scholarly journals Star Formation in Expanding Shells: When and Where

1997 ◽  
Vol 166 ◽  
pp. 413-416
Author(s):  
S. Ehlerová ◽  
J. Palouš ◽  
Ch. Theis ◽  
G. Hensler
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Analytical Model ◽  
Computer Simulations ◽  
Sound Speed ◽  
Finite Thickness ◽  
Gaseous Disk ◽  
Expanding Shells

AbstractThe fragmentation of expanding shells and subsequent star formation are analyzed using an analytical model and computer simulations. We discuss the role of the sound speed in the ambient interstellar medium and the influence of the finite thickness of the gaseous disk.

scholarly journals Gravitational and Dynamical Instabilities of a Decelerating Plane-Parallel Slab of Finite Thickness

1988 ◽  
Vol 101 ◽  
pp. 509-512
Author(s):  
G. Mark Voit
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Incompressible Fluid ◽  
Gravity Wave ◽  
Finite Thickness ◽  
Blast Waves ◽  
Plane Parallel ◽  
The Stability ◽  
Dynamical Instabilities ◽  
Symmetric And Antisymmetric Modes

AbstractIn order to explore how supernova blast waves might catalyze star formation, we investigate the stability of a slab of decelerating gas of finite thickness. We examine the early work in the field by Elmegreen and Lada and Elmegreen and Elmegreen and demonstrate that it is flawed. Contrary to their claims, blast waves can indeed accelerate the rate of star formation in the interstellar medium. Also, we demonstrate that in an incompressible fluid, the symmetric and antisymmetric modes in the case of zero acceleration transform continuously into Rayleigh-Taylor and gravity-wave modes as acceleration grows more important.

The role of automated methods for filament finding in understanding the complex relationship between filaments, magnetic fields and star formation

2018 ◽  
Vol 14 (S345) ◽  
pp. 23-26
Author(s):  
Maria R. Cunningham ◽  
Claire-Elise Green ◽  
Paul A. Jones ◽  
Giles Novak ◽  
Laura Fissel
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Interstellar Medium ◽  
Massive Stars ◽  
Field Measurements ◽  
Complex Relationship ◽  
Dense Cores ◽  
Magnetic Field Measurements ◽  
Automated Methods

AbstractThe discovery of the ubiquity of filaments in the interstellar medium in the last two decades has begged the question: “What role do filaments play in star formation?” Here we describe how our automated filament finding algorithms can combine with both magnetic field measurements and high-resolution observations of dense cores in these filaments, to provide a statistically large sample to investigate the effect of filaments on star formation. We find that filaments are likely actively accreting mass from the interstellar medium, explaining why some 60% of stars, and all massive stars, form “on-filament”.

scholarly journals Hard X-Ray Irradiation Potentially Drives Negative AGN Feedback by Altering Molecular Gas Properties

2021 ◽  
Vol 257 (2) ◽  
pp. 64
Author(s):  
Taiki Kawamuro ◽  
Claudio Ricci ◽  
Takuma Izumi ◽  
Masatoshi Imanishi ◽  
Shunsuke Baba ◽  
...  
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Active Galactic Nucleus ◽  
Accretion Rate ◽  
Spatial Separation ◽  
Molecular Gas ◽  
X Ray ◽  
Mass Accretion Rate ◽  
Nuclear Regions

Abstract To investigate the role of active galactic nucleus (AGN) X-ray irradiation on the interstellar medium (ISM), we systematically analyzed Chandra and Atacama Large Millimeter/submillimeter Array CO (J = 2–1) data for 26 hard X-ray (>10 keV) selected AGNs at redshifts below 0.05. While Chandra unveils the distribution of X-ray-irradiated gas via Fe-Kα emission, the CO (J = 2–1) observations reveal that of cold molecular gas. At high resolutions ≲1″, we derive Fe-Kα and CO (J = 2–1) maps for the nuclear 2″ region and for the external annular region of 2″–4″, where 2″ is ∼100–600 pc for most of our AGNs. First, focusing on the external regions, we find the Fe-Kα emission for six AGNs above 2σ. Their large equivalent widths (≳1 keV) suggest a fluorescent process as their origin. Moreover, by comparing the 6–7 keV/3–6 keV ratio, as a proxy of Fe-Kα, and CO (J = 2–1) images for three AGNs with the highest significant Fe-Kα detections, we find a possible spatial separation. These suggest the presence of X-ray-irradiated ISM and the change in the ISM properties. Next, examining the nuclear regions, we find that (1) the 20–50 keV luminosity increases with the CO (J = 2–1) luminosity; (2) the ratio of CO (J = 2–1)/HCN (J = 1–0) luminosities increases with 20–50 keV luminosity, suggesting a decrease in the dense gas fraction with X-ray luminosity; and (3) the Fe-Kα-to-X-ray continuum luminosity ratio decreases with the molecular gas mass. This may be explained by a negative AGN feedback scenario: the mass accretion rate increases with gas mass, and simultaneously, the AGN evaporates a portion of the gas, which possibly affects star formation.

scholarly journals Fragmentation in turbulent primordial gas

2010 ◽  
Vol 6 (S270) ◽  
pp. 499-502 ◽  
Author(s):  
S. C. O. Glover ◽  
P. C. Clark ◽  
R. S. Klessen ◽  
V. Bromm
Keyword(s):  
Mass Spectrum ◽  
Star Formation ◽  
Velocity Field ◽  
Numerical Simulations ◽  
Early Universe ◽  
Sound Speed ◽  
Turbulent Velocity ◽  
Local Properties ◽  
Turbulent Velocity Field

AbstractWe report results from numerical simulations of star formation in the early universe that focus on the role of subsonic turbulence, and investigate whether it can induce fragmentation of the gas. We find that dense primordial gas is highly susceptible to fragmentation, even for rms turbulent velocity dispersions as low as 20% of the initial sound speed. The resulting fragments cover over two orders of magnitude in mass, ranging from ~0.1 M⊙ to ~40 M⊙. However, our results suggest that the details of the fragmentation depend on the local properties of the turbulent velocity field and hence we expect considerable variations in the resulting stellar mass spectrum in different halos.

scholarly journals Observations of supershells in the interstellar medium of nearby galaxies

2006 ◽  
Vol 2 (S237) ◽  
pp. 76-83
Author(s):  
Elias Brinks ◽  
Ioannis Bagetakos ◽  
Fabian Walter ◽  
Erwin de Blok
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Detection Threshold ◽  
Nearby Galaxy ◽  
Late Type ◽  
First Results ◽  
Nearby Galaxies ◽  
Gas Layer ◽  
Expanding Shells ◽  
Major Project

AbstractHI observations at sufficiently high spatial and velocity resolution have revealed a wealth of structures such as shells and bubbles in the ISM of late–type galaxies. These structures are filled with metal–enriched, coronal gas from SNe which, through overpressure, powers their expansion. Material swept up by these expanding shells can go “critical” and form subsequent (secondary or propagating) star formation. Shells that grow larger than the thickness of the gas layer will blow out of the disk, spilling enriched material into the halo (or in the case of violent starbursts, the Intergalactic Medium). We review what has been achieved to date and present some first results of a major project based on THINGS (The HI Nearby Galaxy Survey), which aims to extend studies of the ISM in galaxies to 34 nearby systems (<10 Mpc), all observed to the same exacting standards (resolution 6″ × 5 km s−1, or better; typical detection threshold of ~5 × 1019 atom cm−2).

The role of interstellar filaments in shaping the IMF and regulating star formation

2015 ◽  
Vol 75-76 ◽  
pp. 137-141
Author(s):  
P. André ◽  
V. Könyves ◽  
A. Roy
Keyword(s):  
Star Formation ◽  
The Imf

scholarly journals The role of mergers and interactions in driving the evolution of dwarf galaxies over cosmic time

2020 ◽  
Vol 500 (4) ◽  
pp. 4937-4957 ◽  
Author(s):  
G Martin ◽  
R A Jackson ◽  
S Kaviraj ◽  
H Choi ◽  
J E G Devriendt ◽  
...  
Keyword(s):  
Star Formation ◽  
Dwarf Galaxies ◽  
Large Fraction ◽  
Structural Evolution ◽  
Cosmic Time ◽  
Stellar Mass ◽  
High Mass ◽  
Key Drivers ◽  
Mass Assembly

ABSTRACT Dwarf galaxies (M⋆ &lt; 109 M⊙) are key drivers of mass assembly in high-mass galaxies, but relatively little is understood about the assembly of dwarf galaxies themselves. Using the NewHorizon cosmological simulation (∼40 pc spatial resolution), we investigate how mergers and fly-bys drive the mass assembly and structural evolution of around 1000 field and group dwarfs up to z = 0.5. We find that, while dwarf galaxies often exhibit disturbed morphologies (5 and 20 per cent are disturbed at z = 1 and z = 3 respectively), only a small proportion of the morphological disturbances seen in dwarf galaxies are driven by mergers at any redshift (for 109 M⊙, mergers drive under 20 per cent morphological disturbances). They are instead primarily the result of interactions that do not end in a merger (e.g. fly-bys). Given the large fraction of apparently morphologically disturbed dwarf galaxies which are not, in fact, merging, this finding is particularly important to future studies identifying dwarf mergers and post-mergers morphologically at intermediate and high redshifts. Dwarfs typically undergo one major and one minor merger between z = 5 and z = 0.5, accounting for 10 per cent of their total stellar mass. Mergers can also drive moderate star formation enhancements at lower redshifts (3 or 4 times at z = 1), but this accounts for only a few per cent of stellar mass in the dwarf regime given their infrequency. Non-merger interactions drive significantly smaller star formation enhancements (around two times), but their preponderance relative to mergers means they account for around 10 per cent of stellar mass formed in the dwarf regime.

scholarly journals A Reference Sample: ISM of the Most Isolated Galaxies

2004 ◽  
Vol 217 ◽  
pp. 220-221
Author(s):  
L. Verdes-Montenegro ◽  
J. Sulentic ◽  
D. Espada ◽  
S. Leon ◽  
U. Lisenfeld ◽  
...  
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Galaxy Evolution ◽  
Reference Sample ◽  
Control Sample ◽  
Evolution Of Galaxies ◽  
Isolated Galaxies ◽  
Internal Evolution

We are constructing the first complete unbiased control sample of the most isolated galaxies of the northern sky to serve as a template in the study of star formation and galaxy evolution in denser environments. Our goal is to compare and quantify the properties of different phases of the interstellar medium in this sample, as well as the level of star formation, both relevant parameters in the internal evolution of galaxies and strongly conditioned by the environment. To achieve this goal we are building a multiwavelength database for this sample to compare and quantify the properties of different phases of the ISM.

scholarly journals Simulated star formation rate functions at z ∼ 4-7, and the role of feedback in high-z galaxies

2014 ◽  
Vol 438 (4) ◽  
pp. 3490-3506 ◽  
Author(s):  
E. Tescari ◽  
A. Katsianis ◽  
J. S. B. Wyithe ◽  
K. Dolag ◽  
L. Tornatore ◽  
...  
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Rate Functions
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