The Global Evolution of Giant Molecular Clouds. I. Model Formulation and Quasi-Equilibrium Behavior

By Mark R. Krumholz, C. Matzner, C. McKee. 2006

161 citations recorded by the source corpus.

We present semianalytic dynamical models for giant molecular clouds evolving under the influence of H II regions launched by newborn star clusters. In contrast to previous work, we neither assume that clouds are in virial or energetic equilibrium, nor do we ignore the effects of star formation feedback. The clouds, which we treat as spherical, can expand and contract homologously. Photoionization drives mass ejection; the recoil of cloud material both stirs turbulent motions and leads to an effective confining pressure. The balance between these effects and the decay of turbulent motions through isothermal shocks determines clouds' dynamical and energetic evolution. We find that for realistic values of the rates of turbulent dissipation, photoevaporation, and energy injection by H II regions, the massive clouds where most molecular gas in the Galaxy resides live for a few crossing times, in good agreement with recent observational estimates that large clouds in Local Group galaxies survive roughly 20-30 Myr. During this time clouds remain close to equilibrium, with virial parameters of 1-3 and column densities near 1022 H atoms cm-2, also in agreement with observed cloud properties. Over their lives they convert 5%-10% of their mass into stars, after which point most clouds are destroyed when a large H II region unbinds them. In contrast, small clouds like those found in the solar neighborhood only survive ~1 crossing time before being destroyed.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/9305bac68060b594da3a5d5f9c02076ebcf8923a

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Citations in the corpus

Why are most molecular clouds not gravitationally bound (2011, background): “This could be magnetic fields and slow ambipolar diffusion (Shu et al. 1987; Basu & Mouschovias 1994; Allen & Shu 2000; Mouschovias et al. 2006; Shu et al. 2007), or microturbulence (Krumholz & McKee 2005; Krumholz et al. 2006).”
Global hierarchical collapse in molecular clouds. Towards a comprehensive scenario (2019, background): “…suggested that the SFR can self-regulate and maintain near-virial balance in the clouds (e.g., Norman & Silk 1980; Franco & Cox 1983; McKee 1989; Krumholz et al. 2006; Goldbaum et al. their surroundings, first as accretion during cloud growth, and then as return of material during the cloud…”
Before the first supernova: combined effects of H II regions and winds on molecular clouds (2014, unknown): “…the clouds with the highest escape velocities, where gravity plays a greater role, are those for which Equation 15 overestimates the ionised mass. Krumholz et al. (2006) and Goldbaum et al. (2011) perform one–dimensional simulations of the effects of HII regions on clouds over much longer…”
WHAT DRIVES THE EXPANSION OF GIANT H ii REGIONS?: A STUDY OF STELLAR FEEDBACK IN 30 DORADUS (2010, background): “This inefficiency can be attributed to the internal processes of HII regions that disrupt their host molecular clouds (e.g., Matzner 2002; Krumholz et al. 2006), but 1 Department of Astronomy and Astrophysics, University of California Santa Cruz, 159 Interdisciplinary Sciences Building, 1156 High…”
MAXIMALLY STAR-FORMING GALACTIC DISKS. I. STARBURST REGULATION VIA FEEDBACK-DRIVEN TURBULENCE (2011, background): “…<∼ ΣGMC is consistent with the idea that spatially-isolated GMCs have an approximately constant specific star formation rate; this rate, and the value of ΣGMC, may be controlled by internal feedback processes within GMCs (e.g. Krumholz et al. 2006), although this is not yet completely understood.”
Dispersal of molecular clouds by ionizing radiation (2012, background): “Krumholz et al. (2006) study the disruptive power of Hii regions using semi-analytical models, and conclude that lower mass clouds (M .”
THE DISRUPTION OF GIANT MOLECULAR CLOUDS BY RADIATION PRESSURE & THE EFFICIENCY OF STAR FORMATION IN GALAXIES (2009, background): “It is possible, in principle, that gravitational contraction of a GMC can sustain the turbulence, maintaining approximate virial equilibrium and a slow contraction of the cloud (Krumholz et al. 2006).”
THE STAR FORMATION RATE OF TURBULENT MAGNETIZED CLOUDS: COMPARING THEORY, SIMULATIONS, AND OBSERVATIONS (2012, background): “…et al. 2004; de Avillez & Breitschwerdt 2005; Tamburro et al. 2009) or growing Hii regions around massive stars and clusters of stars (McKee 1989; Krumholz et al. 2006; Gritschneder et al. 2009; Peters et al. 2010; Goldbaum et al. 2011) as well as compression of ISM gas in galactic spiral shocks…”
Modeling UV Radiation Feedback from Massive Stars. II. Dispersal of Star-forming Giant Molecular Clouds by Photoionization and Radiation Pressure (2018, background): “The former expression multiplied by a factor two has also been applied for blister H II regions, assuming that in addition to thermal pressure the cloud back-reacts to photoevaporation from a D-critical IF with ρic 2 i Ai = Ṁionci (e.g., Matzner 2002; Krumholz et al. 2006).”
The CO-H2 Conversion Factor in Disc Galaxies and Mergers (2011, background): “The origin of these observed elationships is debated, but their universality argues for some sort of internal regulation mechanism operating in GMCs (e.g. Krumholz et al. 2006; Shetty & Ostriker 2008).”
Massive stars in massive clusters II: Disruption of bound clusters by photoionization (2012, background): “Vázquez-Semadeni et al. (2010) examine the effect of ionizing feedback on both accretion of material onto GMCs themselves, and on the star formation rates within.”