Molecular cooling of a collapsing protocloud

New Astronomy ◽  
1997 ◽  
Vol 2 (4) ◽  
pp. 299-308 ◽  
Author(s):  
Denis Puy ◽  
Monique Signore
Keyword(s):  
Molecular Cooling

scholarly journals Legacy of star formation in the pre-reionization universe

2019 ◽  
Vol 488 (2) ◽  
pp. 2202-2221 ◽  
Author(s):  
Jason Jaacks ◽  
Steven L Finkelstein ◽  
Volker Bromm
Keyword(s):  
Star Formation ◽  
Luminosity Function ◽  
Star Formation Rate ◽  
Direct Detection ◽  
Formation Rate ◽  
Mass Function ◽  
James Webb Space Telescope ◽  
Current Limiting ◽  
Molecular Cooling ◽  
Low Mass

ABSTRACT We utilize gizmo, coupled with newly developed sub-grid models for Population III (Pop III) and Population II (Pop II), to study the legacy of star formation in the pre-reionization Universe. We find that the Pop II star formation rate density (SFRD), produced in our simulation (${\sim } 10^{-2}\ \mathrm{M}_\odot \, {\rm yr^{-1}\, Mpc^{-3}}$ at z ≃ 10), matches the total SFRD inferred from observations within a factor of <2 at 7 ≲ z ≲ 10. The Pop III SFRD, however, reaches a plateau at ${\sim }10^{-3}\ \mathrm{M}_\odot \, {\rm yr^{-1}\, Mpc^{-3}}$ by z ≈ 10, remaining largely unaffected by the presence of Pop II feedback. At z  = 7.5, ${\sim } 20{{\ \rm per\ cent}}$ of Pop III star formation occurs in isolated haloes that have never experienced any Pop II star formation (i.e. primordial haloes). We predict that Pop III-only galaxies exist at magnitudes MUV ≳ −11, beyond the limits for direct detection with the James Webb Space Telescope. We assess that our stellar mass function (SMF) and UV luminosity function (UVLF) agree well with the observed low mass/faint-end behaviour at z = 8 and 10. However, beyond the current limiting magnitudes, we find that both our SMF and UVLF demonstrate a deviation/turnover from the expected power-law slope (MUV,turn = −13.4 ± 1.1 at z  = 10). This could impact observational estimates of the true SFRD by a factor of 2(10) when integrating to MUV = −12 (−8) at z ∼ 10, depending on integration limits. Our turnover correlates well with the transition from dark matter haloes dominated by molecular cooling to those dominated by atomic cooling, for a mass Mhalo ≈ 108 M⊙ at z ≃ 10.

scholarly journals Molecular Spectroscopy as Diagnostics of Outer Atmosphere of Cool Luminous Stars: Quasi-Static Turbulent Molecular Formation Zone and Stellar Mass-Loss

1988 ◽  
Vol 108 ◽  
pp. 158-166
Author(s):  
Takashi Tsuji
Keyword(s):  
Mass Loss ◽  
Molecular Spectroscopy ◽  
Recent Theory ◽  
Cool Component ◽  
Giant Stars ◽  
Molecular Formation ◽  
Formation Zone ◽  
Thermally Driven ◽  
Molecular Cooling ◽  
Outer Atmosphere

AbstractThe origin of mass-loss in cool luminous stars is still obscure; several known mechanisms such as thermally driven wind, radiation-driven wind(via dust), wave-driven wind etc all have serious difficulties, if examined in the light of recent observations. At the same time, recent observations in the infrared and radio spectral domains revealed that outer envelope of red (super)giant stars has highly complicated spatial and velocity structures, while inner envelope may have new component that had not been recognized before. For example, recent high resolution infrared spectroscopy revealed a possible presence of a quasi-static turbulent molecular dissociation zone somewhere in the outer atmosphere. This new component may represent a transition zone between the warm chromosphere and the huge expanding molecular envelope, and may be a cool component of chromospheric inhomogeneity or a moleclar condensation in a cool corona extended by turbulent pressure. Such a result can be regarded as observational evidence in support of a recent theory of autocatalytic molecular formation by thermal instability due to molecular cooling. Thus, observation and theory consistently show the presence of a new component - quasi-static turbulent molecular formation zone - in outer atmosphere of cool luminous stars, and a possibility of a unified understanding of outer atmospheric structure and mass-loss, in which turbulence may play important role, can be proposed.

scholarly journals A hydrodynamical study of fragmenting gas clouds

1991 ◽  
Vol 147 ◽  
pp. 464-465
Author(s):  
Joe Monaghan ◽  
John Lattanzio
Keyword(s):  
Molecular Cooling

We present 3-D hydrodynamical calculations of collapsing rotating gas clouds, with molecular cooling. We find that cooling significantly inreases the number of fragments.

Cosmic-Ray Heating and Molecular Cooling of Dense Clouds

1973 ◽  
Vol 179 ◽  
pp. L147 ◽  
Author(s):  
A. E. Glassgold ◽  
William D. Langer
Keyword(s):  
Cosmic Ray ◽  
Molecular Cooling

Vibrationally excited benzene molecular cooling in supersonic beams

1998 ◽  
Author(s):  
V. N. Ishchenko ◽  
S. A. Kochubei ◽  
V. I. Makarov
Keyword(s):  
Vibrationally Excited ◽  
Supersonic Beams ◽  
Molecular Cooling

scholarly journals Hydrogen Molecules and the Radiative Cooling of Pregalactic Shocks

1987 ◽  
Vol 117 ◽  
pp. 365-365
Author(s):  
Paul R. Shapiro ◽  
Hyesung Kang
Keyword(s):  
Shock Wave ◽  
Initial Density ◽  
Density Fluctuations ◽  
Time Dependent ◽  
Radiative Cooling ◽  
Number Density ◽  
Molecule Formation ◽  
Hydrogen Molecules ◽  
Molecular Cooling ◽  
Sufficient Concentration

When a pregalactic gas of H and He is heated and reionized, as by a shock wave occurring in the nonlinear collapse of density fluctuations or in the case of explosions in the IGM, the gas cools radiatively and recombines out of equilibrium. The temperature drops faster than the ions can recombine. When the temperature falls below 104K, the residual electron concentration is large enough, as a result, to form H− ions which form H2 molecules, via (H + e → H− + hν) and (H + H− → H2 + e). Molecules also form via (H+ + H → H2+ + hν) and (H2+ + H → H2 + H+). As a consequence, H2 can form with a sufficient concentration (∼10−3) to cool the gas further, by rot-vibrational line excitation and the formation process itself, to ∼102K. This has an important effect on the Jeans mass and fragmentation. We show some illustrative results below for the time-dependent cooling and non-equilibrium recombination and molecule formation. The three cases are as follows: (1) isochoric cooling at hydrogen number density 1 cm−3; (2) isochoric cooling at 3×107 cm−3; (3) isobaric cooling starting at initial density 1 cm−3. At high densities, molecular cooling is suppressed.

scholarly journals Direct collapse to supermassive black hole seeds: the critical conditions for suppression of H2 cooling

2020 ◽  
Vol 492 (4) ◽  
pp. 4917-4926
Author(s):  
Yang Luo ◽  
Isaac Shlosman ◽  
Kentaro Nagamine ◽  
Taotao Fang
Keyword(s):  
Radiation Field ◽  
Gas Flow ◽  
Background Radiation ◽  
High Redshift ◽  
Fixed Ratio ◽  
Critical Curve ◽  
Critical Conditions ◽  
Wide Range ◽  
Molecular Cooling ◽  
Atomic Cooling

ABSTRACT Observations of high-redshift quasars imply the presence of supermassive black holes (SMBHs) already at $z$ ∼ 7.5. An appealing and promising pathway to their formation is the direct collapse scenario of a primordial gas in atomic-cooling haloes at $z$ ∼ 10–20, when the $\rm H_{2}$ formation is inhibited by a strong background radiation field, whose intensity exceeds a critical value, Jcrit. To estimate Jcrit, typically, studies have assumed idealized spectra, with a fixed ratio of $\rm H_{2}$ photodissociation rate $k_{\rm H_2}$ to the $\rm H^-$ photodetachment rate $k_{\rm H^-}$. This assumption, however, could be too narrow in scope as the nature of the background radiation field is not known precisely. In this work we argue that the critical condition for suppressing the H2 cooling in the collapsing gas could be described in a more general way by a combination of $k_{\rm H_2}$ and $k_{\rm H^-}$ parameters, without any additional assumptions about the shape of the underlying radiation spectrum. By performing a series of cosmological zoom-in simulations covering a wide range of relevant $k_{\rm H_2}$ and $k_{\rm H^-}$ parameters, we examine the gas flow by following evolution of basic parameters of the accretion flow. We test under what conditions the gas evolution is dominated by $\rm H_{2}$ and/or atomic cooling. We confirm the existence of a critical curve in the $k_{\rm H_2}{\!-\!}k_{\rm H^-}$ plane and provide an analytical fit to it. This curve depends on the conditions in the direct collapse, and reveals domains where the atomic cooling dominates over the molecular cooling. Furthermore, we have considered the effect of $\rm H_{2}$ self-shielding on the critical curve, by adopting three methods for the effective column density approximation in $\rm H_{2}$. We find that the estimate of the characteristic length scale for shielding can be improved by using λJeans25, which is 0.25 times that of the local Jeans length, which is consistent with previous one-zone modelling.

scholarly journals Molecular Cooling in the Outer Atmospheres of Red Giants

1989 ◽  
Vol 106 ◽  
pp. 381-381
Author(s):  
David Muchmore
Keyword(s):  
Shock Waves ◽  
Dissociation Energy ◽  
Convection Zone ◽  
Radiative Cooling ◽  
Red Giants ◽  
Post Shock ◽  
Molecular Cooling

In the outer atmospheres of cool giants and supergiants there is a competition between heating by shock waves which develop from noise lower down in the convection zone and radiative cooling. The post-shock cooling is most effective in keeping temperatures low and in damping shocks if molecules (especially CO) form. CO is important both because of its high dissociation energy (11 eV) and its large IR opacity.

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