2018A&A...617L...4R


C.D.S. - SIMBAD4 rel 1.7 - 2020.05.30CEST23:37:55

2018A&A...617L...4R - Astronomy and Astrophysics, volume 617, L4-4 (2018/9-1)

The double population of Chamaeleon I detected by Gaia DR2.

ROCCATAGLIATA V., SACCO G.G., FRANCIOSINI E. and RANDICH S.

Abstract (from CDS):


Context. Chamaeleon I represents an ideal laboratory to study the cluster formation in a low-mass environment. Recently, two sub-clusters spatially located in the northern and southern parts of Chamaeleon I were found with different ages and radial velocities.
Aims. In this Letter we report new insights into the structural properties, age, and distance of Chamaeleon I based on the astrometric parameters from Gaia data release 2 (DR2).
Methods. We identified 140 sources with a reliable counterpart in the Gaia DR2 archive. We determined the median distance of the cluster using Gaia parallaxes and fitted the distribution of parallaxes and proper motions assuming the presence of two clusters. We derived the probability of each single source of belonging to the northern or southern sub-clusters, and compared the HR diagram of the most probable members to pre-main sequences isochrones.
Results. The median distance of Chamaeleon I is ∼190pc. This is consistent with the revised estimate using the Tycho-Gaia Astrometric Solution, but it is about 20pc larger than the value commonly adopted in the literature. From a Kolmogorov-Smirnov test of the parallaxes and proper-motion distributions we conclude that the northern and southern clusters do not belong to the same parent population. The northern population has a distance dN=192.7+0.4–0.4pc, while the southern one dS=186.5+0.7–0.7pc. The two sub-clusters appear coeval, at variance with literature results, and most of the sources are younger than 3Myr. The northern cluster is more elongated and extends towards the southern direction partially overlapping with the more compact cluster located in the south. A hint of a relative rotation between the two sub-clusters is also found.

Abstract Copyright: © ESO 2018

Journal keyword(s): stars: pre-main sequence - open clusters and associations: individual: Chamaeleon I - parallaxes - proper motions

Status at CDS:  

Simbad objects: 5

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Number of rows : 5

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14750 1
2 RMC 136 Cl* 05 38 42.396 -69 06 03.36           ~ 1726 1
3 NAME Cha I MoC 11 06 48 -77 18.0           ~ 965 1
4 NAME Cha I-S reg 11 07 44 -77 34.8           ~ 9 0
5 NAME Cha in reg 11 09 29.4 -76 33 28           ~ 12 0

    Equat.    Gal    SGal    Ecl

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2020.05.30-23:37:55

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