12CO, 13CO, and C18O J = 1–0 observations of the W 43 giant molecular cloud complex in the tangential direction of the Scutum arm (l ∼30°) as a part of the FUGIN project. The low-density gas traced by 12CO is distributed over 150 pc × 100 pc (l × b), and has a large velocity dispersion (20–30 km s−1). However, the dense gas traced by C18O is localized in the W 43 Main, G30.5, and W 43 South (G29.96−0.02) high-mass star-forming regions in the W 43 giant molecular cloud (GMC) complex, which have clumpy structures. We found at least two clouds with a velocity difference of ∼10–20 km s−1, both of which are likely to be physically associated with these high-mass star-forming regions based on the results of high 13CO J = 3–2 to J = 1–0 intensity ratio and morphological correspondence with the infrared dust emission. The velocity separation of these clouds in W 43 Main, G30.5, and W 43 South is too large for each cloud to be gravitationally bound. We also revealed that the dense gas in the W 43 GMC has a high local column density, while “the current SFE” (star formation efficiency) of the entire GMC is low ($\sim\!\! 4\%$) compared with the W 51 and M 17 GMC. We argue that the supersonic cloud–cloud collision hypothesis can explain the origin of the local mini-starbursts and dense gas formation in the W 43 GMC complex.

scholarly journals The Formation and Destruction of Molecular Clouds and Galactic Star Formation

2015 ◽  
Vol 11 (S315) ◽  
pp. 61-68
Author(s):  
Shu-ichiro Inutsuka ◽  
Tsuyoshi Inoue ◽  
Kazunari Iwasaki ◽  
Takashi Hosokawa ◽  
Masato I. N. Kobayashi
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Massive Stars ◽  
Age Determination ◽  
Mass Function ◽  
Mass Star ◽  
Nearby Star ◽  
Star Forming ◽  
Star Forming Regions

AbstractWe discuss an overall picture of star formation in the Galaxy. Recent high-resolution magneto-hydrodynamical simulations of two-fluid dynamics with cooling/heating and thermal conduction have shown that the formation of molecular clouds requires multiple episodes of supersonic compression. This finding enables us to create a new scenario of molecular cloud formation through interacting shells or bubbles on galactic scales. We estimate the ensemble-averaged growth rate of individual molecular clouds, and predict the associated cloud mass function. This picture naturally explains the accelerated star formation over many million years that was previously reported by stellar age determination in nearby star forming regions. The recent claim of cloud-cloud collisions as a mechanism for forming massive stars and star clusters can be naturally accommodated in this scenario. This explains why massive stars formed in cloud-cloud collisions follows the power-law slope of the mass function of molecular cloud cores repeatedly found in low-mass star forming regions.

scholarly journals The atomic hydrogen/molecular cloud association: an unavoidable relationship

1991 ◽  
Vol 147 ◽  
pp. 37-40
Author(s):  
G. Joncas
Keyword(s):  
Atomic Hydrogen ◽  
Molecular Clouds ◽  
Large Scale ◽  
Young Stars ◽  
Physical Processes ◽  
Star Forming ◽  
Dark Clouds ◽  
Star Forming Regions ◽  
The Impact

The presence of HI in the interstellar medium is ubiquitous. HI is the principal actor in the majority of the physical processes at work in our Galaxy. Restricting ourselves to the topics of this symposium, atomic hydrogen is involved with the formation of molecular clouds and is one of the byproducts of their destruction by young stars. HI has different roles during a molecular cloud's life. I will discuss here a case of coexisting HI and H2 at large scale and the origin of HI in star forming regions. For completeness' sake, it should be mentionned that there are at least three other aspects of HI involvement: HI envelopes around molecular clouds, the impact of SNRs (see work on IC 443), and the role of HI in quiescent dark clouds (see van der Werf's work).

scholarly journals Dusty magnetohydrodynamics in star-forming regions

2010 ◽  
Vol 76 (3-4) ◽  
pp. 569-578
Author(s):  
S. VAN LOO ◽  
S. A. E. G. FALLE ◽  
T. W. HARTQUIST ◽  
O. HAVNES ◽  
G. E. MORFILL
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Number Density ◽  
Star Forming ◽  
Star Forming Regions ◽  
Neutral Gas ◽  
Gas Phase Ions ◽  
Fractional Ionization ◽  
Magnetohydrodynamic Models ◽  
The Magnetic Field

AbstractStar formation occurs in dark molecular regions where the number density of hydrogen nuclei nH exceeds 104 cm−3 and the fractional ionization is 10−7 or less. Dust grains with sizes ranging up to tenths of microns and perhaps down to tens of nanometers contain just less than 1% of the mass. Recombination on grains is important for the removal of gas-phase ions, which are produced by cosmic rays penetrating the dark regions. Collisions of neutrals with charged grains contribute significantly to the coupling of the magnetic field to the neutral gas. Consequently, the dynamics of the grains must be included in the magnetohydrodynamic models of large-scale collapse, the evolution of waves and the structures of shocks important in star formation.

scholarly journals The atomic hydrogen/molecular cloud association: an unavoidable relationship

1991 ◽  
Vol 147 ◽  
pp. 37-40
Author(s):  
G. Joncas
Keyword(s):  
Atomic Hydrogen ◽  
Molecular Clouds ◽  
Large Scale ◽  
Young Stars ◽  
Physical Processes ◽  
Star Forming ◽  
Dark Clouds ◽  
Star Forming Regions ◽  
The Impact

The presence of HI in the interstellar medium is ubiquitous. HI is the principal actor in the majority of the physical processes at work in our Galaxy. Restricting ourselves to the topics of this symposium, atomic hydrogen is involved with the formation of molecular clouds and is one of the byproducts of their destruction by young stars. HI has different roles during a molecular cloud's life. I will discuss here a case of coexisting HI and H2 at large scale and the origin of HI in star forming regions. For completeness' sake, it should be mentionned that there are at least three other aspects of HI involvement: HI envelopes around molecular clouds, the impact of SNRs (see work on IC 443), and the role of HI in quiescent dark clouds (see van der Werf's work).

scholarly journals Deterministic Self-Propagating Star Formation

1989 ◽  
Vol 120 ◽  
pp. 518-523
Author(s):  
Jan Palouš
Keyword(s):  
Star Formation ◽  
Simple Model ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Large Scale ◽  
Galactic Evolution ◽  
Cloud Formation ◽  
Rotating Disks ◽  
Atomic Gas ◽  
High Column

AbstractThe evolution of large scale expanding structures in differentially rotating disks is studied. High column densities in some places may eventually lead to molecular cloud formation and initiate also star-formation. After some time, multi-structured arms evolve, where regions of intensive star-formation are separated from each other by regions of atomic gas or molecular clouds. This is due to the deterministic nature and to the coherence of this process. A simple model of galactic evolution is introduced and the different behaviour of Sa, Sb, and Sc galaxies is shown.

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