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Levin, Marvin E.; O’Neal, Lawrence W.

doi:10.1016/b978-84-8086-367-4.50038-2

Cited by 18 publications

(32 citation statements)

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“…These considerations were confirmed by Levin (2005), who studied analytically the distribution of escapers created by an SMBH–IMBH pair in a dense stellar cusp. He found that the ejection of stars in case of a black hole binary is happening mainly in a burst which lasts a few dynamical friction time‐scales and that if the IMBH is initially in a nearly circular orbit, the velocity vectors of the ejected stars also cluster around the orbital plane.…”

Section: Introductionmentioning

confidence: 67%

Ejection of hypervelocity stars from the Galactic Centre by intermediate-mass black holes

Baumgardt

Gualandris

Zwart

2006

Monthly Notices of the Royal Astronomical Society

115

153

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We have performed N‐body simulations of the formation of hypervelocity stars (HVS) in the centre of the Milky Way due to inspiralling intermediate‐mass black holes (IMBHs). We considered IMBHs of different masses, all starting from circular orbits at an initial distance of 0.1 pc. We find that the IMBHs sink to the centre of the Galaxy due to dynamical friction, where they deplete the central cusp of stars. Some of these stars become HVS and are ejected with velocities sufficiently high to escape the Galaxy. Since the HVS carry with them information about their origin, in particular in the moment of ejection, the velocity distribution and the direction in which they escape the Galaxy, detecting a population of HVS will provide insight in the ejection processes and could therefore provide indirect evidence for the existence of IMBHs. Our simulations show that HVS are generated in short bursts which last only a few Myr until the IMBH is swallowed by the supermassive black hole (SMBH). HVS are ejected almost isotropically, which makes IMBH‐induced ejections hard to distinguish from ejections due to encounters of stellar binaries with a SMBH. After the HVS have reached the galactic halo, their escape velocities correlate with the distance from the Galactic Centre in the sense that the fastest HVS can be found furthest away from the centre. The velocity distribution of HVS generated by inspiralling IMBHs is also nearly independent of the mass of the IMBH and can be quite distinct from one generated by binary encounters. Finally, our simulations show that the presence of an IMBH in the Galactic Centre changes the stellar density distribution inside r < 0.02 pc into a core profile, which takes at least 100 Myr to replenish.

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Section: Introductionmentioning

confidence: 67%

Ejection of hypervelocity stars from the Galactic Centre by intermediate-mass black holes

Baumgardt

Gualandris

Zwart

2006

Monthly Notices of the Royal Astronomical Society

115

153

View full text Add to dashboard Cite

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“…A related point is that steady‐state constant accretion rate disc models show that there is always the minimum radius where star formation becomes impossible as Q > 1 there (e.g. Goodman 2003; Nayakshin & Cuadra 2005; Levin 2006). The value of the minimum distance where star formation should be expected is comparable to the minimum radius for which we predict favourable conditions for development of a top‐heavy IMF.…”

Section: Discussionmentioning

confidence: 99%

“…The appropriate accretion disc equations for Q ∼ 1 have been discussed by many authors (see references in the Introduction and, for the protoplanetary disc case, Rafikov 2005). In particular, we follow most closely the logic of Levin (2006). In our picture, as the mass is fed into the disc from outside, from e.g.…”

Section: Pre‐collapse Accretion Discmentioning

confidence: 96%

“…With more and more mass available to drive self‐gravitational turbulence, α increases, and t cool eventually approaches the value at which the disc just satisfies the Gammie (2001) cooling criterion. Levin (2006) suggests α≃ 0.3, whereas numerical simulations suggests a rather smaller value of α≃ 0.1 (Rice, Lodato & Armitage 2005).…”

Section: Pre‐collapse Accretion Discmentioning

confidence: 97%

“…Numerical simulations with a constant cooling time show (e.g. Gammie 2001) that if the disc cooling time is at the threshold for the fragmentation to take place, then the first gas clumps will grow very rapidly by inelastic collisions with other clumps, possibly until they reach the isolation mass M iso ∼ (π R 2 Σ) 3/2 / M 1/2 BH (Levin 2006). If this is the case, then the main point of our paper (that stars born in an accretion disc near an SMBH are massive on average) is proven, because the isolation mass can be hundreds of to as much as 10 4 M ⊙ (Goodman & Tan 2004).…”

Section: Pre‐collapse Accretion Discmentioning

confidence: 99%

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Massive stars in subparsec rings around galactic centres

Nayakshin

2006

Monthly Notices of the Royal Astronomical Society

104

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We consider the structure of self‐gravitating marginally stable accretion discs in galactic centres in which a small fraction of the disc mass has been converted into protostars. We find that protostars accrete gaseous disc matter at prodigious rates. Mainly due to the stellar accretion luminosity, the disc heats up and thickens geometrically, shutting off further disc fragmentation. The existing protostars, however, continue to gain mass by gas accretion. As a result, the initial mass function for disc‐born stars at distances R∼ 0.03–3 pc from the supermassive black hole should be top‐heavy. The effect is most pronounced at around R∼ 0.1 pc. We suggest that this result explains observations of rings of young massive stars in our Galaxy and in M31, and we predict that more such rings will be discovered.

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The Chaotropic Effect as an Assembly Motif in Chemistry

2018

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Following up on scattered reports on interactions of conventional chaotropic ions (for example, I−, SCN−, ClO4 −) with macrocyclic host molecules, biomolecules, and hydrophobic neutral surfaces in aqueous solution, the chaotropic effect has recently emerged as a generic driving force for supramolecular assembly, orthogonal to the hydrophobic effect. The chaotropic effect becomes most effective for very large ions that extend beyond the classical Hofmeister scale and that can be referred to as superchaotropic ions (for example, borate clusters and polyoxometalates). In this Minireview, we present a continuous scale of water–solute interactions that includes the solvation of kosmotropic, chaotropic, and hydrophobic solutes, as well as the creation of void space (cavitation). Recent examples for the association of chaotropic anions to hydrophobic synthetic and biological binding sites, lipid bilayers, and surfaces are discussed.

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Cited by 18 publications

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Ejection of hypervelocity stars from the Galactic Centre by intermediate-mass black holes

Ejection of hypervelocity stars from the Galactic Centre by intermediate-mass black holes

Massive stars in subparsec rings around galactic centres

The Chaotropic Effect as an Assembly Motif in Chemistry

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