Stellar Processes Near the Massive Black Hole in the Galactic Center

By T. Alexander. 2005

270 citations recorded by the source corpus.

A massive black hole resides in the center of most, perhaps all galaxies. The one in the center of our home galaxy, the Milky Way, provides a uniquely accessible laboratory for studying in detail the connections and interactions between a massive black hole and the stellar system in which it grows; for investigating the effects of extreme density, velocity and tidal fields on stars; and for using stars to probe the central dark mass and probe post-Newtonian gravity in the weak- and strong-field limits. Recent results, open questions and future prospects are reviewed in the wider context of the theoretical framework and physical processes that underlie them. Contents: [1] Introduction (1.1) Astrophysical context (1.2) Science questions (1.3) Scope and connections to related topics [2] Observational overview: Stars in the Galactic center (2.1) The central 100 parsecs (2.2) The central parsec [3] Stellar dynamics at extreme densities (3.1) Physical processes and scales (3.2) The stellar cusp in the Galactic center (3.3) Mass segregation (3.4) Stellar Collisions [4] Probing the dark mass with stellar dynamics (4.1) Weighing and pinpointing the dark mass (4.2) Constraints on non-BH dark mass alternatives (4.3) Limits on MBH binarity (4.4) High-velocity runaway stars [5] Probing post-Newtonian gravity near the MBH (5.1) Relativistic orbital effects (5.2) Gravitational lensing [6] Strong star-MBH interactions (6.1) Tidal disruption (6.2) Dissipative interactions with the MBH [7] The riddle of the young stars (7.1) The difficulties of forming or importing stars near a MBH (7.2) Proposed solutions (7.3) Feeding the MBH with stellar winds [8] Outlook (8.1) Progress report (8.2) Future directions

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/f50538744122962029c6fd38f1647b867b215841

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In Astronomy and Astrophysics

1. T. Alexander
2. R. Genzel
3. F. Antonini
4. P. Hopkins
5. E. Quataert
6. B. Kocsis
7. B. Metzger
8. F. Eisenhauer

Citations in the corpus

• Stellar Dynamics and Stellar Phenomena Near a Massive Black Hole (2017, methodology): “For example, for a Milky Way-like nucleus, where rh ∼ few × 1 pc and ai ∼ few × 0.01 pc (Hopman & Alexander 2005), the ratio of GW inspiral rate to plunge rate 12 is Γi/Γp ∼ O(0.01).”
• STRONG MASS SEGREGATION AROUND A MASSIVE BLACK HOLE (2008, methodology): “…but instead assume for simplicity a non-evolving mass function that is based on a model of the GC’s present day mass mass function (PMF) as an old, continuously star forming population with the “universal” initial mass function (IMF) (Alexander & Sternberg 1999; Alexander 2005, table 2.1).”
• A DISK OF YOUNG STARS AT THE GALACTIC CENTER AS DETERMINED BY INDIVIDUAL STELLAR ORBITS (2008, background): “The origin of such young stars has been difficult to explain since the gas densities observed today are orders of magnitude too low for a gas clump to overcome the extreme tidal forces and collapse to form stars (e.g. Sanders 1992; Morris 1993; Ghez et al. 2005b; Alexander 2005, for reviews).”
• Optical Flares from the Tidal Disruption of Stars by Massive Black Holes (2009, background): “For realistic stellar density profiles, the disruption rate is dominated by the boundary between these two regimes (e.g., Alexander 2005), so many stars probably do take large enough angular momentum steps to arrive at Rp ≪ RT.”
• The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics, and Formation (2006, background): “The GC has many features that are thought to occur in other nuclei (for reviews, see Genzel & Townes 1987; Morris & Serabyn 1996; Mezger, Duschl & Zylka 1996; Alexander 2005).”
• Doing Science with eLISA: Astrophysics and Cosmology in the Millihertz Regime (2012, background): “Dynamical effects, in particular mass segregation, will lead to many interactions close to the central black hole so that wide binaries will become tighter or will be disrupted (for a review see Alexander, 2005).”
• The structure of the nuclear stellar cluster of the Milky Way (2006, methodology): “The mean mass of the entire population (including fainter stars and remnants) is 〈M 〉 = 0.5 M (Alexander 2005, Table 2.1).”
• Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole (2020, background): “The Galactic Centre (GC) currently provides the best ‘laboratory’ for testing GR near MBHs and ultimately for testing the MBH paradigm (Alexander 2005, 2017; Genzel et al. 2010; Psaltis et al. 2016).”
• Massive Perturber-driven Interactions between Stars and a Massive Black Hole (2006, background): “For inspiral processes such as GW emission, rc is ∼ 100 times smaller still (Hopman & Alexander 2005, 2006b).”
• Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole (2018, background): “These terms can be parameterised spectroscopically as (e.g. Misner et al. 1973; Alexander 2005; Zucker et al. 2006). z = ∆λ λ = B0 + B0.”
• Eccentric Black Hole Gravitational-wave Capture Sources in Galactic Nuclei: Distribution of Binary Parameters (2017, background): “Here, Ci represents the number fraction ratios of MSs, WDs, and NSs as 1:0.1:0.01 for continuous star-forming populations (Alexander 2005), implying that a a = = = - - ( )C C C1, 0.1, 0.01 3 3 .”
• Resonant Relaxation near a Massive Black Hole: The Stellar Distribution and Gravitational Wave Sources (2006, methodology): “To verify that RR does not significantly affect the transition phase of inspiral and the value of the critical energy, we followed the approach used by Hils & Bender (1995) and Hopman & Alexander (2005), who performed Monte Carlo (MC) simulations of the scattering of stars inJ-space.”
• TIDAL DISRUPTION AND IGNITION OF WHITE DWARFS BY MODERATELY MASSIVE BLACK HOLES (2008, background): “Because of this reason, the innermost ∼ 0.1 pc of our Galaxy can be considered an efficient stellar collider (Alexander 2005).”
• Merging Binaries in the Galactic Center: The eccentric Kozai-Lidov mechanism with stellar evolution (2016, background): “It is unclear if these binaries could have formed there as the gravitational and tidal forces should prevent the formation of stars so close to the MBH (see, for example, Allen & Sanders 1986; Morris 1993; Ghez et al. 2003; Alexander 2005; Genzel et al. 2010).”
• Stellar Remnants in Galactic Nuclei: Mass Segregation (2006, methodology): “At the same time, as already pointed out in the pioneering work of Hils & Bender (1995) and analyzed in detail by Hopman & Alexander (2005), encounters with other stars may cause an inspiraling star to plunge prematurely before its orbital frequency has entered the LISA band.”
• Testing the General Relativistic “No-Hair” Theorems Using the Galactic Center Black Hole Sagittarius A* (2007, background): “…infrared telescopes, of stars orbiting within an arcsecond of the central object SgrA∗ in our galaxy, together with accurate determinations of their orbits, has provided strong evidence for the existence there of a massive black hole (MBH) of around 3.6×106 M⊙ (see Alexander (2005) for a review).”
• The old Nuclear Star Cluster in the Milky Way (2014, background): “The relaxation time of the NSC within 1 pc is tr ∼ 1010 yr (Alexander 2005; Merritt 2013), indicating that the NSC is not fully relaxed and is likely to be evolving.”