J/AJ/119/1225 Stroemgren photometry of Omega Cen and NGC 6397 (Hughes+, 2000)
Age and metallicity effects in Omega Centauri: Stroemgren photometry at
the main-sequence turnoff
Hughes J. Wallerstein G.
<Astron. J. 119, 1225 (2000)>
=2000AJ....119.1225H 2000AJ....119.1225H
ADC_Keywords: Clusters, globular ; Photometry, uvby
Keywords: globular clusters: individual
(ω Centauri, NGC 6397) - techniques: photometric
Abstract:
We have observed (with vby filters) a field north of the core of the
most massive globular cluster in our galaxy, ω Centauri. We have
found a correlation of age and metallicity in a region that avoids the
dense core and the inhomogeneous foreground dust emission shown by
IRAS. Our observations show that the comparatively metal-rich stars
(as defined by the b-y and m1 colors) are younger than the
metal-poor stars by at least 3 Gyr.
Description:
The observations were carried out with the CTIO 0.9 m telescope in
1996 May. We used the Tek 2048 No. 3 chip (and Arcon 3.3), which gives
a pixel size of 0.396'' (focal ratio f/13.5; pixel size 24 µm). The
read noise was 3.6 e- and the gain in e- ADU-1 was 1.6. The
instrument-control gain was on the No. 4 setting (which gave full well
at approximately 65,000 ADU).
Objects:
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RA (2000) DE Designation(s)
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13 26 45.89 -47 28 36.7 Omega Cen = HD 116790 = NGC 5139
17 40 41.36 -53 40 25.3 NGC 6397
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 70 2473 Objects in ω Centauri
table3.dat 62 536 Objects in the off-cluster field
table4.dat 70 976 Objects in NGC 6397
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See also:
J/AJ/108/1350 : Omega Cen FUV photometry (Whitney+, 1994)
J/MNRAS/250/314 : CCD photometry of omega Cen (Noble+ 1991)
J/A+AS/115/297 : BVRI photometry of Central Field of Omega Cen (Lynga+, 1996)
J/PASP/106/828 : BVRI photometry of Omega Cen (Walker 1994)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Name Object name
8- 13 F6.3 mag b-y The Stromgren b-y color
17- 21 F5.3 mag e_b-y Uncertainty in b-y
25- 30 F6.3 mag Vmag The V band magnitude (1)
33- 37 F5.3 mag e_Vmag Uncertainty in Vmag
40- 45 F6.3 mag v-b The Stromgren v-b color
49- 53 F5.3 mag e_v-b Uncertainty in v-b
57- 62 F6.3 mag m1 Metallicity index ((v-b) - (b-y))
65- 70 F6.3 mag VMag The absolute V band magnitude
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Note (1): V band magnitude calculated from y and b-y observations (see
equations 2, 5, 8, and 11). Data with V > 16.4 are from the
longer exposures in Table 1, whereas data with V < 16.4 come
from the 300 s exposures
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Name Object name
8- 13 F6.3 mag b-y The Stromgren b-y color
17- 21 F5.3 mag e_b-y Uncertainty in b-y
25- 30 F6.3 mag Vmag The V band magnitude (1)
33- 37 F5.3 mag e_Vmag Uncertainty in Vmag
40- 45 F6.3 mag v-b The Stromgren v-b color
49- 53 F5.3 mag e_v-b Uncertainty in v-b
57- 62 F6.3 mag m1 Metallicity index ((v-b) - (b-y))
--------------------------------------------------------------------------------
Note (1): V band magnitude calculated from y and b-y observations (see
equations 2, 5, 8, and 11).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- N6397 Object name (in NGC 6397)
8- 13 F6.3 mag b-y The Stromgren b-y color
17- 21 F5.3 mag e_b-y Uncertainty in b-y
25- 30 F6.3 mag Vmag The V band magnitude (1)
33- 37 F5.3 mag e_Vmag Uncertainty in Vmag
40- 45 F6.3 mag v-b The Stromgren v-b color
49- 53 F5.3 mag e_v-b Uncertainty in v-b
57- 62 F6.3 mag m1 Metallicity index ((v-b) - (b-y))
65- 70 F6.3 mag VMag The absolute V band magnitude
--------------------------------------------------------------------------------
Note (1): V band magnitude calculated from y and b-y observations (see
equations 2, 5, 8, and 11).
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History:
From AJ electronic edition
(End) Greg Schwarz [AAS] 12-Apr-2000