2010A&A...510A..78S


Query : 2010A&A...510A..78S

2010A&A...510A..78S - Astronomy and Astrophysics, volume 510, A78-78 (2010/2-1)

Cluster radius and sampling radius in the determination of cluster membership probabilities.

SANCHEZ N., VICENTE B. and ALFARO E.J.

Abstract (from CDS):

We analyze the dependence of the membership probabilities obtained from kinematical variables on the radius of the field of view around open clusters (the sampling radius, Rs). From simulated data, we show that optimal discrimination between cluster members and non-members is achieved when the sampling radius is very close to the cluster radius. At higher Rs values, more field stars tend to be erroneously assigned as cluster members. From real data of two open clusters (NGC 2323 and NGC 2311), we infer that the number of identified cluster members always increases with increasing Rs. However, there is a threshold value Rs,opt above which the identified cluster members are severely contaminated by field stars and the effectiveness of membership determination is relatively small. This optimal sampling radius is ≃14-arcmin for NGC 2323 and ≃13-arcmin for NGC 2311. We discuss the reasons for this behavior and the relationship between cluster radius and optimal sampling radius. We suggest that, independently of the method used to estimate membership probabilities, several tests using different sampling radius should be performed to evaluate possible biases.

Abstract Copyright:

Journal keyword(s): methods: data analysis - open clusters and associations: general - open clusters and associations: individual: NGC 2311 - open clusters and associations: individual: NGC 2323

Simbad objects: 2

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Number of rows : 2
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 NGC 2311 OpC 06 57 47.3 -04 36 36     9.6     ~ 36 0
2 NGC 2323 OpC 07 02 47.5 -08 20 16           ~ 180 0

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2022.11.28-12:24:58

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