Surface brightness profile of the Milky Way’s nuclear star cluster

Schödel, R.; Feldmeier, A.; Kunneriath, D.; Stolovy, S.; Neumayer, Nadine; Amaro-Seoane, Pau; Nishiyama, Shogo

doi:10.1051/0004-6361/201423481

Cited by 185 publications

(279 citation statements)

References 86 publications

(187 reference statements)

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“…Recent observations of the Milky Way's nuclear star cluster show that it is significantly flattened in the same direction as the Galactic disc (Schodel et al 2014), supporting the idea that it has Figure 18. Line-of-sight kinematic maps for the model at 10 Gyr projected to the orientation of NGC 3945 (bar PA = 88 • , here measured from the x-axis, inclination = 55 • ).…”

Section: Implications For Nuclear Star Clustersmentioning

confidence: 78%

The formation of stellar nuclear discs in bar-induced gas inflows

Cole

Debattista

Erwin

et al. 2014

Monthly Notices of the Royal Astronomical Society

123

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The role of gas in the mass assembly at the nuclei of galaxies is still subject to some uncertainty. Stellar nuclear discs bridge the gap between the large-scale galaxy and the central massive objects that reside there. Using a high resolution simulation of a galaxy forming out of gas cooling and settling into a disc, we study the formation and properties of nuclear discs. Gas, driven to the centre by a bar, settles into a rotating star-forming nuclear disc (ND). This ND is thinner, younger, kinematically cooler, and more metal-rich than the surrounding bar. The ND is elliptical and orthogonal to the bar. The complex kinematics in the region of the ND are a result of the superposition of older stars streaming along the bar and younger stars circulating within the ND. The signature of the ND is therefore subtle in the kinematics. Instead the ND stands out clearly in metallicity and age maps. We compare the model to the density and kinematics of real galaxies with NDs finding qualitative similarities. Our results suggest that gas dissipation is very important for forming nuclear structures.

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Section: Implications For Nuclear Star Clustersmentioning

confidence: 78%

The formation of stellar nuclear discs in bar-induced gas inflows

Cole

Debattista

Erwin

et al. 2014

Monthly Notices of the Royal Astronomical Society

123

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“…However, the photometric position angle PA phot was measured by Schödel et al (2014) using Spitzer data to ∼0 • . This means that there is an offset between PA phot and PA kin .…”

Section: Stellar Kinematics and Population Resultsmentioning

confidence: 99%

“…The resulting λ R profile is shown in Fig. 9, where r is the mean radius of the ellipses, and r eff = 4.2 pc (110 , Schödel et al 2014). Assuming a smaller value for decreases λ R and the slope of λ R , but even with = 0, we obtain λ R > 0.2 for all radii.…”

Section: Emsellemmentioning

confidence: 94%

“…The cluster forms a distinct component, with a half-light radius or effective radius r eff of ∼110−127 (4.2−5 pc, Schödel et al 2014;Fritz et al 2014), and a mass of (2−3) × 10 7 M (Launhardt et al 2002;Schödel et al 2014). However, the formation and growth of the nuclear star cluster and the supermassive Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (289.B-5010(A)).…”

Section: Introductionmentioning

confidence: 99%

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

Feldmeier

Neumayer

Seth

et al. 2014

A&A

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133

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Context. Within the central 10 pc 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. Aims. Because the Milky Way nuclear star cluster is at a distance of only 8 kpc, 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. Methods. 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 ∼9.5 × 8 pc of our Galaxy, and six smaller fields out to 19 pc 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. Results. 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 ∼0.8 pc. We determine the mass of the nuclear star cluster within r = 4.2 pc to (1.4 +0.6 −0.7 ) × 10 7 M . We also show that our kinematic data results in a significant underestimation of the supermassive black hole (SMBH) mass. Conclusions. 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 r eff − M NSC 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.

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“…The cluster was first detected by Becklin & Neugebauer (1968) in the infrared. It has a half-light radius or effective radius r eff of ∼110−127 (4.2−5 pc, Schödel et al 2014a;Fritz et al 2014) and a mass of M MWNSC = (2.5 ± 0.4) × 10 7 M (Schödel et al 2014a). The central parsec of the Milky Way nuclear star cluster is extensively studied.…”

Section: Introductionmentioning

confidence: 99%

KMOS view of the Galactic centre

Feldmeier-Krause

Neumayer

Schödel

et al. 2015

A&A

Self Cite

106

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Context. The Galactic centre hosts a crowded, dense nuclear star cluster with a half-light radius of 4 pc. Most of the stars in the Galactic centre are cool late-type stars, but there are also > ∼ 100 hot early-type stars in the central parsec of the Milky Way. These stars are only 3−8 Myr old. Aims. Our knowledge of the number and distribution of early-type stars in the Galactic centre is incomplete. Only a few spectroscopic observations have been made beyond a projected distance of 0.5 pc of the Galactic centre. The distribution and kinematics of earlytype stars are essential to understand the formation and growth of the nuclear star cluster. Methods. We cover the central >4 pc 2 (0.75 sq. arcmin) of the Galactic centre using the integral-field spectrograph KMOS (VLT). We extracted more than 1000 spectra from individual stars and identified early-type stars based on their spectra. Results. Our data set contains 114 bright early-type stars: 6 have narrow emission lines, 23 are Wolf-Rayet stars, 9 stars have featureless spectra, and 76 are O/B type stars. Our wide-field spectroscopic data confirm that the distribution of young stars is compact, with 90% of the young stars identified within 0.5 pc of the nucleus. We identify 24 new O/B stars primarily at large radii. We estimate photometric masses of the O/B stars and show that the total mass in the young population is > ∼ 12 000 M . The O/B stars all appear to be bound to the Milky Way nuclear star cluster, while less than 30% belong to the clockwise rotating disk. We add one new star to the sample of stars affiliated with this disk. Conclusions. The central concentration of the early-type stars is a strong argument that they have formed in situ. An alternative scenario, in which the stars formed outside the Galactic centre in a cluster that migrated to the centre, is refuted. A large part of the young O/B stars is not on the disk, which either means that the early-type stars did not all form on the same disk or that the disk is dissolving rapidly.

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Surface brightness profile of the Milky Way’s nuclear star cluster

Cited by 185 publications

References 86 publications

The formation of stellar nuclear discs in bar-induced gas inflows

The formation of stellar nuclear discs in bar-induced gas inflows

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

KMOS view of the Galactic centre

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