The Need for a Second Black Hole at the Galactic Center

By Brad M. S. Hansen, Milos Milosavljevic. 2003

145 citations recorded by the source corpus.

Deep infrared observations and long-term monitoring programs have provided dynamical evidence of a supermassive black hole of mass 3 × 106 M☉ associated with the radio source Sagittarius A* at the center of our Galaxy. The brightest stars orbiting within 0.1 pc of the black hole appear to be young, massive main-sequence stars, in spite of an environment near the black hole that is hostile to star formation. We discuss mechanisms by which stars born outside the central parsec can sink toward the black hole and conclude that the drag coming from plausible stellar populations does not operate on the short timescales required by the stellar ages. We propose that these stars were dragged in by a second black hole of mass ~103-104 M☉, which would be classified as an intermediate-mass black hole. We discuss the implications for the stellar populations and the kinematics in the Galactic center. Finally, we note that continued astrometric monitoring of the central radio source offers us the prospect for a direct detection of such objects.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/f6364553562ec235455f137032afb882e0af4b04

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. T. Alexander
2. F. Antonini
3. R. Genzel
4. D. Merritt
5. Clovis Hopman
6. A. Ghez
7. F. Eisenhauer
8. H. Perets

In Atomic and Molecular Physics, and Optics

1. T. Alexander
2. R. Genzel
3. T. Ott
4. S. Gillessen
5. A. Ghez
6. F. Eisenhauer
7. A. Eckart
8. S. Tremaine

Citations in the corpus

• Intermediate - mass black holes (2003, background): “Intriguingly, some of the specifics of the stellar distribution very near the Galactic center may be best explained by the presence of an intermediate-mass black hole (Hansen & Milosavljevic 2003).”
• Starbursts near supermassive black holes: young stars in the Galactic Centre, and gravitational waves in LISA band (2006, background): “In the alternative scenario (Gerhard 2001, Hansen and Milosavljevic 2003), the stars were born tens of parsecs from SgrA* c© 0000 RAS and were originally members of a massive star cluster.”
• STELLAR POPULATIONS IN THE CENTRAL 0.5 pc OF THE GALAXY. II. THE INITIAL MASS FUNCTION (2013, background): “…years, the cluster must be very massive and centrally concentrated and perhaps even host an intermediate mass black hole (IMBH) at its center (Kim & Morris 2003; Portegies Zwart et al. 2003; McMillan & Portegies Zwart 2003; Gürkan & Rasio 2005; Hansen & Milosavljević 2003; Kim et al. 2004).”
• Massive Perturber-driven Interactions between Stars and a Massive Black Hole (2006, background): “Alternatively, it must contain an unusually massive central IMBH to hold it together against the tidal field of the GC (Hansen & Milosavljević 2003).”
• The Proper Motion of Sagittarius A*. II. The Mass of Sagittarius A* (2004, background): “The possibility that a binary black hole exists in the center of the Galaxy has been discussed by Hansen & Milosavljević (2003) and Yu & Tremaine (2003).”
• Stellar Remnants in Galactic Nuclei: Mass Segregation (2006, background): “…sharp opposition to our simplifying assumptions, is that the Sgr A cluster and its central MBH have been formed progressively by the infall of rich stellar clusters, some of them containing intermediate-mass black holes ( IMBHs; Hansen & Milosavljević 2003; Kim et al. 2004; Gürkan & Rasio 2005).”
• HCN and HCO+ Observations of the Galactic Circumnuclear Disk (2005, background): “…numerical simulations have found that a 105 M⊙ cluster at the radius of the CND (or a less massive cluster harboring an intermediate mass black hole) could spiral into the inner parsec within the lifetime of the 2-7 Myr stars (Kim & Morris 2003; Kim et al. 2004; Hansen & Milosavljevic 2003).”
• Massive Primordial Black Holes as Dark Matter and their detection with Gravitational Waves (2017, background): “Moreover, PBH could also be responsible for the observed ultra luminous x-ray sources, the SMBH and IMBH at centers of galaxies and globular clusters, and alleviate the substructure and too-big-to-fail problems of the standard CDM paradigm.”
• Ejection of Hypervelocity Stars by the (Binary) Black Hole in the Galactic Center (2003, methodology): “SgrA∗ may be one component of a BBH (Hansen & Milosavljević 2003).”
• Stellar Orbits around the Galactic Center Black Hole (2003, background): “The implications of such a cluster-produced IBH for the distribution of early-type stars in the central parsec have recently been investigated by Hansen & Milosavljević (2003).”
• The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics, and Formation (2006, background): “…orbits in the central light month around the central black hole, probably requires yet another explanation (recently Ghez et al. 2003, 2005; Genzel et al. 2003; Hansen & Milosavljevic 2003; Gould & Quillen 2003; Alexander & Livio 2004; Eisenhauer et al. 2005; Alexander 2005; Davies & King 2005).”
• MONITORING STELLAR ORBITS AROUND THE MASSIVE BLACK HOLE IN THE GALACTIC CENTER (2008, result): “Similar arguments constraining the binarity of Sgr A* have been put forward by Hansen & Milosavljevic (2003), whose results we also show in Figure 18.”
• A DISK OF YOUNG STARS AT THE GALACTIC CENTER AS DETERMINED BY INDIVIDUAL STELLAR ORBITS (2008, background): “…and centrally concentrated (Kim & Morris 2003; Portegies Zwart et al. 2003; McMillan & Portegies Zwart 2003; Gürkan & Rasio 2005), and it may even require the existence of an intermediate-mass black hole (IMBH) as an anchor in the cluster core (Hansen & Milosavljević 2003; Kim et al. 2004).”
• Formation of Massive Black Holes in Dense Star Clusters. I. Mass Segregation and Core Collapse (2003, background): “…time to its presentday state with t rh ≥ 10 8 yr (Lauer et al. 1998), or that the growth of the central BH was predominantly from accretion of smaller star clusters with short relaxation times (each one carrying an IMBH at its center ; Ebisuzaki et al. 2001; Hansen & Milosavljevi´c 2003).”
• Massive Black Hole Binary Evolution (2004, background): “This process might explain the puzzling presence of early-type stars [66, 68] deep inside the sphere of influence of the SBH at the Galactic center ([84], but see [99]).”
• SINFONI in the Galactic Center: Young Stars and Infrared Flares in the Central Light-Month (2005, background): “…properties) to the center: (1) the dissolving sinking cluster (Gerhard 2001; Portegies Zwart et al. 2003) bound by an intermediate-mass black hole (Hansen & Milosavljevic 2003; Kim et al. 2004); (2) the massive binary exchange (Gould & Quillen 2003); and (3) exchange capture with stellar…”