Aims. We aim to investigate the polarization properties of a starless core in an early evolutionary stage. Linear polarization data reveal the properties of the dust grains in the distinct phases of ...the interstellar medium. Our goal is to investigate how the polarization degree and angle correlate with the cloud and core gas. Methods. We use optical, near infrared, and submillimeter polarization observations on the starless object Pipe-109 in the Pipe nebula. Our data cover a physical scale range of 0.08 to 0.4 pc, comprising the dense gas, envelope, and the surrounding cloud. Results. The cloud polarization is well traced by the optical data. The near infrared polarization is produced by a mixed population of grains from the core border and the cloud gas. The optical and near infrared polarization toward the cloud reaches the maximum possible value and saturates with respect to the visual extinction. The core polarization is predominantly traced by the submillimeter data and has a steep decrease with respect to the visual extinction. Modeling of the submillimeter polarization indicates a magnetic field main direction projected onto the plane-of-sky and loss of grain alignment for densities higher than 6 × 104 cm-3 (or AV> 30 mag). Conclusions. The object is immersed in a magnetized medium with a very ordered magnetic field. The absence of internal source of radiation significantly affects the polarization efficiencies in the core, creating a polarization hole at the center of the starless core. This result supports the theory of dust grain alignment via radiative torques
We present subarcsecond angular resolution observations carried out with the Submillimeter Array (SMA) at 880 m centered at the B0-type protostar GGD27 MM1, the driving source of the parsec scale HH ...80-81 jet. We constrain its polarized continuum emission to 0.8% at this wavelength. Its submillimeter spectrum is dominated by sulfur-bearing species tracing a rotating-disk-like structure (SO and SO2 isotopologues mainly), but also shows HCN-bearing and CH3OH lines, which trace the disk and the outflow cavity walls excavated by the HH 80-81 jet. The presence of many sulfurated lines could indicate the presence of shocked gas at the disk's centrifugal barrier or that MM1 is a hot core at an evolved stage. The resolved SO2 emission traces the disk kinematics very well and we fit the SMA observations using a thin-disk Keplerian model, which gives the inclination (47°), the inner ( 170 au) and outer (∼950-1300 au) radii, and the disk's rotation velocity (3.4 km s−1 at a putative radius of 1700 au). We roughly estimate a protostellar dynamical mass of 4-18 . MM2 and WMC cores show, comparatively, an almost empty spectra, suggesting that they are associated with extended emission detected in previous low-angular resolution observations, and therefore indicating youth (MM2) or the presence of a less massive object (WMC).
We present high angular resolution observations of the massive star-forming core DR21(OH) at 880 mu m using the Submillimeter Array (SMA). The dense core exhibits an overall velocity gradient in a ...Keplerian-like pattern, which breaks at the center of the core where SMA 6 and SMA 7 are located. The dust polarization shows a complex magnetic field, compatible with a toroidal configuration. This is in contrast with the large, parsec-scale filament that surrounds the core, where there is a smooth magnetic field. The total magnetic field strengths in the filament and in the core are 0.9 and 2.1 mG, respectively. We found evidence of magnetic field diffusion at the core scales, far beyond the expected value for ambipolar diffusion. It is possible that the diffusion arises from fast magnetic reconnection in the presence of turbulence. The dynamics of the DR 21 (OH) core appear to be controlled energetically in equal parts by the magnetic field, magnetohydrodynamic turbulence, and the angular momentum. The effect of the angular momentum (this is a fast rotating core) is probably causing the observed toroidal field configuration. Yet, gravitation overwhelms all the forces, making this a clear supercritical core with a mass-to-flux ratio of Asymptotically = to6 times die critical value. However, simulations show that this is not enough for the high level of fragmentation observed at 1000 AU scales. Thus, rotation and outflow feedback are probably the main causes of the observed fragmentation.
ABSTRACT Water fountains are evolved stars showing early stages of collimated mass-loss during transition from the asymptotic giant branch, providing valuable insight into the formation of asymmetric ...planetary nebulae. We report the results of multi-epoch VLBI observations, which determine the spatial and three-dimensional kinematic structure of H2O masers associated with the water fountain IRAS 18113−2503. The masers trace three pairs of high-velocity (∼150–300 km s−1) bipolar bow shocks on a scale of 0${^{\prime\prime}_{.}}$18 (∼2000 au). The expansion velocities of the bow shocks exhibit an exponential decrease as a function of distance from the central star, which can be explained by an episodic, jet-driven outflow decelerating due to drag forces in a circumstellar envelope. Using our model, we estimate an initial ejection velocity ∼840 km s−1, a period for the ejections ∼10 yr, with the youngest being ∼12 yr old, and an average envelope density within the H2O maser region $n_{\text{H}_2}{\approx }10^{6}$ cm−3. We hypothesize that IRAS 18113−2503 hosts a binary central star with a separation of ∼10 au, revealing novel clues about the launching mechanisms of high-velocity collimated outflows in water fountains.
Context. NGC 7538 IRS 1−3 is a high-mass star-forming cluster with several detected dust cores, infrared sources, (ultra)compact H II regions, molecular outflows, and masers. In such a complex ...environment, interactions and feedback among the embedded objects are expected to play a major role in the evolution of the region. Aims. We study the dust, kinematic, and polarimetric properties of the NGC 7538 IRS 1−3 region to investigate the role of the different forces in the formation and evolution of high-mass star-forming clusters. Methods. We performed SMA high angular resolution observations at 880 μm with the compact configuration. We developed the RATPACKS code to generate synthetic velocity cubes from models of choice to be compared to the observational data. To quantify the stability against gravitational collapse we developed the “mass balance” analysis that accounts for all the energetics on core scales. Results. We detect 14 dust cores from 3.5 M⊙ to 37 M⊙ arranged in two larger scale structures: a central bar and a filamentary spiral arm. The spiral arm presents large-scale velocity gradients in H13CO+ 4−3 and C17O 3−2, and magnetic field segments aligned well to the dust main axis. The velocity gradient is reproduced well by a spiral arm expanding at 9 km s-1 with respect to the central core MM1, which is known to power a large precessing outflow. The energy of the outflow is comparable to the spiral-arm kinetic energy, which dominates gravitational and magnetic energies. In addition, the dynamical ages of the outflow and spiral arm are comparable. On core scales, those embedded in the central bar seem to be unstable against gravitational collapse and prone to forming high-mass stars, while those in the spiral arm have lower masses that seem to be supported by non-thermal motions and magnetic fields. Conclusions. The NGC 7538 IRS 1−3 cluster seems to be dominated by protostellar feedback. The dusty spiral arm appears to be formed in a snowplow fashion owing to the outflow from the MM1 core. We speculate that the external pressure from the redshifted lobe of the outflow could trigger star formation in the spiral arm cores. This scenario would form a small cluster with a few central high-mass stars, surrounded by a number of low-mass stars formed through protostellar feedback.
Rabbits constitute an interesting model to understand gamete interaction and test novel Artificial Reproductive Techniques, but in vitro fertilization (IVF) is particularly problematic in this ...species. We have conducted a series of experiments to develop a consistent IVF technique. Initially, we checked viability, acrosome integrity, capacitation and motility in ejaculated sperm purified by a density gradient and incubated at different times in three different media: Tyrode's Albumin Lactate Pyruvate (TALP), human tubal fluid (HTF), and Brackett and Oliphant (BO). Total and progressive motility at 10–24 h and linearity from 3 h onwards was significantly higher in BO medium compared to TALP and HTF. Subsequently, cumulus-oocyte complexes (COCs) collected 10 h after induction of ovulation were incubated with sperm in TALP, HTF or BO for 18 h with or without performing sperm pre-incubation for 6 h. Pronuclear formation rate at 18 h was significantly higher in BO compared to other media (∼84 % vs. 17–22 %) and was not improved by pre-incubation. As COCs recovery rate was low at 10 h after induction of ovulation, COCs were collected at 12 h and co-incubated with sperm in BO. Pronuclear formation rate was similar than those obtained in COCs collected at 10 h (∼85 %), and when embryos were allowed to develop in vitro, the protocol yielded high cleavage and blastocyst rates (91 and 59 %, respectively). In conclusion, ejaculated rabbit sperm purified in a density gradient fertilize efficiently COCs collected at 12 h in BO medium.
•Motility parameters of rabbit sperm after prolonged incubation were better in BO medium compared to TALP and HTF.•Fertilization rates were significantly higher in BO medium compared to TALP or HTF.•Sperm pre-incubation for 6 h in BO did not improved fertilization rates compared to no pre-incubation.•Rabbit sperm purified by a density gradient fertilize efficiently COCs collected at 10–12 h after ovulation induction.
The Pipe nebula is a molecular cloud that lacks star formation feedback and has a relatively simple morphology and velocity structure. This makes it an ideal target for testing cloud evolution ...through collisions. We aim at drawing a comprehensive picture of this relatively simple cloud to better understand the formation and evolution of molecular clouds on large scales. We use archival data to compare the optical polarization properties, the visual extinction, and the 13CO velocities and line-widths of the entire cloud in order to identify trends among the observables. The velocity pattern points to a collision between the filaments in the bowl region. The magnetic field seems to be compressed and strengthened in the shocked region. The proportional increase in density and magnetic field strength by a factor similar to the Alfvenic Mach number suggests a continuous shock at low Alfvenic Mach number under the flux-freezing condition. Shocked regions seem to enhance the formation and clustering of dense cores.
We use the new IRAM 30-m FTS backend to perform an unbiased ~15 GHz wide survey at 3 mm toward the Pipe nebula young diffuse starless cores. We discover an unexpectedly rich chemistry. We propose a ...new observational classification based on the 3 mm molecular line emission normalized by the core visual extinction (AV). On the basis of this classification, we report a clear differentiation between cores in terms of chemical composition and line emission properties, which enables us to define three molecular core groups. The “diffuse” cores, AV ≲ 15, have a poor chemistry with mainly simple species (e.g. CS and C2H). The “oxo-sulfurated” cores, AV ≃ 15–22, appear to be abundant in species such as SO and SO2, but also in HCO, which seem to disappear at higher densities. Finally, the “deuterated” cores, AV ≳ 22, have a typical evolved chemistry prior to the onset of the star formation process, with nitrogenated and deuterated species, as well as carbon chain molecules. On the basis of these categories, one of the “diffuse” cores (core 47) has the spectral line properties of the “oxo-sulfurated” ones, which suggests that it is a failed core.
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