We perform imaging and analysis of SMA 1.3 mm continuum, Csup 18O(2-1) and sup 12CO(2-1) line data of 17Class 0 and 0/I protostars to study their gas kinematics on a 1000 AU scale. Continuum and Csup ...18O (2-1) emission are detected toward all the sample sources and show central primary components with sizes of ~ 600-1500 AU associated with protostars. We construct a simple kinematic model to reproduce the observed velocity gradients, estimate the infalling and rotational velocities, and infer the disk radii and the protostellar masses. We discuss our results in comparison with theoretical models of collapsing dense cores with and without magnetic fields in the context of disk formation.
We demonstrate all-optical nonlinear switching in compact GaAs-AlGaAs microring resonators at the 1.55-μm wavelength. Switching is accomplished in the pump-and-probe configuration in which the ...pump-and-probe signals are tuned to different resonance wavelengths of the microring. Refractive index change in the microring due to free carriers generated by two photon absorption is used to switch the probe beam in and out of resonance. Measured transient responses of the pump and probe through the microring show good agreement with theoretical predictions based on nonlinear pump-probe interaction due to two photon absorption.
Current methods of locating the epidural space rely on surface anatomical landmarks and loss-of-resistance (LOR). We are not aware of any data describing real-time ultrasound (US)-guided epidural ...access in adults.
We evaluated the feasibility of performing real-time US-guided paramedian epidural access with the epidural needle inserted in the plane of the US beam in 15 adults who were undergoing groin or lower limb surgery under an epidural or combined spinal–epidural anaesthesia.
The epidural space was successfully identified in 14 of 15 (93.3%) patients in 1 (1–3) attempt using the technique described. There was a failure to locate the epidural space in one elderly man. In 8 of 15 (53.3%) patients, studied neuraxial changes, that is, anterior displacement of the posterior dura and widening of the posterior epidural space, were seen immediately after entry of the Tuohy needle and expulsion of the pressurized saline from the LOR syringe into the epidural space at the level of needle insertion. Compression of the thecal sac was also seen in two of these patients. There were no inadvertent dural punctures or complications directly related to the technique described. Anaesthesia adequate for surgery developed in all patients after the initial spinal or epidural injection and recovery from the epidural or spinal anaesthesia was also uneventful.
We have demonstrated the successful use of real-time US guidance in combination with LOR to saline for paramedian epidural access with the epidural needle inserted in the plane of the US beam.
Super-fast Rotation in the OMC 2/FIR 6b Jet Matsushita, Yuko; Takahashi, Satoko; Ishii, Shun ...
The Astrophysical journal,
07/2021, Letnik:
916, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
We present Atacama Large Millimeter/submillimeter Array CO (
J
= 2–1) and 1.3 mm continuum observations of the high-velocity jet associated with the FIR 6b protostar located in the Orion ...Molecular Cloud-2. We detect a velocity gradient along the short axis of the jet in both the red- and blueshifted components. The position–velocity diagrams along the short axis of the redshifted jet show a typical characteristic of a rotating cylinder. We attribute the velocity gradient in the redshifted component to rotation of the jet. The rotation velocity (>20 km s
−1
) and specific angular momentum (>10
22
cm
2
s
−1
) of the jet around FIR 6b are the largest among all jets in which rotation has been observed. By combining disk wind theory with our observations, the jet launching radius is estimated to be in the range of 2.18–2.96 au. The rapid rotation, large specific angular momentum, and a launching radius far from the central protostar can be explained by a magnetohydrodynamic disk wind that contributes to the angular momentum transfer in the late stages of protostellar accretion.
Abstract
The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is a three-layered imaging survey aimed at addressing some of the most important outstanding questions in astronomy today, including ...the nature of dark matter and dark energy. The survey has been awarded 300 nights of observing time at the Subaru Telescope, and it started in 2014 March. This paper presents the first public data release of HSC-SSP. This release includes data taken in the first 1.7 yr of observations (61.5 nights), and each of the Wide, Deep, and UltraDeep layers covers about 108, 26, and 4 square degrees down to depths of i ∼ 26.4, ∼26.5, and ∼27.0 mag, respectively (5 σ for point sources). All the layers are observed in five broad bands (grizy), and the Deep and UltraDeep layers are observed in narrow bands as well. We achieve an impressive image quality of 0${^{\prime\prime}_{.}}$6 in the i band in the Wide layer. We show that we achieve 1%–2% point spread function (PSF) photometry (root mean square) both internally and externally (against Pan-STARRS1), and ∼10 mas and 40 mas internal and external astrometric accuracy, respectively. Both the calibrated images and catalogs are made available to the community through dedicated user interfaces and database servers. In addition to the pipeline products, we also provide value-added products such as photometric redshifts and a collection of public spectroscopic redshifts. Detailed descriptions of all the data can be found online. The data release website is https://hsc-release.mtk.nao.ac.jp.
Although it is widely accepted that most galaxies have supermassive black holes at their centres, concrete proof has proved elusive. Sagittarius A* (Sgr A*), an extremely compact radio source at the ...centre of our Galaxy, is the best candidate for proof, because it is the closest. Previous very-long-baseline interferometry observations (at 7 mm wavelength) reported that Sgr A* is ∼2 astronomical units (au) in size, but this is still larger than the 'shadow' (a remarkably dim inner region encircled by a bright ring) that should arise from general relativistic effects near the event horizon of the black hole. Moreover, the measured size is wavelength dependent. Here we report a radio image of Sgr A* at a wavelength of 3.5 mm, demonstrating that its size is ∼1 au. When combined with the lower limit on its mass, the lower limit on the mass density is 6.5 × 1021M pc-3 (where M is the solar mass), which provides strong evidence that Sgr A* is a supermassive black hole. The power-law relationship between wavelength and intrinsic size (size∝wavelength1.09) explicitly rules out explanations other than those emission models with stratified structure, which predict a smaller emitting region observed at a shorter radio wavelength.
Extreme Active Molecular Jets in L1448C Hirano, Naomi; Ho, Paul P.T; Liu, Sheng-Yuan ...
The Astrophysical journal,
07/2010, Letnik:
717, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The protostellar jet driven by L1448C was observed in the SiO J = 8-7 and CO J = 3-2 lines, and 350 GHz dust continuum at {approx}1'' resolution with the Submillimeter Array. A narrow jet from the ...northern source L1448C(N) was observed in the SiO and the high-velocity CO. The jet consists of a chain of emission knots with an inter-knot spacing of {approx}2'' (500 AU) and a semi-periodic velocity variation. These knots are likely to be the internal bow shocks in the jet beam that were formed due to the periodic variation of the ejection velocity with a period of {approx}15-20 yr. The innermost pairs of knots, which are significant in the SiO map but barely seen in the CO, are located at {approx}1'' (250 AU) from the central source, L1448C(N). Since the dynamical timescale for the innermost pair is only {approx}10 yr, SiO may have been formed in the protostellar wind through the gas-phase reaction, or formed on the dust grain and directly released into the gas phase by means of shocks. It is found that the jet is extremely active with a mechanical luminosity of {approx}7 L{sub sun}, which is comparable to the bolometric luminosity of the central source (7.5 L{sub sun}). The mass accretion rate onto the protostar derived from the mass-loss rate is {approx}10{sup -5} M{sub sun} yr{sup -1}. Such a high mass accretion rate suggests that the mass and the age of the central star are 0.03-0.09 M{sub sun} and (4-12)x10{sup 3} yr, respectively, implying that the central star is in the very early stage of protostellar evolution. The low-velocity CO emission delineates two V-shaped shells with a common apex at L1448C(N). The kinematics of these shells are reproduced by the model of a wide-opening angle wind. The co-existence of the highly collimated jets and the wide-opening angle shells can be explained by the 'unified X-wind model' in which highly collimated jet components correspond to the on-axis density enhancement of the wide-opening angle wind. The CO J = 3-2 map also revealed the second outflow driven by the southern source L1448C(S) located at {approx}8.''3 (2000 AU) from L1448C(N). Although L1448C(S) is brighter than L1448C(N) in the mid-IR bands, the momentum flux of the outflow from L1448C(S) is 2 or 3 orders of magnitude smaller than that of the L1448C(N) outflow. It is likely that the evolution of L1448C(S) has been strongly affected by the powerful outflow from L1448C(N).
Abstract
The Hyper Suprime-Cam (HSC) is an 870 megapixel prime focus optical imaging camera for the 8.2 m Subaru telescope. The wide-field corrector delivers sharp images of 0${^{\prime\prime}_{.}}$2 ...(FWHM) in the HSC-i band over the entire 1${^{\circ}_{.}}$5 diameter field of view. The collimation of the camera with respect to the optical axis of the primary mirror is done with hexapod actuators, the mechanical accuracy of which is a few microns. Analysis of the remaining wavefront error in off-focus stellar images reveals that the collimation of the optical components meets design specifications. While there is a flexure of mechanical components, it also is within the design specification. As a result, the camera achieves its seeing-limited imaging on Maunakea during most of the time; the median seeing over several years of observing is 0${^{\prime\prime}_{.}}$67 (FWHM) in the i band. The sensors use p-channel, fully depleted CCDs of 200 μm thickness (2048 × 4176 15 μm square pixels) and we employ 116 of them to pave the 50 cm diameter focal plane. The minimum interval between exposures is 34 s, including the time to read out arrays, to transfer data to the control computer, and to save them to the hard drive. HSC on Subaru uniquely features a combination of a large aperture, a wide field of view, sharp images and a high sensitivity especially at longer wavelengths, which makes the HSC one of the most powerful observing facilities in the world.
HH 212 is a nearby (400 pc) Class 0 protostellar system showing several components that can be compared with theoretical models of core collapse. We have mapped it in the 350 GHz continuum and ...HCO{sup +} J = 4-3 emission with ALMA at up to ∼0.''4 resolution. A flattened envelope and a compact disk are seen in the continuum around the central source, as seen before. The HCO{sup +} kinematics shows that the flattened envelope is infalling with small rotation (i.e., spiraling) into the central source, and thus can be identified as a pseudodisk in the models of magnetized core collapse. Also, the HCO{sup +} kinematics shows that the disk is rotating and can be rotationally supported. In addition, to account for the missing HCO{sup +} emission at low-redshifted velocity, an extended infalling envelope is required, with its material flowing roughly parallel to the jet axis toward the pseudodisk. This is expected if it is magnetized with an hourglass B-field morphology. We have modeled the continuum and HCO{sup +} emission of the flattened envelope and disk simultaneously. We find that a jump in density is required across the interface between the pseudodisk and the disk. A jet is seen in HCO{sup +} extending out to ∼500 AU away from the central source, with the peaks upstream of those seen before in SiO. The broad velocity range and high HCO{sup +} abundance indicate that the HCO{sup +} emission traces internal shocks in the jet.
Recent fabrication advances have enabled compact semiconductor microring resonators to be fabricated with high-finesse values and picosecond cavity lifetimes. These devices have potential ...applications in optical signal processing as all-optical switches, multiplexers and logic gates. Theoretical analysis shows a maximum reduction in the switching power proportional to the fourth power of the field enhancement in the microring. An enhancement in the wavelength conversion efficiency by four-wave mixing which is proportional to the eighth power of the field enhancement is also predicted and experimentally confirmed. Experimental results demonstrating bistability, picosecond switching using pump and probe excitation, optical time-division demultiplexing, spatial pulse routing and four-wave mixing in GaAs-AlGaAs microring resonators are reported. Apart from the bistable response, which was thermally induced, the nonlinear effects observed in the microrings were caused by the two-photon absorption process. Applications of microrings to realize all-optical logic gates are also proposed.
PDF
