J/MNRAS/473/105 LMC Washington CMT1 photometry of star clusters (Piatti+, 2018)
Star cluster formation history along the minor axis of the
Large Magellanic Cloud.
Piatti A.E., Cole A.A., Emptage B.
<Mon. Not. R. Astron. Soc., 473, 105-115 (2018)>
=2018MNRAS.473..105P 2018MNRAS.473..105P (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Associations, stellar ; Photometry, CMT1T2V
Keywords: techniques: photometric - galaxies: individual: LMC -
galaxies: star clusters: general
Abstract:
We analysed Washington CMT1 photometry of star clusters located along
the minor axis of the Large Magellanic Cloud (LMC), from the LMC
optical centre up to ∼39° outwards to the North-West. The data
base was exploited in order to search for new star cluster candidates,
to produce cluster CMDs cleaned from field star contamination and to
derive age estimates for a statistically complete cluster sample. We
confirmed that 146 star cluster candidates are genuine physical
systems, and concluded that an overall ∼30 per cent of catalogued
clusters in the surveyed regions are unlikely to be true physical
systems. We did not find any new cluster candidates in the outskirts
of the LMC (deprojected distance ≳8°). The derived ages of the
studied clusters are in the range 7.2<log(t[yr-1])≤9.4, with the
sole exception of the globular cluster NGC 1786
(log(t[yr-1])=10.10). We also calculated the cluster frequency for
each region, from which we confirmed previously proposed outside-in
formation scenarios. In addition, we found that the outer LMC fields
show a sudden episode of cluster formation (log(t[yr-1])∼7.8-7.9)
which continued until log(t[yr-1])∼7.3 only in the outermost LMC
region. We link these features to the first pericentre passage of the
LMC to the Milky Way (MW), which could have triggered cluster
formation due to ram pressure interaction between the LMC and MW halo.
Description:
The data used in this work come from the Cerro-Tololo Inter-American
Observatory (CTIO) programme 2008B-0296 (PI: Cole) that focused on
surveying the most metal poor stars outside the MW. We downloaded from
the National Optical Astronomy Observatory (NOAO) Science Data
Management (SDM) Archives1 Washington CM and Kron-Cousins R images
obtained with the Mosaic II imager, an array of 8Kx8K CCDs covering a
36-arcminx36-arcmin field, attached to the 4m Blanco telescope.
In this work, we analysed Washington CMT1 photometry of star clusters
located along the minor axis of the LMC. We covered a wide baseline in
deprojected distances, from the very optical LMC centre up to ∼39°
outwards to the North-West.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 66 75 Fundamental properties of the star cluster sample
clusters/* . 75 Photometric catalogue of stars of each clusters
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Field Field number
4- 16 A13 --- Cluster Cluster name
18- 21 F4.2 mag E(V-I) Colour excess in V-I
23- 27 F5.2 [yr-1] log(t)TW Age from this work
29- 32 F4.2 [yr-1] e_log(t)TW rms uncertainty on log(t)TW
34- 38 F5.2 [yr-1] log(t)L ? Age from literature
40- 43 F4.2 [yr-1] e_log(t)L ? rms uncertainty on log(t)L
45- 47 A3 --- r_log(t)L ? Reference for log(t)L (1)
49- 66 A18 --- FileName Name of the table with photometry in
subdirectory clusters
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Note (1): References as follows:
1 = Piatti (2011MNRAS.418L..40P 2011MNRAS.418L..40P)
2 = Glatt et al. (2010, Cat. J/A+A/517/A50)
3 = Piatti (2012, Cat. J/A+A/540/A58)
4 = Choudhury, Subramaniam & Piatti (2015AJ....149...52C 2015AJ....149...52C)
5 = Piatti (2014MNRAS.440.3091P 2014MNRAS.440.3091P)
6 = Brocato et al. (1996MNRAS.282..614B 1996MNRAS.282..614B)
7 = Carretta et al. (2000ApJ...533..215C 2000ApJ...533..215C)
8 = Piatti et al. (2009, Cat. J/A+A/501/585)
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Byte-by-byte Description of file: clusters/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
2- 7 I6 --- ID ID number
10- 11 I2 h RAh Right ascension (J2000)
12 A1 --- --- [:]
13- 14 I2 min RAm Right ascension (J2000)
15 A1 --- --- [:]
16- 21 F6.3 s RAs Right ascension (J2000)
23 A1 --- DE- Declination sign (J2000)
24- 25 I2 deg DEd Declination (J2000)
26 A1 --- --- [:]
27- 28 I2 arcmin DEm Declination (J2000)
29 A1 --- --- [:]
30- 34 F5.2 arcsec DEs Declination (J2000)
36- 43 F8.3 pix Xpos X position
45- 52 F8.3 pix Ypos Y position
55- 61 F7.4 mag Cmag ?=99.9999 C magnitude
65- 70 F6.4 mag e_Cmag ?=9.9999 rms uncertainty on Cmag
73- 79 F7.4 mag Mmag M magnitude
83- 88 F6.4 mag e_Mmag rms uncertainty on Mmag
91- 97 F7.4 mag T1mag T1 magnitude
101-106 F6.4 mag e_T1mag rms uncertainty on T1mag
109-115 F7.4 --- chi2 chi2 value
117-124 F8.4 --- Sharp Sharpness
128 I1 --- Memb [1/4] Membership (1)
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Note (1): Membership code as follows:
1 = 25%
2 = 50%
3 = 75%
4 = 100&
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 31-Jul-2020