J/ApJ/706/1277 Stromgren photometry in ω Cen (Calamida+, 2009)
Stromgren photometry of Galactic globular clusters.
II. Metallicity distribution of red giants in ω Centauri.
Calamida A., Bono G., Stetson P.B., Freyhammer L.M., Piersimoni A.M.,
Buonanno R., Caputo F., Cassisi S., Castellani M., Corsi C.E., Dall'Ora M.,
Degl'Innocenti S., Ferraro I., Grundahl F., Hilker M., Iannicola G.,
Monelli M., Nonino M., Patat N., Pietrinferni A., Prada Moroni P.G.,
Primas F., Pulone L., Richtler T., Romaniello M., Storm J., Walker A.R.
<Astrophys. J., 706, 1277-1298 (2009)>
=2009ApJ...706.1277C 2009ApJ...706.1277C
ADC_Keywords: Clusters, globular ; Photometry, uvby ; Photometry, infrared
Keywords: globular clusters: general - globular clusters: individual
(Omega Centauri) - stars: abundances - stars: evolution
Abstract:
We present new intermediate-band Stromgren photometry based on more
than 300 u, v, b, y images of the Galactic globular cluster ω
Cen. Optical data were supplemented with new multiband near-infrared
(NIR) photometry (350 J, H, Ks images). The final optical-NIR catalog
covers a region of more than 20x20arcmin squared across the cluster
center. We use different optical-NIR color-color planes together with
proper-motion data available in the literature to identify candidate
cluster red-giant (RG) stars. By adopting different Stromgren
metallicity indices, we estimate the photometric metallicity for ∼4000
RGs, the largest sample ever collected. We identify four distinct
subpopulations, namely, MP ([Fe/H]≤-1.49), metal-intermediate (MI;
-1.49<[Fe/H]≤-0.93), metal-rich (MR; -0.95<[Fe/H]≤-0.15), and solar
metallicity ([Fe/H]∼0). The last group includes only a small fraction
of stars (∼8%±5%) and should be confirmed spectroscopically.
Moreover, using the difference in metallicity based on different
photometric indices, we find that the 19%±1% of RGs are candidate
CN-strong stars.
Description:
A set of 110 uvby Stromgren images centered on the cluster ω Cen
was collected by one of us L. Freyhammer (LF) over 11 nights between
1999 March 27 to April 9, with the 1.54m Danish Telescope (ESO, La
Silla).
This data set has been supplemented with 30 uv by images of the SW
quadrant of ω Cen collected by one of us F. Grundahl (FG) during
four nights in 1999 April and two nights in 1999 June with the Danish
Telescope.
Together with the aforementioned images, we also acquired 210 vby
images collected with the same telescope by two of us (M. Hilker (MH),
T. Richtler (TR)) in two observing runs (1993 and 1995; see Hilker
2000A&A...355..994H 2000A&A...355..994H). See Figure 1.
NIR J-, H-, and Ks-band images of ω Cen were collected in two
different runs - 2001 February 5, 7, and 2002 February 2, 3, 24, 25 -
with the NIR camera SOFI at the NTT (ESO, La Silla).
Moreover, we also retrieved from the ESO archive two more data sets
collected during the nights 2004 June 3, 4 and 2005 April 2.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 74 135 Log of scientific CCD images of ω Cen
collected by L. Freyhammer (central field) and
by F. Grundahl (SW fields)
table4.dat 74 193 Log of scientific CCD images of ω Centauri
collected by M. Hilker (see fields in Figure 1)
table6.dat 74 355 Log of scientific NIR CCD images of ω
Centauri
table7.dat 27 114 Set of Stroemgren standard stars observed by
F. Grundahl (FG)
table8.dat 26 88 Log of standard stars of the reference
photometric night
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See also:
J/ApJ/698/2048 : Abundances of red giants in ω Cen (Johnson+, 2009)
J/MNRAS/396/2183 : Radial velocities of red giants in ω Cen (Sollima+
2009)
J/MNRAS/357/265 : BVI photometry of omega Cen red giants (Sollima+, 2005)
J/A+A/420/173 : JK photometry of Omega Cen red giants (Sollima+, 2004)
J/AJ/127/1227 : Synthetic Stroemgren photometry (Clem+, 2004)
J/AJ/119/1225 : Stroemgren photometry of Omega Cen and NGC 6397 (Hughes+,
2000)
J/A+AS/104/429 : uvby Photometry of G-type dwarfs (Olsen 1994)
J/A+AS/102/89 : uvby-beta Photometry of G5 stars (Olsen 1993)
Byte-by-byte Description of file: table3.dat table4.dat table6.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Run Observation run identification
14- 27 A14 --- Frame Frame identification
29- 32 A4 --- Field Field identification
34- 43 A10 "YYYY/MM/DD" Date UT Day of the observation
45- 56 F12.4 d HJD Heliocentric Julian Date
58- 61 I4 s Exp Individual exposure time (G2)
63- 69 A7 --- Filt Stromgren or near-IR filter used (G1)
71- 74 F4.2 arcsec See Individual seeing
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Star name (1)
10- 19 A10 "YYYY/MM/DD" Date UT Day of the observation (2)
21- 27 A7 --- Filt [u,v,b,y] Filter used (u,v,b,y together)
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Note (1): Standard stars have been selected from catalogs of photometric
standards of Olsen (1993, Cat. J/A+AS/102/89) and Schuster & Nissen
(1988A&AS...73..225S 1988A&AS...73..225S). See text for more details.
Note (2): Data set collected between April 1999 and June 1999 with the
1.54m Danish Telescope available at ESO (La Silla).
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Star name (1)
10- 21 F12.4 d HJD Heliocentric Julian Date
23- 24 I2 s Exp Individual exposure time
26 A1 --- Filt [buvy] Filter used (Stromgren b,u,v or y)
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Note (1): HD standard stars have been observed during the night of June the
6th, 1999, with the 1.54m Danish Telescope available at ESO (La Silla).
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Global Notes:
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Note (G1): filters are:
* either the u, v, b, y Stromgren filters of the 1.54m Danish Telescope
(ESO, La Silla) in tables 3 and 4
* or the J, H, Ks NIR filters of the NTT Telescope (ESO, La Silla).
"NB_" data were collected using two narrowband filters centered on
λ=1.21um and λ=2.19um from the NIR camera ISAAC at the
VLT (ESO, Paranal) in table 6.
Note (G2): Exp is the total exposure time: ET=DIT*NDIT
(with DIT: detector integration time and NDIT: number of DIT).
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History:
From electronic version of the journal
References:
Calamida et al. Paper I. 2007ApJ...670..400C 2007ApJ...670..400C
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 15-Dec-2011