Stellar Dynamics in the Central Arcsecond of Our Galaxy

By R. Schoedel, T. Ott, R. Genzel, A. Eckart, N. Mouawad, T. Alexander. 2003

318 citations recorded by the source corpus.

With 10 years of high-resolution imaging data now available on the stellar cluster in the Galactic center, we present proper motions for more than 40 stars at projected distances ≤1.″2 from Sagittarius A* (Sgr A*). We find evidence on a ≥2 σ level for radial anisotropy of the cluster of stars within 1'' of Sgr A*. For a brightness limit of K ~ 15.5, we find no evidence for a stationary source at the position of Sgr A* or for a source at this position that would be variable on a timescale of at least several hours to days. On timescales of seconds to tens of minutes, we find no variability at the Sgr A* position on brightness levels K ≤ 13.5. We confirm/find accelerated motion for six stars, with four stars having passed the pericenter of their orbits during the observed time span. We calculated/constrained the orbital parameters of these stars. All orbits have moderate to high eccentricities. We discuss the possible bias in detecting preferentially orbits with high eccentricities and find that measured values of e > 0.9 might be detected by about a factor of 1.5-2 more frequently. We find that the center of acceleration for all the orbits coincides with the radio position of Sgr A*. From the orbit of the star S2, the currently most tightly constrained one, we determine the mass of Sgr A* to be × 106 M☉ and its position to 2.0 ± 2.4 mas east and 2.7 ± 4.5 mas south of the nominal radio position. The mass estimate for the central dark mass from the orbit of S2 is fully consistent with the mass estimate of × 106 M☉ obtained from stellar proper motions within 1.″2 of Sgr A* using a Leonard-Merritt mass estimator. We find that radio astronomical observations of the proper motion of Sgr A*, in combination with its intrinsic source size, place at the moment the tightest constraints on the mass density of Sgr A*, which must exceed ρ > 3 × 1019 M☉ pc-3.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/1df0380e728daa08b0fa67a4ba0296e44f3feae1

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Citations in the corpus

The Low End of the Supermassive Black Hole Mass Function: Constraining the Mass of a Nuclear Black Hole in NGC 205 via Stellar Kinematics (2005, background): “Below 107M only twomeasurements exist: in theMilky Way (MBH ¼ 4 ; 106 M ; Ghez et al. 2003; Schödel et al. 2003) and in M32 (MBH ¼ 2:5 ; 106 M ; Verolme et al. 2002; van der Marel et al. 1998).”
Radiative transfer modeling of three-dimensional clumpy AGN tori and its application to NGC 1068 (2006, methodology): “For an isothermal cnSC, as observed in the center of our galaxy (e.g. Schödel et al. 2003),M(r) is proportional tor so that τcl(r) ∝ r−1.”
Measuring Distance and Properties of the Milky Way’s Central Supermassive Black Hole with Stellar Orbits (2008, background): “The passage of more time then led to full astrometric orbital solutions (Schödel et al. 2002, 2003; Ghez et al. 2003, 2005a), which increased the implied dark mass densities by a factor of 104 compared to earlier velocity dispersion work and thereby solidified the case for a supermassive black 1…”
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A DISK OF YOUNG STARS AT THE GALACTIC CENTER AS DETERMINED BY INDIVIDUAL STELLAR ORBITS (2008, background): “The center of our Galaxy harbors not only a supermassive black hole (Sgr A*, M• ∼ 4× 106 M⊙ ; Eckart & Genzel 1996; Genzel et al. 1996; Ghez et al. 1998, 2000, 2003, 2005b; Schödel et al. 2002; Schödel et al. 2003; Eisenhauer et al. 2005), but also a population of massive (10-120 M⊙ ), young (.10-”
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A Fundamental Relation between Compact Stellar Nuclei, Supermassive Black Holes, and Their Host Galaxies (2006, background): “However, nuclei and SBHs might coexist in some galaxies; the most promising cases being M32 (Verolme et al. 2002) and the Milky Way (Ghez et al. 2003; Schödel et al. 2003).”
Stellar Remnants in Galactic Nuclei: Mass Segregation (2006, background): “These parameters are adapted to fit the observed enclosed mass profile of theMW center (Schödel et al. 2003; Ghez et al. 2005).”
US 708 – an unbound hyper-velocity subluminous O star (2005, background): “Hills (1988) predicted that velocities even in excess of 1000 km s−1 can be gained by the disruption of a binary through tidal interaction with the super-massive black hole (SMBH) in the GC (Schödel et al. 2003; Ghez et al. 2005).”
Black Hole Masses and Enrichment of z ~ 6 SDSS Quasars (2007, methodology): “The central black hole mass of our Galaxy was measured by very high spatial resolution imaging and subsequent modelling of the stellar dynamics (Schödel et al. 2003), but this method cannot be applied to extragalactic black holes as the required spatial resolution cannot be attained.”
The structure of the nuclear stellar cluster of the Milky Way (2006, result): “…that the estimates of the enclosed mass in the GC must be corrected significantly upwards, contrary to what has been published earlier (e.g., Schödel et al. 2003) because these earlier estimates were based on measurements of gas velocities and an incomplete knowledge of the velocity…”
Hard X-ray view of the past activity of Sgr A in a natural Compton mirror (2004, background): “Our Galactic Center (GC) harbors a black hole (BH) with a mass of 3 × 106M⊙ (e.g. Schödel et al. 2003).”
The nuclear star cluster of the Milky Way: proper motions and mass (2009, background): “The measurements of stellar orbits have provided, so far, the best evidence for its nature (e.g., Schödel et al. 2003; Ghez et al. 2003).”
STELLAR POPULATIONS IN THE CENTRAL 0.5 pc OF THE GALAXY. II. THE INITIAL MASS FUNCTION (2013, background): “…our own Milky Way Galaxy, located only 8 kpc away and surrounding a supermassive black hole (SMBH) of mass M∼ 4 × 106 M⊙ (Eckart & Genzel 1997; Ghez et al. 1998, 2000, 2003, 2005, 2008; Genzel et al. 2000; Schödel et al. 2002; Schödel et al. 2003; Eisenhauer et al. 2005; Gillessen et al. 2009a).”
A Geometric Determination of the Distance to the Galactic Center (2003, methodology): “For fitting the orbit of S2, we expanded our existing IDL program codes for Keplerian orbits (see Schödel et al. 2003) to take into account the additional information provided by line-of-sight velocity measurements.”
Formation of supermassive black holes (2010, background): “The evidence is particularly compelling for our own galaxy, hosting a central MBH with mass ' 4×106M (e.g., Schödel et al, 2003; Ghez et al, 2005).”
A Universal Stellar Initial Mass Function? A critical look at variations in extreme environments (2010, background): “2.4.2 Galactic center The central region of the Galaxy is a rather unique place as the dynamics are heavily influenced by the presence of a massive black hole, MBH ∼ 3 × 10 6M⊙ (e.g. Ghez et al. 2003; Schödel et al. 2003).”
Massive Black Hole Binary Evolution (2004, background): “Indeed evidence for variability has even been claimed for the Milky Way SBH, at radio wavelengths; the ostensible period is 106 days [231].”