Search

Start Over Subject bok globules
1. CB17 dust emission (100-500um), N(H) and T maps
ID:
ivo://CDS.VizieR/J/A+A/569/A7
Title:
CB17 dust emission (100-500um), N(H) and T maps
Short Name:
J/A+A/569/A7
Date:
21 Oct 2021
Publisher:
CDS
Description:
The initial conditions for the gravitational collapse of molecular cloud cores and the subsequent birth of stars are still not well constrained. The characteristic cold temperatures (~10K) in such regions require observations at sub-millimetre and longer wavelengths. The Herschel Space Observatory and complementary ground-based observations presented in this paper have the unprecedented potential to reveal the structure and kinematics of a prototypical core region at the onset of stellar birth. This paper aims to determine the density, temperature, and velocity structure of the star-forming Bok globule CB 17. This isolated region is known to host (at least) two sources at different evolutionary stages: a dense core, SMM1, and a Class I protostar, IRS. We modeled the cold dust emission maps from 100{mu}m to 1.2mm with both a modified blackbody technique to determine the optical depth-weighted line-of-sight temperature and column density and a ray-tracing technique to determine the core temperature and volume density structure. Furthermore, we analysed the kinematics of CB17 using the high-density gas tracer N_2_H^+
2. Dark clouds imaging polarimetry
ID:
ivo://CDS.VizieR/J/A+AS/141/175
Title:
Dark clouds imaging polarimetry
Short Name:
J/A+AS/141/175
Date:
21 Oct 2021
Publisher:
CDS
Description:
A set of eight Bok Globules CB3, CB25, CB39, CB52, CB54, CB58, CB62 and CB246 were observed polarimetrically in white light, using our Imaging Polarimater (IMPOL), from the 1.2m IR telescope at Mount Abu, India. The observations were carried out on different nights during the period December 1997 and April 1998. The CCD images obtained from the instrument (IMPOL) were analyzed, to produce polarization map of the Bok Globules. The stars in the field, which are mostly background to the cloud show typically 2% linear polarization. Clouds which are less dynamic (having ^12^CO line widths {Delta}V<2.5km/s) in general show slightly better alignment of polarization vectors with the projected direction of galactic plane. On the other hand, the more dynamic group of clouds has polarization vectors more scattered and poorly aligned with the projected direction of the galactic plane. However one of the clouds observed, CB58, does not follow this trend very well.
3. Isolated starless cores dust temperature
ID:
ivo://CDS.VizieR/J/A+A/592/A61
Title:
Isolated starless cores dust temperature
Short Name:
J/A+A/592/A61
Date:
21 Oct 2021
Publisher:
CDS
Description:
Constraining the temperature and density structure of dense molecular cloud cores is fundamental for understanding the initial conditions of star formation. We use Herschel observations of the thermal FIR dust emission from nearby isolated molecular cloud cores and combine them with ground-based submillimeter continuum data to derive observational constraints on their temperature and density structure. The aim of this study is to verify the validity of a ray-tracing inversion technique developed to derive the dust temperature and density structure of isolated starless cores directly from the dust emission maps and to test if the resulting temperature and density profiles are consistent with physical models. Using this ray-tracing inversion technique, we derive the dust temperature and density structure of six isolated starless cloud cores. We employ self-consistent radiative transfer modeling to the derived density profiles, treating the ISRF as the only heating source. The best-fit values of local strength of the ISRF and the extinction by the outer envelope are derived by comparing the self-consistently calculated temperature profiles with those derived by the ray-tracing method. We find that all starless cores are significantly colder inside than outside, with the core temperatures showing a strong negative correlation with peak column density. This suggests that their thermal structure is dominated by external heating from the ISRF and shielding by dusty envelopes. The temperature profiles derived with the ray-tracing inversion method can be well-reproduced with self-consistent radiative transfer models.
4. LDN 1570 BV(RI)c polarisation and photometry
ID:
ivo://CDS.VizieR/J/A+A/556/A65
Title:
LDN 1570 BV(RI)c polarisation and photometry
Short Name:
J/A+A/556/A65
Date:
21 Oct 2021
Publisher:
CDS
Description:
We wish to map the magnetic field geometry and to study the dust properties of the starless cloud, L1570, using multiwavelength optical polarimetry and photometry of the stars projected on the cloud. We made R-band imaging polarimetry of the stars projected on a cloud, L1570, to trace the magnetic field orientation. We also made multi-wavelength polarimetric and photometric observations to constrain the properties of dust in L1570. We estimated a distance of 394+/-70pc to the cloud using 2MASS JHKs colours. Using the values of the Serkowskiparameters namely {sigma}_1_, {overline}{epsilon}, {lambda}_max_ and the position of the stars on near infrared color-color diagram, we identified 13 stars that could possibly have intrinsic polarization and/or rotation in their polarization angles. One star, 2MASS J06075075+1934177, which is a B4Ve spectral type, show the presence of diffuse interstellar bands in the spectrum apart from showing H_{alpha} line in emission. There is an indication for the presence of slightly bigger dust grains towards L1570 on the basis of the dust grain size-indicators such as {lambda}_max_ and R_V_ values. The magnetic field lines are found to be parallel to the cloud structures seen in the 250um images (also in 8um and 12um shadow images) of L1570. Based on the magnetic field geometry, the cloud structure and the complex velocity structure, we believe that L1570 is in the process of formation due to the converging flow material mediated by the magnetic field lines. Structure function analysis showed that in the L1570 cloud region the large scale magnetic fields are stronger when compared with the turbulent component of magnetic fields. The estimated magnetic field strengths suggest that the L1570 cloud region is sub-critical and hence could be strongly supported by the magnetic field lines.
5. MAMBO Mapping of c2d Clouds and Cores
ID:
ivo://CDS.VizieR/J/A+A/487/993
Title:
MAMBO Mapping of c2d Clouds and Cores
Short Name:
J/A+A/487/993
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present maps from our MAMBO 1.2mm wavelength dust emission survey of nearby (<500pc) dense starless and star-forming cores. This data was collected to study evolutionary trends among the dense cores and the associated young stellar objects. This survey was specifically designed to complement Spitzer Space Telescope imaging of these regions. The maps are unusually sensitive and rich in structure.
6. UBVRI images of Barnard 207
ID:
ivo://CDS.VizieR/J/A+A/605/A99
Title:
UBVRI images of Barnard 207
Short Name:
J/A+A/605/A99
Date:
21 Oct 2021
Publisher:
CDS
Description:
Barnard 207 (B207, LDN 1489, LBN 777), also known as the Vulture Head nebula, is a cometary globule in the Taurus-Auriga-Perseus Molecular Cloud region. B207 is known to host a Class I protostar, IRAS 04016+2610, located at a projected distance of ~8400au from the dense core centre. Using imaging and photometry over a wide wavelength range, from UV to sub-mm, we study the physical properties of B207 and the dust grains contained within. The core density, temperature, and mass are typical of other globules found in the Milky Way interstellar medium (ISM). The increase in the dust albedo with increasing optical wavelengths, along with the detection of coreshine in the near infrared, indicates the presence of larger dust grains in B207. The measured optical, near-, mid- and far-infrared intensities are in agreement with the CMM+AMM and CMM+AMMI dust grain type of the THEMIS model, suggesting mantle formation on the dust grains throughout the globule. We investigate the possibility of turbulence being responsible for diffusing dust grains from the central core to external outer layers of B207. However, in situ formation of large dust grains cannot be excluded.