Imaging polarimetry of some 
selected dark clouds

Sen, A. K.; Gupta, Ranjan; Ramaprakash, A. N.; Tandon, S. N.

doi:10.1051/aas:2000117

Cited by 16 publications

(31 citation statements)

References 32 publications

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“…Based on these findings, it can be claimed here that the optical polarization values which are included here for the analysis, are tracing the physical conditions within the clouds. Plots of p (from Sen et al 2000) vs. E(B − V)) for all the three clouds with R V = 3.1 and 4.0 are reproduced in Figs. 5 and 6, with first p as dependent and then as independent variable.…”

Section: Resultsmentioning

confidence: 98%

“…Polarimetric observations of a set of eight Bok globules CB3, CB25, CB39, CB52, CB54, CB62, and CB246 were made previously by Sen et al (2000). From the given list of eight clouds, three clouds CB3, CB25, and CB39 have been observed photometrically for the present study.…”

Section: Observationmentioning

confidence: 99%

“…These three clouds were selected at random from the set of eight clouds, based on their Figure 1 shows the CCD image of the cloud CB3 with the field stars numbered, as in Table 1. The images of all the clouds with their background stars included in the present work are available from our previous work (Sen et al 2000).…”

Section: Observationmentioning

confidence: 99%

“…It is believed that the grains get aligned by an ambient magnetic field by a mechanism originally suggested by Davis & Greenstein (1951) and subsequently modified by many authors. Recently, many photometric, polarimetric, spectrometric, and radiometric studies have been reported on star-forming clouds by various authors (Huard et al 2000;Larson et al 2000;Sen et al 2000;Wiebe & Watson 2001;Khanzadyan et al 2002;Launhardt & Sargent 2001;Matthews & Wilson 2002;Wolf-Chase et al 2003;Draine 2003;Ghosh et al 2005;Sen et al 2005;Kandori et al 2005;Massi et al 2004Massi et al , 2005Kirk et al 2006;Gouliermis et al 2006;Maheswar & Bhatt 2006;Naoi et al 2006;Vaidya et al 2007; Ward- Thompson et al 2000;Whittet 2007). It is generally expected that the increasing extinction along a line of sight corresponds to increasing polarization.…”

Section: Introductionmentioning

confidence: 99%

“…For that purpose, three clouds CB3, CB25, and CB39 have been observed photometrically. The collected photometric data were reduced and analysed and then compared with the polarimetric data earlier reported by Sen et al (2000). For some selected sample stars in some clouds independent spectroscopic measurements were also made.…”

Section: Introductionmentioning

confidence: 99%

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Photopolarimetric study of the star-forming clouds CB3, CB25, and CB39

Sen

Polcaro

Dey³

et al. 2010

A&A

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Context. The small compact isolated dark clouds also known as "Bok globules" are believed to be ideal sites for low-mass star formation. Some of these clouds are undergoing gravitational collapse, and the ambient magnetic field plays a key role in collapse dynamics. The background star polarimetry is generally accepted as a good tool to map the magnetic field, which is responsible for the alignment of dichroic grains that produce polarization. Aims. The background star polarization when studied together with extinction is expected to help us to understand various grain properties and the role of polarimetry as a tracer of magnetic field in these star-forming clouds. With this idea, polarization and colour excess E(B − V) values for a set of background stars have been studied together to understand various astrophysical process in some star-forming dark clouds. Methods. Optical photometric observations of the three clouds CB3, CB25, and CB39 were carried out at the 2 m H.C. Telescope, India, to determine the colour excess E(B − V) of the background stars by following a technique adopted by Bernabei & Polacaro (2001, A&A, 371, 123). These three clouds were selected from a set of eight clouds previously observed by us in optical polarimetry (Sen et al. 2000, A&AS, 141, 175). Further independent spectroscopic measurements of a few selected sample stars were recently carried out during February and March 2010 from 1.52 m Cassini Telescope, Loinao, Italy, to confirm the correctness of estimated E(B − V) values obtained by this photometric technique. Results. The colour excess E(B − V) values so obtained were compared with optical polarization values obtained for the same set of stars. It was found that the measured extinction values increase with the increase in percentage polarization for the cloud CB39 and to some extent for CB25. However, for cloud CB31 no such correlation was observed. It is normally expected that the grains causing extinction should also cause polarization of the light from background stars. Any possible deviation from this under different circumstances here has been discussed in the light of the ongoing physical processes in the star-forming clouds.

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Section: Resultsmentioning

confidence: 98%

Section: Observationmentioning

confidence: 99%

Section: Observationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Photopolarimetric study of the star-forming clouds CB3, CB25, and CB39

Sen

Polcaro

Dey³

et al. 2010

A&A

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Strömgren Hβ ‐photometry of stars in dark clouds

2011

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We present uvbyβ photometry of 64 stars in 6 small dark clouds. From the photometry we infer approximate spectral types of the observed stars and derive distances and color excesses for each of them. We further derive new distance estimates to some of the globules based on the distances of individual stars possibly included in their peripheries. For clouds where sufficient target stars are available (CB3, CB52, and CB54), a clear trend of increasing linear polarization (as measured by Sen et al. 2000) with extinction is observed. We also find excellent correlation between polarization and extinction for the entire sample. The location of the stars on the polarization-extinction diagram is consistent with that for field stars found by Serkowski et al. (1975). The relation between polarization and extinction evident for the stars of our sample suggests perfect grain alignment and constant grain properties along each line of sight.

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On the origin of de‐polarization in CB54

2023

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We present polarimetric observations of the Bok globule CB54 in the far-infrared via SOFIA/HAWC+ bands D (154 𝜇m) and E (214 𝜇m). We detect polarization with mean polarization degrees of p 154 μm = 7.7 % ± 5.4% and p 214 μm = 8.5 % ± 5.4 % at 154 and 214 𝜇m, respectively. The polarization degree decreases toward the inner region of CB54, revealing a "polarization hole". This finding can be explained by the impact of dichroic absorption counteracting the effect of polarized emission. The same effect allows us to explain the observed wavelength-dependent orientation of the linear polarization in the dense, central region of CB54. The polarization pattern appears uniform at core scales but un-ordered at larger scales-similar to what was found in previous studies of this object. The mean polarization angle amounts to 𝜃 154 μm = 62.4 ± 44.5 • and 𝜃 214 μm = −80.1± 60.0 • at 154 and 214 𝜇m, respectively.

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Imaging polarimetry of some selected dark clouds

Cited by 16 publications

References 32 publications

Photopolarimetric study of the star-forming clouds CB3, CB25, and CB39

Photopolarimetric study of the star-forming clouds CB3, CB25, and CB39

Strömgren Hβ ‐photometry of stars in dark clouds

On the origin of de‐polarization in CB54

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