Kinematic decoupling of globular clusters with the extended horizontal branch

Young-Wook Lee, Hansung B. Gim, Dana I. Casetti-Dinescu

Research output: Contribution to journalArticle

78 Citations (Scopus)

Abstract

About 25% of the Milky Way globular clusters (GCs) exhibit unusually extended color distribution of stars in the core helium-burning horizontal-branch (HB) phase. This phenomenon is now best understood as due to the presence of helium-enhanced second-generation subpopulations, which has raised the possibility that these peculiar GCs might have a unique origin. Here we show that these GCs with extended HB are clearly distinct from other normal GCs in kinematics and mass. The GCs with extended HB are more massive than normal GCs and are dominated by random motion with no correlation between kinematics and metallicity. Surprisingly, however, when they are excluded, most normal GCs in the inner halo show clear signs of dissipational collapse that apparently led to the formation of the disk. Normal GCs in the outer halo share their kinematic properties with the extended HB GCs, which is consistent with the accretion origin. Our result further suggests heterogeneous origins of GCs, and we anticipate this to be a starting point for more detailed investigations of Milky Way formation, including early mergers, collapse, and later accretion.

Original languageEnglish
JournalAstrophysical Journal
Volume661
Issue number1 II
DOIs
Publication statusPublished - 2007 May 20

Fingerprint

globular clusters
decoupling
kinematics
helium
accretion
subpopulation
merger
halos
metallicity
color
stars

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Lee, Young-Wook ; Gim, Hansung B. ; Casetti-Dinescu, Dana I. / Kinematic decoupling of globular clusters with the extended horizontal branch. In: Astrophysical Journal. 2007 ; Vol. 661, No. 1 II.
@article{f375bcb255354619bd26b2569f61022b,
title = "Kinematic decoupling of globular clusters with the extended horizontal branch",
abstract = "About 25{\%} of the Milky Way globular clusters (GCs) exhibit unusually extended color distribution of stars in the core helium-burning horizontal-branch (HB) phase. This phenomenon is now best understood as due to the presence of helium-enhanced second-generation subpopulations, which has raised the possibility that these peculiar GCs might have a unique origin. Here we show that these GCs with extended HB are clearly distinct from other normal GCs in kinematics and mass. The GCs with extended HB are more massive than normal GCs and are dominated by random motion with no correlation between kinematics and metallicity. Surprisingly, however, when they are excluded, most normal GCs in the inner halo show clear signs of dissipational collapse that apparently led to the formation of the disk. Normal GCs in the outer halo share their kinematic properties with the extended HB GCs, which is consistent with the accretion origin. Our result further suggests heterogeneous origins of GCs, and we anticipate this to be a starting point for more detailed investigations of Milky Way formation, including early mergers, collapse, and later accretion.",
author = "Young-Wook Lee and Gim, {Hansung B.} and Casetti-Dinescu, {Dana I.}",
year = "2007",
month = "5",
day = "20",
doi = "10.1086/518653",
language = "English",
volume = "661",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1 II",

}

Kinematic decoupling of globular clusters with the extended horizontal branch. / Lee, Young-Wook; Gim, Hansung B.; Casetti-Dinescu, Dana I.

In: Astrophysical Journal, Vol. 661, No. 1 II, 20.05.2007.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Kinematic decoupling of globular clusters with the extended horizontal branch

AU - Lee, Young-Wook

AU - Gim, Hansung B.

AU - Casetti-Dinescu, Dana I.

PY - 2007/5/20

Y1 - 2007/5/20

N2 - About 25% of the Milky Way globular clusters (GCs) exhibit unusually extended color distribution of stars in the core helium-burning horizontal-branch (HB) phase. This phenomenon is now best understood as due to the presence of helium-enhanced second-generation subpopulations, which has raised the possibility that these peculiar GCs might have a unique origin. Here we show that these GCs with extended HB are clearly distinct from other normal GCs in kinematics and mass. The GCs with extended HB are more massive than normal GCs and are dominated by random motion with no correlation between kinematics and metallicity. Surprisingly, however, when they are excluded, most normal GCs in the inner halo show clear signs of dissipational collapse that apparently led to the formation of the disk. Normal GCs in the outer halo share their kinematic properties with the extended HB GCs, which is consistent with the accretion origin. Our result further suggests heterogeneous origins of GCs, and we anticipate this to be a starting point for more detailed investigations of Milky Way formation, including early mergers, collapse, and later accretion.

AB - About 25% of the Milky Way globular clusters (GCs) exhibit unusually extended color distribution of stars in the core helium-burning horizontal-branch (HB) phase. This phenomenon is now best understood as due to the presence of helium-enhanced second-generation subpopulations, which has raised the possibility that these peculiar GCs might have a unique origin. Here we show that these GCs with extended HB are clearly distinct from other normal GCs in kinematics and mass. The GCs with extended HB are more massive than normal GCs and are dominated by random motion with no correlation between kinematics and metallicity. Surprisingly, however, when they are excluded, most normal GCs in the inner halo show clear signs of dissipational collapse that apparently led to the formation of the disk. Normal GCs in the outer halo share their kinematic properties with the extended HB GCs, which is consistent with the accretion origin. Our result further suggests heterogeneous origins of GCs, and we anticipate this to be a starting point for more detailed investigations of Milky Way formation, including early mergers, collapse, and later accretion.

UR - http://www.scopus.com/inward/record.url?scp=34249944531&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34249944531&partnerID=8YFLogxK

U2 - 10.1086/518653

DO - 10.1086/518653

M3 - Article

VL - 661

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1 II

ER -