scholarly journals Atomic and Molecular Phases of the Interstellar Medium

2015 ◽  
Vol 11 (S315) ◽  
pp. 1-8
Author(s):  
Mordecai-Mark Mac Low
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Molecular Hydrogen ◽  
Filling Factor ◽  
Interstellar Clouds ◽  
Atomic Gas ◽  
Cold Gas

AbstractThis review covers four current questions in the behavior of the atomic and molecular interstellar medium. These include whether the atomic gas originates primarily in cold streams or hot flows onto galaxies; what the filling factor of cold gas actually is in galactic regions observationally determined to be completely molecular; whether molecular hydrogen determines or merely traces star formation; and whether gravity or turbulence drives the dynamical motions observed in interstellar clouds, with implications on their star formation properties.

scholarly journals On the Mechanism of H2 Formation in the Interstellar Medium

1987 ◽  
Vol 120 ◽  
pp. 167-169
Author(s):  
Valerio Pirronello
Keyword(s):  
Interstellar Medium ◽  
Molecular Hydrogen ◽  
Formation Rate ◽  
Cosmic Ray ◽  
Interstellar Clouds ◽  
H2 Formation ◽  
Reduced Mobility

The problem of the formation of molecular hydrogen in interstellar clouds is revisited. the role played by cosmic ray bombardment under certain circumstances is considered mainly in the light of the low formation rate of H2 on grains due to the reduced mobility of adsorbed H atoms on their amorphous surfaces at interstellar temperatures.

scholarly journals Interstellar Medium and Star Formation in Dwarf Galaxies

2018 ◽  
Vol 14 (S344) ◽  
pp. 233-239
Author(s):  
Alberto D. Bolatto
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Dwarf Galaxies ◽  
Gas Content ◽  
Star Formation Activity ◽  
The Galaxy ◽  
Cold Gas

AbstractThis is a brief review of our understanding of the properties of the interstellar medium (ISM) in dwarf galaxies in connection to their star formation activity. What are the dominant phases of the ISM in these objects? How do the properties of these phases depend on the galaxy properties? What do we know about their cold gas content and its link to star formation activity? Does star formation proceed differently in these galaxies? How does star formation feedback operate in dwarf galaxies? The availability of observations from space-based facilities such as FUSE, Spitzer, Herschel, and Fermi, as well as observatories such as SOFIA and ALMA, is allowing us to make significant strides in our understanding of these questions.

scholarly journals Galactic star formation in parsec-scale resolution simulations

2010 ◽  
Vol 6 (S270) ◽  
pp. 487-490
Author(s):  
Leila C. Powell ◽  
Frederic Bournaud ◽  
Damien Chapon ◽  
Julien Devriendt ◽  
Adrianne Slyz ◽  
...  
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Interstellar Medium ◽  
Molecular Clouds ◽  
Giant Molecular Clouds ◽  
Gas Distribution ◽  
Computational Problem ◽  
Cold Gas

AbstractThe interstellar medium (ISM) in galaxies is multiphase and cloudy, with stars forming in the very dense, cold gas found in Giant Molecular Clouds (GMCs). Simulating the evolution of an entire galaxy, however, is a computational problem which covers many orders of magnitude, so many simulations cannot reach densities high enough or temperatures low enough to resolve this multiphase nature. Therefore, the formation of GMCs is not captured and the resulting gas distribution is smooth, contrary to observations. We investigate how star formation (SF) proceeds in simulated galaxies when we obtain parsec-scale resolution and more successfully capture the multiphase ISM. Both major mergers and the accretion of cold gas via filaments are dominant contributors to a galaxy's total stellar budget and we examine SF at high resolution in both of these contexts.

scholarly journals The Exploration of the ISM from Antarctica

2012 ◽  
Vol 8 (S288) ◽  
pp. 139-145
Author(s):  
Mark G. Wolfire
Keyword(s):  
Life Cycle ◽  
Water Vapor ◽  
Star Formation ◽  
Interstellar Medium ◽  
Galactic Evolution ◽  
Interstellar Clouds ◽  
Scientific Questions ◽  
Key Questions

AbstractAntarctica presents a unique environment for the exploration of the interstellar medium. The low column of water vapor opens windows for sub-mm and THz astronomy from ground and sub-orbital observatories while the stable atmosphere holds promise for THz interferometry. Various current and potentially future facilities occupy a niche not available to current space or stratospheric instruments. These allow line and continuum observations addressing key questions in e.g., star formation, galactic evolution, and the life-cycle of interstellar clouds. This review presents scientific questions that can be addressed by the suite of current and future Antarctic observatories.

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.

Dirt-cheap gas scaling relations: Using dust attenuation and galaxy radius to predict gas masses for large samples of AGNs

2019 ◽  
Vol 15 (S356) ◽  
pp. 173-173
Author(s):  
Hassen Yesuf
Keyword(s):  
Star Formation ◽  
Molecular Hydrogen ◽  
Partial Correlation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Scaling Relations ◽  
Host Galaxies ◽  
Atomic Gas ◽  
Stellar Properties ◽  
Far Ultraviolet

AbstractWe analyze the molecular and atomic gas data from the GALEX Arecibo SDSS Survey (xGASS) and the extended CO Legacy Database (xCOLD GASS) IRAM survey using novel survival analysis techniques to identify a small number of stellar properties that best correlate with the gas mass. We find that the dust absorption, AV, and the stellar half-light radius, R50, are likely the two best secondary parameters than improve the Kennicutt - Schmidt type relation between the gas mass and the star formation rate, SFR. We fit multiple regression, taking into account gas mass upper limits, to summarize the median, mean, and the 0.15/0.85 quantile multivariate relationships between the gas mass (atomic or molecular hydrogen), SFR, AV and/or R50. In particular, we find that the AV of both the stellar continuum and nebular gas emission shows a significant partial correlation with the molecular hydrogen after controlling for the effect of SFR. The partial correlation between the AV and the atomic gas, however, is weak and their zero-order correlation may be explained by SFR. This is expected since in poorly dust-shielded regions molecular hydrogen is dissociated by the far ultraviolet photons and HI is the dominant phase. Similarly, R50 shows significant partial correlations with both atomic and molecular gas masses. This hints at the importance of environment (e.g., galacto-centric distance) on the gas contents galaxies and on the interplay between gas and star formation rate. We apply the gas scaling relations we found to a large sample of type 2 and type 1 AGNs and infer that the gas mass correlates with AGN luminosity. This correlation is inconsistent with the prediction of AGN feedback models that strong AGNs remove or heat cold gas in their host galaxies.

scholarly journals Studying the Atomic and Molecular Hydrogen Mass (MHI, MH2) Properties of the Extragalactic Spectra

2020 ◽  
pp. 1233-1243
Author(s):  
M. N. Al Najm
Keyword(s):  
Star Formation ◽  
Molecular Hydrogen ◽  
Partial Correlation ◽  
Far Infrared ◽  
Infrared Emission ◽  
Molecular Gas ◽  
Strongly Correlated ◽  
Hydrogen Mass ◽  
Formation Efficiency ◽  
Cold Gas

The purpose of this study is to deal with dust and interstellar molecular and atomic gas owing to obtaining a proportion of cold gas to dust and to understand the characteristics of the molecular gas in extragalactic data selected from the Herschel SPIRE/ FTS archive. The physical properties of a sample of 65 extragalactic spectra characterized by the activity of star formation were discussed in this work. Statistical analyses, using STATISTICA program, were made for the content of cold gas (MHI, MH2), dust mass (Mdust), cold temperature of dust (Td) and luminosities in Far-infrared to CO line radiations, while coefficients of partial correlation within those characteristics were established. The results showed that the molecular hydrogen mass (MH2) is strongly correlated with the HI or the total gas mass corresponding to the Far-infrared emission (LFIR) resulting from dust in the galaxies molecular clouds. The results also indicated that these kinds of galaxies have large molecular mass as well as high star formation efficiency per unit mass.

scholarly journals The Galactic interstellar medium: foregrounds and star formation

2017 ◽  
Vol 12 (S333) ◽  
pp. 138-145
Author(s):  
Marc-Antoine Miville-Deschênes
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Structure Formation ◽  
Statistical Properties ◽  
Line Of Sight ◽  
First Stars ◽  
Atomic Gas ◽  
Multi Phase

AbstractThis review presents briefly two aspects of Galactic interstellar medium science that seem relevant for studying EoR. First, we give some statistical properties of the Galactic foreground emission in the diffuse regions of the sky. The properties of the emission observed in projection on the plane of the sky are then related to how matter is organised along the line of sight. The diffuse atomic gas is multi-phase, with dense filamentary structures occupying only about 1% of the volume but contributing to about 50% of the emission. The second part of the review presents aspect of structure formation in the Galactic interstellar medium that could be relevant for the subgrid physics used to model the formation of the first stars.

scholarly journals Insights into the physics when modelling cold gas clouds in a hot plasma

2019 ◽  
Vol 490 (1) ◽  
pp. L52-L56
Author(s):  
Bastian Sander ◽  
Gerhard Hensler
Keyword(s):  
Adaptive Mesh Refinement ◽  
Adaptive Mesh ◽  
Careful Consideration ◽  
Necessary Condition ◽  
Interstellar Clouds ◽  
Hot Plasma ◽  
Magnetic Dipole Field ◽  
Set Up ◽  
Self Gravity ◽  
Cold Gas

ABSTRACT This paper aims at studying the reliability of a few frequently raised, but not proven, arguments for the modelling of cold gas clouds embedded in or moving through a hot plasma and at sensitizing modellers to a more careful consideration of unavoidable acting physical processes and their relevance. At first, by numerical simulations we demonstrate the growing effect of self-gravity on interstellar clouds and, by this, moreover argue against their initial set-up as homogeneous. We apply the adaptive-mesh refinement code flash with extensions to metal-dependent radiative cooling and external heating of the gas, self-gravity, mass diffusion, and semi-analytic dissociation of molecules, and ionization of atoms. We show that the criterion of Jeans mass or Bonnor–Ebert mass, respectively, provides only a sufficient but not a necessary condition for self-gravity to be effective, because even low-mass clouds are affected on reasonable dynamical time-scales. The second part of this paper is dedicated to analytically study the reduction of heat conduction by a magnetic dipole field. We demonstrate that in this configuration, the effective heat flow, i.e. integrated over the cloud surface, is suppressed by only 32 per cent by magnetic fields in energy equipartition and still insignificantly for even higher field strengths.

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