Open Clusters in Carina: NGC 3603, Westerlund 2 and Sher 1 1
Ana María Orsatti2,3,4, E. Irene Vega2,4, and Ruben E. Martínez2,3
2 Facultad de Ciencias Astronómicas y Geofísicas, Observatorio Astronómico, Universidad Nacional de La Plata, C.P. 1900, La Plata, Argentina. (aorsatti@fcaglp.unlp.edu.ar), (irene@fcaglp.unlp.edu.ar), (ruben@fcaglp.unlp.edu.ar)
3 Instituto de Astrofísica de La Plata, CONICET, Argentina.
4 Member of the Carrera del Investigador Científico, CONICET, Argentina.
]]>Received 2013 May 10.
Accepted 2013 July 26.
RESUMEN
Se presentan observaciones polarimétricas en las bandas U BV RI de estrellas situadas en la dirección de los cúmulos NGC 3603, Westerlund 2 y Sher 1, con el propósito de estudiar las características del polvo entre el Sol y los cúmulos, evidencias polarimétricas de la existencia (o no) de enrojecimiento anómalo en NGC 3603 y en Westerlund 2, y la identificación de estrellas con indicios de polarización intrínseca.
40% de las estrellas observadas en Westerlund 2 presentan indicios de polarización intrínseca, porcentaje similar al encontrado en NGC 6611 y en IC 2944; en cambio, en NGC 3603 es mucho menor. Las eficiencias polarimétricas medias son bajas por la presencia de varias nubes de polvo interestelar entre los objetos y el Sol. Se apoya la existencia de enrojecimiento anómalo en NGC 3603, mientras que en Westerlund 2 existen leves indicios de ello.
ABSTRACT
We present polarimetric observations in the U BV RI bands of stars located in the directions of NGC 3603, Westerlund 2 and Sher 1. Our main objectives are to study the characteristics of the dust lying between the Sun and the clusters, to analyze polarimetric evidence on the existence (or not) of abnormal reddening in NGC 3603 and Westerlund 2; and to identify stars with signatures of intrinsic polarization.
]]> 40% of the stars observed in Westerlund 2 display indications of intrinsic polarization, a percentage similar to those found in the open clusters NGC 6611 and IC 2944: but in NGC 3603 it is very small. Mean polarization efficiencies are low, due to the presence of several dust clouds located in the way to the clusters. We are in favor of the existence of abnormal reddening in NGC 3603, while in Westerlund 2 there are only indications.Key Words: ISM: dust, extinction — open clusters and associations: individual (NGC 3603, Westerlund 2, Sher 1).
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1 Based on observations obtained at Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the Universities of La Plata, Córdoba, and San Juan, Argentina.
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