scholarly journals Control of galactic scale star formation by gravitational instability or midplane pressure?

2010 ◽  
Vol 6 (S270) ◽  
pp. 371-375
Author(s):  
Mordecai-Mark Mac Low
Keyword(s):  
Star Formation ◽  
Molecular Hydrogen ◽  
Large Scale ◽  
Gravitational Instability ◽  
Numerical Models ◽  
Star Formation In Galaxies

AbstractStar formation in galaxies has been suggested to depend on large-scale gravitational instability or on the pressure required to form molecular hydrogen. I present numerical models and analysis of observations in support of the gravitational instability hypothesis. I also consider whether the correlation between the surface densities of molecular hydrogen and star formation implies causation, and if so in which direction.

Large-scale star formation in galaxies

2003 ◽  
Vol 173 (1) ◽  
pp. 3 ◽  
Author(s):  
Yurii N. Efremov ◽  
Artur D. Chernin
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Star Formation In Galaxies

scholarly journals Star formation thresholds derived From THINGS

2006 ◽  
Vol 2 (S237) ◽  
pp. 397-397
Author(s):  
F. Bigiel ◽  
F. Walter ◽  
E. de Blok ◽  
E. Brinks ◽  
B. Madore
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Gravitational Instability ◽  
Critical Density ◽  
Nearby Galaxy ◽  
Uv Emission ◽  
Radial Profiles ◽  
Wide Range ◽  
First Results ◽  
Type Mass

AbstractWe present first results from THINGS (The HI Nearby Galaxy Survey), which consists of high quality HI maps obtained with the VLA of 34 galaxies across a wide range of galaxy parameters (Hubble type, mass/luminosity). We compare the distribution of HI to the UV emission in our sample galaxies. In particular we present radial profiles of the HI (tracing the neutral interstellar medium) and UV (mainly tracing regions of recent star formation) in our sample galaxies. The azimuthally averaged HI profiles are compared to the predicted critical density above which organized large-scale star formation is believed to start (this threshold is based on the Toomre-Q parameter, which in turn is a measure for local gravitational instability).

scholarly journals Large Scale Star Formation: Density Waves, Superassociations and Propagation

1987 ◽  
Vol 115 ◽  
pp. 457-481 ◽  
Author(s):  
Bruce G. Elmegreen
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Density Waves ◽  
Spiral Arms ◽  
Gravitational Instabilities ◽  
Significant Difference ◽  
Star Formation In Galaxies ◽  
The Difference ◽  
The Waves

The hypothesis that density waves trigger star formation is critically examined. Much of the former evidence in favor of the hypothesis is shown to be inconsistent with modern observations. A comparison between galaxies with and without density waves reveals no significant difference in their star formation rates. A new role for density waves in the context of star formation might be based on four principles: 1. density waves are intrinsically strong, 2. the gas is compressed more than the stars in the wave, 3. star formation follows the gas, with no preferential trigger related to the wave itself, and 4. regions of star formation are larger in the spiral arms than they are between the arms. This new role for density waves is primarily one of organization: the waves place most of the gas in the arms, so most of the star formation is in the arms too. The waves also promote the coagulation of small clouds into large cloud complexes, or superclouds, by what appears to be a combination of collisional agglomeration and large-scale gravitational instabilities. Special regions where density waves do trigger a true excess of star formation are discussed, and possible reasons for the difference between these triggering waves and the more common, organizing, waves are mentioned. Other aspects of large-scale star formation, such as the occurrence of kiloparsec-size regions of activity and kiloparsec-range propagation, are illustrated with numerous examples. The importance of these largest scales to the overall mechanism of star formation in galaxies is emphasized.

scholarly journals Gas inflow and star formation near supermassive black holes: the role of nuclear activity

2019 ◽  
Vol 489 (1) ◽  
pp. 52-77
Author(s):  
Christopher C Frazer ◽  
Fabian Heitsch
Keyword(s):  
Star Formation ◽  
Gravitational Instability ◽  
Numerical Models ◽  
Three Dimensional ◽  
Lower Surface ◽  
Nuclear Activity ◽  
Radiation Fields ◽  
Accretion Rates ◽  
Inflow Event ◽  
Uv Photons

ABSTRACT Numerical models of gas inflow towards a supermassive black hole (SMBH) show that star formation may occur in such an environment through the growth of a gravitationally unstable gas disc. We consider the effect of nuclear activity on such a scenario. We present the first three-dimensional grid-based radiative hydrodynamic simulations of direct collisions between infalling gas streams and a 4 × 106 M⊙ SMBH, using ray-tracing to incorporate radiation consistent with an active galactic nucleus (AGN). We assume inflow masses of ≈105 M⊙ and explore radiation fields of 10 per cent and 100 per cent of the Eddington luminosity (Ledd). We follow our models to the point of central gas disc formation preceding star formation and use the Toomre Q parameter (QT) to test for gravitational instability. We find that radiation pressure from UV photons inhibits inflow. Yet, for weak radiation fields, a central disc forms on time-scales similar to that of models without feedback. Average densities of >108 cm−3 limit photoheating to the disc surface allowing for QT ≈ 1. For strong radiation fields, the disc forms more gradually resulting in lower surface densities and larger QT values. Mass accretion rates in our models are consistent with 1–60 per cent of the Eddington limit, thus we conclude that it is unlikely that radiative feedback from AGN activity would inhibit circumnuclear star formation arising from a massive inflow event.

scholarly journals 1D, 2D and 3D Collapse of Interstellar Clouds

1980 ◽  
Vol 58 ◽  
pp. 235-246
Author(s):  
W.M. Tscharnuter
Keyword(s):  
Star Formation ◽  
Gravitational Instability ◽  
Numerical Models ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Interstellar Clouds ◽  
B Stars ◽  
Theoretical Investigations ◽  
2D And 3D

This review is concerned with recent theoretical investigations and numerical models of star formation with varions symmetries. Observations strongly support the fact that stars condense out of cool (≈10 K) and dense (103-104 atoms/cm3) interstellar clouds due to gravitational instability and collapse. Bright, young stellar objects (0- and B-stars are always found in the vicinity of coloud complexes.

scholarly journals Large‐Scale Gravitational Instability and Star Formation in the Large Magellanic Cloud

2007 ◽  
Vol 671 (1) ◽  
pp. 374-379 ◽  
Author(s):  
Chao‐Chin Yang ◽  
Robert A. Gruendl ◽  
You‐Hua Chu ◽  
Mordecai‐Mark Mac Low ◽  
Yasuo Fukui
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Gravitational Instability ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud

scholarly journals Wide Field Star Count Mapping of Large Scale Areas of Star Formation in the Large Magellanic Cloud

1994 ◽  
Vol 161 ◽  
pp. 516-517 ◽  
Author(s):  
E. Kontizas ◽  
S.E. Maravelias ◽  
A. Dapergolas ◽  
Y. Bellas-Velidis ◽  
M. Kontizas
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Large Magellanic Cloud ◽  
Wide Field ◽  
Dark Clouds ◽  
Star Count ◽  
Astrophysical Problem ◽  
Star Formation In Galaxies ◽  
The Individual ◽  
Parent Galaxy

Star formation in galaxies is a major astrophysical problem which can be investigated in several ways. The distribution and loci of all kinds of young objects, including OB associations, young clusters, HII regions, GMCs, Bok globules, dark clouds, dust lanes, protostars, as well as YSOs detected in NIR and FIR surveys constitute the principal signposts for this investigation. The individual nature of all these objects has been and is still continously studied. However it is also extremely interesting to associate the coexistence of these objects, and their relation to the structure of the parent galaxy. Such studies have been carried out by several investigators and are frequently summarized when star formation processes are examined.

scholarly journals Large-scale star formation in galaxies

2002 ◽  
Vol 384 (1) ◽  
pp. 24-32 ◽  
Author(s):  
A. Vicari ◽  
P. Battinelli ◽  
R. Capuzzo–Dolcetta ◽  
T. K. Wyder ◽  
G. Arrabito
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Star Formation In Galaxies

scholarly journals Spitzer Planck Herschel Infrared Cluster (SPHerIC) survey: Candidate galaxy clusters at 1.3 < z < 3 selected by high star-formation rate

2018 ◽  
Vol 620 ◽  
pp. A198 ◽  
Author(s):  
C. Martinache ◽  
A. Rettura ◽  
H. Dole ◽  
M. Lehnert ◽  
B. Frye ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Formation Rate ◽  
Physical Processes ◽  
Cluster Galaxies ◽  
Star Forming ◽  
Efficient Detection ◽  
Star Formation In Galaxies ◽  
The Individual ◽  
Massive Clusters

There is a lack of large samples of spectroscopically confirmed clusters and protoclusters at high redshifts, z > 1.5. Discovering and characterizing distant (proto-)clusters is important for yielding insights into the formation of large-scale structure and on the physical processes responsible for regulating star-formation in galaxies in dense environments. The Spitzer Planck Herschel Infrared Cluster (SPHerIC) survey was initiated to identify these characteristically faint and dust-reddened sources during the epoch of their early assembly. We present Spitzer/IRAC observations of 82 galaxy (proto-)cluster candidates at 1.3 < zp < 3.0 that were vetted in a two step process: (1) using Planck to select by color those sources with the highest star-formation rates, and (2) using Herschel at higher resolution to separate out the individual red sources. The addition of the Spitzer data enables efficient detection of the central and massive brightest red cluster galaxies (BRCGs). We find that BRCGs are associated with highly significant, extended and crowded regions of IRAC sources which are more overdense than the field. This result corroborates our hypothesis that BRCGs within the Planck–Herschel sources trace some of the densest and actively star-forming proto-clusters in the early Universe. On the basis of a richness-mass proxy relation, we obtain an estimate of their mean masses which suggests our sample consists of some of the most massive clusters at z ≈ 2 and are the likely progenitors of the most massive clusters observed today.

scholarly journals Star Formation in Interacting Galaxies

2010 ◽  
Vol 6 (S270) ◽  
pp. 475-482
Author(s):  
Curtis Struck
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Gravitational Instability ◽  
Interacting Galaxies ◽  
Physical Processes ◽  
Wide Range

AbstractThis brief review emphasizes the wide range of environments where interaction induced star formation occurs. In these environments we can study the numerous elaborations of a few basic physical processes, including: gravitational instability, accretion and large-scale shocks.

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