Stellar Populations in the Central 0.5 pc of Our Galaxy. III. The Dynamical Substructures

Abstract

We measure the 3D kinematic structures of the young stars within the central 0.5 pc of our Galactic Center using the 10 m telescopes of the W. M. Keck Observatory over a time span of 25 yr. Using high-precision measurements of positions on the sky and proper motions and radial velocities from new observations and the literature, we constrain the orbital parameters for each young star. Our results show two statistically significant substructures: a clockwise stellar disk with 18 candidate stars, as has been proposed before, but with an improved disk membership; and a second, almost edge-on plane of 10 candidate stars oriented east–west on the sky that includes at least one IRS 13 star. We estimate the eccentricity distribution of each substructure and find that the clockwise disk has 〈e〉 = 0.39 and the edge-on plane has 〈e〉 = 0.68. We also perform simulations of each disk/plane with incompleteness and spatially variable extinction to search for asymmetry. Our results show that the clockwise stellar disk is consistent with a uniform azimuthal distribution within the disk. The edge-on plane has an asymmetry that cannot be explained by variable extinction or incompleteness in the field. The orientation, asymmetric stellar distribution, and high eccentricity of the edge-on plane members suggest that this structure may be a stream associated with the IRS 13 group. The complex dynamical structure of the young nuclear cluster indicates that the star formation process involved complex gas structures and dynamics and is inconsistent with a single massive gaseous disk.

The Evaporating Massive Embedded Stellar Cluster IRS 13 Close to Sgr A*. II. Kinematic Structure

“…We would like to add that the assumed link between the gas and the cluster members may be premature. However, the listed proper motion and radial velocity in Paumard et al (2006), Bartko et al (2009), andJia et al (2023) reveal with Equation (3) a similar 3D distance for the E-stars 9 as derived in this section. Using the velocity dispersion of the cluster members of v prop = 128.86 ± 0.14 km s −1 , we derive an upper limit for the 3D distance of about 1 pc with Equation (3) by setting the radial velocity to 0 km s −1 .…”

“…Based on this figure, it becomes clear that the IRS 13 population forms an individual arrangement that does not follow any known stellar density structures, such as the CWD, CCWD/F1, F2, and F3 (Paumard et al 2006;Yelda et al 2014;von Fellenberg et al 2022). Recently, Jia et al (2023) mentioned the reduced significance of the large-scale features F1-F3 following the argumentation of the disputed CCWD by Lu et al (2006Lu et al ( , 2009. In addition, the reduced significance of the CCWD was already mentioned by Bartko et al (2008) but without excluding this feature.…”

Candidate young stellar objects in the S-cluster: Kinematic analysis of a subpopulation of the low-mass G objects close to Sgr A*

“…Therefore, it is plausible that multiple clouds could result in the formation of different disks. Although there is no theoretical basis for this claim yet, observations by Ali et al (2020), von Fellenberg et al (2022), and Jia et al (2023 favor a multidisk arrangement of the stars of the inner parsec. A plausible origin of the initial clouds could be clumps in the CND that are formed under the influence of turbulent convection streams (Dinh et al 2021).…”

High-resolution, Mid-infrared Color Temperature Mapping of the Central 10″ of the Galaxy

“…We astrometrically calibrate the NIR data by selecting 29 wellisolated sources of known absolute position (Jia et al 2023) and distributed broadly over the field of view. 7 We measure the detector position of each source centroid using point-spread function (PSF) fitting, as has been done in previous publications (Gautam et al 2019).…”