2016A&A...586A..51M


Query : 2016A&A...586A..51M

2016A&A...586A..51M - Astronomy and Astrophysics, volume 586A, 51-51 (2016/2-1)

GeMS MCAO observations of the Galactic globular cluster NGC 2808: the absolute age.

MASSARI D., FIORENTINO G., McCONNACHIE A., BONO G., DALL'ORA M., FERRARO I., IANNICOLA G., STETSON P.B., TURRI P. and TOLSTOY E.

Abstract (from CDS):

Globular clusters are the oldest stellar systems in the Milky Way, and they probe the early epoch of the Galaxy formation. However, the uncertainties on their absolute age are still too large to soundly constrain how the Galactic structures have assembled. The aim of this work is to obtain an accurate estimate of the absolute age of the globular cluster NGC 2808 using deep IR data obtained with the multi-conjugate adaptive optics system operating at the Gemini South telescope (GeMS). This exquisite photometry, combined with that obtained in V and I-bands with HST, allowed us to detect the faint Main Sequence Knee feature in NGC 2808 colour magnitude diagram. The difference between this point and the main sequence turn-off is a good age estimator that provides ages with unprecedented accuracy. We find that NGC 2808 has an age of t=10.9±0.7 (intrinsic) ±0.45 (metallicity term) Gyr. A possible contamination by He-enhanced population could make the cluster up to 0.25Gyr older. Although this age estimate agrees with the age coming from the classical turn-off method (t=11.0Gyr), its uncertainty is a factor ∼3 better, since it avoids systematics in reddening, distance assumptions, and photometric zero point determination. The final absolute age indicates that NGC 2808 is slightly younger than other Galactic globular clusters with similar metallicity.

Abstract Copyright:

Journal keyword(s): globular clusters: individual: NGC 2808 - instrumentation: adaptive optics - techniques: photometric

VizieR on-line data: <Available at CDS (J/A+A/586/A51): table1.dat photom.dat>

Status at CDS : All or part of tables of objects will not be ingested in SIMBAD.

Simbad objects: 2

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Number of rows : 2
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NGC 2808 GlC 09 12 03.10 -64 51 48.6           ~ 1345 0
2 M 71 GlC 19 53 46.49 +18 46 45.1   7.91 6.1     ~ 1078 0

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2022.09.24-19:08:00

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