scholarly journals Magnetic Field Structure in Dark Clouds

1987 ◽  
Vol 115 ◽  
pp. 48-50
Author(s):  
M. Tamura ◽  
T. Nagata ◽  
S. Sato ◽  
M. Tanaka ◽  
N. Kaifu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Single Mode ◽  
Polarization Degree ◽  
List Type ◽  
Dark Cloud ◽  
Dark Clouds ◽  
Central Regions ◽  
Field Geometry ◽  
Cloud Complex ◽  
The Magnetic Field

The magnetic field geometry in the central regions of two dark clouds has been mapped by measuring the polarization at 2.2 μm of background stars and of stars embedded in the clouds. The observations were done with the Kyoto polarimeter on the Agematsu 1m IR telescope in December 1984 for Heiles Cloud 2 in the Taurus dark cloud complex, and on the UKIRT 3.8m in May and July 1985 for the ρ Ophiuchus dark cloud core. The main results are: i)Most of the stars in both regions show polarization and their maxima are 2.7% in Heiles Cloud 2 and 7.6% in ρ Oph, respectively. There are similar positive relations between polarization degree and extinct ion Av's.ii)The distribution of position angles for Heiles Cloud 2 shows a single mode at about 50° and that for ρ Oph shows a bimode, at about 50° and 150°.iii)The magnetic fields, as delineated by the infrared polarization, appear perpendicular to the flattened elongations of the molecular clouds.

scholarly journals Is the Magnetic Field Preserved During Core Formation?

2004 ◽  
Vol 221 ◽  
pp. 97-103
Author(s):  
Brenda C. Matthews ◽  
Shih-Ping Lai ◽  
Richard M. Crutcher ◽  
Christine D. Wilson
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Position Angle ◽  
Dark Cloud ◽  
Field Orientation ◽  
Nearby Star ◽  
Star Forming ◽  
Ordered Fields ◽  
Field Geometry ◽  
The Magnetic Field

We present recent JCMT and BIMA array polarimetry data of nearby star-forming regions in order to compare the core and cloud-scale magnetic field geometries in two regions of Orion. The similarity of the magnetic field geometry in these cores to that of their ambient clouds is contrasted with JCMT data toward the Barnard 1 dark cloud in Perseus, which reveal a different magnetic field orientation between the majority of the cores and the surrounding cloud; each of the cores exhibits a different mean polarization position angle. We conclude that the preservation of the magnetic field geometry is better in cores formed within clouds with ordered large scale structures. In Barnard 1, the cores may quickly exhibit a different polarization pattern if they have, for example, rotation which differs from the large scale cloud motions, or a weaker component of ordered fields. This could also explain why the cores exhibit such different geometries from each other in Barnard 1.

scholarly journals Distance, magnetic field, and kinematics of the filamentary cloud LDN 1157

2020 ◽  
Vol 639 ◽  
pp. A133
Author(s):  
Ekta Sharma ◽  
Maheswar Gopinathan ◽  
Archana Soam ◽  
Chang Won Lee ◽  
Shinyoung Kim ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Galactic Plane ◽  
Young Stellar Objects ◽  
Kinematic Structure ◽  
Single Filament ◽  
Stellar Objects ◽  
Density Peaks ◽  
Field Geometry ◽  
Cloud Complex ◽  
The Magnetic Field

Context. LDN 1157 is one of several clouds that are situated in the cloud complex LDN 1147/1158. The cloud presents a coma-shaped morphology with a well-collimated bipolar outflow emanating from a Class 0 protostar, LDN 1157-mm, that resides deep inside the cloud. Aims. The main goals of this work are (a) mapping the intercloud magnetic field (ICMF) geometry of the region surrounding LDN 1157 to investigate its relationship with the cloud morphology, outflow direction, and core magnetic field (CMF) geometry inferred from the millimeter- and submillimeter polarization results from the literature, and (b) to investigate the kinematic structure of the cloud. Methods. We carried out optical (R-band) polarization observations of the stars projected on the cloud to map the parsec-scale magnetic field geometry. We made spectroscopic observations of the entire cloud in the 12CO, C18O, and N2H+ (J = 1–0) lines to investigate its kinematic structure. Results. We obtained a distance of 340 ± 3 pc to the LDN 1147/1158, complex based on the Gaia DR2 parallaxes and proper motion values of the three young stellar objects (YSOs) associated with the complex. A single filament of ~1.2 pc in length (traced by the Filfinder algorithm) and ~0.09 pc in width (estimated using the Radfil algorithm) is found to run throughout the coma-shaped cloud. Based on the relationships between the ICMF, CMF, filament orientations, outflow direction, and the hourglass morphology of the magnetic field, it is likely that the magnetic field played an important role in the star formation process in LDN 1157. LDN 1157-mm is embedded in one of the two high-density peaks detected using the Clumpfind algorithm. The two detected clumps lie on the filament and show a blue-red asymmetry in the 12CO line. The C18O emission is well correlated with the filament and presents a coherent structure in velocity space. Combining the proper motions of the YSOs and the radial velocity of LDN 1147/1158 and an another complex, LDN 1172/1174, that is situated ~2° east of it, we found that the two complexes are moving collectively toward the Galactic plane. The filamentary morphology of the east-west segment of LDN 1157 may have formed as a result of mass lost by ablation through interaction of the moving cloud with the ambient interstellar medium.

The magnetic field in the Ophiuchus dark cloud complex

1994 ◽  
Vol 424 ◽  
pp. 208 ◽  
Author(s):  
Alyssa A. Goodman ◽  
Carl Heiles
Keyword(s):  
Magnetic Field ◽  
Dark Cloud ◽  
Cloud Complex ◽  
The Magnetic Field

scholarly journals Polarization measurements in B5, L1 34 and Heiles Cloud 2 and evidence of newly born stars

1987 ◽  
Vol 122 ◽  
pp. 137-139
Author(s):  
U. C. Joshi ◽  
P. V. Kulkarni ◽  
M. R. Deshpande ◽  
A. Sen ◽  
A. K. Kulshrestha
Keyword(s):  
Magnetic Field ◽  
Polarization Measurement ◽  
Indian Institute ◽  
Dark Clouds ◽  
Polarization Measurements ◽  
University Of Arizona ◽  
Field Geometry ◽  
Formation And Evolution ◽  
The Magnetic Field

Polarization measurement of the background stars in the region of dark globules is important to study the magnetic field geometry and grants characteristics in the globule. These parameters are important for the formation and evolution of dark globules. We made Polarimetric observations of stars in three nearby dark clouds - B5, L134 and Heiles Cloud 2. Polarization measurements of stars in the region of B5 were made with ‘MINIPOL’ (Frecker and Serkowski, 1976) on 61″ telescope of University of Arizona. Observations for the stars in the region of L134 and Heiles Cloud 2 were made using PRL Polarimeter (Deshpande et al. 1985) on 1 meter telescope of Indian Institute of Astrophysics, Bangalore. Results are presented and discussed here. Figure 1 shows the polarization vectors projected on the sky plane for the above globules.

Polarimetric and photometric observations of CB54, with analysis of four other dark clouds

2021 ◽  
Vol 503 (4) ◽  
pp. 5274-5290
Author(s):  
A K Sen ◽  
V B Il’in ◽  
M S Prokopjeva ◽  
R Gupta
Keyword(s):  
Magnetic Field ◽  
Near Infrared ◽  
Galactic Plane ◽  
Photometric Data ◽  
Dust Particles ◽  
Dark Cloud ◽  
Dark Clouds ◽  
High Polarization ◽  
Field Parallel ◽  
Photometric Observations

ABSTRACT We present the results of our BVR-band photometric and R-band polarimetric observations of ∼40 stars in the periphery of the dark cloud CB54. From different photometric data, we estimate E(B − V) and E(J − H). After involving data from other sources, we discuss the extinction variations towards CB54. We reveal two main dust layers: a foreground, E(B − V) ≈ 0.1 mag, at ∼200 pc and an extended layer, $E(B-V) \gtrsim 0.3$ mag, at ∼1.5 kpc. CB54 belongs to the latter. Based on these results, we consider the reason for the random polarization map that we have observed for CB54. We find that the foreground is characterized by low polarization ($P \lesssim 0.5$ per cent) and a magnetic field parallel to the Galactic plane. The extended layer shows high polarization (P up to 5–7 per cent). We suggest that the field in this layer is nearly perpendicular to the Galactic plane and both layers are essentially inhomogeneous. This allows us to explain the randomness of polarization vectors around CB54 generally. The data – primarily observed by us in this work for CB54, by A. K. Sen and colleagues in previous works for three dark clouds CB3, CB25 and CB39, and by other authors for a region including the B1 cloud – are analysed to explore any correlation between polarization, the near-infrared, E(J − H), and optical, E(B − V), excesses, and the distance to the background stars. If polarization and extinction are caused by the same set of dust particles, we should expect good correlations. However, we find that, for all the clouds, the correlations are not strong.

scholarly journals Near Infrared Polarimetry of Dark Clouds and Star Forming Regions - Two Micron Polarization Survey of T Tauri Stars

1990 ◽  
Vol 140 ◽  
pp. 327-328
Author(s):  
M. Tamura ◽  
S. Sato
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Near Infrared ◽  
Background Field ◽  
Star Forming ◽  
Dark Clouds ◽  
Star Forming Regions ◽  
Stellar Sources ◽  
Geometrical Relationship ◽  
The Magnetic Field

Infrared polarimetry is one of the most useful methods to delineate the magnetic field structure in dark clouds and star-forming regions, where the intracloud extinction is so large that optical polarimetry is inaccessible. We have been conducting a near-infrared polarization survey of background field stars and embedded sources toward nearby dark clouds and star-forming regions (Tamura 1988). Particularly, the magnetic field structure in the denser regions of the clouds are well revealed in Heiles Cloud 2 in Taurus, ρ Oph core, and NGC1333 region in Perseus (Tamura et al. 1987; Sato et al. 1988; Tamura et al. 1988). This survey also suggests an interesting geometrical relationship between magnetic field and star-formation: the IR polarization of young stellar sources associated with mass outflow phenomena is perpendicular to the magnetic fields. This relationship suggests a presence of circumstellar matter (probably dust disk) with its plane perpendicular to the ambient magnetic field. Combining with another geometrical relationship that the elongation of the denser regions of the cloud is perpendicular to the magnetic field, the geometry suggests that the cloud contraction and subsequent star-formation have been strongly affected by the magnetic fields. Thus, it is important to study the universality of such geometrical relationship between IR polarization of young stellar sources and magnetic fields. In this paper, we report the results on a 2 micron polarization survey of 39 T Tauri stars, 8 young stellar objects and 11 background field stars in Taurus dark cloud complex.

scholarly journals Infrared polarimetry of dark clouds - II. Magnetic field structure in the   Ophiuchi dark cloud

1988 ◽  
Vol 230 (2) ◽  
pp. 321-329 ◽  
Author(s):  
S. Sato ◽  
M. Tamura ◽  
T. Nagata ◽  
N. Kaifu ◽  
J. Hough ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Structure ◽  
Dark Cloud ◽  
Magnetic Field Structure ◽  
Dark Clouds

The magnetic field geometry of HD 215441

1978 ◽  
Vol 222 ◽  
pp. 226 ◽  
Author(s):  
E. F. Borra ◽  
J. D. Landstreet
Keyword(s):  
Magnetic Field ◽  
Field Geometry ◽  
The Magnetic Field
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