scholarly journals 6.2. Efficiency in nuclear fueling

1998 ◽  
Vol 184 ◽  
pp. 265-266
Author(s):  
M. Noguchi
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Numerical Simulations ◽  
Observational Data ◽  
Formation Process ◽  
Large Body ◽  
Merging Galaxies ◽  
Numerical Studies ◽  
Galactic Astronomy ◽  
Theoretical Side

Starburst phenomena in interacting and merging galaxies have been one of the most widely investigated subjects in today's galactic astronomy. On the theoretical side, a large body of numerical studies have been performed in order to interpret available observational data. Numerical simulations have been advanced to the point where they can include interstellar medium (ISM) and star formation process.

scholarly journals Relations Between Star Formation and the Interstellar Medium

1998 ◽  
Vol 179 ◽  
pp. 165-171 ◽  
Author(s):  
Y. Fukui ◽  
Y. Yonekura
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Formation Process ◽  
Molecular Clouds ◽  
Future Prospects

We review observational results concerning star formation and dense molecular clouds, the interstellar medium most relevant to star-formation process, as well as future prospects.

scholarly journals Arp 220 – IC 4553/4: understanding the system and diagnosing the ISM

2007 ◽  
Vol 3 (S242) ◽  
pp. 437-445
Author(s):  
W. A. Baan
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Observational Data ◽  
X Ray ◽  
Infrared Galaxy ◽  
Luminous Infrared Galaxy

AbstractArp 220 is a nearby system in final stages of galaxy merger with powerful ongoing star-formation at and surrounding the two nuclei. Arp 220 was detected in HI absorption and OH Megamaser emission and later recognized as the nearest ultra-luminous infrared galaxy also showing powerful molecular and X-ray emissions. In this paper we review the available radio and mm-wave observational data of Arp 220 in order to obtain an integrated picture of the dense interstellar medium that forms the location of the powerful star-formation at the two nuclei.

scholarly journals Statistical tools of interstellar turbulence: connecting observations with theory

2010 ◽  
Vol 6 (S274) ◽  
pp. 365-368
Author(s):  
B. Burkhart ◽  
A. Lazarian
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Numerical Simulations ◽  
Observational Studies ◽  
Critical Component ◽  
Mhd Turbulence ◽  
Statistical Tools ◽  
Interstellar Turbulence ◽  
Gas Compressibility ◽  
Difficult Subject

AbstractMHD Turbulence is a critical component of the current paradigms of star formation, particle transport, magnetic reconnection and evolution of the ISM, to name just a few. Progress on this difficult subject is made via numerical simulations and observational studies, however in order to connect these two, statistical methods are required. This calls for new statistical tools to be developed in order to study turbulence in the interstellar medium. Here we briefly review some of the recently developed statistics that focus on characterizing gas compressibility and magnetization and their uses to interstellar studies.

scholarly journals Recent Developments in Simulations of Low-mass Star Formation

2010 ◽  
Vol 6 (S270) ◽  
pp. 65-72
Author(s):  
Masahiro N. Machida
Keyword(s):  
Star Formation ◽  
Numerical Simulations ◽  
Formation Process ◽  
Molecular Clouds ◽  
Circumstellar Disks ◽  
Mass Star ◽  
Star Forming ◽  
Protostellar Jets ◽  
Recent Developments ◽  
Low Mass

AbstractIn star forming regions, we can observe different evolutionary stages of various objects and phenomena such as molecular clouds, protostellar jets and outflows, circumstellar disks, and protostars. However, it is difficult to directly observe the star formation process itself, because it is veiled by the dense infalling envelope. Numerical simulations can unveil the star formation process in the collapsing gas cloud. Recently, some studies showed protostar formation from the prestellar core stage, in which both molecular clouds and protostars are resolved with sufficient spatial resolution. These simulations showed fragmentation and binary formation, outflow and jet driving, and circumstellar disk formation in the collapsing gas clouds. In addition, the angular momentum transfer and dissipation process of the magnetic field in the star formation process were investigated. In this paper, I review recent developments in numerical simulations of low-mass star formation.

scholarly journals Sequentially triggered star formation in OB associations

2006 ◽  
Vol 2 (S237) ◽  
pp. 270-277 ◽  
Author(s):  
Thomas Preibisch ◽  
Hans Zinnecker
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Formation Process ◽  
Large Scale ◽  
Observational Evidence ◽  
Star Formation History ◽  
The Sun ◽  
Formation History ◽  
Triggering Mechanisms ◽  
Ob Associations

AbstractWe discuss observational evidence for sequential and triggered star formation in OB associations. We first review the star formation process in the Scorpius-Centaurus OB association, the nearest OB association to the Sun, where several recent extensive studies have allowed us to reconstruct the star formation history in a rather detailed way. We then compare the observational results with those obtained for other OB associations and with recent models of rapid cloud and star formation in the turbulent interstellar medium. We conclude that the formation of whole OB subgroups (each consisting of several thousand stars) requires large-scale triggering mechanisms such as shocks from expanding wind and supernova driven superbubbles surrounding older subgroups. Other triggering mechanisms, like radiatively driven implosion of globules, also operate, but seem to be secondary processes, forming only small stellar groups rather than whole OB subgroups with thousands of stars.

scholarly journals The Roles of Protostellar Outflow Feedback in Clustered Star Formation

2012 ◽  
Vol 8 (S292) ◽  
pp. 54-54
Author(s):  
Fumitaka Nakamura ◽  
Zhi-Yun Li
Keyword(s):  
Star Formation ◽  
Observational Data ◽  
Formation Process ◽  
Cluster Formation ◽  
Parent Cluster

AbstractWe discuss the roles of protostellar outflow feedback in cluster formation using observational data of nearby cluster-forming regions like rho Oph, NGC1333, and Serpens. The observations suggest that observed protostellar outflow feedback appears to be sufficient both to maintain supersonic turbulence and to dynamically support the parent cluster-forming clumps. However, it is not enough to destroy the parent clumps by the current outflow activity. This implies that star formation process may not be too short and probably last at least for several local dynamical times.

scholarly journals Galaxies as simple dynamical systems: observational data disfavor dark matter and stochastic star formation

2015 ◽  
Vol 93 (2) ◽  
pp. 169-202 ◽  
Author(s):  
Pavel Kroupa
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Cosmological Model ◽  
Observational Data ◽  
Large Body ◽  
Initial Mass Function ◽  
Modern Theory ◽  
Dynamical Friction ◽  
The Galaxy ◽  
Satellite Galaxies

According to modern theory, galactic evolution is driven by the dynamics of dark matter and stochastic star formation, but galaxies are observed to be simple systems. The existence of dark matter particles is a key hypothesis in present-day cosmology and galactic dynamics. Given the large body of high-quality work within the standard model of cosmology (SMoC), the validity of this hypothesis is challenged significantly by two independent arguments: (i) The dual dwarf galaxy theorem must be true in any realistic cosmological model. But the data now available appear to falsify this postulate when the dark-matter-based model is compared with the observational data. A consistency test for this conclusion comes from the significantly anisotropic distributions of satellite galaxies (baryonic mass <108M⊙) that orbit in the same direction around their hosting galaxies in disk-like structures, which cannot be derived from dark matter models. (ii) The action of dynamical friction due to expansive and massive dark matter halos must be evident in the galaxy population. The evidence for dynamical friction is poor or even absent. Indendently of this, the long history of failures of the SMoC have reduced the likelihood that it describes the observed Universe to less than 10−4%. The implication for fundamental physics is that exotic dark matter particles do not exist and that consequently effective gravitational physics on the scales of galaxies and beyond ought to be non-Newtonian and (or) non-Einsteinian. An analysis of the kinematic data in galaxies shows them to be described elegantly in the weak-gravitational regime by scale-invariant dynamics, as discovered by Milgrom. The full classical regime of gravitation is effectively described by Milgromian dynamics. This leads to a natural emergence of the simple laws that galaxies are indeed observed to obey. Such success has not been forthcoming in dark-matter-based models. Observations of stellar populations in galaxies suggest that the galaxy-wide initial mass function varies with star formation rate and that stochastic descriptions of star formation are inconsistent with the data. This requires a reinterpretation of the stellar mass assembly in galaxies and thus of the accretion rates onto galaxies. A consequence of this understanding of galactic astrophysics is that most dwarf satellite galaxies are formed as tidal dwarf galaxies in galaxy–galaxy encounters, that they follow the mass–metallicity relation, that galactic mergers are rare, that galaxies immersed in external potentials are physically larger than isolated galaxies, and that star-forming galaxies form a main sequence. Eight predictions are offered that will allow the concepts raised here to be tested. A very conservative, cold- and warm-dark-matter-free cosmological model may be emerging from these considerations.

scholarly journals Magnetic fields and star formation – new observational results

2006 ◽  
Vol 2 (S237) ◽  
pp. 141-147
Author(s):  
Richard M. Crutcher ◽  
Thomas H. Troland
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Magnetic Fields ◽  
Interstellar Medium ◽  
Observational Data ◽  
Molecular Clouds ◽  
Dark Cloud ◽  
Magnetic Field Model ◽  
Field Lines ◽  
Cloud Cores

AbstractAlthough the subject of this meeting is triggered star formation in a turbulent interstellar medium, it remains unsettled what role magnetic fields play in the star formation process. This paper briefly reviews star formation model predictions for the ratio of mass to magnetic flux, describes how Zeeman observations can test these predictions, describes new results – an extensive OH Zeeman survey of dark cloud cores with the Arecibo telescope, and discusses the implications. Conclusions are that the new data support and extend the conclusions based on the older observational results – that observational data on magnetic fields in molecular clouds are consistent with the strong magnetic field model of star formation. In addition, the observational data on magnetic field strengths in the interstellar medium strongly suggest that molecular clouds must form primarily by accumulation of matter along field lines. Finally, a future observational project is described that could definitively test the ambipolar diffusion model for the formation of cores and hence of stars.

scholarly journals Physical and Dynamical Conditions in Interstellar Clouds

1980 ◽  
Vol 87 ◽  
pp. 1-19 ◽  
Author(s):  
N.J. Evans
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Formation Process ◽  
Molecular Clouds ◽  
Interstellar Molecules ◽  
Interstellar Clouds ◽  
New Class ◽  
Galactic Structures ◽  
To Come

The most far-reaching result to come from the study of interstellar molecules has been the recognition of a new class of galactic structures - molecular clouds. These clouds appear to contain most of the mass of the interstellar medium and are the objects from which new stars are formed. Thus, a prerequisite for any understanding of the star formation process is a knowledge of the physical and dynamical conditions in molecular clouds.

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.

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