Physical Processes in the Interstellar Medium

Spitzer, Lyman

doi:10.1002/9783527617722

Cited by 1,276 publications

(1,295 citation statements)

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“…It indicates that SMS formation by accretion requires strong mechanisms for extracting angular momentum from the accretion disc like magnetic fields (Schober et al 2012;Latif & Schleicher 2016), viscosity (Popham & Narayan 1991;Takahashi & Omukai 2017) or gravitational torques (Wise et al 2008). This is a particular case of the classical angular momentum problem (Spitzer 1978;Bodenheimer 1995;Maeder 2009). The constraint obtained here is much stronger than in the case of massive Pop I stars (j accr 1/3 j K , Haemmerlé et al 2017a).…”

Section: Constraints On the Accretion Of Angular Momentummentioning

confidence: 99%

“…Star formation requires processes that remove angular momentum from the inner regions of collapsing prestellar clouds, otherwise the centrifugal force would overcome gravity and prevent further collapse (Spitzer 1978;Bodenheimer 1995;Maeder 2009). Numerical studies of Pop III star formation indicate that primordial protostellar seeds rotate near their critical limit (Stacy et al 2011(Stacy et al , 2013, at which the centrifugal force exceeds the gravitational attraction.…”

Section: Introductionmentioning

confidence: 99%

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On the Rotation of Supermassive Stars

Haemmerlé

Woods

Klessen

et al. 2018

ApJL

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Supermassive stars born from pristine gas in atomically-cooled haloes are thought to be the progenitors of supermassive black holes at high redshifts. However, the way they accrete their mass is still an unsolved problem. In particular, for accretion to proceed, a large amount of angular momentum has to be extracted from the collapsing gas. Here, we investigate the constraints stellar evolution imposes on this angular momentum problem. We present an evolution model of a supermassive Population III star including simultaneously accretion and rotation. We find that, for supermassive stars to form by accretion, the accreted angular momentum has to be about 1% of the Keplerian angular momentum. This tight constraint comes from the ΩΓ-limit, at which the combination of radiation pressure and centrifugal force cancels gravity. It implies that supermassive stars are slow rotators, with a surface velocity less than 10 -20% of their first critical velocity, at which the centrifugal force alone cancels gravity. At such low velocities, the deformation of the star due to rotation is negligible.

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Section: Constraints On the Accretion Of Angular Momentummentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On the Rotation of Supermassive Stars

Haemmerlé

Woods

Klessen

et al. 2018

ApJL

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“…One of the persistent puzzles in the study of gas and dust in external galaxies is that the gas-to-dust ratios derived are significantly larger than the Galactic value of ∼150 (Spitzer 1978). This discrepancy is thought to arise from the far-IR (λ ≤ 100 µm) measurements used to derive the dust masses in external galaxies are not sensitive to the cold (10-20 K) dust component, and the derived gas-to-dust mass ratio is expected to approach the Galactic value with the inclusion of longer wavelength measurements.…”

Section: Improved Determination Of Gas and Dust Massmentioning

confidence: 98%

Investigations of star formation in galaxies using ALMA

Yun

2007

Astrophys Space Sci

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ALMA provides unprecedented sensitivity and resolution to study gas and dust emission in the millimeter and submillimeter bands. The magnitude of the improvement is such that not only conventional studies can be done much better but entirely new tools and research fields should also become accessible. In this article, I examine several specific areas where new capabilities of ALMA will bring significant quantitative improvements to the determination of star formation rate and properties of the gas fueling the activities. I propose a survey of nearby galaxies with well measured metallicity gradient during the early phase of the ALMA operation as one of the key science projects.

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“…Krall and Trivelpiece 1973, Eq. 6.8.7) σ = (n e e 2 )/(m e v col ), where n e is the electron number density, −e and m e the electron charge and mass, and v col = nσ col (kT /m e ) 1/2 is the collision frequency for electrons with neutrals of number density n. Taking the electronneutral cross-section σ col ≈ 4 × 10 −15 cm 2 (as in Spitzer 1978) and the mean temperature inside the protoplanet T ≈ 2000 K, and denoting Jupiter values with the subscript Jup, the Ohmic dissipation time …”

Section: Magnetic Torque Requirementsmentioning

confidence: 99%

A magnetic mechanism for halting inward protoplanet migration: I. Necessary conditions and angular momentum transfer timescales

Fleck

2007

Astrophys Space Sci

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A magnetic torque associated with the magnetic field linking a giant, gaseous protoplanet to its host premain-sequence star can halt inward protoplanet migration. This torque results from a toroidal magnetic field generated from the star's poloidal (dipole) field by the twisting differential motion between the star's rotation and the protoplanet's revolution. Outside the corotation radius, where a protoplanet orbits slower than its host star spins, this torque transfers angular momentum from the star to the protoplanet, halting inward migration. Necessary conditions for angular momentum transfer include the requirement that the Alfvén speed v A in the region magnetically linking a protoplanet to its host star exceeds the protoplanet's orbital speed v K . In addition, the timescale for Ohmic dissipation τ D must exceed the protoplanet's orbital period P to ensure that the protoplanet is magnetically coupled to its host star. For a Jupiter-mass protoplanet orbiting a solar-mass premain-sequence star, v A > v K and τ D > P only when the migrating protoplanet approaches within about 0.1 AU of its host star, primarily because of the rapid drop in the strength of the magnetic field with increasing distance from the central star. Because of this restricted reach, inwardly migrating gaseous protoplanets can be expected to "pile up" very close to their central stars, as is indeed observed for extrasolar planets. The characteristic timescale required for a magnetic torque to transfer angular momentum outward from a more rapidly spinning central star to a magnetically coupled protoplanet is found to be comparable to planet-forming disk lifetimes and protoplanet migration timescales.

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Physical Processes in the Interstellar Medium

Cited by 1,276 publications

References 0 publications

On the Rotation of Supermassive Stars

On the Rotation of Supermassive Stars

Investigations of star formation in galaxies using ALMA

A magnetic mechanism for halting inward protoplanet migration: I. Necessary conditions and angular momentum transfer timescales

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