The globular cluster system of NGC 6822

J. Veljanoski; A. M.N. Ferguson; A. D. Mackey; A. P. Huxor; J. R. Hurley; E. J. Bernard; P. Côté; M. J. Irwin; N. F. Martin; W. S. Burgett; K. C. Chambers; H. Flewelling; R. Kudritzki; C. Waters

doi:10.1093/mnras/stv1259

The globular cluster system of NGC 6822

J. Veljanoski^*, A. M.N. Ferguson, A. D. Mackey, A. P. Huxor, J. R. Hurley, E. J. Bernard, P. Côté, M. J. Irwin, N. F. Martin, W. S. Burgett, K. C. Chambers, H. Flewelling, R. Kudritzki, C. Waters

^*Corresponding author for this work

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19 Citations (Scopus)

Abstract

We present a comprehensive analysis of the globular cluster (GC) system of the Local Group dwarf irregular galaxy NGC 6822. Our study is based on homogeneous optical and near-IR photometry, as well as long-slit spectroscopic observations which are used to determine new radial velocities for six GCs, two of which had no previous spectroscopic information. We construct optical-near-IR colour-colour diagrams and through comparison to simple stellar population models infer that the GCs have old ages consistent with being 9 Gyr or older, while their metallicities are in the range between -1.6 ≲ [Fe/H] ≲ -0.4. We conduct a kinematic analysis of the GC population and find tentative evidence for weak net rotation of the GC system, in the same sense as that exhibited by the underlying spheroid. The most likely amplitude of rotation is ≈10 km s^-1, approximately half the magnitude of the observed velocity dispersion. Finally, we use the GCs to estimate the dynamical mass of NGC 6822 within ~11 kpc and we formally find it to be in the range between (3 and 4) × 10⁹ M_⊙. This implies an overall mass-to-light ratio in the range of ~30-40 and indicates that NGC 6822 is highly dark-matter-dominated. The mass and the corresponding mass-to-light ratio estimates are affected by various additional systematic effects due to limitations of the data and the model that are not necessary reflected in the formal uncertainties.

Original language	English
Pages (from-to)	320-332
Number of pages	13
Journal	Monthly Notices of the Royal Astronomical Society
Volume	452
Issue number	1
DOIs	https://doi.org/10.1093/mnras/stv1259
Publication status	Published - 28 Apr 2015

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10.1093/mnras/stv1259

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title = "The globular cluster system of NGC 6822",

abstract = "We present a comprehensive analysis of the globular cluster (GC) system of the Local Group dwarf irregular galaxy NGC 6822. Our study is based on homogeneous optical and near-IR photometry, as well as long-slit spectroscopic observations which are used to determine new radial velocities for six GCs, two of which had no previous spectroscopic information. We construct optical-near-IR colour-colour diagrams and through comparison to simple stellar population models infer that the GCs have old ages consistent with being 9 Gyr or older, while their metallicities are in the range between -1.6 ≲ [Fe/H] ≲ -0.4. We conduct a kinematic analysis of the GC population and find tentative evidence for weak net rotation of the GC system, in the same sense as that exhibited by the underlying spheroid. The most likely amplitude of rotation is ≈10 km s-1, approximately half the magnitude of the observed velocity dispersion. Finally, we use the GCs to estimate the dynamical mass of NGC 6822 within ~11 kpc and we formally find it to be in the range between (3 and 4) × 109 M⊙. This implies an overall mass-to-light ratio in the range of ~30-40 and indicates that NGC 6822 is highly dark-matter-dominated. The mass and the corresponding mass-to-light ratio estimates are affected by various additional systematic effects due to limitations of the data and the model that are not necessary reflected in the formal uncertainties.",

keywords = "Galaxies: individual: NGC 6822, Galaxies: kinematics and dynamics, Globular clusters: general, Local Group",

author = "J. Veljanoski and Ferguson, {A. M.N.} and Mackey, {A. D.} and Huxor, {A. P.} and Hurley, {J. R.} and Bernard, {E. J.} and P. C{\^o}t{\'e} and Irwin, {M. J.} and Martin, {N. F.} and Burgett, {W. S.} and Chambers, {K. C.} and H. Flewelling and R. Kudritzki and C. Waters",

note = "Publisher Copyright: {\textcopyright} 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.",

year = "2015",

month = apr,

day = "28",

doi = "10.1093/mnras/stv1259",

language = "English",

volume = "452",

pages = "320--332",

journal = "Monthly Notices of the Royal Astronomical Society",

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TY - JOUR

T1 - The globular cluster system of NGC 6822

AU - Veljanoski, J.

AU - Ferguson, A. M.N.

AU - Mackey, A. D.

AU - Huxor, A. P.

AU - Hurley, J. R.

AU - Bernard, E. J.

AU - Côté, P.

AU - Irwin, M. J.

AU - Martin, N. F.

AU - Burgett, W. S.

AU - Chambers, K. C.

AU - Flewelling, H.

AU - Kudritzki, R.

AU - Waters, C.

PY - 2015/4/28

Y1 - 2015/4/28

N2 - We present a comprehensive analysis of the globular cluster (GC) system of the Local Group dwarf irregular galaxy NGC 6822. Our study is based on homogeneous optical and near-IR photometry, as well as long-slit spectroscopic observations which are used to determine new radial velocities for six GCs, two of which had no previous spectroscopic information. We construct optical-near-IR colour-colour diagrams and through comparison to simple stellar population models infer that the GCs have old ages consistent with being 9 Gyr or older, while their metallicities are in the range between -1.6 ≲ [Fe/H] ≲ -0.4. We conduct a kinematic analysis of the GC population and find tentative evidence for weak net rotation of the GC system, in the same sense as that exhibited by the underlying spheroid. The most likely amplitude of rotation is ≈10 km s-1, approximately half the magnitude of the observed velocity dispersion. Finally, we use the GCs to estimate the dynamical mass of NGC 6822 within ~11 kpc and we formally find it to be in the range between (3 and 4) × 109 M⊙. This implies an overall mass-to-light ratio in the range of ~30-40 and indicates that NGC 6822 is highly dark-matter-dominated. The mass and the corresponding mass-to-light ratio estimates are affected by various additional systematic effects due to limitations of the data and the model that are not necessary reflected in the formal uncertainties.

AB - We present a comprehensive analysis of the globular cluster (GC) system of the Local Group dwarf irregular galaxy NGC 6822. Our study is based on homogeneous optical and near-IR photometry, as well as long-slit spectroscopic observations which are used to determine new radial velocities for six GCs, two of which had no previous spectroscopic information. We construct optical-near-IR colour-colour diagrams and through comparison to simple stellar population models infer that the GCs have old ages consistent with being 9 Gyr or older, while their metallicities are in the range between -1.6 ≲ [Fe/H] ≲ -0.4. We conduct a kinematic analysis of the GC population and find tentative evidence for weak net rotation of the GC system, in the same sense as that exhibited by the underlying spheroid. The most likely amplitude of rotation is ≈10 km s-1, approximately half the magnitude of the observed velocity dispersion. Finally, we use the GCs to estimate the dynamical mass of NGC 6822 within ~11 kpc and we formally find it to be in the range between (3 and 4) × 109 M⊙. This implies an overall mass-to-light ratio in the range of ~30-40 and indicates that NGC 6822 is highly dark-matter-dominated. The mass and the corresponding mass-to-light ratio estimates are affected by various additional systematic effects due to limitations of the data and the model that are not necessary reflected in the formal uncertainties.

KW - Galaxies: individual: NGC 6822

KW - Galaxies: kinematics and dynamics

KW - Globular clusters: general

KW - Local Group

UR - http://www.scopus.com/inward/record.url?scp=84940069095&partnerID=8YFLogxK

U2 - 10.1093/mnras/stv1259

DO - 10.1093/mnras/stv1259

M3 - Article

SN - 0035-8711

VL - 452

SP - 320

EP - 332

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 1

ER -

The globular cluster system of NGC 6822

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