CCD photometry of the globular cluster ω Centauri. II. Stellar populations and age-metallicity relation

Soo Chang Rey, Young Wook Lee, Chang H. Ree, Jong Myung Joo, Young Jong Sohn, Alistair R. Walker

Research output: Contribution to journalReview article

62 Citations (Scopus)

Abstract

We present wide-field and high-precision BV and Ca and Strömgren by photometry of ω Centauri, which represents one of the most extensive photometric surveys to date for this cluster. The member stars of ω Cen are well discriminated from foreground Galactic field stars in the hk[=(Ca-b)-(b-y)] versus b-y diagram. The resulting "cleaned" color-magnitude diagram (CMD) has allowed us to obtain an accurate distribution of the red horizontal-branch (HB) and the asymptotic giant branch stars. We confirm the presence of several red giant branches (RGBs), with the most metal-rich sequence well separated from other bluer metal-poor ones. Our population models suggest that four populations with different metallicities can reproduce the observed nature of the RGB. The HB distribution is also found to be consistent with the multiple stellar populations of the RGB. From our population models, we propose that the most metal-rich population is about 4 Gyr younger than the dominant metal-poor population, indicating that ω Cen was enriched over this timescale. We identify, for the first time, a continuous and slanting RGB bump in the CMD of ω Cen, which is due to the metallicity spread among the RGB stars. Our photometry also reveals a significant population of blue straggler stars. The discovery of several populations and the internal age-metallicity relation of ω Cen provides good evidence that ω Cen was once part of a more massive system that merged with the Milky Way, as the Sagittarius dwarf galaxy is in the process of doing at the present time.

Original languageEnglish
Pages (from-to)958-979
Number of pages22
JournalAstronomical Journal
Volume127
Issue number2 1778
DOIs
Publication statusPublished - 2004 Feb 1

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globular clusters
metallicity
photometry
charge coupled devices
metal
diagram
color-magnitude diagram
metals
timescale
blue stars
stars
star distribution
asymptotic giant branch stars
dwarf galaxies
diagrams
distribution

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Rey, Soo Chang ; Lee, Young Wook ; Ree, Chang H. ; Joo, Jong Myung ; Sohn, Young Jong ; Walker, Alistair R. / CCD photometry of the globular cluster ω Centauri. II. Stellar populations and age-metallicity relation. In: Astronomical Journal. 2004 ; Vol. 127, No. 2 1778. pp. 958-979.
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abstract = "We present wide-field and high-precision BV and Ca and Str{\"o}mgren by photometry of ω Centauri, which represents one of the most extensive photometric surveys to date for this cluster. The member stars of ω Cen are well discriminated from foreground Galactic field stars in the hk[=(Ca-b)-(b-y)] versus b-y diagram. The resulting {"}cleaned{"} color-magnitude diagram (CMD) has allowed us to obtain an accurate distribution of the red horizontal-branch (HB) and the asymptotic giant branch stars. We confirm the presence of several red giant branches (RGBs), with the most metal-rich sequence well separated from other bluer metal-poor ones. Our population models suggest that four populations with different metallicities can reproduce the observed nature of the RGB. The HB distribution is also found to be consistent with the multiple stellar populations of the RGB. From our population models, we propose that the most metal-rich population is about 4 Gyr younger than the dominant metal-poor population, indicating that ω Cen was enriched over this timescale. We identify, for the first time, a continuous and slanting RGB bump in the CMD of ω Cen, which is due to the metallicity spread among the RGB stars. Our photometry also reveals a significant population of blue straggler stars. The discovery of several populations and the internal age-metallicity relation of ω Cen provides good evidence that ω Cen was once part of a more massive system that merged with the Milky Way, as the Sagittarius dwarf galaxy is in the process of doing at the present time.",
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CCD photometry of the globular cluster ω Centauri. II. Stellar populations and age-metallicity relation. / Rey, Soo Chang; Lee, Young Wook; Ree, Chang H.; Joo, Jong Myung; Sohn, Young Jong; Walker, Alistair R.

In: Astronomical Journal, Vol. 127, No. 2 1778, 01.02.2004, p. 958-979.

Research output: Contribution to journalReview article

TY - JOUR

T1 - CCD photometry of the globular cluster ω Centauri. II. Stellar populations and age-metallicity relation

AU - Rey, Soo Chang

AU - Lee, Young Wook

AU - Ree, Chang H.

AU - Joo, Jong Myung

AU - Sohn, Young Jong

AU - Walker, Alistair R.

PY - 2004/2/1

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N2 - We present wide-field and high-precision BV and Ca and Strömgren by photometry of ω Centauri, which represents one of the most extensive photometric surveys to date for this cluster. The member stars of ω Cen are well discriminated from foreground Galactic field stars in the hk[=(Ca-b)-(b-y)] versus b-y diagram. The resulting "cleaned" color-magnitude diagram (CMD) has allowed us to obtain an accurate distribution of the red horizontal-branch (HB) and the asymptotic giant branch stars. We confirm the presence of several red giant branches (RGBs), with the most metal-rich sequence well separated from other bluer metal-poor ones. Our population models suggest that four populations with different metallicities can reproduce the observed nature of the RGB. The HB distribution is also found to be consistent with the multiple stellar populations of the RGB. From our population models, we propose that the most metal-rich population is about 4 Gyr younger than the dominant metal-poor population, indicating that ω Cen was enriched over this timescale. We identify, for the first time, a continuous and slanting RGB bump in the CMD of ω Cen, which is due to the metallicity spread among the RGB stars. Our photometry also reveals a significant population of blue straggler stars. The discovery of several populations and the internal age-metallicity relation of ω Cen provides good evidence that ω Cen was once part of a more massive system that merged with the Milky Way, as the Sagittarius dwarf galaxy is in the process of doing at the present time.

AB - We present wide-field and high-precision BV and Ca and Strömgren by photometry of ω Centauri, which represents one of the most extensive photometric surveys to date for this cluster. The member stars of ω Cen are well discriminated from foreground Galactic field stars in the hk[=(Ca-b)-(b-y)] versus b-y diagram. The resulting "cleaned" color-magnitude diagram (CMD) has allowed us to obtain an accurate distribution of the red horizontal-branch (HB) and the asymptotic giant branch stars. We confirm the presence of several red giant branches (RGBs), with the most metal-rich sequence well separated from other bluer metal-poor ones. Our population models suggest that four populations with different metallicities can reproduce the observed nature of the RGB. The HB distribution is also found to be consistent with the multiple stellar populations of the RGB. From our population models, we propose that the most metal-rich population is about 4 Gyr younger than the dominant metal-poor population, indicating that ω Cen was enriched over this timescale. We identify, for the first time, a continuous and slanting RGB bump in the CMD of ω Cen, which is due to the metallicity spread among the RGB stars. Our photometry also reveals a significant population of blue straggler stars. The discovery of several populations and the internal age-metallicity relation of ω Cen provides good evidence that ω Cen was once part of a more massive system that merged with the Milky Way, as the Sagittarius dwarf galaxy is in the process of doing at the present time.

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