J/A+A/590/A50 eMSTOs in low mass clusters (Piatti+, 2016)
Extended main sequence turn-offs in low mass intermediate age clusters.
Piatti A.E., Bastian N.
<Astron. Astrophys. 590, A50 (2016)>
=2016A&A...590A..50P 2016A&A...590A..50P (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Associations, stellar ; Stars, dwarfs ;
Photometry, SDSS
Keywords: techniques: photometric - galaxies: individual: LMC -
Magellanic Clouds
Abstract:
We present an imaging analysis of four low mass stellar clusters
(≲5000M☉) in the outer regions of the LMC in order to shed
light on the extended main sequence turn-off (eMSTO) phenomenon
observed in high mass clusters. The four clusters have ages between
1-2Gyr and two of them appear to host eMTSOs. The discovery of
eMSTOs in such low mass clusters - more than 5 times less massive
than the eMSTO clusters previously studied - suggests that mass is
not the controlling factor in whether clusters host eMSTOs.
Additionally, the narrow extent of the eMSTO in the two older clusters
(∼2Gyr) is in agreement with predictions of the stellar rotation
scenario, as lower mass stars are expected to be magnetically braked,
meaning that their colour magnitude diagrams should be better
reproduced by canonical simple stellar populations. We also performed
a structural analysis on all the clusters and found that a large core
radius is not a requisite for a cluster to exhibit an eMSTO.
Description:
We obtained images of four previously selected unstudied LMC clusters
with the Gemini South telescope and the GMOS-S instrument through g
and i filters. In imaging mode GMOS-S has a field of view of
approximately 5.5'x5.5' at a scale of 0.16-arcsec per (2x2 binned)
pixel. The detector array consists of three 2Kx4K Hamamatsu chips
arranged in a row. Observations were executed in queue mode (under
programme GS-2015A-Q-44, PI: Piatti), which enabled the data to be
obtained in excellent seeing and under photometric conditions.
Objects:
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RA (ICRS) DE Designation(s)
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06 24 49 -71 39 30 LW 477 = KMHK 1752
06 33 01 -71 07 42 LW 483 = KMHK 1760
06 24 28 -66 30 24 KMHK 1751 = OHSC 34
06 25 41.7 -67 59 50 KMHK 1754 = OHSC 35
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 75 3862 Magnitudes and colours of stars in the field of
LW 477
table3.dat 75 2271 Magnitudes and colours of stars in the field of
LW 483
table4.dat 75 1885 Magnitudes and colours of stars in the field of
KMHK 1751
table5.dat 75 3197 Magnitudes and colours of stars in the field of
KMHK 1754
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See also:
J/A+A/565/A121 : Abundances of 47 Tuc turn-off stars (Dobrovolskas+, 2014)
Byte-by-byte Description of file: table2.dat table3.dat table4.dat table5.dat
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Bytes Format Units Label Explanations
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4- 7 I4 --- ID Star number
11- 12 I2 h RAh Right ascension (J2000)
14- 15 I2 min RAm Right ascension (J2000)
17- 22 F6.3 s RAs Right ascension (J2000)
24 A1 --- DE- Declination sign (J2000)
25- 26 I2 deg DEd Declination (J2000)
28- 29 I2 arcmin DEm Declination (J2000)
31- 35 F5.2 arcsec DEs Declination (J2000)
39- 44 F6.3 mag gmag g magnitude
49- 53 F5.3 mag e_gmag rms uncertainty on gmag
57- 62 F6.3 mag g-i g-i colour index
67- 71 F5.3 mag e_g-i rms uncertainty on g-i
75 I1 --- o_gmag Number of observations
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Acknowledgements:
Andres Piatti, andres(at)oac.unc.edu.ar
(End) Patricia Vannier [CDS] 25-Mar-2016