J/ApJ/896/100 Kinematic structure of the Galactic Center S cluster (Ali+, 2020)
Kinematic structure of the Galactic Center S cluster.
Ali B., Paul D., Eckart A., Parsa M., Zajacek M., Peissker F.,
Subroweit M., M. Valencia-S, Thomkins L., Witzel G.
<Astrophys. J., 896, 100 (2020)>
=2020ApJ...896..100A 2020ApJ...896..100A
ADC_Keywords: Galactic center; Infrared sources; Associations, stellar
Keywords: Galactic center ; Black holes ; Star clusters ; Stellar dynamics
Abstract:
We present a detailed analysis of the kinematics of 112 stars that
mostly comprise the high-velocity S cluster and orbit the supermassive
black hole Sgr A* at the center of the Milky Way. For 39 of them,
orbital elements are known; for the remainder, we know proper motions.
The distribution of the inclinations and the proper motion flight
directions deviate significantly from a uniform distribution, which
one expects if the orientation of the orbits are random. Across the
central arcseconds, the S-cluster stars are arranged in two almost
edge-on disks that are located at a position angle approximately
±45° with respect to the Galactic plane. The angular momentum
vectors for stars in each disk point in both directions, i.e., the
stars in a given disk rotate in opposite ways. The poles of this
structure are located only about 25° from the line of sight. This
structure may be the result of a resonance process that started with
the formation of the young B-dwarf stars in the cluster about 6Myr
ago. Alternatively, it indicated the presence of a disturber at a
distance from the center comparable to the distance of the compact
stellar association IRS 13.
Description:
The positions of the S stars are calculated from the AO-assisted
imaging data of the GC from 2002-2015 taken by the NAOS-CONICA (NACO)
instrument installed at the fourth (from 2001-2013) and then the first
(from 2014 on) unit telescope of the Very Large Telescope (VLT;
Program IDs: 60.A-9026(A), 713-0078(A), 073.B-0775(A), 073.B-0085(E),
073.B-0085(F), 077.B-0552(A), 273.B.5023(C), 073-B-0085(I),
077.B-0014(C), 077.B-0014(D), 077.B-0014(F), 078.B-0136(A),
179.B-0261(A), 179.B-0261(H), 179.B-0261(L), 179.B-0261(M),
179.B-0261(T), 179.B-0261(N), 179.B-0261(U), 178.B-0261(W),
183.B-0100(G), 183.B-0100(D), 183.B-0100(I), 183.B-0100(J),
183.B-0100(T), 183.B-0100(U), 183.B-0100(V), 087.B-0017(A),
089.B-0145(A), 091.B-0183(A), 095.B-0003(A), 081.B-0648(A),
091.B-0172(A)).
The Ks-band (2.18um) images obtained by the S13 camera (with a
13mas/pix scale) and the S27 camera of NACO (with a 27mas/pix scale)
are used.
Objects:
-----------------------------------------------------------------
RA (ICRS) DE Designation(s)
-----------------------------------------------------------------
17 45 40.0 -29 00 28 S cluster = NAME Gal Center Cluster
-----------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 93 19 Orbital elements for stars in the black disk
table3.dat 93 20 Orbital elements for stars in the red disk
table4.dat 50 19 Position angles of the black disk
table5.dat 49 20 Position angles of the red disk
table6.dat 49 73 Position angles of the linear stellar trajectories
--------------------------------------------------------------------------------
See also:
J/ApJ/643/1011 : Early-type stars in the center of the Galaxy (Paumard+, 2006)
J/A+A/499/483 : NIR obs. of sources in galactic center (Buchholz+, 2009)
J/A+A/502/91 : Proper motions of stars near SgrA* (Schoedel+, 2009)
J/ApJ/779/L6 : 3D kinematic obs. of stars in Galactic Centre (Do+, 2013)
J/ApJ/783/131 : Kinematic of stars in Galactic center (Yelda+, 2014)
J/ApJ/808/106 : NIR spectroscopic obs. in the Galactic Center (Stostad+, 2015)
J/ApJ/830/17 : Gal. Center secondary IR astrometric standards (Boehle+, 2016)
J/ApJ/837/30 : 25yrs obs. of stellar orbits in the GC (Gillessen+, 2017)
J/A+A/641/A102 : Milky Way nuclear star cluster HKs phot. (Schoedel+, 2020)
Byte-by-byte Description of file: table[23].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Name Star name
6- 12 F7.3 mpc a [3.6/184.2] Semi-major axis,
in milli-parsec units
14- 19 F6.3 mpc e_a [0.001/11] Uncertainty in a
21- 25 F5.3 --- e [0.08/1] Ellipticity
27- 31 F5.3 --- e_e [0/0.3] Uncertainty in e
33- 39 F7.3 deg i [24.6/157.8] Inclination
41- 46 F6.3 deg e_i [0.001/22] Uncertainty in i
48- 54 F7.3 deg omega [11/379] Argument of periapse
56- 61 F6.3 deg e_omega [0.001/32] Uncertainty in omega
63- 69 F7.3 deg Omega [14.3/353] Longitude of ascending node
71- 76 F6.3 deg e_Omega [0.001/27] Uncertainty in Omega
78- 85 F8.3 yr Tclos [627.6/2161.6] Time of closest approach
86- 86 A1 --- q_Tclos Uncertainty flag on Tclos
88- 93 F6.3 yr e_Tclos [0.001/23] Uncertainty in Tclos
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table[456].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Name Star name
6- 12 F7.3 mas/yr m1 [-22.8/29.1] slope, R.A. data as a
function of time
14- 19 F6.3 mas/yr e_m1 [0.005/2] Uncertainty in m1
21- 27 F7.3 mas/yr m2 [-22.3/29] slope, Dec. data as a
function of time
29- 33 F5.3 mas/yr e_m2 [0.005/1.8] Uncertainty in m2
35- 42 F8.3 deg PA [-169.7/178] Position angle, φ
44- 50 F7.4 deg e_PA [0.05/18] Uncertainty in PA
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 29-Oct-2021