The Formation of Massive Stars from Turbulent Cores

By C. McKee, Jonathan C. Tan. 2002

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Observations indicate that massive stars in the Galaxy form in regions of very high surface density, Σ ~ 1 g cm-2. Clusters containing massive stars and globular clusters have a column density comparable to this. The total pressure in clouds of such a column density is P/k ~ 108-109 K cm-3, far greater than that in the diffuse interstellar medium or the average in giant molecular clouds. Observations show that massive-star-forming regions are supersonically turbulent, and we show that the molecular cores out of which individual massive stars form are as well. The protostellar accretion rate in such a core is approximately equal to the instantaneous mass of the star divided by the free-fall time of the gas that is accreting onto the star, as described by Stahler, Shu, & Taam. The star formation time in this turbulent core model for massive-star formation is several times the mean free-fall time of the core out of which the star forms but is about equal to that of the region in which the core is embedded. The high densities in regions of massive-star formation lead to typical timescales for the formation of a massive star of about 105 yr. The corresponding accretion rate is high enough to overcome the radiation pressure due to the luminosity of the star. For the typical case we consider, in which the cores out of which the stars form have a density structure ρ ∝ r-1.5, the protostellar accretion rate grows with time as * ∝ t. We present a new calculation of the evolution of the radius of a protostar and determine the protostellar accretion luminosity. At the high accretion rates that are typical in regions of massive-star formation, protostars join the main sequence at about 20 M☉. We apply these results to predict the properties of protostars thought to be powering several observed hot molecular cores, including the Orion hot core and W3(H2O). In the appendices we discuss the pressure in molecular clouds and argue that "logatropic" models for molecular clouds are incompatible with observation.

Subfields: Astronomy and Astrophysics, Materials Chemistry, Physical and Theoretical Chemistry

View Paper: https://www.semanticscholar.org/paper/b57e15b78e2460f455fbdce69e175f93f0fe5120

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Citations in the corpus

Ammonia from cold high-mass clumps discovered in the inner Galactic disk by the ATLASGAL survey (2012, background): “…(1) in the turbulent core model massive star forming clouds are supported against gravitational collapse mainly by supersonic turbulence (McKee & Tan 2003; Mac Low & Klessen 2004); (2) according to recent simulations of star formation in clusters (e.g. Bonnell et al. 1997, 2001), the…”
Fragmentation and mass segregation in the massive dense cores of Cygnus X (2009, methodology): “The targeted MDCs of Cygnus X have globally the properties proposed as initial conditions by McKee & Tan (2003) for the turbulence-regulated, monolithic collapse.”
LOW VIRIAL PARAMETERS IN MOLECULAR CLOUDS: IMPLICATIONS FOR HIGH-MASS STAR FORMATION AND MAGNETIC FIELDS (2013, methodology): “The non–magnetized version of the “turbulent core” HMSF model by McKee & Tan (2002, 2003) posits that high accretion rates in HMSF do indeed result from the collapse of cloud fragments initially supported by high velocity dispersions.”
Probing the formation of intermediate- to high-mass stars in protoclusters - A detailed millimeter study of the NGC 2264 clumps (2005, background): “…the formation of a highmass∼ 10-20 M⊙ star in the central part of NGC 2264- C. Based on this comparison, we propose a picture of high-mass star formation in protoclusters intermediate between the highly dynamic scenario of Bonnell et al. (1998) and the turbulent core scenario of McKee & Tan (2003).”
RADIATION-HYDRODYNAMIC SIMULATIONS OF THE FORMATION OF ORION-LIKE STAR CLUSTERS. II. THE INITIAL MASS FUNCTION FROM WINDS, TURBULENCE, AND RADIATION (2012, methodology): “We can make the link between the massive cores and the stars they form more quantitative by comparing to the massive core evolution model of McKee & Tan (2002, 2003) and Tan & McKee (2004).”
LIMITING ACCRETION ONTO MASSIVE STARS BY FRAGMENTATION-INDUCED STARVATION (2010, background): “An alternative approach is to argue that high-mass stars form just like low-mass stars by accretion of ambient gas that goes through a rotationally supported disk caused by angular momentum conservation (McKee & Tan 2003).”
ATLASGAL — towards a complete sample of massive star forming clumps ⋆ (2014, methodology): “Using the turbulent core-collapse model with accelerating accretion rates proposed by McKee & Tan (2003) as their starting point, they calculated how the clump mass and source bolometric luminosity should change as the protostar evolves, producing evolutionary tracks for stars with final masses…”
The Global Evolution of Giant Molecular Clouds. I. Model Formulation and Quasi-Equilibrium Behavior (2006, neutral): “…correspond to the regime of formation of individual OB associations and open clusters, which is characterized by relatively high column densities (McKee & Tan 2003) and star formation efficiencies >∼ 10% (Lada & Lada 2003), and probably requires many crossing times to complete (Tan et al. 2006).”
ATLASGAL - The APEX telescope large area survey of the galaxy at 870 μm (2009, background): “High-mass star formation is even less well constrained (e.g., Zinnecker & Yorke 2007; Beuther et al. 2007, for reviews) and there is controversy about how these stars attain their final masses: either driven by turbulence (McKee & Tan 2003) or competitive accretion (e.g., Bonnell et al. 2004).”
SIMBA survey of southern high-mass star forming regions. I. Physical parameters of the 1.2-mm/IRAS sources (2004, background): “Due to the intrinsic scarcity of highmass stars and the short timescales involved in their formation (t ∼ 105 yr, McKee & Tan 2003), the early stages of such formation have been only recently explored by systematic surveys (Plume et al. 1992, 1997; Bronfman et al. 1996; Beuther et al. 2002;…”
Gravitational Instabilities in Circumstellar Disks (2016, background): “…yr−1, where the lower end is consistent with accretion rates observed on actively accreting T Tauri stars towards the end of their lives, and the highest rates represent a generous upper limit set by infall from a supersonic core for more massive stars (McKee & Tan 2003; Klaassen et al. 2011) .”
Gravity or turbulence? Velocity dispersion–size relation (2010, background): “Such Virial equilibrium states require that the mass fragments are bound by an external pressure (Elmegreen 1989; McKee & Tan 2003; Field et al. 2010).”
Theory of Star Formation (2007, background): “The high accretion rates characteristic of HMPOs delay the point at which the stars reach the main sequence (McKee & Tan, 2003; Krumholz & Thompson, 2007), thereby delaying the time at which the photosphere is hot enough to produce an H II region.”
Fragmentation of massive protostellar discs (2006, methodology): “To calculate core and core collapse properties, we adopt c© 0000 RAS, MNRAS 000, 000–000 the McKee & Tan (2003) models and fiducial parameters.”
CIRCUMVENTING THE RADIATION PRESSURE BARRIER IN THE FORMATION OF MASSIVE STARS VIA DISK ACCRETION (2010, background): “Previous theoretical models focused on different points of view, namely, the competitive accretion (Bonnell et al. 1998; Bonnell & Bate 2002; Bonnell et al. 2004; Bate 2009a, 2009b) and the turbulent core model (McKee & Tan 2003), but they agree on the formation of accretion disks.”
The RMS Survey: Ammonia and water maser analysis of massive star forming regions. ⋆ (2011, background): “This means that once the accreted mass exceeds∼20 M⊙ the star arrives on the main-sequence, even if accretion is still ongoing (see also McKee & Tan 2003).”
Massive star formation: nurture, not nature (2004, background): “In the first scenario, the stellar environment is unimportant and the mass is decided by the amount of mass which is necessary to be self-gravitating considering either thermal or turbulent support (Yorke & Kruegel 1977; McKee & Tan 2002, 2003).”
THE RED MSX SOURCE SURVEY: THE MASSIVE YOUNG STELLAR POPULATION OF OUR GALAXY (2013, background): “The high densities and degree of turbulence and short timescales involved in such regions lead to accretion rates sufficient to ensure the infalling material overcomes the radiation pressure (eg McKee & Tan 2003).”