Isochrone fitting of Galactic globular clusters - III. NGC 288, NGC 362, and NGC 6218 (M12)

Георгий Гончаров, Максим Юрьевич Ховричев, Александр Владимирович Мосенков, Владимир Борисович Ильин, Александр Александрович Марчук, Сергей Сергеевич Савченко, Антон Александрович Смирнов, Павел Александрович Усачев, Денис Михайлович Поляков

Research output: Contribution to journalArticlepeer-review

Abstract

We present new isochrone fits to colour-magnitude diagrams of the Galactic globular clusters NGC 288, NGC 362, and NGC 6218 (M12). We utilize a lot of photometric bands from the ultraviolet to mid-infrared by use of data from the HST, Gaia, unWISE, Pan-STARRS, and other photometric sources. In our isochrone fitting, we use theoretical models and isochrones from the Dartmouth Stellar Evolution Program and Bag of Stellar Tracks and Isochrones for α-enhanced abundance [α/Fe] = +0.40, different helium abundances, and a metallicity of about [Fe/H] = -1.3 adopted from the literature. We derive the most probable distances 8.96 ± 0.05, 8.98 ± 0.06, and 5.04 ± 0.05 kpc, ages 13.5 ± 1.1, 11.0 ± 0.6, and 13.8 ± 1.1 Gyr, extinctions AV = 0.08 ± 0.03, 0.11 ± 0.04, and 0.63 ± 0.03 mag, and reddenings E(B - V) = 0.014 ± 0.010, 0.028 ± 0.011, and 0.189 ± 0.010 mag for NGC 288, NGC 362, and NGC 6218, respectively. The distance estimates from the different models are consistent, while those of age, extinction, and reddening are not. The uncertainties of age, extinction, and reddening are dominated by some intrinsic systematic differences between the models. However, the models agree in their relative age estimates: NGC 362 is 2.6 ± 0.5 Gyr younger than NGC 288 and 2.8 ± 0.5 Gyr younger than NGC 6218, confirming age as the second parameter for these clusters. We provide reliable lists of the cluster members and precise cluster proper motions from the Gaia Early Data Release 3.

Original languageEnglish
Pages (from-to)2688-2705
Number of pages18
JournalMonthly Notices of the Royal Astronomical Society
Volume508
Issue number2
Early online date25 Sep 2021
DOIs
StatePublished - 1 Dec 2021

Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Hertzsprung-Russell and colour-magnitude diagrams
  • dust, extinction
  • globular clusters: general
  • globular clusters: individual: NGC 288, NGC 362, NGC 6218 (M12)
  • HORIZONTAL-BRANCH STARS
  • I.
  • COLOR-MAGNITUDE DIAGRAM
  • ACS SURVEY
  • POPULATIONS
  • Russell and colour
  • STELLAR EVOLUTION MODELS
  • magnitude diagrams
  • GAIA EDR3
  • CATALOG
  • Hertzsprung
  • UV LEGACY SURVEY
  • EXTINCTION

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