The role of outflows in the formation of stars and the protostellar disks that generate them is a central question in astrophysics. Outflows are associated with star formation across the entire ...stellar mass spectrum. In this review, we describe the observational, theoretical, and computational advances on magnetized outflows, and their role in the formation of disks and stars of all masses in turbulent, magnetized clouds. The ability of torques exerted on disks by magnetized winds to efficiently extract and transport disk angular momentum was developed in early theoretical models and confirmed by a variety of numerical simulations. The recent high resolution Atacama Large Millimeter Array (ALMA) observations of disks and outflows now confirm several key aspects of these ideas, e.g., that jets rotate and originate from large regions of their underlying disks. New insights on accretion disk physics show that magneto-rotational instability (MRI) turbulence is strongly damped, leaving magnetized disk winds as the dominant mechanism for transporting disk angular momentum. This has major consequences for star formation, as well as planet formation. Outflows also play an important role in feedback processes particularly in the birth of low mass stars and cluster formation. Despite being almost certainly fundamental to their production and focusing, magnetic fields in outflows in protostellar systems, and even in the disks, are notoriously difficult to measure. Most methods are indirect and lack precision, as for example, when using optical/near-infrared line ratios. Moreover, in those rare cases where direct measurements are possible—where synchrotron radiation is observed, one has to be very careful in interpreting derived values. Here we also explore what is known about magnetic fields from observations, and take a forward look to the time when facilities such as SPIRou and the SKA are in routine operation.
Synchrotron emission has recently been detected in the jet of a massive protostar, providing further evidence that certain jet formation characteristics for young stars are similar to those found for ...highly relativistic jets from active galactic nuclei. We present data at 325 and 610 MHz taken with the Giant Metrewave Radio Telescope of the young, low-mass star DG Tau, an analog of the Sun soon after its birth. This is the first investigation of a low-mass young stellar object at such low frequencies. We detect emission with a synchrotron spectral index in the proximity of the DG Tau jet and interpret this emission as a prominent bow shock associated with this outflow. This result provides tentative evidence for the acceleration of particles to relativistic energies due to the shock impact of this otherwise very low-power jet against the ambient medium. We calculate the equipartition magnetic field strength B sub(min) approximate 0.11 mG and particle energy E sub(min) approximate 4 x 10 super(40) erg, which are the minimum requirements to account for the synchrotron emission of the DG Tau bow shock. These results suggest the possibility of low energy cosmic rays being generated by young Sun-like stars.
The understanding of planet formation has changed recently, embracing the new idea of pebble accretion. This means that the influx of pebbles from the outer regions of planet-forming disks to their ...inner zones could determine the composition of planets and their atmospheres. The solid and molecular components delivered to the planet-forming region can be best characterized by mid-infrared spectroscopy. With Spitzer low-resolution (
R
= 100, 600) spectroscopy, this approach was limited to the detection of abundant molecules, such as H
2
O, C
2
H
2
, HCN and CO
2
. This contribution will present the first results of the MINDS (MIRI mid-INfrared Disk Survey, PI:Th Henning) project. Due do the sensitivity and spectral resolution provided by the James Webb Space Telescope (JWST), we now have a unique tool to obtain the full inventory of chemistry in the inner disks of solar-type stars and brown dwarfs, including also less-abundant hydrocarbons and isotopologues. The Integral Field Unit (IFU) capabilities will enable at the same time spatial studies of the continuum and line emission in extended sources such as debris disks, the flying saucer and also the search for mid-IR signatures of forming planets in systems such as PDS 70. These JWST observations are complementary to ALMA and NOEMA observations of outer-disk chemistry; together these datasets will provide an integral view of the processes occurring during the planet-formation phase.
The Mid-InfraRed Instrument/Medium-Resolution Spectrometer (MIRI/MRS) on board the James Webb Space Telescope reveals the rich and diverse chemistry in the planet forming regions around Sun-like and low-mass stars.
We present observations of three active sites of star formation in the Taurus molecular cloud complex taken at 323 and 608 MHz (90 and 50 cm, respectively) with the Giant Metrewave Radio Telescope ...(GMRT). Three pointings were observed as part of a pathfinder project, targeted at the young stellar objects (YSOs) L1551 IRS 5, T Tau and DG Tau (the results for these target sources were presented in a previous paper). In this paper, we search for other YSOs and present a survey comprising of all three fields; a by-product of the large instantaneous field of view of the GMRT. The resolution of the survey is of order 10 arcsec and the best rms noise at the centre of each pointing is of order 100 μJy beam−1 at 323 MHz and 50 μJy beam−1 at 608 MHz. We present a catalogue of 1815 and 687 field sources detected above 5σrms at 323 and 608 MHz, respectively. A total of 440 sources were detected at both frequencies, corresponding to a total unique source count of 2062 sources. We compare the results with previous surveys and showcase a sample of extended extragalactic objects. Although no further YSOs were detected in addition to the target YSOs based on our source-finding criteria, these data can be useful for targeted manual searches, studies of radio galaxies or to assist in the calibration of future observations with the Low-Frequency Array towards these regions.
Abstract We present the first results of the JWST program PROJECT-J (PROtostellar JEts Cradle Tested with JWST), designed to study the Class I source HH46 IRS and its outflow through NIRSpec and MIRI ...spectroscopy (1.66–28 μ m). The data provide line images (∼6.″6 in length with NIRSpec, and up to ∼20″ with MIRI) revealing unprecedented details within the jet, the molecular outflow, and the cavity. We detect, for the first time, the redshifted jet within ∼90 au from the source. Dozens of shock-excited forbidden lines are observed, including highly ionized species such as Ne iii 15.5 μ m, suggesting that the gas is excited by high velocity (>80 km s −1 ) shocks in a relatively high-density medium. Images of H 2 lines at different excitations outline a complex molecular flow, where a bright cavity, molecular shells, and a jet-driven bow shock interact with and are shaped by the ambient conditions. Additional NIRCam 2 μ m images resolve the HH46 IRS ∼110 au binary system and suggest that the large asymmetries observed between the jet and the H 2 wide-angle emission could be due to two separate outflows being driven by the two sources. The spectra of the unresolved binary show deep ice bands and plenty of gaseous lines in absorption, likely originating in a cold envelope or disk. In conclusion, JWST has unraveled for the first time the origin of the HH46 IRS complex outflow demonstrating its capability to investigate embedded regions around young stars, which remain elusive even at near-IR wavelengths.
Context . The MIRI instrument on board JWST is now offering high-contrast imaging capacity at mid-IR wavelengths, thereby opening a completely new field of investigation for characterizing young ...exoplanetary systems. Aims . The multiplanet system HR 8799 is the first target observed with MIRI’s coronagraph as part of the MIRI-EC Guaranteed Time Observations (GTO) exoplanet program, launched in November 2022. We obtained deep observations in three coronagraphic filters, from ∼10 to 15 µm (F1065C, F1140C, F1550C), and one standard imaging filter at ∼20 µm ( F 2100 W ). The goal of this work is to extract photometry for the four planets and to detect and investigate the distribution of circumstellar dust. Methods . Using dedicated observations of a reference star, we tested several algorithms to subtract the stellar diffraction pattern, while preserving the fluxes of planets, which can be significantly affected by over-subtraction. To obtain correct measurements of the planet’s flux values, the attenuation by the coronagraphs as a function of their position must be accounted for, as well as an estimation of the normalisation with respect to the central star. We tested several procedures to derive averaged photometric values and error bars. Results . These observations have enabled us to obtain two main results. First, the four planets in the system are well recovered and we were able to compare their mid-IR fluxes, combined with near-IR flux values from the literature, to two exoplanet atmosphere models: ATMO and Exo-REM . As a main outcome, the MIRI photometric data points imply larger radii (1.04 or 1.17 R J for planet b) and cooler temperatures (950 or 1000 K for planet b), especially for planet b, in better agreement with evolutionary models. Second, these JWST/MIRI coronagraphic data also deliver the first spatially resolved detection of the inner warm debris disk, the radius of which is constrained to about 15 au, with flux densities that are comparable to (but lower than) former unresolved spectroscopic measurements with Spitzer. Conclusions . The coronagraphs coming from MIRI ushers in a new vision of known exoplanetary systems that differs significantly from shorter wavelength, high-contrast images delivered by extreme adaptive optics from the ground. Inner dust belts and background galaxies become dominant at some mid-IR wavelengths, potentially causing confusion in detecting exoplanets. Future observing strategies and data reductions ought to take such features into account.
Radio emission in jets from young stellar objects (YSOs) in the form of nonthermal emission has been seen toward several YSOs. Thought to be synchrotron emission from strong shocks in the jet, it ...could provide valuable information about the magnetic field in the jet. Here we report on the detection of synchrotron emission in two emission knots in the jet of the low-mass YSO DG Tau A at 152 MHz using the Low-Frequency Array, the first time nonthermal emission has been observed in a YSO jet at such low frequencies. In one of the knots, a low-frequency turnover in its spectrum is clearly seen compared to higher frequencies. This is the first time that such a turnover has been seen in nonthermal emission in a YSO jet. We consider several possible mechanisms for the turnover and fit models for each of these to the spectrum. Based on the physical parameters predicted by each model, the Razin effect appears to be the most likely explanation for the turnover. From the Razin effect fit, we can obtain an estimate for the magnetic field strength within the emission knot of ∼20 G. If the Razin effect is the correct mechanism, this is the first time that the magnetic field strength along a YSO jet has been measured based on a low-frequency turnover in nonthermal emission.
Patients with cardiac arrest were assigned to either early analysis of cardiac rhythm (after 30 to 60 seconds of cardiopulmonary resuscitation) or later analysis (after 180 seconds). There was no ...significant difference between the groups in survival to hospital discharge.
Out-of-hospital cardiac arrest is a common and lethal problem, leading to an estimated 330,000 deaths each year in the United States and Canada.
1
Overall, the rate of survival to hospital discharge among patients with an out-of-hospital cardiac arrest who are treated by emergency medical services (EMS) personnel is low but varies greatly, with rates ranging from 3.0% to 16.3%.
1
This variation in the rate of survival can be attributed partly to local variations in the five key links in the chain of survival: rapid EMS access, early cardiopulmonary resuscitation (CPR), early defibrillation, early advanced cardiac life support, and effective care . . .
Abstract
SY Cha is a T Tauri star surrounded by a protoplanetary disk with a large cavity seen in the millimeter continuum but has the spectral energy distribution of a full disk. Here we report the ...first results from JWST/Mid-InfraRed Instrument (MIRI) Medium Resolution Spectrometer (MRS) observations taken as part of the MIRI mid-INfrared Disk Survey (MINDS) GTO Program. The much improved resolution and sensitivity of MIRI-MRS compared to Spitzer enables a robust analysis of the previously detected H
2
O, CO, HCN, and CO
2
emission as well as a marginal detection of C
2
H
2
. We also report the first robust detection of mid-infrared OH and rovibrational CO emission in this source. The derived molecular column densities reveal the inner disk of SY Cha to be rich in both oxygen- and carbon-bearing molecules. This is in contrast to PDS 70, another protoplanetary disk with a large cavity observed with JWST, which displays much weaker line emission. In the SY Cha disk, the continuum, and potentially the line, flux varies substantially between the new JWST observations and archival Spitzer observations, indicative of a highly dynamic inner disk.
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