A UBVI AND uvbyCaH{beta} ANALYSIS OF THE INTERMEDIATE-AGE OPEN CLUSTER, NGC 5822
- ESO, Alonso de Cordova 3107, Santiago de Chile (Chile)
- Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045-7582 (United States)
- Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile)
NGC 5822 is a richly populated, moderately nearby, intermediate-age open cluster covering an area larger than the full moon on the sky. A CCD survey of the cluster on the UBVI and uvbyCaH{beta} systems shows that the cluster is superposed upon a heavily reddened field of background stars with E(B - V) > 0.35 mag, while the cluster has small and uniform reddening at E(b - y) = 0.075 {+-} 0.008 mag or E(B - V) = 0.103 {+-} 0.011 mag, based upon 48 and 61 probable A and F dwarf single-star members, respectively. The errors quoted include both internal photometric precision and external photometric uncertainties. The metallicity derived from 61 probable single F-star members is [Fe/H] = -0.058 {+-} 0.027 (sem) from m{sub 1} and 0.010 {+-} 0.020 (sem) from hk, for a weighted average of [Fe/H] = -0.019 {+-} 0.023, where the errors refer to the internal errors from the photometry alone. With reddening and metallicity fixed, the cluster age and apparent distance modulus are obtained through a comparison to appropriate isochrones in both VI and BV, producing 0.9 {+-} 0.1 Gyr and 9.85 {+-} 0.15, respectively. The giant branch remains dominated by two distinct clumps of stars, though the brighter clump seems a better match to the core-He-burning phase while the fainter clump straddles the first-ascent red giant branch. Four potential new clump members have been identified, equally split between the two groups. Reanalysis of the UBV two-color data extending well down the main sequence shows it to be optimally matched by reddening near E(B - V) = 0.10 rather than the older value of 0.15, leading to [Fe/H] between -0.16 and 0.00 from the ultraviolet excess of the unevolved dwarfs. The impact of the lower reddening and younger age of the cluster on previous analyses of the cluster is discussed.
- OSTI ID:
- 21582826
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 142, Issue 4; Other Information: DOI: 10.1088/0004-6256/142/4/127; ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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