OPEN CLUSTER DETECTION IN EXTENSIVE SKY REGIONS USING ASTROMETRIC PARAMETERS

L. G. PAIZ, M. S. DE BIASI AND R. B. ORELLANA

Florianópolis

Congreso; XIV Latin American Regional IAU Meeting; 2013

IAU

We have developed a non-parametric method for identifying open clusters in large areas of the sky us- ing accurate data position and stellar proper motion. Two binary codes have been established from the analysis of the empirical probability density func- tions in position and proper motion, after eliminat- ing the contamination due to field stars in the region. For each star, these codes provide a parameter that indicates stellar membership to a space and proper motion overdensity. The validity of the method was tested by apply- ing it to the region between 7h 8m (117°) and 7h 28m (112 °) in right ascension and -33° and -29° in declination. In this region, open clusters Collinder 140 and Collinder 132 are present. The data used were obtained from UCAC2 and its supplement UCAC2 BSS astrometric catalog. 1300 stars in the region were found up to the magni- tude R=11, limiting the proper motion errors to 1-3 mas/yr. We detected 6 stellar groups having spatial and proper motion overdensities, a detailed analysis re- vealed that 3 of them could be open clusters. Among the 3 possible detected clusters, we con- firmed that one of them is Collinder 140 and ob- tained mean coordinates alfa   =110.8° and delta=-32.0°, a radius of about 12´ and mean proper motion compo- nents mualfa cosdelta = -9 mas/yr, mudelta=+4 das/yr, in good agreement with the literatura consulted. The other two possible clusters have memebers fainter than magnitude 10.0 and they are not found in the literature. The low density of the UCAC2 catalog and its supplement stars up to the considered magnitude in the area did not allow us to detect Collinder132. REFERENCES Dias, W. S., Lpine, J. ,Alessi, B. S., Moitinho, A.,http://www.astro.iag.usp.br/wilton/ Kharchenko N.V., Piskunov A.E., R¨oser S. et al., 2005, A&A, 438, 1163 Siverman B., 1986, Density Estimation for Statistics and Data Analysis, J.W. Arrowsmith Ltd. 1Facultad de Ciencias Astron´omicas y Geof´ýsicas, UNLP, Paseo del Bosque s/n, 1900, La Plata, Argentina. 2Instituto de Astrof´ýsica de La Plata (CCT La Plata - CONICET, UNLP). Stock, J., Abad, C., 1988, Rev. Mexicana Astron. Astrof ´ýs., 16, 63 Urban S.E., Zacharias N., Wycoff G.L., 2004-2006 AJ (unpublished) 2004. The UCAC2 Bright Star Supplement Zacharias N., Urban S.E., Zacharias M.I. et al., 2004, AJ, 127: 3043-3059