J/MNRAS/481/3887 Astrometry and photometry of 7 open clusters (Dias+, 2018)
Astrometric and photometric study of Dias 4, Dias 6, and other five open
clusters using ground-based and Gaia DR2 data.
Dias W.S., Monteiro H., Lepine J.R.D., Prates R., Gneiding C.D., Sacchi M.
<Mon. Not. R. Astron. Soc., 481, 3887-3901 (2018)>
=2018MNRAS.481.3887D 2018MNRAS.481.3887D (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Photometry ; Positional data ; Proper motions ;
Optical
Keywords: open clusters and associations: general
Abstract:
We present a study of seven southern open clusters based on UBVRI CCD
photometry (Johnsons-Cousins system) and Gaia DR2 data. Dias4, Dias6,
and four other clusters had UBVRI photometric observations determined
for the first time. From the observational UBVRI data we obtained
photometric membership probability estimates and, using the proper
motions from the UCAC5 catalogue, we also determined the kinematic
membership. From Gaia DR2 astrometric data we determine the stellar
membership using proper motions and parallaxes, taking into account
the full covariance matrix. For both independent sets of data and
membership we apply our non-subjective multidimensional global
optimization tool to fit theoretical isochrones to determine the
distance, age, reddening, metallicity, and binary fraction of the
clusters. The results of the mean proper motions, distances, and ages
are in agreement, but the ones obtained from Gaia DR2 data are more
precise in both membership selection and estimated parameters. In the
case of NGC 6087, the Cepheid S Nor, member of the open cluster, was
used to obtain an independent distance estimate, confirming the one
determined by our fitting method. We also report a serendipitous
discovery of two new clusters in the extended field near what was
originally Dias4.
Description:
The open clusters investigated in this study (Collinder 307, Dias 4,
Dias 6, IC 4651, NGC 5138, NGC 6087 and NGC 6178) were selected from
DAML02 (Dias et al. 2002A&A...389..871D 2002A&A...389..871D, Cat. B/ocl) with the aim to
provide a set of homogeneous UBVRI data and parameters determined from
them in a non-subjective isochrone-fitting approach.
The observations were carried out using the B&C 0.6m telescope at Pico
dos Dias Observatory (LNA-Brazil) on the nights of 5, 6, and 7 July
2013 under photometric conditions. The main detector of the survey was
a SITe 1024x1024 back-illuminated CCD with the plate scale of
0.6arcsec/pixel, and the square field of 10arcmin approximately and a
Johnson-Cousins UBVRI filter set was employed. For each studied
cluster we give the catalogue of calibrated data which includes our
UBVRI photometry and error estimates, equatorial coordinates, proper
motion, and JHKs magnitudes.
In this work we also use Gaia DR2 catalogue that presents all sky
astrometric and photometric data with unprecedented precision for more
than one billion objects with Gmag less than 21. We searched for Gaia
DR2 stars in the sky area of the selected clusters, using the central
coordinates and the apparent diameters taken from the DAML02
Catalogue. To include virtually all possible members of the studied
clusters, we opted to use radius 2arcmin bigger than those provided by
DAML02 catalogue.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
c307g.dat 96 8750 Collinder 307 Gaia DR2 Data
d4ag2.dat 140 3915 Dias 4a Gaia DR2 Data
d4bg2.dat 140 7106 Dias 4b Gaia DR2 Data
d6g.dat 96 4934 Dias 6 Gaia DR2 Data
ic4651g.dat 96 11477 IC 4651 Gaia DR2 Data
ngc5138g.dat 96 13650 NGC 5138 Gaia DR2 Data
ngc6087g.dat 96 28667 NGC 6087 Gaia DR2 Data
ngc6178g.dat 96 9539 NGC 6178 Gaia DR2 Data
c307p.dat 195 1089 Collinder 307 UBVRI and JHKs Data with
photometric membership
d4p.dat 195 773 Dias 4 UBVRI and JHKs Data with photometric
membership
d6p.dat 195 966 Dias 6 UBVRI and JHKs Data with photometric
membership
ic4651p.dat 195 2437 IC 4651 UBVRI and JHKs Data with photometric
membership
ngc5138p.dat 195 1308 NGC 5138 UBVRI and JHKs Data with photometric
membership
ngc6087p.dat 195 2020 NGC 6087 UBVRI and JHKs Data with photometric
membership
ngc6178p.dat 195 1584 NGC 6178 UBVRI and JHKs Data with photometric
membership
c307k.dat 197 208 Collinder 307 UBVRI and JHKs Data with the
computed mean of photometric and kinematic
memberships
d4k.dat 197 150 Dias 4 UBVRI and JHKs Data with the computed
mean of photometric and kinematic memberships
d6k.dat 197 193 Dias 6 UBVRI and JHKs Data with the computed
mean of photometric and kinematic memberships
ic4651k.dat 197 507 IC 4651 UBVRI and JHKs Data with the computed
mean of photometric and kinematic memberships
ngc5138k.dat 197 290 NGC 5138 UBVRI and JHKs Data with the computed
mean of photometric and kinematic memberships
ngc6087k.dat 197 450 NGC 6078 UBVRI and JHKs Data with the computed
mean of photometric and kinematic memberships
ngc6178k.dat 197 328 NGC 6178 UBVRI and JHKs Data with the computed
mean of photometric and kinematic memberships
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/340 : UCAC5 Catalogue (Zacharias+ 2017)
Byte-by-byte Description of file: *g.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- ID Star ID
7- 16 F10.6 deg RAdeg Right Ascension (J2000)
18- 27 F10.6 deg DEdeg Declination (J2000)
29- 35 F7.4 mag Gmag G magnitude from Gaia DR2
37- 42 F6.4 mag e_Gmag Error on Gmag
44- 50 F7.4 mag BPmag ? BP magnitude from Gaia DR2
52- 58 F7.4 mag e_BPmag ? Error on BPmag
60- 66 F7.4 mag RPmag ? RP magnitude from Gaia DR2
68- 74 F7.4 mag e_RPmag ? Error on RPmag
76- 82 F7.4 mas plx Parallax
84- 89 F6.4 mas e_plx Error on parallax
91- 96 F6.4 --- Prob Probability of being a member (1)
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Note (1): From the statistical point of view, the clustering of the stars in
space comes together with clustering in the data space of proper
motion plus parallax. Therefore, the closer a given star is to the
density peak in that space, the higher the probability of the star
being a member. In the space formed by the proper motion and parallax,
the problem can be formulated as a maximum likelihood one, based on
the assumption of normally distributed uncertainties in proper motion
and parallax
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Byte-by-byte Description of file: d4ag2.dat d4bg2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- ID Star ID
6- 15 F10.6 deg RAdeg Right Ascension (J2000)
17- 26 F10.6 deg DEdeg Declination (J2000)
28- 34 F7.4 mag Gmag G magnitude from Gaia DR2
36- 41 F6.4 mag e_Gmag Error on Gmag
43- 49 F7.4 mag BPmag ? BP magnitude from Gaia DR2
51- 56 F6.4 mag e_BPmag ? Error on BPmag
58- 64 F7.4 mag RPmag ? RP magnitude from Gaia DR2
66- 71 F6.4 mag e_RPmag ? Error on RPmag
73- 80 F8.4 mas/yr pmRA Proper motion in right ascension from Gaia DR2
82- 87 F6.4 mas/yr e_pmRA Error on pmRA
89- 95 F7.4 mas/yr pmDE Proper motion in declination from Gaia DR2
97-102 F6.4 mas/yr e_pmDE Error on pmDE
104-110 F7.4 mas plx Parallax
112-117 F6.4 mas e_plx Error on plx
119-126 F8.4 km/s RV ? Radial velocity
128-133 F6.4 km/s e_RV ? Error on RV
135-140 F6.4 --- Prob Probability of being a member
--------------------------------------------------------------------------------
Byte-by-byte Description of file: *p.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- ID Star ID
6- 15 F10.6 deg RAdeg Right ascension (J2000)
17- 26 F10.6 deg DEdeg Declination (J2000)
28- 34 F7.4 mag Umag ? U magnitude from Johnson-Cousins system
36- 41 F6.4 mag e_Umag ? Error on Umag
43- 49 F7.4 mag Bmag B magnitude from Johnson-Cousins system
51- 56 F6.4 mag e_Bmag Error on Bmag
58- 64 F7.4 mag Vmag V magnitude from Johnson-Cousins system
66- 71 F6.4 mag e_Vmag Error on Vmag
73- 79 F7.4 mag Rmag ? R magnitude from Johnson-Cousins system
81- 86 F6.4 mag e_Rmag ? Error on Rmag
88- 94 F7.4 mag Imag ? I magnitude from Johnson-Cousins system
96-101 F6.4 mag e_Imag ? Error on Imag
103-108 F6.3 mag Jmag ? J magnitude from 2MASS
110-115 F6.3 mag Hmag ? H magnitude from 2MASS
117-122 F6.3 mag Ksmag ? Ks magnitude from 2MASS
124-128 F5.3 mag e_Jmag ? Error on Jmag
130-134 F5.3 mag e_Hmag ? Error on Hmag
136-140 F5.3 mag e_Ksmag ? Error on Ksmag
142-147 F6.3 mag UCmag ? Magnitude in UCAC system
149-154 F6.2 mas/yr pmRA ? Proper motion in right ascension (1)
156-161 F6.2 mas/yr pmDE ? Proper motion in declination (1)
163-167 F5.2 mas/yr e_pmRA ? Error on pmRA (1)
169-173 F5.2 mas/yr e_pmDE ? Error on pmDE (1)
175-181 F7.5 deg e_RAdeg Error on RAdeg
183-189 F7.5 deg e_DEdeg Error on DEdeg
191-195 F5.3 --- Pphot Photometric membership (2)
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Note (1): Proper motions from UCAC5 Zacharias, Finch & Frouard
(2017AJ....153..166Z 2017AJ....153..166Z, Cat. I/340)
Note (2): In Dias et al. (2012A&A...539A.125D 2012A&A...539A.125D, B/ocl) our group presented a
non-parametric technique to estimate the membership of stars in the
field of the open clusters from photometric data. It was improved by
Monteiro et al. (2017NewA...51...15M 2017NewA...51...15M) (Paper II) with the update of
the code for performing isochrone fits based on the cross-entropy
global optimization algorithm.
In this work we used the same procedures defined in Paper II to
determine the membership of the stars in the field of each studied
clusters. The membership considers, for each star, the position in
the field, the spatial star density in that position, and the star
density in the multidimensional magnitude space, taking into account
the photometric errors in each filter. The procedure works
essentially as a multivariate kernel density estimate and we define
the value obtained in this way for each star as its photometric
membership.
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Byte-by-byte Description of file: *k.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- ID Star ID
6- 15 F10.6 deg RAdeg Right ascension (J2000)
17- 26 F10.6 deg DEdeg Declination (J2000)
28- 34 F7.4 mag Umag ? U magnitude from Johnson-Cousins system
36- 41 F6.4 mag e_Umag ? Error on Umag
43- 49 F7.4 mag Bmag B magnitude from Johnson-Cousins system
51- 56 F6.4 mag e_Bmag Error on Bmag
58- 64 F7.4 mag Vmag V magnitude from Johnson-Cousins system
66- 71 F6.4 mag e_Vmag Error on Vmag
73- 79 F7.4 mag Rmag ? R magnitude from Johnson-Cousins system
81- 86 F6.4 mag e_Rmag ? Error on Rmag
88- 94 F7.4 mag Imag ? I magnitude from Johnson-Cousins system
96-101 F6.4 mag e_Imag ? Error on Imag
103-108 F6.3 mag Jmag ? J magnitude from 2MASS
110-115 F6.3 mag Hmag ? H magnitude from 2MASS
117-122 F6.3 mag Ksmag ? Ks magnitude from 2MASS
124-128 F5.3 mag e_Jmag ? Error on Jmag
130-134 F5.3 mag e_Hmag ? Error on Hmag
136-140 F5.3 mag e_Ksmag ? Error on Ksmag
142-147 F6.3 mag UCmag ? Magnitude in UCAC system
149-155 F7.2 mas/yr pmRA ? Proper motion in right ascension (1)
157-163 F7.2 mas/yr pmDE ? Proper motion in declination (1)
165-169 F5.2 mas/yr e_pmRA ? Error on pmRA (1)
171-175 F5.2 mas/yr e_pmDE ? Error on pmDE (1)
177-183 F7.5 deg e_RAdeg Error on RAdeg
185-191 F7.5 deg e_DEdeg Error on DEdeg
193-197 F5.3 --- Pp+Pk Combined probability defined as the mean of the
photometric and kinematic memberships (2)
--------------------------------------------------------------------------------
Note (1): Proper motions from UCAC5 Zacharias, Finch & Frouard
(2017AJ....153..166Z 2017AJ....153..166Z, Cat. I/340)
Note (2): We determined the membership of the stars in the region of each
cluster using proper motion data from UCAC5 catalogue
(Zacharias et al. 2017AJ....153..166Z 2017AJ....153..166Z, Cat. I/340). The method
described below is the same used in Dias et al. (2014A&A...564A..79D 2014A&A...564A..79D,
Cat. J/A+A/564/A79) and Dias et al. (2018MNRAS.478.5184D 2018MNRAS.478.5184D,
Cat. J/MNRAS/478/5184).
The model considers that the distribution of proper motions of the
stars in a cluster's region can be represented by two elliptical
bivariate Gaussians following Zhao & He (1990A&A...237...54Z 1990A&A...237...54Z),
including the proper motion's errors in the frequency function.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 08-Jun-2022