The nuclear cluster of the Milky Way: total mass and luminosity

Fritz, Tobias; Chatzopoulos, S.; Gerhard, Ortwin; Gillessen, S.; Genzel, R.; Pfuhl, O.; Tacchella, Sandro; Eisenhauer, F.; Ott, Thomas

doi:10.1017/s1743921314000684

Cited by 6 publications

(19 citation statements)

References 140 publications

(569 reference statements)

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“…Becklin & Neugebauer 1968, Launhardt et al 2002, Graham & Spitler 2009, Schödel 2011, Fritz et al 2014 as well as with the results of kinematic modeling of the MWNSC (see section 5). But, in contrast to the previous work, Schödel et al (2014) showed, for the first time, that the MWNSC is not spherically symmetric and derived the intrinsic shape and overall properties of the MWNSC without having to rely on assumptions about the symmetry or centering of the cluster in projection on the plane of the sky.…”

Section: Overall Properties Of the Mwnscmentioning

confidence: 87%

“…Assuming spherical symmetry, recent studies (e.g. Trippe et al 2008, Do et al 2013b, Fritz et al 2014 found that the central cluster kinematics is consistent with being isotropic (i.e. β=0).…”

Section: Kinematics Of the Mwnscmentioning

confidence: 94%

“…The rotation velocity is increasing from the centre and flattening out beyond ∼1.5 pc to ∼40 km/s , Fritz et al 2014. Trippe et al (2008) derived a higher rotation velocity of ∼90 km/s, but they used only a subset of the McGinn et al (1989) data, which was contaminated by individual bright stars.…”

Section: Kinematics Of the Mwnscmentioning

confidence: 99%

“…In the case of Feldmeier et al (2014), r is the mean radius of elliptical apertures. These mass measurements did not strictly disentangle the MWNSC from the nuclear stellar disk, only Fritz et al (2014) and Schödel et al (2014) analysed both entities separately. Beside the different kinematic data, the assumed density profiles influence the results.…”

Section: Kinematics Of the Mwnscmentioning

confidence: 99%

“…Enclosed stellar mass of the MWNSC from 0.01pc to 100 pc obtained by various studies (McGinn et al 1989, Lindqvist et al 1992, Deguchi et al 2004, Oh et al 2009. Results from studies that provide the total mass of the MWNSC (Launhardt et al 2002, Fritz et al 2014) are all plotted in red at the same (somewhat arbitrary) distance of 10 pc, more than twice the half-light radius, to facilitate their comparison. At this distance some of the enclosed mass can already be assigned to the nuclear stellar disk.…”

Section: Kinematics Of the Mwnscmentioning

confidence: 99%

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The nuclear cluster of the Milky Way: our primary testbed for the interaction of a dense star cluster with a massive black hole

Schödel

Feldmeier

Neumayer

et al. 2014

Class. Quantum Grav.

108

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Abstract.This article intends to provide a concise overview, from an observational pointof-view, of the current state of our knowledge of the most relevant properties of the Milky Way's nuclear star cluster (MWNSC). The MWNSC appears to be a typical specimen of nuclear star clusters, which are found at the centers of the majority of all types of galaxies. Nuclear clusters represent the densest and most massive stellar systems in the present-day Universe and frequently coexist with central massive black holes. They are therefore of prime interest for studying stellar dynamics and the MWNSC is the only one that allows us to obtain data on milli-parsec scales. After discussing the main observational constraints, we start with a description of the overall structure and kinematics of the MWNSC, then focus on a comparison to extragalactic systems, summarize the properties of the young, massive stars in the immediate environment of the Milky Way's central black hole, Sagittarius A*, and finally focus on the dynamics of stars orbiting the black hole at distances of a few to a few tens of milli parsecs.

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Section: Overall Properties Of the Mwnscmentioning

confidence: 87%

Section: Kinematics Of the Mwnscmentioning

confidence: 94%

Section: Kinematics Of the Mwnscmentioning

confidence: 99%

Section: Kinematics Of the Mwnscmentioning

confidence: 99%

Section: Kinematics Of the Mwnscmentioning

confidence: 99%

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The nuclear cluster of the Milky Way: our primary testbed for the interaction of a dense star cluster with a massive black hole

Schödel

Feldmeier

Neumayer

et al. 2014

Class. Quantum Grav.

108

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Nuclear Star Clusters

Neumayer

2015

Proc. IAU

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We review the current knowledge about nuclear star clusters (NSCs), the spectacularly dense and massive assemblies of stars found at the centers of most galaxies. Recent observational and theoretical work suggest that many NSC properties, including their masses, densities, and stellar populations vary with the properties of their host galaxies. Understanding the formation, growth, and ultimate fate of NSCs therefore is crucial for a complete picture of galaxy evolution. Throughout the review, we attempt to combine and distill the available evidence into a coherent picture of NSC evolution. Combined, this evidence points to a clear transition mass in galaxies of ∼ 10 9 M where the characteristics of nuclear star clusters change. We argue that at lower masses, NSCs are formed primarily from globular clusters that inspiral into the center of the galaxy, while at higher masses, star formation within the nucleus forms the bulk of the NSC. We also discuss the coexistence of NSCs and central black holes, and how their growth may be linked. The extreme densities of NSCs and their interaction with massive black holes lead to a wide range of unique phenomena including tidal disruption and gravitational wave events. Lastly, we review the evidence that many NSCs end up in the halos of massive galaxies stripped of the stars that surrounded them, thus providing valuable tracers of the galaxies' accretion histories.

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

Schödel

Feldmeier

Kunneriath

et al. 2014

A&A

185

242

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Context. Although the Milky Way nuclear star cluster (MWNSC) was discovered more than four decades ago, several of its key properties have not been determined unambiguously up to now because of the strong and spatially highly variable interstellar extinction toward the Galactic centre. Aims. In this paper we aim at determining the shape, size, and luminosity/mass of the MWNSC. Methods. To investigate the properties of the MWNSC, we used Spitzer/IRAC images at 3.6 and 4.5 µm, where interstellar extinction is at a minimum but the overall emission is still dominated by stars. We corrected the 4.5 µm image for polycyclic aromatic hydrocarbon (PAH) emission with the help of the IRAC 8.0 µm map and for extinction with the help of a [3.6−4.5] colour map. Finally, we investigated the symmetry of the nuclear cluster and fit it with Sérsic, Moffat, and King models. Results. We present an extinction map for the central ∼300 × 200 pc 2 of the Milky Way, as well as a PAH-emission-and extinctioncorrected image of the stellar emission, with a resolution of about 0.20 pc. We find that the MWNSC appears in projection to be intrinsically point-symmetric, that it is significantly flattened, with its major axis aligned along the Galactic plane, and that it is centred on the black hole, Sagittarius A*. Its density follows the well known approximate ρ ∝ r −2 -law at distances of a few parsec from Sagittarius A*, but becomes as steep as ρ ∝ r −3 at projected radii around 5 pc. We derive a half light radius of 4.2 ± 0.4 pc, a total luminosity of L MWNSC,4.5 µm = 4.1 ± 0.4 × 10 7 L , and a mass of M MWNSC = 2.5 ± 0.4 × 10 7 M . Conclusions. The overall properties of the MWNSC agree well with the ones of its extragalactic counterparts, which underlines its role as a template for these objects. Its flattening agrees well with its previously established rotation parallel to Galactic rotation and suggests that it was formed by accretion of material that tended to fall in along the Galactic plane. Our findings support the in situ growth scenario for nuclear clusters and emphasise the need to increase the complexity of theoretical models for their formation and for the interaction between their stars and the central black hole in order to include rotation, axisymmetry, and growth in recurrent episodes.

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The nuclear cluster of the Milky Way: total mass and luminosity

Cited by 6 publications

References 140 publications

The nuclear cluster of the Milky Way: our primary testbed for the interaction of a dense star cluster with a massive black hole

The nuclear cluster of the Milky Way: our primary testbed for the interaction of a dense star cluster with a massive black hole

Nuclear Star Clusters

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

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