ALMA detects a radial disk wind in DG Tauri

Güdel, M.; Eibensteiner, Cosima; Dionatos, O.; Audard, M.; Forbrich, Jan; Kraus, Stefan; Rab, Ch.; Schneider, Ch.; Skinner, Stephen L.; Vorobyov, Eduard I.

doi:10.1051/0004-6361/201834271

Cited by 28 publications

(25 citation statements)

References 30 publications

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“…Guilloteau et al (2013) suggest that the single-peaked profile of SO and H 2 CO is due to envelope emission, while the fundamental H 2 O lines have double-peaked profiles and fluxes in agreement with disk model predictions (Podio et al 2013). Interferometric maps of CO and its isotopologues show that the envelope dominate the molecular emission on large scales (Schuster et al 1993;Kitamura et al 1996), while disk emission is detected on scales < 2" (Testi et al 2002;Güdel et al 2018). Given the complexity of the circumstellar environment, spatially resolved maps are crucial to reveal the origin of the molecular emission.…”

Section: Introductionsupporting

confidence: 65%

“…Then the optical depth rapidly drops to ∼ 0.5 at 20 au and < 0.3 for r > 30 au 2 . On the other hand, observations of 13 CO 2−1 and C 18 O 2 − 1 show a hole in the inner 25 au, which could be due to the thickness of the continuum up to this radius (Güdel et al 2018). To further check the continuum optical depth we compared its brightness temperature (T cont , see Fig.…”

Section: H 2 Co Formationmentioning

confidence: 99%

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

Podio

Bacciotti

Fedele

et al. 2019

A&A

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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-H 2 CO 3 1,2 − 2 1,1 and CH 3 OH 3 −2,2 − 4 −1,4 E, 5 0,5 − 4 0,4 A transitions at an unprecedented resolution of ∼ 0 ′′ . 15, i.e., ∼ 18 au at a distance of 121 pc. Results. The H 2 CO 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. CH 3 OH emission is not detected down to an r.m.s. of 3 mJy/beam 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 H 2 CO column density is ∼ 0.3 − 4 × 10 14 cm −2 , while that of CH 3 OH is < 0.04 − 0.7 × 10 14 cm −2 . In the inner 40 au no o-H 2 CO emission is detected with an upper limit on its beam-averaged column density of ∼ 0.5 − 6 × 10 13 cm −2 . Conclusions. The H 2 CO ring in the disk of DG Tau is located beyond the CO iceline (R CO ∼ 30 au). This suggests that the H 2 CO 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 H 2 CO in the gas phase caused by increased UV penetration and/or temperature inversion. The CH 3 OH/H 2 CO abundance ratio is < 1, in agreement with disk chemistry models. The inner edge of the H 2 CO ring coincides with the radius where the polarization of the dust continuum changes orientation, hinting at a tight link between the H 2 CO chemistry and the dust properties in the outer disk and at the possible presence of substructures in the dust distribution.

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Section: Introductionsupporting

confidence: 65%

Section: H 2 Co Formationmentioning

confidence: 99%

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

Podio

Bacciotti

Fedele

et al. 2019

A&A

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“…These knots move along the jet axis away from the driving source. Cooler jet components are seen as molecular emission lines, which can be studied at radio-frequencies even for highly embedded sources [121,122]. In recent years, the observing window for jet studies opened significantly and now spans from the highest photon energies in the X-ray regime [123][124][125] down to m-wavelength radiation [126].…”

Section: Jets and Outflowsmentioning

confidence: 99%

The UV Perspective of Low-Mass Star Formation

Schneider¹,

Günther²

2020

Galaxies

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The formation of low-mass (M 2 M ) stars in molecular clouds involves accretion disks and jets, which are of broad astrophysical interest. Accreting stars represent the closest examples of these phenomena. Star and planet formation are also intimately connected, setting the starting point for planetary systems like our own. The ultraviolet (UV) spectral range is particularly suited to study star formation, because virtually all relevant processes radiate at temperatures associated with UV emission processes or have strong observational signatures in the UV. In this review, we describe how UV observations provide unique diagnostics for the accretion process, the physical properties of the protoplanetary disk, and jets and outflows.CTTSs were initially identified as a new class of objects due their optical variability. Very early on, it was realized that they also show signs of enhanced chromospheric activity, i.e., "emission lines resembling those of the solar chromosphere" [2]. These emission lines are superposed on a photospheric spectrum similar to main sequence stars of late spectral type. Initially, the source of emission in excess of a normal photosphere was speculated to be circumstellar or chromospheric in origin [3].The discovery that CTTSs are above and to the right of the main sequence in an HR-diagram demonstrated in conjunction with theoretical work [4], that these objects must be young and, thus, the progenitors of the large main sequence population [5,6]. This notion is corroborated by the presence of strong Li absorption, which requires ∼ 100× the Li abundance of the Sun [e.g. 7]. Because Li is depleted quickly in stellar interiors, the amount of surface lithium decreases with time in convective stars. Therefore, strong Li absorption can only be found in young stars and thus CTTS must be young [e.g. review by 8].Meanwhile the number of peculiarities found in CTTSs grew, but their established youth alone was insufficient to explain those peculiarities and the "mysteries" of CTTSs remained. Many features, like the origin of the "chromospheric emission" remained unexplained, until the early 1980s when a large variety of models were proposed to explain features of CTTSs including envelopes, outflows, infall, and dust disks.Specifically, the "ultraviolet excess" (measured around 3700 Å) and the "blue continuum", which go along with a weakening of photosperic absorption lines due to veiling [9,10], were shown to correlate with the strength of Hα [11,12]. Such a correlation indicates a common origin of both features as observed for chromospheric emission on the Sun. Thus, it was natural to ascribe the excess continuum emission at short wavelengths to a Balmer continuum, i.e., emission following the capture of a free electron by an ionized hydrogen atom. While that finding pinpoints neither the physical origin nor location of the emitting material, it paved the way for explanations involving a suitably tuned chromosphere for producing the observed (Balmer & Ca II H+K) line fluxes in CTTSs. Quantitative mod...

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“…DG Tau is surrounded by a compact and massive dusty disk imaged with CARMA (Isella et al 2010) and ALMA in polarimetric mode (Bacciotti et al 2018). Interferometric maps of CO and its isotopologs show that the envelope dominates over the molecular emission on large scales (Kitamura et al 1996;Schuster et al 1993) while disk emission is detected on scales <2" (Güdel et al 2018;Testi et al 2002;Zhang et al 2020). The origin of the molecular emission detected with the IRAM 30 m and Herschel (Fedele et al 2013;Guilloteau et al 2013;Podio et al 2012Podio et al , 2013 is unclear because DG Tau is also associated with a residual envelope and a jet (Bacciotti et al 2000;Eislöffel & Mundt 1998).…”

Section: Introductionmentioning

confidence: 99%

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

Podio

Garufi

Codella

et al. 2020

A&A

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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.

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ALMA detects a radial disk wind in DG Tauri

Cited by 28 publications

References 30 publications

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

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

The UV Perspective of Low-Mass Star Formation

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

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