The Proper Motion of Sagittarius A*. II. The Mass of Sagittarius A*

By M. J. Reid, A. B. H. C. F. Astrophysics, M. F. Radioastronomie, Joint Institute for Vlbi in Europe. 2004

609 citations recorded by the source corpus.

We report measurements with the Very Long Baseline Array (VLBA) of the position of Sgr A* with respect to two extragalactic radio sources over a period of 8 yr. The apparent proper motion of Sgr A* relative to J1745-283 is 6.379 ± 0.024 mas yr-1 along a position angle of 209.°60 ± 0.°18, almost entirely in the plane of the Galaxy. The effects of the orbit of the Sun around the Galactic center can account for this motion, and the residual proper motion of Sgr A* perpendicular to the plane of the Galaxy is -0.4 ± 0.9 km s-1. A maximum likelihood analysis of the motion expected for a massive object within the observed Galactic center stellar cluster indicates that Sgr A* contains more than about 10% of the ≈4 × 106 M☉ deduced from stellar orbits. The intrinsic size of Sgr A*, as measured by several investigators, is less than 1 AU, and the implied mass density of ~1022 M☉ pc-3 is within about 3 orders of magnitude of a comparable supermassive black hole within its Schwarzschild radius. Our observations provide the first direct evidence that a compact radiative source at the center of a galaxy contains of order 106 M☉ and provides overwhelming evidence that it is in the form of a supermassive black hole. Finally, the existence of "intermediate-mass" black holes more massive than ~104 M☉ between roughly 103 and 105 AU from Sgr A* is excluded.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/9130b98d214bc5c3e82d1f5078f2463f037d3fa5

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Citations in the corpus

• Milky Way mass models for orbit calculations (2012, methodology): “′′01, as mentioned in the appendix of Reid & Brunthaler (2004).”
• MONITORING STELLAR ORBITS AROUND THE MASSIVE BLACK HOLE IN THE GALACTIC CENTER (2008, background): “However, an even stronger constraint comes from the radio measurements of Sgr A* (Reid & Brunthaler 2004).”
• THE SAGITTARIUS DWARF GALAXY: A MODEL FOR EVOLUTION IN A TRIAXIAL MILKY WAY HALO (2010, methodology): “We note that if we were instead to adopt the proper motion of Sgr A∗ measured by Reid & Brunthaler (2004) it would imply vLSR = 235.6 km s −1 for our adopted value of R⊙ = 8.0 kpc.”
• The uncertainty in Galactic parameters (2009, methodology): “…Sgr A* is justified by the observation that the velocity of Sgr A* perpendicular to the plane is consistent with zero, with uncertainties ∼ 1 km s−1 (Reid & Brunthaler 2004), and because this motion is thought to be due to stochastic forces from ⋆ E-mail: p.mcmillan1@physics.ox.ac.uk discrete…”
• The GALAH survey and Gaia DR2: dissecting the stellar disc’s phase space by age, action, chemistry, and location (2018, methodology): “To convert velocities from the heliocentric to the Galactocentric frame, we take the angular velocity of the Sun to be = ( 0 + V )/R0 = 30.24 km s−1 kpc−1 from the measure proper motion of Sgr A∗ (Reid & Brunthaler 2004).”
• Microarcsecond Radio Astrometry (2013, background): “…observed to move with speeds exceeding 5000 km s−1 (Schödel et al. 2002), the velocity component perpendicular to the Galactic plane of Sgr A* is less than ≈ 1 km s−1, requiring that most of the 4×106 M required by the stellar orbits is tied to the radiative source Sgr A* (Reid & Brunthaler 2004).”
• CONSTRAINING THE MILKY WAY POTENTIAL WITH A SIX-DIMENSIONAL PHASE-SPACE MAP OF THE GD-1 STELLAR STREAM (2009, background): “Ghez et al. (2008) recently combined radio data (Reid & Brunthaler 2004) with near-IR data on the Galactic center kinematics to arrive at Vc(R0, 0) = 229 ± 18 km/s.”
• THE MILKY WAY'S CIRCULAR-VELOCITY CURVE BETWEEN 4 AND 14 kpc FROM APOGEE DATA (2012, methodology): “The most robust of those measurements is that derived from the observed proper motion of Sgr A∗ (Reid & Brunthaler 2004), even though this requires an estimate of R0.”
• The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics, and Formation (2006, methodology): “Second, an intermediate mass black hole with a mass in excess of 104M⊙ would be inconsistent with the 2 km s−1 proper motion velocity limit perpendicular to the Galactic plane deduced by the VLBA observations of Reid & Brunthaler (2004).”
• Constraining the Galaxy's dark halo with RAVE stars (2014, background): “Reid & Brunthaler (2004) measured the proper motion of the radio source SgrA* in the GC to be μSgrA = −6.379 ± 0.024 mas yr−1.”
• A geometric distance measurement to the Galactic center black hole with 0.3% uncertainty (2019, methodology): “Reid & Brunthaler (2004) measured the motion of Sgr A* perpendicular to the Galactic plane to be 0.4± 0.9 km s−1.”
• A TRIGONOMETRIC PARALLAX OF Sgr B2 (2009, methodology): “Since the position of J1745–2820 was known to better than 10 mas accuracy (Reid & Brunthaler 2004), we could measure its apparent map offset when phase referenced to a maser spot and correct the position of the maser (to better than 10 mas accuracy) before final processing.”
• The distance to the Orion Nebula (2007, methodology): “The main source of systematic error for cm-wave phasereferenced observations is uncompensated interferometric delays introduced by the Earth’s atmosphere and ionosphere, and we conducted supplementary observations that allowed us to correct for these effects (Reid & Brunthaler 2004).”
• DETECTING FLARING STRUCTURES IN SAGITTARIUS A* WITH HIGH-FREQUENCY VLBI (2008, background): “Radio interferometric proper motion measurements (Backer & Sramek 1999; Reid & Brunthaler 2004) limit the motion of Sgr A* to < 15 km s−1, implying that Sgr A* must trace at least 10% of the mass determined from stellar orbits.”
• The dynamical evolution of molecular clouds near the Galactic Centre - I. Orbital structure and evolutionary timeline (2014, background): “Note that the ‘primed’ variables are directly observable as they include the proper motion induced by the Sun’s orbital motion {µl, µb}⊙ = {−6.379,−0.202} mas yr−1 (Reid & Brunthaler 2004; Reid et al. 2009), for instance{µ′l, µ′b} ≡ {µl, µb} + {µl, µb}⊙.”
• Mass models of the Milky Way (2011, methodology): “In this study, we use the proper motion of Sgr A* in the plane of the Galaxy, as determined by Reid & Brunthaler (2004) µSgrA∗ = −6.379 ± 0.026mas yr −1.”
• Mean proper motions, space orbits, and velocity dispersion profiles of Galactic globular clusters derived fromGaiaDR2 data (2018, methodology): “We also assumed a circular velocity of 240 km/sec at the position of the Sun, which is in agreement with the proper motion of Sgr A* as determined by Reid & Brunthaler (2004) and our adopted distance to the Galactic centre.”