Journal Article

A multiwavelength polarimetric study towards the open cluster NGC 1893

C. Eswaraiah, A. K. Pandey, G. Maheswar, Biman J. Medhi, J. C. Pandey, D. K. Ojha and W. P. Chen

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 411, issue 3, pages 1418-1434
Published in print March 2011 | ISSN: 0035-8711
Published online February 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.17780.x
A multiwavelength polarimetric study towards the open cluster NGC 1893

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We present multiwavelength linear polarimetric observations for 44 stars of the NGC 1893 young open cluster region along with V-band polarimetric observations of stars of four other open clusters located between l∼ 160° and 175°. We found evidence for the presence of two dust layers located at a distance of ∼170 and ∼360 pc. The dust layers produce a polarization PV∼ 2.2 per cent. It is evident from the clusters studied in this work that, in the Galactic longitude range from l∼ 160° to 175° and within the Galactic plane (|b| < 2°), the polarization angles remain almost constant, with a mean of ∼163° and a dispersion of 6°. The small dispersion in polarization angle could be due to the presence of a uniform dust layer beyond 1 kpc. Present observations reveal that in the case of NGC 1893, the foreground two dust layers, in addition to the intracluster medium, seem to be responsible for the polarization effects. It is also found that towards the direction of NGC 1893, the dust layer that exists between 2 and 3 kpc has a negligible contribution towards the total observed polarization. The weighted mean for percentage of polarization (Pmax) and the wavelength at maximum polarization (λmax) are found to be 2.59 ± 0.02 per cent and 0.55 ± 0.01 μm, respectively. The estimated mean value of λmax indicates that the average size of the dust grains within the cluster is similar to that in the general interstellar medium. The spatial variation of the polarization is found to decrease towards the outer region of the cluster. In this work, we support the notion, as has already been shown in previous studies, that polarimetry, in combination with the (UB)–(BV) colour–colour diagram, is a useful tool for identifying non-members in a cluster.

Keywords: polarization; dust, extinction; open clusters and associations: individual: NGC 2281; open clusters and associations: individual: NGC 1664; open clusters and associations: individual: NGC 1960; open clusters and associations: individual: Stock 8; open clusters and associations: individual: NGC 1893

Journal Article.  10435 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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