J/AcA/50/337 OGLE LMC star clusters (Pietrzynski+, 2000)
The Optical Gravitational Lensing Experiment.
Ages of about 600 star clusters from the LMC.
Pietrzynski G., Udalski A.
<Acta Astron., 50, 337 (2000)>
=2000AcA....50..337P 2000AcA....50..337P
ADC_Keywords: Magellanic Clouds ; Associations, stellar ; Stars, ages
Keywords: Magellanic Clouds - galaxies: star clusters
Abstract:
We present results of age determination based on the standard
procedure of isochrone fitting for about 600 star clusters younger
than about 1.2Gyr from the central parts of the LMC. Comparison of age
distributions of star clusters from the LMC and the SMC shows that
cluster formation histories are different in these galaxies. The age
distribution of the LMC clusters reveals bursty nature of cluster
formation in this galaxy, with contrast to the relatively uniform
distribution of cluster ages in the SMC. We detected three extended
peaks in the distribution of ages of LMC clusters, located at about
7Myr, 125Myr and 0.8Gyr. All detected peaks have complex structure.
While the structure of the youngest and the oldest peaks may be
spurious due to accuracy of age determination, in the middle peak two
evident sub-peaks at 100Myr and 160Myr are clearly seen. Similar peaks
are seen in the distribution of ages of clusters from the SMC, which
indicates that increased cluster formation ratio during these periods
might be caused by the last encounter between the Magellanic Clouds.
The sample of clusters from the LMC is overabundant in very young
(<10Myr) anal old (>400Myr) clusters, and underabundant in clusters
having ages in the range from 80 to 15Myr with respect to the studied
sample of clusters from the SMC.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 55 600 Ages of the LMC clusters
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See also:
J/AcA/49/521 : OGLE LMC star clusters BVI photometry (Pietrzynski+, 1999)
J/AcA/50/355 : OGLE Multiple Cluster Candidates in LMC (Pietrzynski+, 2000)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [LMC]
4- 7 I4 --- OGLE-CL [1-745]+ Sequential number (OGLE-CL LMC NNNN)
9- 10 I2 h RAh Right ascension (J2000)
12- 13 I2 min RAm Right ascension (J2000)
15- 19 F5.2 s RAs Right ascension (J2000)
21 A1 --- DE- Declination sign (J2000)
22- 23 I2 deg DEd Declination (J2000)
25- 26 I2 arcmin DEm Declination (J2000)
28- 31 F4.1 arcsec DEs Declination (J2000)
33- 35 I3 arcsec Rad Apparent radius of cluster
37 A1 --- l_logt Limit flag on logt
38- 41 F4.2 [yr] logt Age of cluster
42 A1 --- --- [,]
43- 45 F3.1 [yr] logt2 ? Second value for Age
47- 50 F4.2 [yr] e_logt ? rms uncertainty on logt
51 A1 --- --- [,]
52- 55 F4.2 [yr] e_logt2 ? rms uncertainty of logt2 if different
of e_logt
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History:
Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer [CDS] 01-Oct-2002