J/A+A/624/A126 New open clusters in Perseus direction (Cantat-Gaudin+, 2019)
Gaia DR2 unravels incompleteness of nearby cluster population:
new open clusters in the direction of Perseus.
Cantat-Gaudin T., Krone-Martins A., Sedaghat N., Farahi A., de Souza R.S.,
Skalidis R., Malz A.I., Macedo S., Moews B., Jordi C., Moitinho A.,
Castro-Ginard A., Ishida E.E.O., Heneka C., Boucaud A., Trindade A.M.M.
<Astron. Astrophys. 624, A126 (2019)>
=2019A&A...624A.126C 2019A&A...624A.126C (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, nearby
Keywords: open clusters and associations: general - methods: numerical
Abstract:
Open clusters (OCs) are popular tracers of the structure and
evolutionary history of the Galactic disk. The OC population is often
considered to be complete within 1.8kpc of the Sun. The recent Gaia
Data Release 2 (DR2) allows the latter claim to be challenged. We
perform a systematic search for new OCs in the direction of Perseus
using precise and accurate astrometry from Gaia DR2. We implement a
coarse-to-fine search method. First, we exploit spatial proximity
using a fast density-aware partitioning of the sky via a k-d tree in
the spatial domain of Galactic coordinates, (l, b). Secondly, we
employ a Gaussian mixture model in the proper motion space to quickly
tag fields around OC candidates. Thirdly, we apply an unsupervised
membership assignment method, UPMASK, to scrutinise the candidates. We
visually inspect colour-magnitude diagrams to validate the detected
objects. Finally, we perform a diagnostic to quantify the significance
of each identified overdensity in proper motion and in parallax space
We report the discovery of 41 new stellar clusters. This represents an
increment of at least 20% of the previously known OC population in
this volume of the Milky Way. We also report on the clear
identification of NGC 886, an object previously considered an
asterism. This letter challenges the previous claim of a near-complete
sample of open clusters up to 1.8 kpc. Our results reveal that this
claim requires revision, and a complete census of nearby open clusters
is yet to be found.
Description:
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
tablea1.dat 96 46 Mean parameters of the OCs characterised in
this study
members.dat 258 14778 List of all members
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Note Cluster category (Grade A, Grade B, known)
9- 20 A12 --- Cluster Cluster name
22- 27 F6.3 deg RAdeg Right ascension (J2000)
29- 34 F6.3 deg DEdeg Declination (J2000)
36- 42 F7.3 deg GLON Galactic longitude
44- 49 F6.3 deg GLAT Galactic latitude
51- 55 F5.3 deg r50 Radius containing half the members identified
in this study
57- 59 I3 --- N Number of stars with the most frequent
membership probability ≥50%
61- 65 F5.2 mas/yr pmRA* Proper motion along RA, pmRA*cosDE
67- 70 F4.2 mas/yr e_pmRA* rms uncertainty on pmRA*
72- 76 F5.2 mas/yr pmDE Proper motion along DE
78- 81 F4.2 mas/yr e_pmDE rms uncertainty on pmDE
83- 86 F4.2 mas plx Parallax
88- 91 F4.2 mas e_plx rms uncertainty on Plx
93- 96 I4 pc d Mode of the distance likelihood after adding
+0.029mas to the measured parallaxes
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Byte-by-byte Description of file: members.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 F15.11 deg RAdeg Barycentric right ascension (ICRS)
at Ep=2015.5 (ra)
17- 31 F15.11 deg DEdeg Barycentric declination (ICRS)
at Ep=2015.5 (dec)
33- 51 I19 --- Source Gaia DR2 Unique source identifier
(source_id)
53- 66 F14.10 deg GLON Galactic longitude (l)
68- 81 F14.10 deg GLAT Galactic latitude (b)
83- 92 F10.4 mas Plx Absolute stellar parallax (parallax)
94- 99 F6.4 mas e_Plx Standard error of parallax (parallax_error)
101-109 F9.3 mas/yr pmRA* Proper motion in right ascension direction
(pmRA*cosDE) (pmra)
111-115 F5.3 mas/yr e_pmRA* Standard error of proper motion in
right ascension direction (pmra_error)
117-125 F9.3 mas/yr pmDE Proper motion in declination direction
(pmdec)
127-131 F5.3 mas/yr e_pmDE Standard error of proper motion in
declination direction (pmdec_error)
133-139 F7.4 --- RADEcor Correlation between right ascension and
declination (radeccorr)
141-147 F7.4 --- RAPlxcor Correlation between right ascension and
parallax (raparallaxcorr)
149-155 F7.4 --- RApmRAcor Correlation between right ascension and
proper motion in right ascension
(rapmracorr)
157-163 F7.4 --- RApmDEcor Correlation between right ascension and
proper motion in declination
(rapmdeccorr)
165-171 F7.4 --- DEPlxcor Correlation between declination and
parallax (decparallaxcorr)
173-179 F7.4 --- DEpmRAcor Correlation between declination and proper
motion in right ascension (decpmracorr)
181-187 F7.4 --- DEpmDEcor Correlation between declination and proper
motion in declination (decpmdeccorr)
189-195 F7.4 --- PlxpmRAcor Correlation between parallax and proper
motion in right ascension
(parallaxpmracorr)
197-203 F7.4 --- PlxpmDEcor Correlation between parallax and proper
motion in declination
(parallaxpmdeccorr)
205-211 F7.4 --- pmRApmDEcor Correlation between proper motion in right
ascension and proper motion in declination
(pmrapmdeccorr)
213-216 I4 --- o_Gmag Number of observations contributing to G
photometry (photgn_obs)
218-226 F9.6 mag Gmag G-band mean magnitude (Vega)
(photgmean_mag)
228-236 F9.6 mag BP-RP ? BP-RP colour
(photBpMeanMag-photRMeanMag) (bp_rp)
238-245 F8.6 --- proba [0/1] Membership probability (proba)
247-258 A12 --- Cluster Cluster name (cluster)
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Acknowledgements:
Tristan Cantat-Gaudin, tcantat(at)fqa.ub.edu
(End) Patricia Vannier [CDS] 28-Mar-2019