Optical polarization observations in the Scorpius region: NGC 6124

Monthly Notices of the Royal Astronomical Society

Maheswar

et al. 2011

We present multiwavelength optical linear polarimetric observations of 69 stars towards the young open cluster Berkeley 59. The observations reveal the presence of three dust layers located at distances of ∼300, ∼500 and ∼700 pc. The dust layers produce a total polarization PV∼ 5.5 per cent. The mean values of polarization and polarization angles due to the dust layers are found to increase systematically with distance. We show that polarimetry in combination with the (U−B)–(B−V) colour–colour diagram yields a better identification of cluster members. The polarization measurements suggest that the polarization due the intracluster medium is ∼2.2 per cent. An anomalous reddening law exists for the cluster region, indicating a relatively larger grain size than that in the diffuse interstellar medium. The spatial variation of polarization and colour excess E(B−V) are found to increase with radial distance from the cluster centre, whereas θV and λmax are found to decrease with increasing radial distance from the cluster centre. About 40 per cent of cluster members show the signatures of either intrinsic polarization or rotation in their polarization angles. There is an indication that the starlight of the cluster members might have been depolarized because of non‐uniform alignment of dust grains in the foreground dust layers and in the intracluster medium.

Section: Polarization Efficiencysupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Section: Dust Propertiesmentioning

confidence: 99%

See 1 more Smart Citation

Broad-band optical polarimetric studies towards the Galactic young star cluster Berkeley 59

Eswaraiah

Monthly Notices of the Royal Astronomical Society

Maheswar

et al. 2011

“…The photometric and spectroscopic information already available for stars in open clusters is specifically important to make a meaningful study of the dust grains located in the foreground and in the intracluster regions (e.g. Trumpler 27, Feinstein et al 2000; Stock 16, Feinstein et al 2003a; NGC 6231, Feinstein et al 2003b; Hogg 22 and NGC 6204, Martínez, Vergne & Feinstein 2004; NGC 5606, Orsatti et al 2007; NGC 5749, Vergne, Feinstein & Martínez 2007; IC 1805, Medhi et al 2007; NGC 6250, Feinstein et al 2008; NGC 654, Medhi et al 2008; NGC 6124, Vergne et al 2010; NGC 6823, Medhi et al 2010). In this paper, we present multiwavelength polarimetry of stars towards NGC 1893.…”

Section: Introductionmentioning

confidence: 99%

A multiwavelength polarimetric study towards the open cluster NGC 1893

Eswaraiah

Monthly Notices of the Royal Astronomical Society

Maheswar

et al. 2010

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 P V ∼ 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 (P max ) and the wavelength at maximum polarization (λ max ) are found to be 2.59 ± 0.02 per cent and 0.55 ± 0.01 µm, respectively. The estimated mean value of λ max 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 (U − B)-(B − V) colour-colour diagram, is a useful tool for identifying non-members in a cluster.

“…The polarization versus distance diagram for many open clusters shows several sudden increments in the value of polarization, indicating the presence of several dust layers in front of them (e.g., Medhi et al 2008;Eswaraiah et al 2011Eswaraiah et al , 2012. Also, using the Q-U diagram, several dust layers were found to present in front of the open clusters (e.g., Waldhausen et al 1999;Martínez et al 2004;Vergne et al 2007;Feinstein et al 2008;Vergne et al 2010Vergne et al , 2018. If we take the case of the cluster Be 59, which is the closest observed cluster for polarization to the Alessi 1, three layers of dust are found to present in front of it (Eswaraiah et al 2012).…”

Section: Distribution Of Interstellar Mattermentioning

confidence: 97%

Optical Linear Polarization toward the Open Star Cluster Casado Alessi 1

Singh

Yadav

et al. 2020

We present B-, V-, R-, and I-bands linear polarimetric observations of 73 stars in the direction of open star cluster Casado Alessi 1 (hereafter Alessi 1). We aim to use polarimetry as a tool to investigate the properties and distribution of dust grains toward the direction of the cluster. The polarimetric observations were carried out using the ARIES IMaging POLarimeter mounted at the 104 cm telescope of ARIES, Nainital (India). Using the Gaia photometric data the age and distance of the cluster are estimated to be 0.8 ± 0.1 Gyr and 673 ± 98 pc, respectively. A total of 66 stars with a 26 radius from the cluster are identified as members of the cluster using the astrometric approach. Out of these 66 members, 15 stars were observed polarimetrically and found to have the same value of polarization. The majority of the stars in the region follow the general law of the polarization for the interstellar medium, indicating that polarization toward the cluster Alessi 1 is dominated by foreground dust grains. The average values of the maximum polarization (P max ) and the wavelength corresponding to the maximum polarization (λ max ) toward the cluster are found to be 0.83±0.03 % and 0.59±0.04 µm, respectively. Also, dust grains toward the cluster appear to be aligned, possibly due to the galactic magnetic field.