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 ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT)

2020 ◽  
Vol 644 ◽  
pp. A119 ◽  
Author(s):  
L. Podio ◽  
A. Garufi ◽  
C. Codella ◽  
D. Fedele ◽  
K. Rygl ◽  
...  
Keyword(s):  
Gas Phase ◽  
Molecular Layer ◽  
Dust Emission ◽  
Protoplanetary Disks ◽  
Temperature Inversion ◽  
Outer Edge ◽  
Molecular Emission ◽  
T Tauri ◽  
Dust Distribution ◽  
The Continuum

Context. Planets form in protoplanetary disks and inherit their chemical composition. It is therefore crucial to understand the molecular content of protoplanetary disks in their gaseous and solid components. Aims. We aim to characterize the distribution and abundance of molecules in the protoplanetary disk of DG Tau and to compare them with its dust distribution. Methods. In the context of the ALMA chemical survey of Disk-Outflow sources in the Taurus star forming region (ALMA-DOT) we analyze ALMA observations of the nearby disk-outflow system around the T Tauri star DG Tau in H2CO 31,2−21,1, CS 5−4, and CN 2−1 emission at an unprecedented resolution of ~0′′.15, which means ~18 au at a distance of 121 pc. Results. Both H2CO and CS emission originate from a disk ring located at the edge of the 1.3 mm dust continuum. CS probes a disk region that is slightly further out with respect to H2CO; their peaks in emission are found at ~70 and ~60 au, with an outer edge at ~130 and ~120 au, respectively. CN originates from an outermost and more extended disk/envelope region with a peak at ~80 au and extends out to ~500 au. H2CO is dominated by disk emission, while CS also probes two streams of material possibly accreting onto the disk with a peak in emission at the location where the stream connects to the disk. CN emission is barely detected and both the disk and the envelope could contribute to the emission. Assuming that all the lines are optically thin and emitted by the disk molecular layer in local thermodynamic equilibrium at temperatures of 20−100 K, the ring- and disk-height-averaged column density of H2CO is 2.4−8.6 × 1013 cm−2, that of CS is ~1.7−2.5 × 1013 cm−2, while that of CN is ~1.9−4.7 × 1013 cm−2. Unsharp masking reveals a ring of enhanced dust emission at ~40 au, which is located just outside the CO snowline (~30 au). Conclusions. Our finding that the CS and H2CO emission is co-spatial in the disk suggests that the two molecules are chemically linked. Both H2CO and CS may be formed in the gas phase from simple radicals and/or desorbed from grains. The observed rings of molecular emission at the edge of the 1.3 mm continuum may be due to dust opacity effects and/or continuum over-subtraction in the inner disk, as well as to increased UV penetration and/or temperature inversion at the edge of the millimeter(mm)-dust which would cause enhanced gas-phase formation and desorption of these molecules. CN emission originates only from outside the dusty disk, and is therefore even more strongly anti-correlated with the continuum, suggesting that this molecule is a good probe of UV irradiation. The H2CO and CS emission originate from outside the ring of enhanced dust emission, which also coincides with a change in the linear polarization orientation at 0.87 mm. This suggests that outside the CO snowline there could be a change in the dust properties that manifests itself as an increase in the intensity (and change of polarization) of the continuum and of the molecular emission.

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 Evidences of protoplanetary disks in a selected sample of weak T Tauri stars

2004 ◽  
Vol 202 ◽  
pp. 335-337
Author(s):  
Jane Gregorio-Hetem ◽  
Annibal Hetem
Keyword(s):  
Main Sequence ◽  
Planetary System ◽  
Protoplanetary Disks ◽  
T Tauri Stars ◽  
Evolutionary Sequence ◽  
Main Sequence Stars ◽  
T Tauri ◽  
Dust Distribution

A model with two dust components is used do explain the circumstellar structure of weak-T Tauri stars. The IR-excess was calculated and compared to spectroscopic criteria in order to classify the objects according an evolutionary sequence. About 46% of the sample correspond to young main sequence stars showing dust distribution consistent with a disrupted disk, that could be possibly caused by the formation of a planetary system.

scholarly journals Gas Cavities inside Dust Cavities in Disks Inferred from ALMA Observations

2015 ◽  
Vol 10 (S314) ◽  
pp. 139-142
Author(s):  
Nienke van der Marel ◽  
Ewine F. van Dishoeck ◽  
Simon Bruderer ◽  
Paola Pinilla ◽  
Tim van Kempen ◽  
...  
Keyword(s):  
Protoplanetary Disks ◽  
Gas Emission ◽  
Chemical Modeling ◽  
Gas Density ◽  
Spatially Resolved ◽  
Outer Disk ◽  
Physical Chemical ◽  
Planetary Mass ◽  
Dust Distribution ◽  
Modeling Code

AbstractProtoplanetary disks with cavities in their dust distribution, also named transitional disks, are expected to be in the middle of active evolution and possibly planet formation. In recent years, millimeter-dust rings observed by ALMA have been suggested to have their origin in dust traps, caused by pressure bumps. One of the ways to generate these is by the presence of planets, which lower the gas density along their orbit and create pressure bumps at the edge. We present spatially resolved ALMA Cycle 0 and Cycle 1 observations of CO and CO isotopologues of several famous transitional disks. Gas is found to be present inside the dust cavities, but at a reduced level compared with the gas surface density profile of the outer disk. The dust and gas emission are quantified using the physical-chemical modeling code DALI. In the majority of these disks we find clear evidence for a drop in gas density of at least a factor of 10 inside the cavity, whereas the dust density drops by at least a factor 1000. The CO isotopologue observations reveal that the gas cavities are significantly smaller than the dust cavities. These gas structures suggest clearing by one or more planetary-mass companions.

scholarly journals Detectability of giant planets in protoplanetary disks by CO emission lines

2010 ◽  
Vol 523 ◽  
pp. A69 ◽  
Author(s):  
Zs. Regály ◽  
Zs. Sándor ◽  
C. P. Dullemond ◽  
R. van Boekel
Keyword(s):  
Protoplanetary Disks ◽  
Giant Planets ◽  
Emission Lines ◽  
Co Emission

scholarly journals Protoplanetary disks of T Tauri binary systems in the Orion nebula cluster

2012 ◽  
Vol 540 ◽  
pp. A46 ◽  
Author(s):  
S. Daemgen ◽  
S. Correia ◽  
M. G. Petr-Gotzens
Keyword(s):  
Binary Systems ◽  
Protoplanetary Disks ◽  
Orion Nebula ◽  
T Tauri

scholarly journals Discovery of the first Ca-bearing molecule in space: CaNC

2019 ◽  
Vol 627 ◽  
pp. L4 ◽  
Author(s):  
J. Cernicharo ◽  
L. Velilla-Prieto ◽  
M. Agúndez ◽  
J. R. Pardo ◽  
J. P. Fonfría ◽  
...  
Keyword(s):  
Column Density ◽  
Abundance Ratio ◽  
Circumstellar Envelope ◽  
Line Profiles ◽  
Upper Limits

We report on the detection of calcium isocyanide, CaNC, in the carbon-rich evolved star IRC+10216. We derived a column density for this species of (2 ± 0.5) × 1011 cm−2. Based on the observed line profiles and the modelling of its emission through the envelope, the molecule has to be produced in the intermediate and outer layers of the circumstellar envelope where other metal-isocyanides have previously been found in this source. The abundance ratio of CaNC relative to MgNC and FeCN is ≃1/60 and ≃1, respectively. We searched for the species CaF, CaCl, CaC, CaCCH, and CaCH3 for which accurate frequency predictions are available. Only upper limits have been obtained for these molecules.

scholarly journals 12C18O in OMC-1: Kinematics, Molecular Column Density, and Kinetic Temperature Distribution

1987 ◽  
Vol 115 ◽  
pp. 145-146
Author(s):  
T. L. Wilson ◽  
E. Serabyn ◽  
C. Henkel ◽  
C. M. Walmsley
Keyword(s):  
Column Density ◽  
Angular Resolution ◽  
Dust Emission ◽  
Line Emission ◽  
Molecular Gas ◽  
Kinetic Temperature ◽  
Line Profiles ◽  
Co Emission ◽  
Continuous Strip ◽  
Made In

A fully sampled map of size ∼1′×3′ (R.A. Dec), centered on BN-KL has been made in the J = 1-0 line of 12C18O with 21″ angular resolution. The 12C18O emission is concentrated in a ← 40″ wide continuous strip running S to NE. Several maxima are superposed on the ridge, but none exceeds the average emission level by more than 40%. There is no intense peak of 12C18O J = 1-0 line emission centered on BN-KL, in contrast to maps of the dust emission. The dust and 12C18O results can be reconciled with a constant (CO/H2) ratio if there are variations in the kinetic temperature and column density of ∼50%. Peaks in both temperature and column density are then located near BN-KL, and 90″ to the south. From the estimated CO column density, about 10% of the carbon is in the form of CO. Near the BN-KL region, the 12C18O line profiles tend to become wider. These wider lines appear to be superposed on a weak, 18 km s−1 (FWHP) wide pedestal. In regions 40″ NE and 30″ S of BN-KL, the 12C18O lines have widths of less than 2 km s−1. Presumably, these are the locations of high density, quiescent molecular gas. The radial velocity of the CO emission increases from 6.5 km s−1 (at 90″ S) to 10.5 km s−1 (at 60″ NE) of BN-KL. Close to BN-KL, however, there is evidence that this trend is reversed.

scholarly journals 3D dust radiative transfer simulations in the inhomogeneous interstellar medium

2006 ◽  
Vol 2 (S237) ◽  
pp. 490-490
Author(s):  
E. Vidal Perez ◽  
M. Baes
Keyword(s):  
Temperature Distribution ◽  
Radiative Transfer ◽  
Interstellar Medium ◽  
Dust Temperature ◽  
T Tauri ◽  
Dust Distribution ◽  
Initial Results

AbstractThe study of dusty discs is an important topic in astrophysics, as they seem to be abundant around different objects and are related to different phenomena. In this poster we present 3D radiative transfer simulations of T Tauri type discs with an inhomogeneous dust distribution to investigate the effect of a clumpy medium on the dust temperature distribution. Our initial results indicate that the structure of the dust temperature distribution is rather insensitive to the structure of the ISM, but nevertheless we find a clear and systematic dependence on the parameters describing the structure of the clumpiness of the dust medium.

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