Context.
The role of bipolar jets in the formation of stars, and in particular how they are launched, is still not well understood.
Aims.
We probe the protostellar jet launching mechanism using ...high-resolution observations of the near-infrared (IR) Fe
II
λ
1.53,1.64
μ
m emission lines.
Methods.
We consider the case of the bipolar jet from Classical T Tauri star, DO Tau, and investigate the jet morphology and kinematics close to the star (within 140 au) using AO-assisted IFU observations from GEMINI/NIFS.
Results.
We find that the brighter, blueshifted jet is collimated very quickly after it is launched. This early collimation requires the presence of magnetic fields. We confirm velocity asymmetries between the two lobes of the bipolar jet, and also confirm no time variability in the asymmetry over a 20-year interval. This sustained asymmetry is in accordance with recent simulations of magnetised disc winds. We examine the data for signatures of jet rotation. We report an upper limit on differences in radial velocity of 6.3 and 8.7 km s
−1
for the blue- and redshifted jets, respectively. Interpreting this as an upper limit on jet rotation implies that any steady, axisymmetric magneto-centrifugal model of jet launching is constrained to a launch radius in the disc plane of
r
0
< 0.5 and 0.3 au for the blue- and redshifted jets, respectively. This supports an X-wind or narrow disc-wind model. However, the result pertains only to the observed high-velocity Fe
II
emission, and does not rule out a wider flow launched from a wider radius. We report the detection of small-amplitude jet axis wiggling in both lobes. We rule out orbital motion of the jet source as the cause. Precession can better account for the observations but requires double the precession angle, and a different phase for the counter-jet. Such non-solid body precession could arise from an inclined massive Jupiter companion, or a warping instability induced by launching a magnetic disc wind.
Conclusions.
Overall, our observations are consistent with an origin of the DO Tau jets from the inner regions of the disc.
Context.
The He I
λ
0830 Å line is a high excitation line which allows us to probe the material in the innermost regions of protostellar disks, and to trace both accreting and outflowing material ...simultaneously.
Aims.
We use X-shooter observations of a sample of 107 young stars in the Lupus (1–3 Myr) and Upper Scorpius (5–10 Myr) star-forming regions to search for correlations between the line properties, as well as the disk inclination and accretion luminosity.
Methods.
We identified eight distinct profile types in the sample. We fitted Gaussian curves to the absorption and/or emission features in the line to measure the maximum velocities traced in absorption, the full-width half-maximum (FWHM) of the line features, and the Gaussian area of the features.
Results.
We compare the proportion of each profile type in our sample to previous studies in Taurus. We find significant variations between Taurus and Lupus in the proportion of P Cygni and inverse P Cygni profiles, and between Lupus and Upper Scorpius in the number of emission-only and combination profile types. We examine the emission-only profiles in our sample individually and find that most sources (nine out of 12) with emission-only profiles are associated with known jets. When examining the absorption features, we find that the blue-shifted absorption features appear less blue-shifted at disk inclinations close to edge-on, which is in line with past works, but no such trend with inclination is observed in the sources with only red-shifted features. Additionally, we do not see a strong correlation between the FWHM and inclination. Higher accretion rates were observed in sources with strong blue-shifted features which, along with the changes in the proportions of each profile type observed in the two regions, indicates that younger sources may drive stronger jets or winds.
Conclusions.
Overall, we observe variations in the proportion of each He I
λ
10830 Å profile type and in the line properties which indicates an evolution of accretion and ejection signatures over time, and with source properties. These results confirm past works and models of the He I
λ
10830 Å line, but for a larger sample and for multiple star-forming regions. This work highlights the power of the He I
λ
0830 Å line as a probe of the gas in the innermost regions of the disk.
The evolution of young stars and disks is driven by the interplay of several processes, notably the accretion and ejection of material. These processes, critical to correctly describe the conditions ...of planet formation, are best probed spectroscopically. Between 2020 and 2022, about 500orbits of the
Hubble
Space Telescope (HST) are being devoted in to the ULLYSES public survey of about 70 low-mass (
M
⋆
≤ 2
M
⊙
) young (age < 10 Myr) stars at UV wavelengths. Here, we present the PENELLOPE Large Program carried out with the ESO Very Large Telescope (VLT) with the aim of acquiring, contemporaneously to the HST, optical ESPRESSO/UVES high-resolution spectra for the purpose of investigating the kinematics of the emitting gas, along with UV-to-NIR X-shooter medium-resolution flux-calibrated spectra to provide the fundamental parameters that HST data alone cannot provide, such as extinction and stellar properties. The data obtained by PENELLOPE have no proprietary time and the fully reduced spectra are being made available to the whole community. Here, we describe the data and the first scientific analysis of the accretion properties for the sample of 13 targets located in the Orion OB1 association and in the
σ
-Orionis cluster, observed in November–December 2020. We find that the accretion rates are in line with those observed previously in similarly young star-forming regions, with a variability on a timescale of days (≲3). The comparison of the fits to the continuum excess emission obtained with a slab model on the X-shooter spectra and the HST/STIS spectra shows a shortcoming in the X-shooter estimates of ≲10%, which is well within the assumed uncertainty. Its origin can be either due to an erroneous UV extinction curve or to the simplicity of the modeling and, thus, this question will form the basis of the investigation undertaken over the course of the PENELLOPE program. The combined ULLYSES and PENELLOPE data will be key in attaining a better understanding of the accretion and ejection mechanisms in young stars.
The evolution of young stars and disks is driven by the interplay of several processes, notably the accretion and ejection of material. These processes, critical to correctly describe the conditions ...of planet formation, are best probed spectroscopically. Between 2020 and 2022, about 500orbits of the Hubble Space Telescope (HST) are being devoted in to the ULLYSES public survey of about 70 low-mass (M⋆ ≤ 2 M⊙) young (age < 10 Myr) stars at UV wavelengths. Here, we present the PENELLOPE Large Program carried out with the ESO Very Large Telescope (VLT) with the aim of acquiring, contemporaneously to the HST, optical ESPRESSO/UVES high-resolution spectra for the purpose of investigating the kinematics of the emitting gas, along with UV-to-NIR X-shooter medium-resolution flux-calibrated spectra to provide the fundamental parameters that HST data alone cannot provide, such as extinction and stellar properties. The data obtained by PENELLOPE have no proprietary time and the fully reduced spectra are being made available to the whole community. Here, we describe the data and the first scientific analysis of the accretion properties for the sample of 13 targets located in the Orion OB1 association and in the σ-Orionis cluster, observed in November–December 2020. We find that the accretion rates are in line with those observed previously in similarly young star-forming regions, with a variability on a timescale of days (≲3). The comparison of the fits to the continuum excess emission obtained with a slab model on the X-shooter spectra and the HST/STIS spectra shows a shortcoming in the X-shooter estimates of ≲10%, which is well within the assumed uncertainty. Its origin can be either due to an erroneous UV extinction curve or to the simplicity of the modeling and, thus, this question will form the basis of the investigation undertaken over the course of the PENELLOPE program. The combined ULLYSES and PENELLOPE data will be key in attaining a better understanding of the accretion and ejection mechanisms in young stars.
A&A 666, A188 (2022) The He I 1 micron line is a high excitation line which allows us to probe the
innermost regions of protostellar disks, and to trace both accreting and
outflowing material. We use ...X-Shooter observations of a sample of 107 young
stars in the Lupus (1-3 Myr) and Upper Scorpius (5-10 Myr) star-forming regions
to search for correlations between the line properties, as well as the disk
inclination and accretion luminosity. We identified eight distinct profile
types in the sample. We fitted Gaussian curves to the line features to measure
the maximum velocities traced in absorption, the full-width half-maximum (FWHM)
of the line features, and the Gaussian area of the features. We compare the
proportion of each profile type in our sample to previous studies in Taurus. We
find significant variations between Taurus and Lupus in the proportion of P
Cygni and inverse P Cygni profiles, and between Lupus and Upper Scorpius in the
number of emission-only and combination profile types. We find that the
blue-shifted absorption features appear less blue-shifted at disk inclinations
close to edge-on, but no such trend with inclination is observed in sources
with only red-shifted features. Higher accretion rates were observed in sources
with strong blue-shifted features which, along with the changes in the
proportions of each profile type observed in the two regions, indicates that
younger sources may drive stronger jets or winds. Overall, we observe
variations in the proportion of each profile type and in the line properties
which indicates and evolution of accretion and ejection signatures over time,
and with source properties. These results confirm past works and models of the
He I line, but for a larger sample and for multiple star-forming regions. The
work highlights the power of the He I line as a probe of the gas in the
innermost regions of the disk.
The role of bipolar jets in the formation of stars, and in particular how they are launched, is still not well understood. We probe the protostellar jet launching mechanism, via high resolution ...observations of the near-IR FeII 1.53,1.64 micron lines. We consider the bipolar jet from the Classical T Tauri star, DO Tau, & investigate jet morphology & kinematics close to the star, using AO-assisted IFU observations from GEMINI/NIFS. The brighter, blue-shifted jet is collimated quickly after launch. This early collimation requires the presence of magnetic fields. We confirm velocity asymmetries between the two jet lobes, & confirm no time variability in the asymmetry over a 20 year interval. This sustained asymmetry is in accordance with recent simulations of magnetised disk-winds. We examine the data for jet rotation. We report an upper limit on differences in radial velocity of 6.3 & 8.7 km/s for the blue & red-shifted jets, respectively. Interpreting this as an upper limit on jet rotation implies that any steady, axisymmetric magneto-centrifugal model of jet launching is constrained to a launch radius in the disk-plane of 0.5 & 0.3 au for the blue & red-shifted jets, respectively. This supports an X-wind or narrow disk-wind model. This pertains only to the observed high velocity FeII emission, & does not rule out a wider flow launched from a wider radius. We report detection of small amplitude jet axis wiggling in both lobes. We rule out orbital motion of the jet source as the cause. Precession can better account for the observations but requires double the precession angle, & a different phase for the counter-jet. Such non-solid body precession could arise from an inclined massive Jupiter companion, or a warping instability induced by launching a magnetic disk-wind. Overall, our observations are consistent with an origin of the DO Tau jets from the inner regions of the disk.
Icy grain mantles are the main reservoir of the volatile elements that link chemical processes in dark, interstellar clouds with the formation of planets and composition of their atmospheres. The ...initial ice composition is set in the cold, dense parts of molecular clouds, prior to the onset of star formation. With the exquisite sensitivity of JWST, this critical stage of ice evolution is now accessible for detailed study. Here we show the first results of the Early Release Science program "Ice Age" that reveal the rich composition of these dense cloud ices. Weak ices, including, \(^{13}\)CO\(_2\), OCN\(^-\), \(^{13}\)CO, OCS, and COMs functional groups are now detected along two pre-stellar lines of sight. The \(^{12}\)CO\(_2\) ice profile indicates modest growth of the icy grains. Column densities of the major and minor ice species indicate that ices contribute between 2 and 19% of the bulk budgets of the key C, O, N, and S elements. Our results suggest that the formation of simple and complex molecules could begin early in a water-ice rich environment.
The Hubble UV Legacy Library of Young Stars as Essential Standards (ULLYSES) Director's Discretionary Program of low-mass pre-main-sequence stars, coupled with forthcoming data from ALMA and JWST, ...will provide the foundation to revolutionize our understanding of the relationship between young stars and their protoplanetary disks. A comprehensive evaluation of the physics of disk evolution and planet formation requires understanding the intricate relationships between mass accretion, mass outflow, and disk structure. Here we describe the Outflows and Disks around Young Stars: Synergies for the Exploration of ULLYSES Spectra (ODYSSEUS) Survey and present initial results of the classical T Tauri Star CVSO 109 in Orion OB1b as a demonstration of the science that will result from the survey. ODYSSEUS will analyze the ULLYSES spectral database, ensuring a uniform and systematic approach in order to (1) measure how the accretion flow depends on the accretion rate and magnetic structures, (2) determine where winds and jets are launched and how mass-loss rates compare with accretion, and (3) establish the influence of FUV radiation on the chemistry of the warm inner regions of planet-forming disks. ODYSSEUS will also acquire and provide contemporaneous observations at X-ray, optical, NIR, and millimeter wavelengths to enhance the impact of the ULLYSES data. Our goal is to provide a consistent framework to accurately measure the level and evolution of mass accretion in protoplanetary disks, the properties and magnitudes of inner-disk mass loss, and the influence of UV radiation fields that determine ionization levels and drive disk chemistry.
The He I 1 micron line is a high excitation line which allows us to probe the innermost regions of protostellar disks, and to trace both accreting and outflowing material. We use X-Shooter ...observations of a sample of 107 young stars in the Lupus (1-3 Myr) and Upper Scorpius (5-10 Myr) star-forming regions to search for correlations between the line properties, as well as the disk inclination and accretion luminosity. We identified eight distinct profile types in the sample. We fitted Gaussian curves to the line features to measure the maximum velocities traced in absorption, the full-width half-maximum (FWHM) of the line features, and the Gaussian area of the features. We compare the proportion of each profile type in our sample to previous studies in Taurus. We find significant variations between Taurus and Lupus in the proportion of P Cygni and inverse P Cygni profiles, and between Lupus and Upper Scorpius in the number of emission-only and combination profile types. We find that the blue-shifted absorption features appear less blue-shifted at disk inclinations close to edge-on, but no such trend with inclination is observed in sources with only red-shifted features. Higher accretion rates were observed in sources with strong blue-shifted features which, along with the changes in the proportions of each profile type observed in the two regions, indicates that younger sources may drive stronger jets or winds. Overall, we observe variations in the proportion of each profile type and in the line properties which indicates and evolution of accretion and ejection signatures over time, and with source properties. These results confirm past works and models of the He I line, but for a larger sample and for multiple star-forming regions. The work highlights the power of the He I line as a probe of the gas in the innermost regions of the disk.
PDF
