scholarly journals An unbiased NOEMA 2.6 to 4 mm survey of the GG Tau ring: First detection of CCS in a protoplanetary disk

2021 ◽  
Vol 653 ◽  
pp. L5
Author(s):  
N. T. Phuong ◽  
A. Dutrey ◽  
E. Chapillon ◽  
S. Guilloteau ◽  
J. Bary ◽  
...  
Keyword(s):  
Protoplanetary Disk ◽  
Vertical Temperature ◽  
Physical Conditions ◽  
Outer Disk ◽  
T Tauri ◽  
Disk Size ◽  
Chemical Content ◽  
Complex Chemical Composition ◽  
Good Laboratory ◽  
Low Temperature Chemistry

Context. Molecular line surveys are among the main tools to probe the structure and physical conditions in protoplanetary disks (PPDs), the birthplace of planets. The large radial and vertical temperature as well as density gradients in these PPDs lead to a complex chemical composition, making chemistry an important step to understand the variety of planetary systems. Aims. We aimed to study the chemical content of the protoplanetary disk surrounding GG Tau A, a well-known triple T Tauri system. Methods. We used NOEMA with the new correlator PolyFix to observe rotational lines at ∼2.6 to 4 mm from a few dozen molecules. We analysed the data with a radiative transfer code to derive molecular densities and the abundance relative to 13CO, which we compare to those of the TMC1 cloud and LkCa 15 disk. Results. We report the first detection of CCS in PPDs. We also marginally detect OCS and find 16 other molecules in the GG Tauri outer disk. Ten of them had been found previously, while seven others (13CN, N2H+, HNC, DNC, HC3N, CCS, and C34S) are new detections in this disk. Conclusions. The analysis confirms that sulphur chemistry is not yet properly understood. The D/H ratio, derived from DCO+/HCO+, DCN/HCN, and DNC/HNC ratios, points towards a low temperature chemistry. The detection of the rare species CCS confirms that GG Tau is a good laboratory to study the protoplanetary disk chemistry, thanks to its large disk size and mass.

scholarly journals Mottled Protoplanetary Disk Ionization by Magnetically Channeled T Tauri Star Energetic Particles

2018 ◽  
Vol 853 (2) ◽  
pp. 112 ◽  
Author(s):  
F. Fraschetti ◽  
J. J. Drake ◽  
O. Cohen ◽  
C. Garraffo
Keyword(s):  
Energetic Particles ◽  
Protoplanetary Disk ◽  
Tauri Star ◽  
T Tauri

scholarly journals Carbon depletion observed inside T Tauri inner rims

2019 ◽  
Vol 632 ◽  
pp. A32 ◽  
Author(s):  
M. K. McClure
Keyword(s):  
Carbon Content ◽  
Near Infrared ◽  
Protoplanetary Disks ◽  
Far Infrared ◽  
T Tauri Stars ◽  
Outer Disk ◽  
Carbon Abundance ◽  
T Tauri ◽  
Medium Resolution ◽  
Complete Set

Context. The carbon content of protoplanetary disks is an important parameter to characterize planets formed at different disk radii. There is some evidence from far-infrared and submillimeter observations that gas in the outer disk is depleted in carbon, with a corresponding enhancement of carbon-rich ices at the disk midplane. Observations of the carbon content inside of the inner sublimation rim could confirm how much carbon remains locked in kilometer size bodies in the disk. Aims. I aim to determine the density, temperature, and carbon abundance inside the disk dust sublimation rim in a set of T Tauri stars with full protoplanetary disks. Methods. Using medium-resolution, near-infrared (0.8–2.5 μm) spectra and the new Gaia DR2 distances, I self-consistently determine the stellar, extinction, veiling, and accretion properties of the 26 stars in my sample. From these values, and non-accreting T Tauri spectral templates, I extract the inner disk excess of the target stars from their observed spectra. Then I identify a series of C0 recombination lines in 18 of these disks and use the CHIANTI atomic line database with an optically thin slab model to constrain the average ne, Te, and nc for these lines in the five disks with a complete set of lines. By comparing these values with other slab models of the inner disk using the Cloudy photoionization code, I also constrain nH and the carbon abundance, XC, and hence the amount of carbon “missing” from the slab. For one disk, DR Tau, I use relative abundances for the accretion stream from the literature to also determine XSi and XN. Results. The inner disks modeled here are extremely dense (nH ~ 1016 cm−3), warm (Te ~ 4500 K), and moderately ionized (log Xe ~ 3.3). Three of the five modeled disks show robust carbon depletion up to a factor of 42 relative to the solar value. I discuss multiple ways in which the “missing” carbon could be locked out of the accreting gas. Given the high-density inner disk gas, evidence for radial drift, and lack of obvious gaps in these three systems, their carbon depletion is most consistent with the “missing” carbon being sequestered in kilometer size bodies. For DR Tau, nitrogen and silicon are also depleted by factors of 45 and 4, respectively, suggesting that the kilometer size bodies into which the grains are locked were formed beyond the N2 snowline. I explore briefly what improvements in the models and observations are needed to better address this topic in the future.

scholarly journals Organic molecules in the protoplanetary disk of DG Tauri revealed by ALMA

2019 ◽  
Vol 623 ◽  
pp. L6 ◽  
Author(s):  
L. Podio ◽  
F. Bacciotti ◽  
D. Fedele ◽  
C. Favre ◽  
C. Codella ◽  
...  
Keyword(s):  
Column Density ◽  
Protoplanetary Disks ◽  
Temperature Inversion ◽  
Abundance Ratio ◽  
Chemical Compositions ◽  
Outer Disk ◽  
T Tauri ◽  
Dust Distribution ◽  
Disk Height ◽  
Co Emission

Context. Planets form in protoplanetary disks and inherit their chemical compositions. Aims. It is thus crucial to map the distribution and investigate the formation of simple organics, such as formaldehyde and methanol, in protoplanetary disks. Methods. We analyze ALMA observations of the nearby disk-jet system around the T Tauri star DG Tau in the o − H2CO 31, 2 − 21, 1 and CH3OH 3−2, 2 − 4−1, 4 E, 50, 5 − 40, 4 A transitions at an unprecedented resolution of $ {\sim}0{{\overset{\prime\prime}{.}}}{15} $, i.e., ∼18 au at a distance of 121 pc. Results. The H2CO emission originates from a rotating ring extending from ∼40 au with a peak at ∼62 au, i.e., at the edge of the 1.3 mm dust continuum. CH3OH emission is not detected down to an rms of 3 mJy beam−1 in the 0.162 km s−1 channel. Assuming an ortho-to-para ratio of 1.8−2.8 the ring- and disk-height-averaged H2CO column density is ∼0.3−4 × 1014 cm−2, while that of CH3OH is < 0.04−0.7 × 1014 cm−2. In the inner 40 au no o − H2CO emission is detected with an upper limit on its beam-averaged column density of ∼0.5−6 × 1013 cm−2. Conclusions. The H2CO ring in the disk of DG Tau is located beyond the CO iceline (RCO ∼ 30 au). This suggests that the H2CO abundance is enhanced in the outer disk due to formation on grain surfaces by the hydrogenation of CO ice. The emission peak at the edge of the mm dust continuum may be due to enhanced desorption of H2CO in the gas phase caused by increased UV penetration and/or temperature inversion. The CH3OH/H2CO abundance ratio is < 1, in agreement with disk chemistry models. The inner edge of the H2CO ring coincides with the radius where the polarization of the dust continuum changes orientation, hinting at a tight link between the H2CO chemistry and the dust properties in the outer disk and at the possible presence of substructures in the dust distribution.

scholarly journals Disks Around T Tauri Stars with SPHERE (DARTTS-S)

2020 ◽  
Vol 633 ◽  
pp. A82 ◽  
Author(s):  
A. Garufi ◽  
H. Avenhaus ◽  
S. Pérez ◽  
S. P. Quanz ◽  
R. G. van Holstein ◽  
...  
Keyword(s):  
Scattered Light ◽  
Spectral Energy Distribution ◽  
Surrounding Medium ◽  
Circumstellar Disks ◽  
T Tauri Stars ◽  
Spectral Energy ◽  
Near Ir ◽  
Nir Imaging ◽  
T Tauri ◽  
Disk Size

Context. Near-IR polarimetric images of protoplanetary disks enable us to characterize substructures that might be due to the interaction with (forming) planets. The available census is strongly biased toward massive disks around old stars, however. Aims. The DARTTS program aims at alleviating this bias by imaging a large number of T Tauri stars with diverse properties. Methods. DARTTS-S employs VLT/SPHERE to image the polarized scattered light from disks. In parallel, DARTTS-A provides ALMA images of the same targets for a comparison of different dust components. In this work, we present new SPHERE images of 21 circumstellar disks, which is the largest sample released to date. We also recalculated some relevant stellar and disk properties following Gaia DR2. Results. The targets of this work are significantly younger than those published thus far with polarimetric near-IR (NIR) imaging. Scattered light is unambiguously resolved in 11 targets, and some polarized unresolved signal is detected in 3 additional sources. Some disk substructures are detected. However, the paucity of spirals and shadows from this sample reinforces the trend according to which these NIR features are associated with Herbig stars, either because they are older or more massive. Furthermore, disk rings that are apparent in ALMA observations of some targets do not appear to have corresponding detections with SPHERE. Inner cavities larger than ~15 au are also absent from our images, even though they are expected from the spectral energy distribution. On the other hand, 3 objects show extended filaments at larger scale that are indicative of strong interaction with the surrounding medium. All but one of the undetected disks are best explained by their limited size (≲20 au), and the high occurrence of stellar companions in these sources suggests an important role in limiting the disk size. One undetected disk is massive and very large at millimeter wavelengths, implying that it is self-shadowed in the NIR. Conclusions. This work paves the way toward a more complete and less biased sample of scattered-light observations, which is required to interpret how disk features evolve throughout the disk lifetime.

scholarly journals Tracing the physical conditions of planet formation with molecular excitation

2019 ◽  
Vol 15 (S350) ◽  
pp. 181-186
Author(s):  
Richard Teague
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Planet Formation ◽  
Physical Structure ◽  
Protoplanetary Disk ◽  
Field Structure ◽  
Magnetic Field Structure ◽  
Physical Conditions ◽  
Molecular Excitation ◽  
The Magnetic Field

AbstractUnderstanding the physical structure of the planet formation environment, the protoplanetary disk, is essential for the interpretation of high resolution observations of the dust and future observations of the magnetic field structure. Observations of multiple transitions of molecular species offers a unique view of the underlying physical structure through excitation analyses. Here we describe a new method to extract high-resolution spectra from low-resolution observations, then provide two case studies of how molecular excitation analyses were used to constrain the physical structure in TW Hya, the closest protoplanetary disk to Earth.

The winter environment of painted turtles, Chrysemys picta: temperature, dissolved oxygen, and potential cues for emergence

1991 ◽  
Vol 69 (9) ◽  
pp. 2493-2498 ◽  
Author(s):  
Kenneth M. Crawford
Keyword(s):  
Dissolved Oxygen ◽  
Aquatic Ecosystems ◽  
Chrysemys Picta ◽  
Vertical Temperature Gradient ◽  
Circannual Rhythm ◽  
Vertical Temperature ◽  
Physical Conditions ◽  
Painted Turtles ◽  
Ann Arbor ◽  
Water Bottom

Water, bottom, and presumed hibernaculum temperatures and dissolved oxygen concentrations were examined over four winter seasons (1981–1985) in a shallow pond near Ann Arbor, Michigan, where a population of painted turtles, Chrysemys picta, overwinter. The minimum presumed hibernaculum temperature varied considerably from year to year (3.7–6.3 °C) and was correlated with the severity of the winter. Turtles hibernating at this site would not have been exposed to temperatures below freezing even in the severest winter. Ice covered the pond continuously for an average of 92 (56–117) days and subsequently, dissolved oxygen fell precipitously, the water becoming severely hypoxic (< 1 ppm O2) for an average of 43 (39–46) days. The timing of emergence varied annually (March 1 to April 14) and was correlated with the severity of the winter. Thus, it appears that photoperiod or a circannual rhythm is not a proximate cue for arousal. Emergence generally occurred after the ice cover was completely melted, when water and bottom temperatures were increasing steadily and the vertical temperature gradient had collapsed or reversed. The annual variability in physical conditions demonstrated in this study strongly suggests that studies involving hibernation in aquatic ecosystems are best conducted over several winters.

scholarly journals The outer disk of the classical Be star ψ Per

2016 ◽  
Vol 12 (S329) ◽  
pp. 414-414
Author(s):  
Robert Klement ◽  
Alex C. Carciofi ◽  
Thomas Rivinius ◽  
Lynn D. Matthews ◽  
Richard Ignace ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Density Measurements ◽  
Outer Disk ◽  
Disk Size ◽  
Gaussian Fit ◽  
Be Star ◽  
Best Fit ◽  
Striking Contrast

AbstractTo this date ψ Per is the only classical Be star that was angularly resolved in radio (by the VLA at λ = 2 cm). Gaussian fit to the azimuthally averaged visibility data indicates a disk size (FWHM) of ~500 stellar radii (Dougherty & Taylor 1992). Recently, we obtained new multi-band cm flux density measurements of ψ Per from the enhanced VLA. We modeled the observed spectral energy distribution (SED) covering the interval from ultraviolet to radio using the Monte Carlo radiative transfer code HDUST (Carciofi & Bjorkman 2006). An SED turndown, that occurs between far-IR and radio wavelengths, is explained by a truncated viscous decretion disk (VDD), although the shallow slope of the radio SED suggests that the disk is not simply cut off, as is assumed in our model. The best-fit size of a truncated disk derived from the modeling of the radio SED is 100+5−15 stellar radii, which is in striking contrast with the result of Dougherty & Taylor (1992). The reasons for this discrepancy are under investigation.

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