J/MNRAS/377/300 CT1 photometry in 6 SMC star clusters (Piatti+, 2007)
Young star clusters immersed in intermediate-age fields in the
Small Magellanic Cloud.
Piatti A.E., Sarajedini A., Geisler D., Clark D., Seguel J.
<Mon. Not. R. Astron. Soc., 377, 300-316 (2007)>
=2007MNRAS.377..300P 2007MNRAS.377..300P (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Associations, stellar ; Photometry, CMT1T2V
Keywords: techniques: photometric - galaxies: individual: SMC -
Magellanic Clouds - galaxies: star clusters
Abstract:
We present CCD photometry in the Washington C and T1 filters for six
star clusters (B 34, NGC 256, NGC 265, NGC 294, IC 1611 and NGC 376)
in the Small Magellanic Cloud (SMC) and their surrounding fields. The
resultant colour-magnitude diagrams (CMDs) extend from T1∼14 to as
faint as T1∼22 revealing the main-sequence turnoffs of the clusters.
Adopting a metallicity of Z=0.004, we compare our cluster photometry
with theoretical isochrones in the Washington system in order to
derive ages. To facilitate age determination of the surrounding
fields, we use the magnitude difference between the helium-burning red
clump stars and the main-sequence turnoff. Finally, we estimate mean
metallicities for the field stars by comparing the location of the
field red giant branch with standard giant branches for Galactic
globular clusters of known abundance, corrected for age effects.
Combining these results with our previous work, we find a clear trend
of younger clusters being located closer to the centre of the SMC. In
addition, there is a tendency for the mean metallicity and its
dispersion to be greater inside 4° of the SMC's centre as compared
to outside this radius. As far as the properties of the field stars
are concerned, we find little correlation between the ages of the
clusters and those of the field stars against which they are
projected. Clearly, more work needs to be done to clarify these
trends.
Description:
The observations were carried out during four nights with the Cerro
Tololo Inter-American Observatory (CTIO) 0.9-m telescope in 2002
October and 2003 December.
Objects:
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RA (2000) DE Designation(s) (Table)
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00 44 52 -73 00 07 B 34 = Bruck 34 = OGLE-SMC 176 (table2)
00 45 54 -73 30 24 NGC 256 = ESO 29-11 (table3)
00 47 12 -73 28 38 NGC 265 = ESO 29-14 (table4)
00 53 06 -73 22 49 NGC 294 = ESO 29-22 (table5)
00 59 48 -73 20 02 IC 1611 = ESO 29-27 (table6)
01 03 53 -72 49 34 NGC 376 = ESO 29-29 (table7)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 53 40325 CCD CT1 data of stars in the field of B 34
table3.dat 53 57984 CCD CT1 data of stars in the field of NGC 256
table4.dat 53 57984 CCD CT1 data of stars in the field of NGC 265
table5.dat 53 67539 CCD CT1 data of stars in the field of NGC 294
table6.dat 53 45141 CCD CT1 data of stars in the field of IC 1611
table7.dat 53 43815 CCD CT1 data of stars in the field of NGC 376
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Byte-by-byte Description of file: table?.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Seq Sequential number of the star (1)
7- 14 F8.3 pix Xpos X position (2)
16- 23 F8.3 pix Ypos Y position (2)
26- 31 F6.3 mag T1mag Washington T1 magnitude
33- 37 F5.3 mag e_T1mag rms uncertainty on T1 (3)
39- 44 F6.3 mag C-T1 ?=99.999 Washington C-T1 colour index
46- 50 F5.3 mag e_C-T1 ?=9.999 rms uncertainty on C-T1 (3)
53 I1 --- o_T1mag Number of observations
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Note (1): Nomenclature note:
Table 2: [PSG2007] Bruck 34 NNN in Simbad
Table 3: Cl* NGC 256 PSG NNN in Simbad
Table 4: Cl* NGC 265 PSG NNN in Simbad
Table 5: Cl* NGC 294 PSG NNN in Simbad
Table 6: Cl* IC 1611 PSG NNN in Simbad
Table 7: Cl* NGC 376 PSG NNN in Simbad
Note (2): (X,Y) coordinates correspond to the reference system of Fig. 1.
North is up and east is to the left. 1pix=0.4".
Note (3): Magnitude and colour errors are the standard deviation of the mean, or
else the observed photometric errors for stars with one measurement.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 08-Oct-2007