J/MNRAS/498/205 The VISCACHA survey II (Santos+, 2020)
The VISCACHA survey - II.
Structure of star clusters in the Magellanic Clouds periphery.
Santos J.F.C., Maia F.F.S., Dias B., de O Kerber L., Piatti A.E., Bica E.,
Angelo M.S., Minniti D., Perez-Villegas A., Roman-Lopes A., Westera P.,
Fraga L., Quint B., Sanmartim D.
<Mon. Not. R. Astron. Soc., 498, 205-222 (2020)>
=2020MNRAS.498..205S 2020MNRAS.498..205S (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Clusters, globular ; Photometry, UBVRI ;
Positional data ; Surveys
Keywords: surveys - galaxies: interactions - Magellanic Clouds -
galaxies: photometry - galaxies: star clusters: general -
galaxies: structure
Abstract:
We provide a homogeneous set of structural parameters of 83 star
clusters located at the periphery of the Small Magellanic Cloud (SMC)
and the Large Magellanic Cloud (LMC). The clusters' stellar density
and surface brightness profiles were built from deep, AO assisted
optical images, and uniform analysis techniques. The structural
parameters were obtained from King (1962AJ.....67..471K 1962AJ.....67..471K) and Elson et
al. (1987ApJ...323...54E 1987ApJ...323...54E) model fittings. Integrated magnitudes and
masses (for a subsample) are also provided. The sample contains mostly
low surface brightness clusters with distances between 4.5 and 6.5kpc
and between 1 and 6.5kpc from the LMC and SMC centres, respectively.
We analysed their spatial distribution and structural properties,
comparing them with those of inner clusters. Half-light and Jacobi
radii were estimated, allowing an evaluation of the Roche volume tidal
filling. We found that: (i) for our sample of LMC clusters, the tidal
radii are, on average, larger than those of inner clusters from
previous studies; (ii) the core radii dispersion tends to be greater
for LMC clusters located towards the southwest, with position angles
of ∼200° and about ∼5° from the LMC centre, i.e. those LMC
clusters nearer to the SMC; (iii) the core radius evolution for
clusters with known age is similar to that of inner clusters; (iv) SMC
clusters with galactocentric distances closer than 4kpc are
overfilling; (v) the recent Clouds collision did not leave marks on
the LMC clusters' structure that our analysis could reveal.
Description:
A description of the VISCACHA Survey and the related observations is
given in paper I, where the instrument setup, observational strategy,
and the methodology for the data reduction and calibration are fully
explained. Here we provide a brief summary.
SAM is a ground-layer adaptive optics (GLAO) instrument using a
Rayleigh laser guide star (LGS) at ∼7km from the telescope (Tokovinin
2013aoel.confE..12T). SAM was employed with its internal CCD detector,
SAMI (4Kx4K CCD). It was set to a gain of 2.1e-/ADU and a readout
noise of 4.7e-. The CCD binning (2x2) provides a plate-scale of
0.091arcsec/pixel with the detector covering 3.1x3.1arcmin2 on the
sky.
Photometric image data with BVI filters were obtained for the cluster
sample during semesters 2015A, 2015B, and 2016B. Total integration
times were 1350s (B), 1125s (V), and 1680s (I) for LMC clusters, 1200s
(V), 1800s (I) for old SMC clusters and 300s (V) and 400s (I) for
young SMC clusters. Short exposures were also acquired (2x30s in all
bands for all clusters) to replace stars saturated in the longer
exposures.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 93 32 SMC clusters' structural parameters from RDPs
table2.dat 93 51 LMC clusters' structural parameters from RDPs
table3.dat 104 32 SMC clusters' structural parameters from SBPs
table4.dat 104 51 LMC clusters' structural parameters from SBPs
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Byte-by-byte Description of file: table[12].dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Cluster name
10 A1 --- f_Name [*] Flag on Name (1)
12- 13 I2 h RAh Right ascension (J2000)
15- 16 I2 min RAm Right ascension (J2000)
18- 19 I2 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- 29 I2 arcsec DEs Declination (J2000)
31- 34 F4.2 arcsec-2 sigo Central surface stellar density from King
model fit (2)
36- 39 F4.2 arcsec-2 e_sigo Error on sigo
41- 42 I2 arcsec rc Core radius from King model fit (2)
44 I1 arcsec e_rc Error on rc
46- 48 I3 arcsec rt Tidal radius from King model fit (2)
50- 51 I2 arcsec e_rt Error on rt
53- 57 F5.3 arcsec-2 sigbg Background stellar density
59- 63 F5.3 arcsec-2 e_sigbg Error on sigbg
65- 68 F4.2 --- chi2King Reduced chi-squared for the King model fit
70- 71 I2 arcsec a ? Scale length related to the core radius
from EFF model fit (3)
73- 74 I2 arcsec e_a ? Error on a
76- 78 F3.1 --- gamma ? γ parameter probing the outermost
cluster structure from EFF model fit (3)
80- 82 F3.1 --- e_gamma ? Error on gamma
84- 87 F4.2 --- chi2EFF ? Reduced chi-squared for the EEF model fit
89- 93 F5.2 mag Vlim Peak value of the cluster plus field
luminosity function
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Note (1): Flag as follows:
* = SBP I-band filter measurements
Note (2): The structural parameters, namely, central surface stellar density
(σo), core radius (rc), and tidal radius (rt) were
estimated by fitting the King model to the clusters' radial number
density profiles according to the expression:
σ(r)=σo[(1+(r/rc)2)-1/2-(1+(rt/rc)2)-1/2]2+
σbg
Note (3): We obtained the structural parameters according to the empirical
function by EFF, i.e.:
σ(r)=σo(1+r2/a2)-γ/2+σbg, where a
is the scale length related to the core radius and γ probes the
outermost cluster structure. Since rc represents the radius at which
the stellar density falls by half of its central value,
rc=asqrt(22/γ-1)
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Byte-by-byte Description of file: table[34].dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Cluster name
10 A1 --- f_Name [*] Flag on Name (1)
12- 13 I2 h RAh Right ascension (J2000)
15- 16 I2 min RAm Right ascension (J2000)
18- 19 I2 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- 29 I2 arcsec DEs Declination (J2000)
31- 35 F5.2 mag/arcsec2 muvo ? Central surface brightness
37- 40 F4.2 mag/arcsec2 e_muvo ? Error on muvo
42- 45 F4.1 arcsec rc ? Core radius from King model fit (2)
47- 50 F4.1 arcsec e_rc ? Error on rc
52- 54 I3 arcsec rt ? Tidal radius from King model fit (2)
56- 58 I3 arcsec e_rt ? Error on rt
60- 64 F5.2 mag/arcsec2 muvbg ? Background surface brightness
66- 69 F4.2 mag/arcsec2 e_muvbg ? Error on muvbg
71- 74 F4.2 --- chi2King ? Reduced chi-squared for the King
model fit
76- 77 I2 arcsec a ? Scale length related to the core
radius from EFF model fit (3)
79- 80 I2 arcsec e_a ? Error on a
82- 84 F3.1 --- gamma ? γ parameter probing the
outermost cluster structure from EFF
model fit (3)
86- 88 F3.1 --- e_gamma ? Error on gamma
90- 93 F4.2 --- chi2EFF ? Reduced chi-squared for the EEF model
fit
95- 99 F5.2 mag Vint ? Integrated apparent magnitude (4)
101- 104 F4.2 mag e_Vint ? Error on Vint
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Note (1): Flag as follows:
* = SBP I-band filter measurements
Note (2): The structural parameters central surface brightness (µo), rc
and rt were estimated by fitting the following expression to the
clusters' surface brightness:
µ(r)=µ'o-5log[(1+(r/rc)2)-1/2-(1+(rt/rc)2)-1/2],
where µ'o=µo+5log[1-(1+(rt/rc)2)-1/2].
Note (3): The clusters' SBP was also fitted by the EFF model using the
following expression: µ(r)=µ'o+1.25γlog(1+r2/a2).
Note (4): The integrated apparent magnitudes (Vint) were determined from the
clusters' SBP by integrating the flux from the centre out to the
limiting radius after subtracting the stellar foreground/background
flux.
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History:
From electronic version of the journal
References:
Maia et al., Paper I 2019MNRAS.484.5702M 2019MNRAS.484.5702M
Dias et al., Paper III 2021A&A...647L...9D 2021A&A...647L...9D
Dias et al., Paper IV 2022MNRAS.512.4334D 2022MNRAS.512.4334D
Bica et al., Paper V 2022MNRAS.517L..41B 2022MNRAS.517L..41B
Rodriguez et al., Paper VI 2023MNRAS.519.3357R 2023MNRAS.519.3357R
Oliveira et al., Paper VII 2023MNRAS.524.2244O 2023MNRAS.524.2244O
(End) Ana Fiallos [CDS] 31-Jul-2023