scholarly journals Modelling of large-scale dense gas–solid bubbling fluidised beds using a novel discrete bubble model

2006 ◽  
Vol 61 (17) ◽  
pp. 5590-5602 ◽  
Author(s):  
G.A. Bokkers ◽  
J.A. Laverman ◽  
M. van Sint Annaland ◽  
J.A.M. Kuipers
Keyword(s):  
Large Scale ◽  
Dense Gas ◽  
Fluidised Beds

scholarly journals Cause and effects of the massive star formation in Messier 8 East

2020 ◽  
Vol 644 ◽  
pp. A25
Author(s):  
M. Tiwari ◽  
K. M. Menten ◽  
F. Wyrowski ◽  
A. Giannetti ◽  
M.-Y. Lee ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Massive Star ◽  
Stellar System ◽  
Ionization Front ◽  
Dense Gas ◽  
Massive Star Formation ◽  
Ancillary Data ◽  
Star Forming ◽  
Physical Conditions

Context. Messier 8 (M8), one of the brightest H II regions in our Galaxy, is powered by massive O-type stars and is associated with recent and ongoing massive star formation. Two prominent massive star-forming regions associated with M8 are M8-Main, the particularly bright part of the large-scale H II region (mainly) ionized by the stellar system Herschel 36 (Her 36) and M8 East (M8 E), which is mainly powered by a deeply embedded young stellar object (YSO), the bright infrared (IR) source M8E-IR. Aims. We study the interaction of the massive star-forming region M8 E with its surroundings using observations of assorted diffuse and dense gas tracers that allow quantifying the kinetic temperatures and volume densities in this region. With a multiwavelength view of M8 E, we investigate the cause of star formation. Moreover, we compare the star-forming environments of M8-Main and M8 E, based on their physical conditions and the abundances of the various observed species toward them. Methods. We used the Institut de Radioastronomía Millimétrica 30 m telescope to perform an imaging spectroscopy survey of the ~1 pc scale molecular environment of M8E-IR and also performed deep integrations toward the source itself. We imaged and analyzed data for the J = 1 → 0 rotational transitions of 12CO, 13CO, N2H+, HCN, H13CN, HCO+, H13CO+, HNC, and HN13C observed for the first time toward M8 E. To visualize the distribution of the dense and diffuse gas in M8 E, we compared our velocity-integrated intensity maps of 12CO, 13CO, and N2H+ with ancillary data taken at IR and submillimeter wavelengths. We used techniques that assume local thermodynamic equilibrium (LTE) and non-LTE to determine column densities of the observed species and constrain the physical conditions of the gas that causes their emission. Examining the class 0/ I and class II YSO populations in M8 E, allows us to explore the observed ionization front (IF) as seen in the high resolution Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) 8 μm emission image. The difference between the ages of the YSOs and their distribution in M8 E were used to estimate the speed of the IF. Results. We find that 12CO probes the warm diffuse gas also traced by the GLIMPSE 8 μm emission, while N2H+ traces the cool and dense gas following the emission distribution of the APEX Telescope Large Area Survey of the Galaxy 870 μm dust continuum. We find that the star-formation in M8 E appears to be triggered by the earlier formed stellar cluster NGC 6530, which powers an H II region giving rise to an IF that is moving at a speed ≥0.26 km s−1 across M8 E. Based on our qualitative and quantitative analysis, the J = 1 → 0 transition lines of N2H+ and HN13C appear to be more direct tracers of dense molecular gas than the J = 1 → 0 transition lines of HCN and HCO+. We derive temperatures of 80 and 30 K for the warm and cool gas components, respectively, and constrain the H2 volume densities to be in the range of 104–106 cm−3. Comparison of the observed abundances of various species reflects the fact that M8 E is at an earlier stage of massive star formation than M8-Main.

scholarly journals Large-scale Molecular Gas Distribution in the M17 Cloud Complex: Dense Gas Conditions of Massive Star Formation?

2020 ◽  
Vol 891 (1) ◽  
pp. 66 ◽  
Author(s):  
Quang Nguyen-Luong ◽  
Fumitaka Nakamura ◽  
Koji Sugitani ◽  
Tomomi Shimoikura ◽  
Kazuhito Dobashi ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Massive Star ◽  
Molecular Gas ◽  
Dense Gas ◽  
Gas Distribution ◽  
Massive Star Formation ◽  
Cloud Complex

Development of a multi-fluid model for poly-disperse dense gas–solid fluidised beds, Part I: Model derivation and numerical implementation

2009 ◽  
Vol 64 (20) ◽  
pp. 4222-4236 ◽  
Author(s):  
M. van Sint Annaland ◽  
G.A. Bokkers ◽  
M.J.V. Goldschmidt ◽  
O.O. Olaofe ◽  
M.A. van der Hoef ◽  
...  
Keyword(s):  
Fluid Model ◽  
Numerical Implementation ◽  
Dense Gas ◽  
Model Derivation ◽  
Fluidised Beds

scholarly journals Dense gas formation and destruction in a simulated Perseus-like galaxy cluster with spin-driven black hole feedback

2019 ◽  
Vol 631 ◽  
pp. A60 ◽  
Author(s):  
R. S. Beckmann ◽  
Y. Dubois ◽  
P. Guillard ◽  
P. Salome ◽  
V. Olivares ◽  
...  
Keyword(s):  
Black Hole ◽  
Adaptive Mesh Refinement ◽  
Large Scale ◽  
Nearby Galaxy ◽  
Dense Gas ◽  
Cluster Galaxy ◽  
Spin Evolution ◽  
Local Ratio ◽  
Hydrodynamical Simulations ◽  
The Impact

Context. Extended filamentary Hα emission nebulae are a striking feature of nearby galaxy clusters but the formation mechanism of the filaments, and the processes which shape their morphology remain unclear. Aims. We conduct an investigation into the formation, evolution and destruction of dense gas in the centre of a simulated, Perseus-like, cluster under the influence of a spin-driven jet. The jet is powered by the supermassive black hole (SMBH) located in the cluster’s brightest cluster galaxy. We particularly study the role played by condensation of dense gas from the diffuse intracluster medium, and the impact of direct uplifting of existing dense gas by the jets, in determining the spatial distribution and kinematics of the dense gas. Methods. We present a hydrodynamical simulation of an idealised Perseus-like cluster using the adaptive mesh refinement code RAMSES. Our simulation includes a SMBH that self-consistently tracks its spin evolution via its local accretion, and in turn drives a large-scale jet whose direction is based on the black hole’s spin evolution. The simulation also includes a live dark matter (DM) halo, a SMBH free to move in the DM potential, star formation and stellar feedback. Results. We show that the formation and destruction of dense gas is closely linked to the SMBH’s feedback cycle, and that its morphology is highly variable throughout the simulation. While extended filamentary structures readily condense from the hot intra-cluster medium, they are easily shattered into an overly clumpy distribution of gas during their interaction with the jet driven outflows. Condensation occurs predominantly onto infalling gas located 5−15 kpc from the centre during quiescent phases of the central AGN, when the local ratio of the cooling time to free fall time falls below 20, i.e. when tcool/tff <  20. Conclusions. We find evidence for both condensation and uplifting of dense gas, but caution that purely hydrodynamical simulations struggle to effectively regulate the cluster cooling cycle and produce overly clumpy distributions of dense gas morphologies, compared to observation.

scholarly journals Star formation in three nearby cloud complexes

1991 ◽  
Vol 147 ◽  
pp. 293-315
Author(s):  
Neal J. Evans ◽  
Elizabeth A. Lada
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Large Scale ◽  
Mass Function ◽  
Open Clusters ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Dense Gas ◽  
Open Clusters And Associations ◽  
Global Efficiency

We consider the distribution and nature of the gas and star formation in three nearby molecular cloud complexes: Taurus-Auriga, Ophiuchus, and Orion. Large-scale studies show that quite different distributions of dense gas and star formation exist in these regions, but that the global efficiency of star formation, so far, is about 1% in all of these complexes, very similar to the final efficiencies deduced for open clusters and associations. Furthermore, evidence for differences in the initial mass function among these regions is weak; all three regions may be compatible with the initial mass function for open clusters and field stars. Finally, we consider specific examples of star formation in each complex; the results indicate that the ideas of Adams, Lada, and Shu (1987) are reasonably consistent with the data on L1551 IRS 5, in the Taurus cloud, but that modifications are likely to be needed for IRAS 16293-2422 in Ophiuchus and for NGC2071 in Orion.

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.

Development of a multi-fluid model for poly-disperse dense gas–solid fluidised beds, Part II: Segregation in binary particle mixtures

2009 ◽  
Vol 64 (20) ◽  
pp. 4237-4246 ◽  
Author(s):  
M. van Sint Annaland ◽  
G.A. Bokkers ◽  
M.J.V. Goldschmidt ◽  
O.O. Olaofe ◽  
M.A. van der Hoef ◽  
...  
Keyword(s):  
Fluid Model ◽  
Dense Gas ◽  
Fluidised Beds
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