270 research outputs found
The magnetic field in the NGC 2024 FIR 5 dense core
We used the Submillimeter Array (SMA) to observe the thermal polarized dust
emission from the protostellar source NGC 2024 FIR 5. The polarized emission
outlines a partial hourglass morphology for the plane-of-sky component of the
core magnetic field. Our data are consistent with previous BIMA maps, and the
overall magnetic field geometries obtained with both instruments are similar.
We resolve the main core into two components, FIR 5A and FIR 5B. A possible
explanation for the asymmetrical field lies in depolarization effects due to
the lack of internal heating from FIR 5B source, which may be in a prestellar
evolutionary state. The field strength was estimated to be 2.2 mG, in agreement
with previous BIMA data. We discuss the influence of a nearby H{\sc ii} region
over the field lines at scales of pc. Although the hot component is
probably compressing the molecular gas where the dust core is embedded, it is
unlikely that the radiation pressure exceeds the magnetic tension. Finally, a
complex outflow morphology is observed in CO (3 2) maps. Unlike
previous maps, several features associated with dust condensations other than
FIR 5 are detected.Comment: 48 pages, 12 figures, accepted for publication in The Astrophysical
Journa
The kinematics of the magnetised protostellar core IRAS15398-3359
Observations of protostellar envelopes are essential to understand better the
process of gravitational collapse toward star and planet formation. From a
theoretical perspective, magnetic fields are considered an important factor
during the early stages of star formation, especially during the main accretion
phase.
We aim to study the relation between kinematics and magnetic fields at a very
early stage of the star formation process by using data from the Atacama
Pathfinder EXperiment (APEX) single dish antenna with the angular resolution of
28".
We observed the two molecular lines C18O(2-1) and DCO+(3-2), toward the Class
0 young stellar object IRAS15398-3359. We implement a multi-component Gaussian
fitting on the molecular data to study the kinematics. Also, we use previous
polarization observations on this source to predict the influence of the
magnetic field on the core.
The velocity gradient along the central object can be explained as an ongoing
outflow motion. We report flowing of material from the filament toward the
central object, and of the merging of two velocity components in the C18O (2-1)
emission around the protostar position, probably due to the merging of
filamentary clouds. Our analysis shows that the large-scale magnetic field line
observed previously is preferentially aligned to the rotation axis of the core
Molecular outflow launched beyond the disk edge
One of the long-standing problems of star formation is the excess of angular
momentum of the parent molecular cloud. In the classical picture, a fraction of
angular momentum of the circumstellar material is removed by the
magneto-centrifugally driven disk wind that is launched from a wide region
throughout the disk. In this work, we investigate the kinematics in the
envelope-disk transition zone of the Class I object BHB07-11, in the B59 core.
For this purpose, we used the Atacama Large Millimeter/submillimeter Array in
extended configuration to observe the thermal dust continuum emission
( 1.3 mm) and molecular lines (CO, CO and HCO),
which are suitable tracers of disk, envelope, and outflow dynamics at a spatial
resolution of AU. We report a bipolar outflow that was launched at
symmetric positions with respect to the disk (80~AU in radius), but was
concentrated at a distance of 90--130~AU from the disk center. The two outflow
lobes had a conical shape and the gas inside was accelerating. The large offset
of the launching position coincided with the landing site of the infall
material from the extended spiral structure (seen in dust) onto the disk. This
indicates that bipolar outflows are efficiently launched within a narrow region
outside the disk edge. We also identify a sharp transition in the gas
kinematics across the tip of the spiral structure, which pinpoints the location
of the so-called centrifugal barrier.Comment: 5 pages, 5 figures, Accepted for publication in A&A Letter
Magnetic field in a young circumbinary disk
We use polarization observations of a circumbinary disk to investigate how
the polarization properties change at distinct frequency bands. Our goal is to
discern the main mechanism responsible for the polarization through comparison
between our observations and model predictions. We used ALMA to perform full
polarization observations at 97.5 GHz, 233 GHz and 343.5 GHz. The target is the
Class I object BHB07-11, which is the youngest object in the Barnard 59
protocluster. Complementary VLA observations at 34.5 GHz revealed a binary
system within the disk. We detect an extended and structured polarization
pattern remarkably consistent among all three bands. The distribution of
polarized intensity resembles a horseshoe shape with polarization angles
following this morphology. From the spectral index between bands 3 and 7, we
derive a dust opacity index consistent with maximum grain sizes
larger than expected to produce self-scattering polarization in each band. The
polarization morphology do not match predictions from self-scattering. On the
other hand, marginal correspondence is seen between our maps and predictions
from radiation field assuming the brightest binary component as main radiation
source. Molecular line data from BHB07-11 indicates disk rotation. We produced
synthetic polarization maps from a rotating magnetized disk model assuming
combined poloidal and toroidal magnetic field components. The magnetic field
vectors (i. e., the polarization vectors rotated by 90\degr) are better
represented by a model with poloidal magnetic field strength about 3 times the
toroidal one. The similarity of our polarization patterns among the three bands
provides a strong evidence against self-scattering and radiation fields. On the
other hand, our data are reasonably well reproduced by a model of disk with
toroidal magnetic field components slightly smaller than poloidal ones.Comment: 8 pages, 8 figures, accepted for publication in Astronomy &
Astrophysic
Near-IR observations of the young star [BHB2007]-1: A sub-stellar companion opening the gap in the disk
The presence of planets or sub-stellar objects still embedded in their native
protoplanetary disks is indirectly suggested by disk sub-structures like gaps,
cavities, and spirals. However, these companions are rarely detected. We
present VLT/NACO high-contrast images in , , , and band
of the young star [BHB2007]-1 probing the inclined disk in scattered light and
revealing the probable presence of a companion. The point source is detected in
the band in spatial correspondence with complementary VLA
observations. This object is constrained to have a mass in the range of 37-47
M and is located at 50 au from the central star, inside the 70 au-large
disk cavity recently imaged by ALMA, that is absent from our NACO data (down to
20 au). This mass range is compatible with the upper end derived from the size
of the ALMA cavity. The NIR disk brightness is highly asymmetric around the
minor axis, with the southern side 5.5 times brighter than the northern side.
The constant amount of asymmetry across all wavelengths suggests that it is due
to a shadow cast by a misaligned inner disk. The massive companion that we
detect could, in principle, explain the possible disk misalignment, as well as
the different cavity sizes inferred by the NACO and ALMA observations. The
confirmation and characterization of the companion is entrusted to future
observations.Comment: 9 pages, 5 figures, 3 tables. Accepted for publication on Ap
A correlation between chemistry, polarization and dust properties in the Pipe Nebula starless core FeSt 1-457
Pre-stellar cores within molecular clouds provide the very initial conditions in which stars are formed. FeSt 1-457 is a prototypical starless core and the most chemically evolved among those isolated, embedded in the most pristine part of the Pipe nebula, the bowl. We use the IRAM 30 m telescope and the PdBI to study the chemical and physical properties of the starless core FeSt 1-457 (Core 109) in the Pipe nebula. We fit the hyperfine structure of the N2H+ (1−0) IRAM 30 m data. This allowed us to measure with high precision the velocity field, line widths and opacity and derive the excitation temperature and column density in the core. We used a modified Bonnor-Ebert sphere model adding a temperature gradient towards the center to fit the 1.2 mm continuum emission and visual extinction maps. Using this model, we have estimated the abundances of the N2H+ and the rest of molecular lines detected in the 30 GHz wide line survey performed at 3 mm with IRAM 30 m using ARTIST software. The core presents a rich chemistry with emission from early (C3H2, HCN, CS) and late-time molecules (e.g., N2H+), with a clear chemical spatial differentiation for nitrogen (centrally peaked), oxygen (peaking to the southwest) and sulfurated molecules (peaking to the east). For most of the molecules detected (HCN, HCO+, CH3OH, CS, SO, 13CO and C18O), abundances are best fit with three values, presenting a clear decrease of abundance of at least one or two orders of magnitude towards the center of the core. The Bonnor-Ebert analysis indicates the core is gravitationally unstable and the magnetic field is not strong enough to avoid the collapse. Depletion of molecules onto the dust grains occurs at the interior of the core, where dust grain growth and dust depolarization also occurs. This suggests that these properties may be related. On the other hand, some molecules exhibit asymmetries in their integrated emission maps, which appear to be correlated with a previously reported submillimetre polarization asymmetry. These asymmetries could be due to a stronger interstellar radiation field in the western side of the core
Oral and maxillofacial lesions in older individuals and associated factors : a retrospective analysis of cases retrieved in two different services
Studies on the oral and maxillofacial lesions (OMLs) in older people usually assess data of laboratory services and data from oral medicine clinic have been poorly described. The aim of this study was to describe and to compare OMLs in older individuals considering two data sources, besides to assess associated factors with the three most frequent lesions. A retrospective study was conducted with individuals aged 60 years or older. Data of individuals and lesions reported in both services were collected. Univariate analysis was used to test the association between the occurrence of the lesion and the independent variables. The level of significance was set at 5%. A total of 1,695 (37.3%) records were from the Oral Medicine clinic and 2,848 (62.7%) from the Laboratory service. Inflammatory/reactive lesion group was the most frequent in both services (40.4% in Oral Medicine Clinic and in 44.2% Laboratory). The second and third groups of lesions in the Oral Medicine clinic were infectious diseases (18.5%), and variations of normality (10.8%), while in the laboratorial service were the malignant neoplasms (17.6%) and potentially malignant disorders (13.3%). Differences between services regarding the frequency of lesion groups occurred (p<0.05), except for pigmented (p=0.054) and infectious (p=0.054) groups. Females (OR: 2.08; CI: 1.81?2.39) and individuals who wore a removable prosthesis (OR: 3.99; CI: 2.83?5.62) were also likely to have inflammatory fibrous hyperplasia. Old?old individuals (OR: 1.70; CI: 1.30?2.21), male (OR: 3.63; CI: 3.00?4.39), smoking (OR: 6.05; CI: 4.84?7.56) or alcohol use (OR: 3.95; CI: 3.12?5.01) were likely to have squamous cell carcinoma. The results showed different frequencies of OMLs in older individuals according to the data sources and age group. The findings are important to direct public policies for this age group
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