J/MNRAS/412/1265 Photometry of 3 open clusters (Andreuzzi+, 2011)
Old open clusters and the galactic metallicity gradient: Berkeley 20,
Berkeley 66 and Tombaugh 2.
Andreuzzi G., Bragaglia A., Tosi M., Marconi G.
<Mon. Not. R. Astron. Soc., 412, 1265-1282 (2011)>
=2011MNRAS.412.1265A 2011MNRAS.412.1265A
ADC_Keywords: Clusters, open ; Photometry, CCD
Keywords: Hertzsprung-Russell and colour-magnitude diagrams;
Galaxy: disc;
open clusters and associations: general;
open clusters and associations: individual: Berkeley 20, Berkeley 66;
open clusters and associations: individual: Tomabugh 2
Abstract:
To study the crucial range of Galactocentric distances between 12 and
16kpc, where little information is available, we have obtained VI CCD
imaging of Berkeley 20 and BVI CCD imaging of Berkeley 66 and Tombaugh
2, three distant, old open clusters. Using the synthetic colour
magnitude diagram (CMD) technique with three types of evolutionary
tracks of different metallicities, we have determined age, distance,
reddening and indicative metallicity of these systems.
The CMD of Be 20 is best reproduced by stellar models with a
metallicity about half of solar (Z=0.008 or 0.01), in perfect
agreement with high resolution spectroscopic estimates. Its age is
between 5 and 6Gyr from stellar models with overshooting and between
4.3 and 4.5Gyr from models without it. The distance modulus from the
best fitting models is always (m-M)=14.7 (corresponding to a
Galactocentric radius of about 16kpc), and the reddening E(B-V) ranges
between 0.13 and 0.16.
A slightly lower metallicity (Z≃0.006) appears to be more appropriate
for Be 66. This cluster is younger (3Gyr), and closer, (m-M)=13.3
(i.e., at 12kpc from the Galactic centre), than Be 20, and suffers
from high extinction, 1.2≤E(B-V)≤1.3, variable at the 2-3% level.
Finally, the results for To 2 indicate that it is an intermediate age
cluster, about 1.4Gyr or 1.6-1.8Gyr for models without and with
overshooting, respectively. The metallicity is about half of solar
(Z=0.006 to 0.01), in agreement with spectroscopic determinations.
The distance modulus is (m-M)=14.5, implying a distance of about 14kpc
from the Galactic centre; the reddening E(B-V) is 0.31-0.4, depending
on the model and metallicity, with a preferred value around 0.34.
Description:
Be20 and Be66 were observed with DOLORES at TNG (Telescopio Nazionale
Galileo) in 24-Nov-2000 and 03-Oct-2000 (Be66); To2 was observed on
07-Mar-1995 (ESO/Danish), 15-May-2001 (ESO/Danish with DFOSC), and
15-Mar-2002 (ESO/NTT with SuSI2)
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
be20.dat 95 751 Optical VIc photometric catalogue for the open
cluster Berkeley 20 obtained with DOLORES (TNG)
be66.dat 95 3503 Optical BVIc photometric catalogue for the open
cluster Berkeley 66 obtained with DOLORES (TNG)
to2.dat 95 6073 Optical BVIc photometric catalogue for the open
cluster Tombaugh 2 obtained with the Danish
telescope and NTT (ESO)
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See also:
J/MNRAS/416/1077 : Photometry of 3 open clusters (Cignoni+ 2011)
Byte-by-byte Description of file: be20.dat be66.dat to2.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID Star identification number
7- 12 F6.3 mag Bmag ?=99.999 B band magnitude
14- 19 F6.3 mag e_Bmag ?=99.999 B band magnitude error
21- 26 F6.3 mag Vmag ?=99.999 V band magnitude
28- 33 F6.3 mag e_Vmag ?=99.999 V band magnitude error
35- 40 F6.3 mag Imag ?=99.999 I band magnitude
42- 47 F6.3 mag e_Imag ?=99.999 I band magnitude error
51- 58 F8.3 pix X X pixel coordinate
61- 68 F8.3 pix Y Y pixel coordinate
71- 72 I2 h RAh Right ascension (J2000) (hour)
74- 75 I2 min RAm Right ascension (J2000) (minutes)
77- 82 F6.3 sec RAs Right ascension (J2000) (seconds)
84 A1 --- DE- Declination (J2000) (sign)
85- 86 I2 deg DEd Declination (J2000) (degrees)
88- 89 I2 arcmin DEm Declination (J2000) (minutes)
91- 95 F5.2 arcsec DEs Declination (J2000) (seconds)
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Acknowledgements:
Angela Bragaglia (angela.bragaglia(at)oabo.inaf.it)
(End) Francois Ochsenbein [CDS] 18-Feb-2012