This image shows mass and distance constraints of Sgr A* from the S2 orbit prior to the availability of GRAVITY (blue, Gillessen et al. 2017) and from a dynamical model of the nuclear cluster (red, Chatzopoulos et al. 2015). The combined constraint is given by the black contours. The small yellow constraint represents the updated values from GRAVITY Collaboration (2022), which are consistent with the older constraints, but much more precise.
This image shows mass and distance constraints of Sgr A* from the S2 orbit prior to the availability of GRAVITY (blue, Gillessen et al. 2017) and from a dynamical model of the nuclear cluster (red, Chatzopoulos et al. 2015). The combined constraint is given by the black contours. The small yellow constraint represents the updated values from GRAVITY Collaboration (2022), which are consistent with the older constraints, but much more precise.
Our long-term monitoring of the Galactic Center region with NACO and SINFONI has led to a very valuable data base of stellar motions: we have measured proper motions for more than 10,000 stars and radial velocities for almost 3,000 stars (Fritz et al. 2016). We can determine the dynamic configuration of the nuclear cluster together with the density profile (Chatzopoulos et al. 2015). This allows us to measure the mass of the central point source, the distance to the system, and the mass profile of the extended cluster completely independently from the stellar orbits. The mass of and distance to Sgr A* are consistent with our results from the stellar orbits, although since the advent of GRAVITY, they are not competitive anymore.
Using the kinematic data together with the stellar number surface density profile, we can determine the dynamic configuration of the nuclear cluster (Chatzopoulos et al. 2015) and the mass profile. The latter shows that the massive black hole dominates the mass in the central parsec.
This picture compiles different data sets that constrain the mass profile in the Galactic Center. The red line represents the dynamical model, describing the large data set of stellar motions and the observed mass profile.
This picture compiles different data sets that constrain the mass profile in the Galactic Center. The red line represents the dynamical model, describing the large data set of stellar motions and the observed mass profile.
This figure shows a summary of the central mass distribution in the Galactic Center. The filled blue circle is the central mass of 4.30 million solar masses, and its uncertainty of 12,000 solar masses, which the current best orbit fitting has established to lie within the 100 astronomical units pericenter of S29. The black arrow denotes the upper limit any extended mass (assuming a Plummer profile with a scale radius of 0.3 arcseconds). The other data points show averages of enclosed masses at larger radii. The magenta dashed line illustrates the extended stellar mass distribution from the literature. All data are in excellent agreement with a point mass plus a star cluster. No extra component from dark matter is required.
This figure shows a summary of the central mass distribution in the Galactic Center. The filled blue circle is the central mass of 4.30 million solar masses, and its uncertainty of 12,000 solar masses, which the current best orbit fitting has established to lie within the 100 astronomical units pericenter of S29. The black arrow denotes the upper limit any extended mass (assuming a Plummer profile with a scale radius of 0.3 arcseconds). The other data points show averages of enclosed masses at larger radii. The magenta dashed line illustrates the extended stellar mass distribution from the literature. All data are in excellent agreement with a point mass plus a star cluster. No extra component from dark matter is required.
At smaller radii, the mass profile can be determined from the shape of the stellar orbits and the mass they enclose. For stars on close orbits, we have not yet detected any deviation in the shape of the orbits from what general relativity predicts. Stars at larger radii only show a marginal increase of the enclosed mass at around 3 arcseconds distance, corresponding to 25,000 astronomical units or 0.1 parsecs. Hence, throughout the central 0.1 parsecs down to the size of the pericenter of the star passing closest to Sgr A* (S29), at 100 astronomical units, the mass of the nuclear cluster is not detectable anymore due to the dominance of Sgr A*’s gravity.