J/A+A/633/A99 Gaia DR2 open clusters in the Milky Way. II (Cantat-Gaudin+, 2020)
Clusters and mirages: cataloguing stellar aggregates in the Milky Way.
Cantat-Gaudin T., Anders F.
<Astron. Astrophys. 633, A99 (2020)>
=2020A&A...633A..99C 2020A&A...633A..99C (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Milky Way
Keywords: open clusters and associations: general - Galaxy: stellar content
Abstract:
Many of the open clusters listed in modern catalogues were first
reported by visual astronomers as apparent over-densities of bright
stars. As observational techniques and analysis methods improved, some
of them have been shown to be chance alignments of stars and are not
true clusters. Recent publications making use of Gaia DR2 data
provided membership list for over a thousand clusters, but many nearby
objects listed in the literature have so far evaded detection. We
update the Gaia DR2 cluster census by performing membership
determinations for known clusters that had been missed by previous
studies, and for recently discovered clusters. We investigate a subset
of non-detected clusters that according to their literature parameters
should be easily visible in the Gaia . Confirming or disproving the
existence of old, inner-disc, high-altitude clusters is especially
important as their survival or disruption is linked to the dynamical
processes that drive the evolution of the Milky Way. We employ the
Gaia DR2 catalogue and a membership assignment procedure, as well as
visual inspection of spatial, proper motion, and parallax
distributions. We use membership lists provided by other authors when
they are available. We derive membership lists for 150 objects,
including 10 that were known prior to Gaia . We compile a final list
of members for 1481 clusters. Among the objects that we are still
unable to identify with Gaia data, we argue that many (mostly putative
old, relatively nearby, high-altitude objects) are not true clusters.
At present, the only confirmed cluster located further than 500pc
away from the Galactic plane within the Solar circle is NGC 6791. It
is likely that the objects discussed in this study only represent a
fraction of the non-physical groupings erroneously listed in the
catalogues as genuine open clusters, and that those lists need further
cleaning.
Description:
The catalogue ibcluses lists of cluster members for objects that were
not included in Cantat-Gaudin et al. (2018, Cat. J/A+A/618/A93) either
because they were not identified or because they had not yet been
discovered. We bring the total number of clusters with available
membership from Gaia DR2 to 1481.
table1:
Mean parameters of the identified clusters.
members:
All columns from the Gaia DR2 catalogue, except the membership
probability which was computed with the unsupervised classification
scheme UPMASK applied to the Gaia DR2 proper motions and parallaxes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 208 1481 Mean parameters of the identified clusters
members.dat 493 435833 *Members
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Note on members.dat: All columns from the Gaia DR2 catalogue, except the
membership probability which was computed with the unsupervised classification
scheme UPMASK applied to the Gaia DR2 proper motions and parallaxes.
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+A/618/A93 : Gaia DR2 open clusters in the Milky Way (Cantat-Gaudin+, 2018)
J/A+A/623/A108 : Age of 269 GDR2 open clusters (Bossini+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- Cluster Cluster name (cluster)
19- 25 F7.3 deg RAdeg [] Mean right ascension of members (ICRS)
at Ep=2015.5 (ra)
27- 33 F7.3 deg DEdeg Mean declination of members (ICRS)
at Ep=2015.5 (dec)
35- 41 F7.3 deg GLON Mean Galactic longitude of members (l)
43- 49 F7.3 deg GLAT Mean Galactic latitude of members (b)
51- 55 F5.3 deg r50 Radius containing half the members (r50)
57- 60 I4 --- N Number of members (probability over 0.5)
(nbstars)
62- 68 F7.3 mas/yr pmRA Mean proper motion along RA of members,
pmRA*cosDE (pmra)
70- 74 F5.3 mas/yr s_pmRA Standard deviation of pmRA of members
(sigpmra)
76- 80 F5.3 mas/yr e_pmRA Standard deviation of pmRA of members over
square root of nbstars (uncertpmra)
82- 88 F7.3 mas/yr pmDE Mean proper motion along DE of members (pmdec)
90- 94 F5.3 mas/yr s_pmDE Standard deviation of pmdec of members
(sigpmdec)
96-100 F5.3 mas/yr e_pmDE Standard deviation of pmdec of members over
square root of nbstars (uncertpmdec)
102-107 F6.3 mas Plx Mean parallax of members (par)
109-113 F5.3 mas s_Plx Standard deviation of parallax of members
(sigpar)
115-119 F5.3 mas e_Plx Standard deviation of parallax of members
over square root of nbstars (uncertpar)
121-127 F7.1 pc dmode05 5th percentile distance confidence interval
(d05)
129-135 F7.1 pc dmode16 16th percentile distance confidence interval
(d16)
137-143 F7.1 pc dmode Most likely distance (dmode)
145-151 F7.1 pc dmode84 84th percentile distance confidence interval
(d84)
153-159 F7.1 pc dmode95 95th percentile distance confidence interval
(d95)
161-166 F6.1 pc dmode+01 Distance if +0.1mas added to parallax
(dmodePLUS01)
168-174 F7.1 pc dmode-01 ? Distance if -0.1mas added to parallax null
if mean parallax under 0.1mas (dmodeMINUS01)
176-183 F8.1 pc X X position in Galactic cartesian coordinates
(X)
185-192 F8.1 pc Y Y position in Galactic cartesian coordinates
(Y)
194-200 F7.1 pc Z Z position in Galactic cartesian coordinates
(Z)
202-208 F7.1 pc Rgc Distance from Galactic centre assuming the
Sun is at 8340pc (Rgc)
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Byte-by-byte Description of file: members.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 21 E21.18 deg RAdeg Barycentric right ascension (ICRS)
at Ep=2015.5 (ra)
23- 43 E21.18 deg DEdeg Barycentric declination (ICRS)
at Ep=2015.5 (dec)
45- 63 I19 --- Source Gaia DR2 source ID (source_id)
65- 85 F21.17 deg GLON Galactic longitude (l)
87-108 E22.19 deg GLAT Galactic latitude (b)
110-131 E22.18 mas Plx Absolute stellar parallax (parallax)
133-152 F20.18 mas e_Plx Standard error of parallax
(parallax_error)
154-175 E22.19 mas/yr pmRA Proper motion in right ascension direction
(pmRA*cosDE) (pmra)
177-196 F20.18 mas/yr e_pmRA Standard error of proper motion in right
ascension direction (pmra_error)
198-219 E22.19 mas/yr pmDE Proper motion in declination direction
(pmdec)
221-240 F20.18 mas/yr e_pmDE Standard error of proper motion in
declination direction (pmdec_error)
242-265 F24.19 km/s RV ? Spectroscopic radial velocity in the
solar barycentric reference frame
(radial_velocity)
267-287 F21.17 km/s e_RV ? Radial velocity error
(radialvelocityerror)
289-302 E14.10 --- RADEcor Correlation between right ascension and
declination (radeccorr)
304-317 E14.10 --- RAPlxcor Correlation between right ascension and
parallax (raparallaxcorr)
319-332 E14.10 --- RApmRAcor Correlation between right ascension and
proper motion in right ascension
(rapmracorr)
334-347 E14.10 --- RApmDEcor Correlation between right ascension and
proper motion in declination
(rapmdeccorr)
349-362 E14.10 --- DEPlxcor Correlation between declination and
parallax (decparallaxcorr)
364-377 E14.10 --- DEpmRAcor Correlation between declination and
proper motion in right ascension
(decpmracorr)
379-392 E14.10 --- DEpmDEcor Correlation between declination and
proper motion in declination
(decpmdeccorr)
394-407 E14.10 --- PlxpmRAcor Correlation between parallax and proper
motion in right ascension
(parallaxpmracorr)
409-422 E14.10 --- PlxpmDEcor Correlation between parallax and proper
motion in declination
(parallaxpmdeccorr)
424-437 E14.10 --- pmRApmDEcor Correlation between proper motion in
right ascension and proper motion in
declination (pmrapmdeccorr)
439-442 I4 --- o_Gmag Number of observations contributing to G
photometry (photgn_obs)
444-453 F10.7 mag Gmag G-band mean magnitude (Vega)
(photgmean_mag)
455-467 E13.10 mag BP-RP ? BP-RP colour (bp_rp)
469-475 F7.5 --- Proba Membership probability (proba) (1)
477-493 A17 --- Cluster Cluster name (cluster)
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Note (1): membership probability was computed with the unsupervised
classification scheme UPMASK applied to the Gaia DR2 proper motions and
parallaxes
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Acknowledgements:
Tristan Cantat-Gaudin, tcantat(at)fqa.ub.edu
(End) Patricia Vannier [CDS] 13-Nov-2019