C.D.S. - SIMBAD4 rel 1.7 - 2020.12.01CET12:31:38

2014A&A...570A...2F - Astronomy and Astrophysics, volume 570A, 2-2 (2014/10-1)

Large scale kinematics and dynamical modelling of the Milky Way nuclear star cluster.


Abstract (from CDS):

Within the central 10pc of our Galaxy lies a dense cluster of stars. This nuclear star cluster forms a distinct component of the Galaxy, and similar nuclear star clusters are found in most nearby spiral and elliptical galaxies. Studying the structure and kinematics of nuclear star clusters reveals the history of mass accretion and growth of galaxy nuclei and central massive black holes. Because the Milky Way nuclear star cluster is at a distance of only 8kpc, we can spatially resolve the cluster on sub-parsec scales. This makes the Milky Way nuclear star cluster a reference object for understanding the formation of all nuclear star clusters. We have used the near-infrared long-slit spectrograph ISAAC (VLT) in a drift-scan to construct an integral-field spectroscopic map of the central ∼9.5x8pc of our Galaxy, and six smaller fields out to 19pc along the Galactic plane. We use this spectroscopic data set to extract stellar kinematics both of individual stars and from the unresolved integrated light spectrum. We present a velocity and dispersion map from the integrated light spectra and model these kinematics using kinemetry and axisymmetric Jeans models. We also measure radial velocities and CO bandhead strengths of 1375 spectra from individual stars. We find kinematic complexity in the nuclear star clusters radial velocity map including a misalignment of the kinematic position angle by 9°counterclockwise relative to the Galactic plane, and indications for a rotating substructure perpendicular to the Galactic plane at a radius of 20'' or ∼0.8pc. We determine the mass of the nuclear star cluster within r=4.2pc to (1.4+0.6–0.7)x107M. We also show that our kinematic data results in a significant underestimation of the supermassive black hole (SMBH) mass. The kinematic substructure and position angle misalignment may hint at distinct accretion events. This indicates that the Milky Way nuclear star cluster grew at least partly by the mergers of massive star clusters. Compared to other nuclear star clusters, the Milky Way nuclear star cluster is on the compact side of the reff-MNSC relation. The underestimation of the SMBH mass might be caused by the kinematic misalignment and a stellar population gradient. But it is also possible that there is a bias in SMBH mass measurements obtained with integrated light, and this might affect SMBH mass determinations of other galaxies.

Abstract Copyright:

Journal keyword(s): Galaxy: nucleus - Galaxy: kinematics and dynamics

VizieR on-line data: <Available at CDS (J/A+A/570/A2): mw_star.dat list.dat fits/*>

Status at CDS : Examining the need for a new acronym. // All or part of tables of objects could be ingested in SIMBAD with priority 2.

Simbad objects: 11

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Number of rows : 11

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
1 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 11102 1
2 NGC 4244 GiG 12 17 29.659 +37 48 25.60   10.71   9.99   ~ 518 1
3 GCM -0.13 -0.08 MoC 17 45 25.2 -29 05 30           ~ 107 1
4 GCIRS 7 * 17 45 39.987 -29 00 22.24           M2 348 0
5 GCIRS 16 Cl* 17 45 40.0 -29 00 28           ~ 311 0
6 NAME Sgr A* X 17 45 40.03599 -29 00 28.1699           ~ 3543 3
7 NAME Gal Center reg 17 45 40.04 -29 00 28.1           ~ 11837 0
8 GCIRS 16C WR* 17 45 40.12 -29 00 27.6           Ofpe/WN9 167 1
9 GCIRS 9 LP* 17 45 40.447 -29 00 34.49           M3III 101 0
10 NAME Quintuplet Cluster OpC 17 46 13.9 -28 49 48           ~ 455 0
11 NAME Galactic Bulge reg ~ ~           ~ 3491 0

    Equat.    Gal    SGal    Ecl

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