Near-infrared photometry of globular clusters towards the Galactic bulge: Observations and photometric metallicity indicators

Roger E. Cohen, Christian Moni Bidin, Francesco Mauro, Charles Bonatto, Douglas Geisler

Resultado de la investigación: Article

11 Citas (Scopus)

Resumen

We present wide-field JHKS photometry of 16 Galactic globular clusters located towards the Galactic bulge, calibrated on the Two Micron All-Sky Survey photometric system. Differential reddening corrections and statistical field star decontamination are employed for all of these clusters before fitting fiducial sequences to the cluster red giant branches (RGBs). Observed values and uncertainties are reported for several photometric features, including the magnitude of the RGB bump, tip, the horizontal branch (HB) and the slope of the upper RGB. The latest spectroscopically determined chemical abundances are used to build distance- and reddening-independent relations between observed photometric features and cluster metallicity, optimizing the sample size and metallicity baseline of these relations by supplementing our sample with results from the literature.We find that the magnitude difference between the HB and the RGB bump can be used to predict metallicities, in terms of both iron abundance [Fe/H] and global metallicity [M/H], with a precision of better than 0.1 dex in all three near-IR bandpasses for relatively metal-rich ([M/H] ≳ -1) clusters. Meanwhile, both the slope of the upper RGB and the magnitude difference between the RGB tip and bump are useful metallicity indicators over the entire sampled metallicity range (-2 ≲ [M/H] ≲ 0) with a precision of 0.2 dex or better, despite model predictions that the RGB slope may become unreliable at high (near-solar) metallicities. Our results agree with previous calibrations in light of the relevant uncertainties, and we discuss implications for clusters with controversial metallicities as well as directions for further investigation.

Idioma originalEnglish
Páginas (desde-hasta)1874-1902
Número de páginas29
PublicaciónMonthly Notices of the Royal Astronomical Society
Volumen464
N.º2
DOI
EstadoPublished - 2017
Publicado de forma externa

Huella dactilar

infrared photometry
galactic bulge
globular clusters
metallicity
near infrared
slopes
calibration
iron
metal
prediction
decontamination
star distribution
indicator
photometry
predictions

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Citar esto

Cohen, Roger E. ; Bidin, Christian Moni ; Mauro, Francesco ; Bonatto, Charles ; Geisler, Douglas. / Near-infrared photometry of globular clusters towards the Galactic bulge : Observations and photometric metallicity indicators. En: Monthly Notices of the Royal Astronomical Society. 2017 ; Vol. 464, N.º 2. pp. 1874-1902.
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Near-infrared photometry of globular clusters towards the Galactic bulge : Observations and photometric metallicity indicators. / Cohen, Roger E.; Bidin, Christian Moni; Mauro, Francesco; Bonatto, Charles; Geisler, Douglas.

En: Monthly Notices of the Royal Astronomical Society, Vol. 464, N.º 2, 2017, p. 1874-1902.

Resultado de la investigación: Article

TY - JOUR

T1 - Near-infrared photometry of globular clusters towards the Galactic bulge

T2 - Observations and photometric metallicity indicators

AU - Cohen, Roger E.

AU - Bidin, Christian Moni

AU - Mauro, Francesco

AU - Bonatto, Charles

AU - Geisler, Douglas

PY - 2017

Y1 - 2017

N2 - We present wide-field JHKS photometry of 16 Galactic globular clusters located towards the Galactic bulge, calibrated on the Two Micron All-Sky Survey photometric system. Differential reddening corrections and statistical field star decontamination are employed for all of these clusters before fitting fiducial sequences to the cluster red giant branches (RGBs). Observed values and uncertainties are reported for several photometric features, including the magnitude of the RGB bump, tip, the horizontal branch (HB) and the slope of the upper RGB. The latest spectroscopically determined chemical abundances are used to build distance- and reddening-independent relations between observed photometric features and cluster metallicity, optimizing the sample size and metallicity baseline of these relations by supplementing our sample with results from the literature.We find that the magnitude difference between the HB and the RGB bump can be used to predict metallicities, in terms of both iron abundance [Fe/H] and global metallicity [M/H], with a precision of better than 0.1 dex in all three near-IR bandpasses for relatively metal-rich ([M/H] ≳ -1) clusters. Meanwhile, both the slope of the upper RGB and the magnitude difference between the RGB tip and bump are useful metallicity indicators over the entire sampled metallicity range (-2 ≲ [M/H] ≲ 0) with a precision of 0.2 dex or better, despite model predictions that the RGB slope may become unreliable at high (near-solar) metallicities. Our results agree with previous calibrations in light of the relevant uncertainties, and we discuss implications for clusters with controversial metallicities as well as directions for further investigation.

AB - We present wide-field JHKS photometry of 16 Galactic globular clusters located towards the Galactic bulge, calibrated on the Two Micron All-Sky Survey photometric system. Differential reddening corrections and statistical field star decontamination are employed for all of these clusters before fitting fiducial sequences to the cluster red giant branches (RGBs). Observed values and uncertainties are reported for several photometric features, including the magnitude of the RGB bump, tip, the horizontal branch (HB) and the slope of the upper RGB. The latest spectroscopically determined chemical abundances are used to build distance- and reddening-independent relations between observed photometric features and cluster metallicity, optimizing the sample size and metallicity baseline of these relations by supplementing our sample with results from the literature.We find that the magnitude difference between the HB and the RGB bump can be used to predict metallicities, in terms of both iron abundance [Fe/H] and global metallicity [M/H], with a precision of better than 0.1 dex in all three near-IR bandpasses for relatively metal-rich ([M/H] ≳ -1) clusters. Meanwhile, both the slope of the upper RGB and the magnitude difference between the RGB tip and bump are useful metallicity indicators over the entire sampled metallicity range (-2 ≲ [M/H] ≲ 0) with a precision of 0.2 dex or better, despite model predictions that the RGB slope may become unreliable at high (near-solar) metallicities. Our results agree with previous calibrations in light of the relevant uncertainties, and we discuss implications for clusters with controversial metallicities as well as directions for further investigation.

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KW - Infrared: stars

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JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

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