scholarly journals Triggered high-mass star formation in the H ii region W 28 A2: A cloud–cloud collision scenario

2020 ◽  
Author(s):  
Katsuhiro Hayashi ◽  
Satoshi Yoshiike ◽  
Rei Enokiya ◽  
Shinji Fujita ◽  
Rin Yamada ◽  
...  
Keyword(s):  
Star Formation ◽  
Intensity Ratio ◽  
Molecular Clouds ◽  
Early Stage ◽  
Infrared Emission ◽  
Radio Continuum ◽  
High Mass ◽  
Continuum Emission ◽  
Mass Star ◽  
H Ii Region

Abstract We report on a study of the high-mass star formation in the H ii region W 28 A2 by investigating the molecular clouds that extend over ∼5–10 pc from the exciting stars using the 12CO and 13CO (J = 1–0) and 12CO (J = 2–1) data taken by NANTEN2 and Mopra observations. These molecular clouds consist of three velocity components with CO intensity peaks at VLSR ∼ −4 km s−1, 9 km s−1, and 16 km s−1. The highest CO intensity is detected at VLSR ∼ 9 km s−1, where the high-mass stars with spectral types O6.5–B0.5 are embedded. We found bridging features connecting these clouds toward the directions of the exciting sources. Comparisons of the gas distributions with the radio continuum emission and 8 μm infrared emission show spatial coincidence/anti-coincidence, suggesting physical associations between the gas and the exciting sources. The 12CO J = 2–1 to 1–0 intensity ratio shows a high value (≳0.8) toward the exciting sources for the −4 km s−1 and +9 km s−1 clouds, possibly due to heating by the high-mass stars, whereas the intensity ratio at the CO intensity peak (VLSR ∼ 9 km s−1) decreases to ∼0.6, suggesting self absorption by the dense gas in the near side of the +9 km s−1 cloud. We found partly complementary gas distributions between the −4 km s−1 and +9 km s−1 clouds, and the −4 km s−1 and +16 km s−1 clouds. The exciting sources are located toward the overlapping region in the −4 km s−1 and +9 km s−1 clouds. Similar gas properties are found in the Galactic massive star clusters RCW 38 and NGC 6334, where an early stage of cloud collision to trigger the star formation is suggested. Based on these results, we discuss the possibility of the formation of high-mass stars in the W 28 A2 region being triggered by cloud–cloud collision.

Preliminary Results of a Survey of Ultracompact H II Regions

1995 ◽  
Vol 12 (2) ◽  
pp. 186-189 ◽  
Author(s):  
A. J. Walsh ◽  
A. R. Hyland ◽  
G. Robinson ◽  
T. L. Bourke ◽  
S. D. James
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Radio Continuum ◽  
High Mass ◽  
Continuum Emission ◽  
H Ii Regions ◽  
Mass Star ◽  
Methanol Maser ◽  
Preliminary Results ◽  
Selection Of

AbstractUltracompact H II regions are small, dense regions of ionised gas surrounding high-mass stars which are still embedded in their natal molecular clouds. A survey of such regions has been commenced in an attempt to improve our understanding of the processes of high-mass star formation. The initial stages of the survey have involved selection of likely candidates from the IRAS Point Source Catalogue, correlation with radio continuum emission at 4·85 GHz and subsequent observations of methanol maser emission at 6·668 GHz. Preliminary results of the methanol maser survey are given.

scholarly journals The complex chemistry of hot cores in Sgr B2(N): influence of cosmic-ray ionization and thermal history

2019 ◽  
Vol 628 ◽  
pp. A27 ◽  
Author(s):  
M. Bonfand ◽  
A. Belloche ◽  
R. T. Garrod ◽  
K. M. Menten ◽  
E. Willis ◽  
...  
Keyword(s):  
Star Formation ◽  
Chemical Composition ◽  
Chemical Evolution ◽  
Environmental Conditions ◽  
Early Stage ◽  
Cosmic Ray ◽  
High Mass ◽  
Continuum Emission ◽  
Mass Star ◽  
The Impact

Context. As the number of complex organic molecules (COMs) detected in the interstellar medium increases, it becomes even more important to place meaningful constraints on the origins and formation pathways of such chemical species. The molecular cloud Sagittarius B2(N) is host to several hot molecular cores in the early stage of star formation, where a great variety of COMs are detected in the gas phase. Given its exposure to the extreme conditions of the Galactic center (GC) region, Sgr B2(N) is one of the best targets to study the impact of environmental conditions on the production of COMs. Aims. Our main goal is to characterize the physico-chemical evolution of Sgr B2(N)’s sources in order to explain their chemical differences and constrain their environmental conditions. Methods. The chemical composition of Sgr B2(N)’s hot cores, N2, N3, N4, and N5 is derived by modeling their 3 mm emission spectra extracted from the Exploring Molecular Complexity with ALMA (EMoCA) imaging spectral line survey performed with the Atacama Large Millimeter/submillimeter Array (ALMA). We derived the density distribution in the envelope of the sources based on the masses computed from the ALMA dust continuum emission maps. We used the radiative transfer code RADMC-3D to compute temperature profiles and inferred the current luminosity of the sources based on the COM rotational temperatures derived from population diagrams. We used published results of 3D radiation-magnetohydrodynamical (RMHD) simulations of high-mass star formation to estimate the time evolution of the source properties. We employed the astrochemical code MAGICKAL to compute time-dependent chemical abundances in the sources and to investigate how physical properties and environmental conditions influence the production of COMs. Results. The analysis of the abundances of 11 COMs detected toward Sgr B2(N2-N5) reveals that N3 and N5 share a similar chemical composition while N2 differs significantly from the other sources. We estimate the current luminosities of N2, N3, N4, and N5 to be 2.6 × 105 L⊙, 4.5 × 104 L⊙, 3.9 × 105 L⊙, and 2.8 × 105 L⊙, respectively. We find that astrochemical models with a cosmic-ray ionization rate of 7 × 10−16 s−1 best reproduce the abundances with respect to methanol of ten COMs observed toward Sgr B2(N2-N5). We also show that COMs still form efficiently on dust grains with minimum dust temperatures in the prestellar phase as high as 15 K, but that minimum temperatures higher than 25 K are excluded. Conclusions. The chemical evolution of Sgr B2(N2-N5) strongly depends on their physical history. A more realistic description of the hot cores’ physical evolution requires a more rigorous treatment with RMHD simulations tailored to each hot core.

scholarly journals High Resolution Radio Continuum Observations of High Mass Star Formation Regions

2001 ◽  
Vol 205 ◽  
pp. 280-281
Author(s):  
S. Kurtz ◽  
P. Hofner ◽  
C. Vargas ◽  
W. Díaz-Merced
Keyword(s):  
Star Formation ◽  
Radio Continuum ◽  
High Mass ◽  
High Angular Resolution ◽  
Mass Star ◽  
High Quality ◽  
Very Large Array ◽  
Adverse Conditions ◽  
Star Formation Regions ◽  
Calibration Techniques

We present high angular resolution centimeter and millimeter continuum observations of several galactic massive star formation regions. Using calibration techniques pioneered at the Very Large Array, we are able to obtain high quality images even under adverse conditions of phase stability. Techniques such as these will be essential if future millimeter arrays are to obtain high quality and high precision images. We provide a current summary of our on-going survey, and present images and a brief discussion of several of the more intriguing sources.

scholarly journals FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 m telescope (FUGIN). VIII. Possible evidence of cloud–cloud collisions triggering high-mass star formation in the giant molecular cloud M 16 (Eagle Nebula)

2020 ◽  
Author(s):  
Atsushi Nishimura ◽  
Shinji Fujita ◽  
Mikito Kohno ◽  
Daichi Tsutsumi ◽  
Tetsuhiro Minamidani ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Velocity Structure ◽  
Galactic Plane ◽  
High Mass ◽  
Mass Star ◽  
Collision Event ◽  
Giant Molecular Cloud ◽  
Eagle Nebula ◽  
H Ii Region

Abstract M 16, the Eagle Nebula, is an outstanding H ii region which exhibits extensive high-mass star formation and hosts remarkable “pillars.” We herein obtained new 12COJ = 1–0 data for the region observed with NANTEN2, which were combined with the 12COJ = 1–0 data obtained using the FOREST unbiased galactic plane imaging with Nobeyama 45 m telescope (FUGIN) survey. These observations revealed that a giant molecular cloud (GMC) of ∼1.3 × 105 M⊙ is associated with M 16, which extends for 30 pc perpendicularly to the galactic plane, at a distance of 1.8 kpc. This GMC can be divided into the northern (N) cloud, the eastern (E) filament, the southeastern (SE) cloud, the southeastern (SE) filament, and the southern (S) cloud. We also found two velocity components (blueshifted and redshifted components) in the N cloud. The blueshifted component shows a ring-like structure, and the redshifted one coincides with the intensity depression of the ring-like structure. The position–velocity diagram of the components showed a V-shaped velocity feature. The spatial and velocity structures of the cloud indicated that two different velocity components collided with each other at a relative velocity of 11.6 km s−1. The timescale of the collision was estimated to be ∼4 × 105 yr. The collision event reasonably explains the formation of the O9V star ALS 15348, as well as the shape of the Spitzer bubble N19. A similar velocity structure was found in the SE cloud, which is associated with the O7.5V star HD 168504. In addition, the complementary distributions of the two velocity components found in the entire GMC suggested that the collision event occurred globally. On the basis of the above results, we herein propose a hypothesis that the collision between the two components occurred sequentially over the last several 106 yr and triggered the formation of O-type stars in the NGC 6611 cluster in M 16.

scholarly journals EVOLUTION OF MAGNETIC FIELDS IN HIGH MASS STAR FORMATION: SUBMILLIMETER ARRAY DUST POLARIZATION IMAGE OF THE ULTRACOMPACT H II REGION G5.89–0.39

2009 ◽  
Vol 695 (2) ◽  
pp. 1399-1412 ◽  
Author(s):  
Ya-Wen Tang ◽  
Paul T. P. Ho ◽  
Josep Miquel Girart ◽  
Ramprasad Rao ◽  
Patrick Koch ◽  
...  
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
High Mass ◽  
Mass Star ◽  
Polarization Image ◽  
H Ii Region

scholarly journals Masers as evolutionary tracers of high-mass star formation

2012 ◽  
Vol 8 (S287) ◽  
pp. 156-160 ◽  
Author(s):  
Shari L. Breen ◽  
Simon P. Ellingsen
Keyword(s):  
Star Formation ◽  
Point Sources ◽  
Radio Continuum ◽  
High Mass ◽  
Mass Star ◽  
Evolutionary Scheme ◽  
Evolutionary Clock ◽  
The Common ◽  
Star Formation Regions ◽  
Made In

AbstractDetermining an evolutionary clock for high-mass star formation is an important step towards realising a unified theory of star formation, as it will enable qualitative studies of the associated high-mass stars to be executed. We have carried out detailed studies of a large number of sources suspected of undergoing high-mass star formation and have found that common maser transitions offer the best opportunity to determine an evolutionary scheme for these objects. We have investigated the relative evolutionary phases of massive star formation associated with the presence or absence of combinations of water, methanol and main-line hydroxyl masers. The locations of the different maser species have been compared with the positions of 1.2 mm dust clumps, radio continuum, GLIMPSE point sources and Extended Green Objects. Comparison between the characteristics of coincident sources has revealed strong evidence for an evolutionary sequence for the different maser species in high-mass star formation regions. We present our proposed sequence for the presence of the common maser species associated with young high-mass stars and highlight recent advances. We discuss future investigations that will be made in this area by comparing data from the Methanol Multibeam (MMB) Survey with chemical clocks from the Millimetre Astronomy Legacy Team 90 GHz (MALT90) Survey.

scholarly journals CORNISH: A 5 GHz VLA survey of the Galactic plane

2009 ◽  
Vol 5 (H15) ◽  
pp. 781-781
Author(s):  
Cormac R. Purcell ◽  
Melvin G. Hoare ◽  
Keyword(s):  
Star Formation ◽  
Galactic Plane ◽  
Radio Continuum ◽  
High Mass ◽  
Mass Star ◽  
Multi Wavelength ◽  
Region 10 ◽  
5 Ghz ◽  
Infrared Survey ◽  
Key Questions

AbstractThe CORNISH (Co-Ordinated Radio ‘N’ Infrared Survey for High-mass star formation) project is the radio continuum part of a series of multi-wavelength surveys of the Galactic Plane that focus on the northern GLIMPSE-I region (10° < l <65°, |b| < 1°) observed by the SPITZER satellite in the mid-infrared (Churchwell et al. 2009). CORNISH has delivered a complementary 5 GHz arcsecond resolution, radio-continuum survey to address key questions in high-mass star formation as well as many other areas of astrophysics.

scholarly journals The Star-formation Law in Galactic High-mass Star-forming Molecular Clouds

2017 ◽  
Vol 839 (2) ◽  
pp. 113 ◽  
Author(s):  
R. Retes-Romero ◽  
Y. D. Mayya ◽  
A. Luna ◽  
L. Carrasco
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
High Mass ◽  
Mass Star ◽  
Star Forming

scholarly journals ALMA Observations of Giant Molecular Clouds in M33. II. Triggered High-mass Star Formation by Multiple Gas Colliding Events at the NGC 604 Complex

2020 ◽  
Vol 903 (2) ◽  
pp. 94
Author(s):  
Kazuyuki Muraoka ◽  
Hiroshi Kondo ◽  
Kazuki Tokuda ◽  
Atsushi Nishimura ◽  
Rie E. Miura ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
High Mass ◽  
Mass Star ◽  
Giant Molecular Clouds
Sign in / Sign up

Export Citation Format

Share Document