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Nuclear star cluster formation in energy-space

Nuclear star cluster formation in energy-space
Nuclear star cluster formation in energy-space
In a virialized stellar system, the mean-square velocity is a direct tracer of the energy per unit mass of the system. Here, we exploit this to estimate and compare root-mean-square velocities for a large sample of nuclear star clusters and their host (late- or early-type) galaxies. Traditional observables, such as the radial surface brightness and second-order velocity moment profiles, are subject to short-term variations due to individual episodes of matter infall and/or star formation. The total mass, energy and angular momentum, on the other hand, are approximately conserved. Thus, the total energy and angular momentum more directly probe the formation of galaxies and their nuclear star clusters, by offering access to more fundamental properties of the nuclear cluster-galaxy system than traditional observables. We find that there is a strong correlation, in fact a near equality, between the root-mean-square velocity of a nuclear star cluster and that of its host. Thus, the energy per unit mass of a nuclear star cluster is always comparable to that of its host galaxy. We interpret this as evidence that nuclear star clusters do not form independently of their host galaxies, but rather that their formation and subsequent evolution are coupled. We discuss how our results can potentially be used to offer a clear and observationally testable prediction to distinguish between the different nuclear star cluster formation scenarios, and/or quantify their relative contributions.
methods: statistical, galaxies: evolution, galaxies: formation, galaxies: kinematics and dynamics, galaxies: nuclei, galaxies: photometry
0035-8711
859-869
Leigh, Nathan W.C.
604a323d-0891-471a-a450-48bef3e9fd71
Georgiev, Iskren Y.
4635c9af-b815-49fb-9978-78f2a505c1d1
Böker, Torsten
30a41c06-cd6c-4571-bfff-488e59fcf184
Knigge, Christian
ac320eec-631a-426e-b2db-717c8bf7857e
den Brok, Mark
2df5003e-9d5b-47f9-a538-adf40be010b8
Leigh, Nathan W.C.
604a323d-0891-471a-a450-48bef3e9fd71
Georgiev, Iskren Y.
4635c9af-b815-49fb-9978-78f2a505c1d1
Böker, Torsten
30a41c06-cd6c-4571-bfff-488e59fcf184
Knigge, Christian
ac320eec-631a-426e-b2db-717c8bf7857e
den Brok, Mark
2df5003e-9d5b-47f9-a538-adf40be010b8

Leigh, Nathan W.C., Georgiev, Iskren Y., Böker, Torsten, Knigge, Christian and den Brok, Mark (2015) Nuclear star cluster formation in energy-space. Monthly Notices of the Royal Astronomical Society, 451 (1), 859-869. (doi:10.1093/mnras/stv1012).

Record type: Article

Abstract

In a virialized stellar system, the mean-square velocity is a direct tracer of the energy per unit mass of the system. Here, we exploit this to estimate and compare root-mean-square velocities for a large sample of nuclear star clusters and their host (late- or early-type) galaxies. Traditional observables, such as the radial surface brightness and second-order velocity moment profiles, are subject to short-term variations due to individual episodes of matter infall and/or star formation. The total mass, energy and angular momentum, on the other hand, are approximately conserved. Thus, the total energy and angular momentum more directly probe the formation of galaxies and their nuclear star clusters, by offering access to more fundamental properties of the nuclear cluster-galaxy system than traditional observables. We find that there is a strong correlation, in fact a near equality, between the root-mean-square velocity of a nuclear star cluster and that of its host. Thus, the energy per unit mass of a nuclear star cluster is always comparable to that of its host galaxy. We interpret this as evidence that nuclear star clusters do not form independently of their host galaxies, but rather that their formation and subsequent evolution are coupled. We discuss how our results can potentially be used to offer a clear and observationally testable prediction to distinguish between the different nuclear star cluster formation scenarios, and/or quantify their relative contributions.

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Published date: 21 July 2015
Keywords: methods: statistical, galaxies: evolution, galaxies: formation, galaxies: kinematics and dynamics, galaxies: nuclei, galaxies: photometry

Identifiers

Local EPrints ID: 430100
URI: http://eprints.soton.ac.uk/id/eprint/430100
ISSN: 0035-8711
PURE UUID: a0f12971-f427-4468-b84c-b84b09c5054a

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Date deposited: 11 Apr 2019 16:30
Last modified: 25 Nov 2021 19:20

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Contributors

Author: Nathan W.C. Leigh
Author: Iskren Y. Georgiev
Author: Torsten Böker
Author: Mark den Brok

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