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J/A+A/501/585       CT1 photometry in five LMC star clusters     (Piatti+, 2009)

Washington photometry of five star clusters in the Large Magellanic Cloud. Piatti A.E., Geisler D., Sarajedini A., Gallart C. <Astron. Astrophys. 501, 585 (2009)> =2009A&A...501..585P
ADC_Keywords: Magellanic Clouds ; Associations, stellar ; Photometry, CMT1T2V Keywords: techniques: photometric - galaxies: individual: LMC - Magellanic Clouds - galaxies: star clusters - stars: Hertzsprung-Russell (HR) and C-M diagrams Abstract: Aims: We present CCD photometry in the Washington system C and T1 passbands down to T1∼22.5 in the fields of NGC 1697, SL 133, NGC 1997, SL 663, and OHSC 28, five mostly unstudied star clusters in the LMC. Methods: Cluster radii were estimated from star counts in appropriate-sized boxes distributed throughout the entire observed fields. We perform a detailed analysis of the field star contamination and derive cluster colour-magnitude diagrams (CMDs). Based on the best fits of isochrones computed by the Padova group to the (T1, C-T1) CMDs, the δ(T1) index and the Standard Giant Branch procedure, we derive metallicities and ages for the five clusters. We combine our sample with clusters with ages and metallicities on a similar scale and examine relationships between position in the LMC, age and metallicity. Results: With the exception of NGC 1697 (age=0.7Gyr, [Fe/H]=0.0dex), the remaining four clusters are of intermediate-age (from 2.2 to 3.0Gyr) and relatively metal-poor ([Fe/H]=0.7dex). The cluster and field age-metallicty realtions show evidence for a metallicity offset but do overlap, particularly on the upper envelope side of the cluster age-metallicity relation. Conclusions: We confirm previous results that clusters younger than ∼1Gyr were formed during an outside-in process; this occurred after a bust of cluster formation that took place mainly in the outer disk and peaked at ∼2Gyr ago. Description: The observations of NGC 1997 and OHSC 28 were performed using the Tektronix 2K CCD #3 at the 0.9m telescope at the Cerro Tololo Inter-American Observatory (CTIO) on 1997 December 20 and 23, respectively, while those of NGC 1697, SL 133 and SL 663 were obtained with the Danish Faint Object Spectrograph and Camera (DFOSC) on the 1.54m Danish telescope at the European Southern Observatory (ESO) on La Silla, during the night 29 December 1999. Objects: -------------------------------------------------------------- RA (2000) DE Designation(s) (files) -------------------------------------------------------------- 04 48 37 -68 33.6 NGC 1697 = KMHK 110 (table2.dat) 04 57 34 -65 16.1 SL 133 = [SL63] 133 (table3.dat) 05 30 34 -63 12.2 NGC 1997 = ESO 86-1 (table4.dat) 05 42 29 -65 21.8 SL 663 = [SL63] 663 (table5.dat) 05 55 35 -62 20.7 OHSC 28 = OHSC 28 (table6.dat) -------------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 53 21265 Magnitudes and colours of stars in field of NGC 1697 table3.dat 53 8470 Magnitudes and colours of stars in field of SL 133 table4.dat 53 4643 Magnitudes and colours of stars in field of NGC 1997 table5.dat 53 12339 Magnitudes and colours of stars in field of SL 663 table6.dat 53 1746 Magnitudes and colours of stars in field of OHSC 28
See also: VII/183 : The Cluster System of the LMC (Kontizas+ 1990) J/AJ/117/238 : LMC extended catalog (Bica+, 1999) J/ApJ/611/270 : Magellanic star clusters IR fluctuations (Gonzalez+, 2004) J/ApJS/161/304 : Star clusters in the Milky Way & satellites (McLaughlin+ 2005) J/AJ/132/781 : 2MASS colours of Magellanic cloud star clusters (Pessev+ 2006) Byte-by-byte Description of file: table*.dat
Bytes Format Units Label Explanations
1- 5 I5 --- Seq Star number 8- 14 F7.2 pix Xpos X coordinate (1) 17- 23 F7.2 pix Ypos Y coordinate (1) 26- 31 F6.3 mag T1 Washington T1 magnitude 34- 38 F5.3 mag e_T1 rms uncertainty on T1 41- 46 F6.3 mag C-T1 Washington C-T1 colour index 49- 53 F5.3 mag e_C-T1 rms uncertainty on C-T1
Note (1): 1 pix = 0.4 arcsec. Cluster central positions: -------------------------------------------------------------- Cluster RA (J2000) DE Xpos Ypos -------------------------------------------------------------- NGC 1697 4 48 45 -68 38 45 1090 950 SL133 4 57 21 -65 20 35 1070 980 NGC 1997 5 30 12 -63 14 22 810 670 SL663 5 42 21 -65 23 3 1060 1245 OHSC 28 5 55 35 -62 20 43 1180 960 --------------------------------------------------------------
Acknowledgements: Andres Piatti, andres(at)iafe.uba.ar
(End) Patricia Vannier [CDS] 19-May-2009
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