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

scholarly journals The resolved magnetic fields of the quiescent cloud GRSMC 45.60+0.30

2012 ◽  
Vol 10 (H16) ◽  
pp. 615-615
Author(s):  
Michael D. Pavel ◽  
Robert C. Marchwinski ◽  
Dan P. Clemens
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Large Scale ◽  
Near Infrared ◽  
Galactic Plane ◽  
Flux Ratio ◽  
High Magnetic Field Strength ◽  
Large Scale Magnetic Field ◽  
Oriented Parallel

Marchwinski et al. (2012) mapped the magnetic field strength across the quiescent cloud GRSMC 45.60+0.30 (shown in Figure 1 subtending 40x10 pc at a distance of 1.88 kpc) with the Chandrasekhar-Fermi method CF; Chandrasekhar & Fermi 1953) using near-infrared starlight polarimetry from the Galactic Plane Infrared Polarization Survey (Clemens et al.2012a, b) and gas properties from the Galactic Ring Survey (Jackson et al.2006). The large-scale magnetic field is oriented parallel to the gas-traced ‘spine’ of the cloud. Seven ‘magnetic cores’ with high magnetic field strength were identified and are coincident with peaks in the gas column density. Calculation of the mass-to-flux ratio (Crutcher 1999) shows that these cores are exclusively magnetically subcritical and that magnetostatic pressure can support them against gravitational collapse.

scholarly journals A Dark-Cloud Complex in Aquila: Small Molecular Clouds Possibly Associated with the Aquila Rift

1999 ◽  
Vol 51 (6) ◽  
pp. 851-858 ◽  
Author(s):  
Akiko Kawamura ◽  
Toshikazu Onishi ◽  
Akira Mizuno ◽  
Hideo Ogawa ◽  
Yasuo Fukui
Keyword(s):  
Molecular Clouds ◽  
Velocity Dispersion ◽  
Galactic Plane ◽  
Dark Cloud ◽  
Dark Clouds ◽  
Order Of Magnitude ◽  
Virial Mass ◽  
The Individual ◽  
Cloud Complex ◽  
Gravitational Equilibrium

Abstract A 12CO(J = 1−0) survey for local molecular clouds was performed toward dark clouds in Aquila (26° < l ≤ 42° and −25° ≤ b < −2°) by using the 4-meter millimeter wave telescope, NANTEN, at Las Campanas Observatory, Chile. A cloud complex consisting of 64 small clouds has been discovered in −25° ≲ b ≲ −12°; at a distance of 220 pc, its height from the galactic plane is ∼ 50–100 pc and the total mass is ∼ 4 × 103M⊙. The spatial and velocity distributions of the complex suggest that it may be connected to the Great Rift in Aquila. This complex, as a whole, has a significantly large virial mass compared with the mass derived from the CO intensities by an order of magnitude, though H I gas of ∼ 104M⊙, possibly associated, may contribute to bind them gravitationally. The individual CO clouds have velocity dispersion and mass similar to those of the high-latitude clouds; also, the clouds are not in gravitational equilibrium. There is no indication of active star formation.

scholarly journals A survey of molecular cores in M 17 SWex

2019 ◽  
Author(s):  
Tomomi Shimoikura ◽  
Kazuhito Dobashi ◽  
Asha Hirose ◽  
Fumitaka Nakamura ◽  
Yoshito Shimajiri ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Massive Star ◽  
Near Infrared ◽  
Young Stellar Objects ◽  
High Mass ◽  
Physical Parameters ◽  
Massive Star Formation ◽  
Dark Cloud ◽  
The Magnetic Field

Abstract A survey of molecular cores covering the infrared dark cloud known as the M 17 southwest extension (M 17 SWex) has been carried out with the 45 m Nobeyama Radio Telescope. Based on the N2H+ (J = 1–0) data obtained, we have identified 46 individual cores whose masses are in the range from 43 to $3026\, {M}_{\odot }$. We examined the relationship between the physical parameters of the cores and those of young stellar objects (YSOs) associated with the cores found in the literature. The comparison of the virial mass and the core mass indicates that most of the cores can be gravitationally stable if we assume a large external pressure. Among the 46 cores, we found four massive cores with YSOs. They have large masses of $\gtrsim 1000\, M_{\odot }$ and line widths of $\gtrsim 2.5\:$km s−1 which are similar to those of clumps forming high-mass stars. However, previous studies have shown that there is no active massive star formation in this region. Recent measurements of near-infrared polarization imply that the magnetic field around M 17 SWex is likely to be strong enough to support the cores against self-gravity. We therefore suggest that the magnetic field may prevent the cores from collapsing, causing the low level of massive star formation in M 17 SWex.

scholarly journals The Observed Characteristics of the Local Magnetic Field

1974 ◽  
Vol 60 ◽  
pp. 137-150 ◽  
Author(s):  
J. B. Whiteoak
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Galactic Plane ◽  
Background Radiation ◽  
Field Structure ◽  
Local Magnetic Field ◽  
Field Parallel ◽  
Scale Field ◽  
Large Scale Field ◽  
Galactic Background

The main investigations of the local magnetic field are reviewed and are found to contain some conflict in interpretation. At radio wavelengths, studies have been made using both the Faraday rotation of the polarized radiation from extragalactic sources and pulsars, and the polarization of the galactic background radiation. With the former type of observation, although more data are available for extragalactic sources, any interpretation may be complicated by the influence of distant field structure. The results are consistent with a large-scale field parallel to the galactic plane, with a field strength of about 2 µG, and which is directed towards l=90°. This field contains irregularities in direction and strength on a scale of about 100–200 pc. The polarization of galactic background radiation may yield the most detailed information about the local field structure – the results to date show loops of magnetic fields extending along the radio spurs.The interpretation in terms of small-scale irregularities embedded in a large-scale field parallel to the galactic plane differs from that proposed to explain the optical polarization of starlight, in which a helical field configuration near the Sun was preferred to a more disordered pattern.

τ9 Eri: a bright pulsating magnetic Bp star in a 5.95-d double-lined spectroscopic binary

2021 ◽  
Vol 502 (4) ◽  
pp. 5200-5209
Author(s):  
K Woodcock ◽  
G A Wade ◽  
O Kochukhov ◽  
J Sikora ◽  
A Pigulski
Keyword(s):  
Magnetic Field ◽  
Longitudinal Magnetic Field ◽  
Rotation Period ◽  
Photometric Data ◽  
Spectral Lines ◽  
Eccentric Orbit ◽  
Typical Error ◽  
Spectroscopic Binary ◽  
Photometric Observations ◽  
Orbital Analysis

ABSTRACT τ9 Eri is a Bp star that was previously reported to be a single-lined spectroscopic binary. Using 17 ESPaDOnS spectropolarimetric (Stokes V) observations, we identified the weak spectral lines of the secondary component and detected a strong magnetic field in the primary. We performed orbital analysis of the radial velocities of both components to find a slightly eccentric orbit (e = 0.129) with a period of 5.95382(2) d. The longitudinal magnetic field (Bℓ) of the primary was measured from each of the Stokes V profiles, with typical error bars smaller than 10 G. Equivalent widths (EWs) of least-squares deconvolution profiles corresponding to only the Fe lines were also measured. We performed frequency analysis of both the Bℓ and EW measurements, as well as of the Hipparcos, SMEI, and TESS photometric data. All sets of photometric observations produce two clear, strong candidates for the rotation period of the Bp star: 1.21 and 3.82 d. The Bℓ and EW measurements are consistent with only the 3.82-d period. We conclude that HD 25267 consists of a late-type Bp star (M = $3.6_{-0.2}^{+0.1}~\mathrm{ M}_\odot$, T = $12580_{-120}^{+150}$ K) with a rotation period of 3.82262(4) d orbiting with a period of 5.95382(2) d with a late-A/early-F type secondary companion (M = 1.6 ± 0.1 M⊙, T = $7530_{-510}^{+580}$ K). The Bp star’s magnetic field is approximately dipolar with i = 41 ± 2°, β = 158 ± 5°, and Bd = 1040 ± 50 G. All evidence points to the strong 1.209912(3)-d period detected in photometry, along with several other weaker photometric signals, as arising from g-mode pulsations in the primary.

scholarly journals Near-infrared imaging polarimetry toward M 17 SWex

2019 ◽  
Vol 71 (Supplement_1) ◽  
Author(s):  
Koji Sugitani ◽  
Fumitaka Nakamura ◽  
Tomomi Shimoikura ◽  
Kazuhito Dobashi ◽  
Quang Nguyen-Luong ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Dark Cloud ◽  
Imaging Polarimetry ◽  
Magnetic Stability ◽  
Almost All ◽  
The Magnetic Field

Abstract We conducted near-infrared ($\mathit {JHK}_{\rm s}$) imaging polarimetry toward the infrared dark cloud (IRDC) M 17 SWex, including almost all of the IRDC filaments as well as its outskirts, with the polarimeter SIRPOL on the IRSF 1.4 m telescope. We revealed the magnetic fields of M 17 SWex with our polarization-detected sources that were selected by some criteria based on their near-IR colors and the column densities toward them, which were derived from the Herschel data. The selected sources indicate not only that the ordered magnetic field is perpendicular to the cloud elongation as a whole, but also that at both ends of the elongated cloud the magnetic field appears to be bent toward its central part, i.e., a large-scale hourglass-shaped magnetic field perpendicular to the cloud elongation. In addition to this general trend, the elongations of the filamentary subregions within the dense parts of the cloud appear to be mostly perpendicular to their local magnetic fields, while the magnetic fields of the outskirts appear to follow the thin filaments that protrude from the dense parts. The magnetic strengths were estimated to be ∼70–$300\, \mu$G in the subregions, of which the lengths and average number densities are ∼3–9 pc and ∼2–7 × 103 cm−3, respectively, by the Davis–Chandrasekhar–Fermi method with the angular dispersion of our polarization data and the velocity dispersion derived from the C18O (J = 1–0) data obtained by the Nobeyama 45 m telescope. These field configurations and our magnetic stability analysis of the subregions imply that the magnetic field has controlled the formation/evolution of the M 17 SWex cloud.

scholarly journals The 15 273 Å diffuse interstellar band in the dark cloud Barnard 68

2017 ◽  
Vol 605 ◽  
pp. L10 ◽  
Author(s):  
Meriem Elyajouri ◽  
Nick L. J. Cox ◽  
Rosine Lallement
Keyword(s):  
Near Infrared ◽  
Volume Density ◽  
Dark Cloud ◽  
Stellar Spectra ◽  
Dark Clouds ◽  
Average Value ◽  
Time Period ◽  
Rate Of Increase ◽  
Central Regions ◽  
Moderate Resolution

High obscuration of background stars behind dark clouds precludes the detection of optical diffuse interstellar bands (DIBs) and hence our knowledge of DIB carriers in these environments. Taking advantage of the reduced obscuration of starlight in the near-infrared (NIR) we used one of the strongest NIR DIBs at 15 273 Å to probe the presence and properties of its carrier throughout the nearby interstellar dark cloud Barnard 68. We measured equivalent widths (EW) for different ranges of visual extinction AV, using VLT/KMOS H-band (1.46–1.85 μm) moderate-resolution (R ~ 4000) spectra of 43 stars situated behind the cloud. To do so, we fitted the data with synthetic stellar spectra from the APOGEE project and TAPAS synthetic telluric transmissions appropriate for the observing site and time period. The results show an increase of DIB EW with increasing AV. However, the rate of increase is much flatter than expected from the EW-AV quasi-proportionality established for this DIB in the Galactic diffuse interstellar medium. Based on a simplified inversion assuming sphericity, it is found that the volume density of the DIB carrier is 2.7 and 7.9 times lower than this expected average value in the external and central regions of the cloud, which have nH≃ 0.4 and 3.5 × 105 cm-3, respectively. Further measurements with multiplex NIR spectrographs should allow detailed modeling of such an edge effect of this DIB and other bands and help clarify its actual origin.

scholarly journals Polarization of background starlight and the structure of the interstellar magnetic field

1991 ◽  
Vol 147 ◽  
pp. 417-423
Author(s):  
Alyssa A. Goodman ◽  
Philip C. Myers ◽  
Pierre Bastien
Keyword(s):  
Magnetic Field ◽  
Position Angle ◽  
Three Dimensions ◽  
Local Magnetic Field ◽  
Line Of Sight ◽  
Dark Cloud ◽  
Interstellar Clouds ◽  
Dark Clouds ◽  
Entire Complex ◽  
Local Plane

We discuss the use of polarization maps of background starlight in studying the structure of the interstellar magnetic field. We make the assumption that the polarization observed is due to magnetically aligned dust grains associated with interstellar clouds along the line of sight, and that the position angle (ΘE) of polarization observed gives the direction (modulo 180°) of , the plane-of-the-sky projection of the (line-of-sight-averaged) magnetic field.There are two basic points in this paper. (1.) Out of context, the projected orientation of an elongated dark cloud may appear special (e.g. roughly "parallel" or “perpendicular”) in relation to the local (plane-of-the-sky) field direction given by polarization observations, but, when the view is expanded to include an entire complex of dark clouds, the shape and orientation of clouds within a complex often appears unrelated to the field structure. (2.) the dispersion in the postion angle of polarization observed in a region of the sky contains information about the ratio of the strength of the uniform (straight) component of the local magnetic field as compared to the dispersion (nonuniform component) in the field. Furthermore, in a region where Zeeman measurements covering the same region as polarization observations have been made, the uniform-to-nonuniform ratio deduced for the field from polarization data, can be combined with information about the line-of-sight field and an estimate of the correlation length of the field, to describe the magnetic field in three dimensions. We discuss the results of such an analysis for the dark cloud Lynds 204 (L204).

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