The Different Evolution of Gas and Dust in Disks Around Sun-Like and Cool Stars

Pascucci, Ilaria; Apai, Dániel; Luhman, K. L.; Henning, Th.; Bouwman, J.; Meyer, M. R.; Lahuis, F.; Natta, A.

doi:10.1088/0004-637x/696/1/143

Cited by 185 publications

(215 citation statements)

References 72 publications

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“…Many observations have demonstrated that disk properties, such as the accretion rate and dust processing speed, depend on their host stellar properties like the effective temperature (T eff ) and mass (Muzerolle et al 2005;Herczeg et al 2009;Pascucci et al 2009;Riaz et al 2009). Correlation analysis is therefore very common in disk studies, although the derivation of both disk and stellar properties always depends on model assumptions.…”

Section: Dependence On the Stellar Propertiesmentioning

confidence: 99%

Herschel/PACS view of disks around low-mass stars and brown dwarfs in the TW Hydrae association

Liu

Herczeg

Gong

et al. 2014

A&A

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We conducted Herschel/PACS observations of five very low-mass stars or brown dwarfs located in the TW Hya association with the goal of characterizing the properties of disks in the low stellar mass regime. We detected all five targets at 70 μm and 100 μm and three targets at 160 μm. Our observations, combined with previous photometry from 2MASS, WISE, and SCUBA-2, enabled us to construct spectral energy distributions (SEDs) with extended wavelength coverage. Using sophisticated radiative transfer models, we analyzed the observed SEDs of the five detected objects with a hybrid fitting strategy that combines the model grids and the simulated annealing algorithm and evaluated the constraints on the disk properties via the Bayesian inference method. The modeling suggests that disks around low-mass stars and brown dwarfs are generally flatter than their higher mass counterparts, but the range of disk mass extends to well below the value found in T Tauri stars, and the disk scale heights are comparable in both groups. The inferred disk properties (i.e., disk mass, flaring, and scale height) in the low stellar mass regime are consistent with previous findings from large samples of brown dwarfs and very low-mass stars. We discuss the dependence of disk properties on their host stellar parameters and find a significant correlation between the Herschel far-IR fluxes and the stellar effective temperatures, probably indicating that the scaling between the stellar and disk masses (i.e., M disk ∝ M ) observed mainly in low-mass stars may extend down to the brown dwarf regime.

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Section: Dependence On the Stellar Propertiesmentioning

confidence: 99%

Herschel/PACS view of disks around low-mass stars and brown dwarfs in the TW Hydrae association

Liu

Herczeg

Gong

et al. 2014

A&A

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“…The inventory of molecular species detected in T Tauri sources in the infrared includes: CO (e.g. Najita et al 2003), OH and H 2 O (e.g., Carr et al 2004;Salyk et al 2008), HCN and C 2 H 2 (e.g., Carr & Najita 2008, 2011Pascucci et al 2009;Mandell et al 2012) and, finally CO 2 (Pontoppidan et al 2010). Are Herbig sources also different from T Tauri sources at far-IR wavelengths?…”

Section: Introductionmentioning

confidence: 99%

DIGIT survey of far-infrared lines from protoplanetary disks

Fedele

Bruderer

Dishoeck

et al. 2013

A&A

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114

146

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We present far-infrared (50−200 μm) spectroscopic observations of young pre-main-sequence stars taken with Herschel/PACS as part of the DIGIT key project. The sample includes 16 Herbig AeBe and 4 T Tauri sources observed in SED mode covering the entire spectral range. An additional 6 Herbig AeBe and 4 T Tauri systems have been observed in SED mode with a limited spectral coverage. Multiple atomic fine structure and molecular lines are detected at the source position:The most common feature is the [O i] 63 μm line detected in almost all of the sources, followed by OH. In contrast with CO, OH is detected toward both Herbig AeBe groups (flared and non-flared sources). An isothermal LTE slab model fit to the OH lines indicates column densities of 10 13 < N OH < 10 16 cm −2 , emitting radii 15 < r < 100 AU and excitation temperatures 100 < T ex < 400 K. We used the non-LTE code RADEX to verify the LTE assumption. High gas densities (n ≥ 10 10 cm −3 ) are needed to reproduce the observations. The OH emission thus comes from a warm layer in the disk at intermediate stellar distances. Warm H 2 O emission is detected through multiple lines toward the T Tauri systems AS 205, DG Tau, S CrA and RNO 90 and three Herbig AeBe systems HD 104237, HD 142527, HD 163296 (through line stacking). Overall, Herbig AeBe sources have higher OH/H 2 O abundance ratios across the disk than do T Tauri disks, from near-to far-infrared wavelengths. Far-infrared CH + emission is detected toward HD 100546 and HD 97048. The slab model suggests moderate excitation (T ex ∼ 100 K) and compact (r ∼ 60 AU) emission in the case of HD 100546.Off-source [O i] emission is detected toward DG Tau, whose origin is likely the outflow associated with this source. The [C ii] emission is spatially extended in all sources where the line is detected. This suggests that not all [C ii] emission is associated with the disk and that there is a substantial contribution from diffuse material around the young stars. The flux ratios of the atomic fine structure linesare analyzed with PDR models and require high gas density (n 10 5 cm −3 ) and high UV fluxes (G o ∼ 10 3 −10 7 ), consistent with a disk origin for the oxygen lines for most of the sources.

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“…Even in dense cores, not all nitrogen appears to have been transformed to molecular form (Maret et al 2006;Daranlot et al 2012). Observations of HCN in the surface layers of protoplanetary disks suggest that the nitrogen chemistry is strongly affected by whether or not a star has sufficiently hard UV radiation to photodissociate N 2 (Pascucci et al 2009). Thus, not only the absolute photodissociation rate but also its wavelength dependence is relevant.…”

Section: Introductionmentioning

confidence: 99%

Photodissociation of interstellar N₂

Heays

Visser

et al. 2013

A&A

138

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Context. Molecular nitrogen is one of the key species in the chemistry of interstellar clouds and protoplanetary disks, but its photodissociation under interstellar conditions has never been properly studied. The partitioning of nitrogen between N and N 2 controls the formation of more complex prebiotic nitrogen-containing species. Aims. The aim of this work is to gain a better understanding of the interstellar N 2 photodissociation processes based on recent detailed theoretical and experimental work and to provide accurate rates for use in chemical models. Methods. We used an approach similar to that adopted for CO in which we simulated the full high-resolution line-by-line absorption + dissociation spectrum of N 2 over the relevant 912-1000 Å wavelength range, by using a quantum-mechanical model which solves the coupled-channels Schrödinger equation. The simulated N 2 spectra were compared with the absorption spectra of H 2 , H, CO, and dust to compute photodissociation rates in various radiation fields and shielding functions. The effects of the new rates in interstellar cloud models were illustrated for diffuse and translucent clouds, a dense photon dominated region and a protoplanetary disk. Results. The unattenuated photodissociation rate in the Draine (1978, ApJS, 36, 595) radiation field assuming an N 2 excitation temperature of 50 K is 1.65 × 10 −10 s −1 , with an uncertainty of only 10%. Most of the photodissociation occurs through bands in the 957-980 Å range. The N 2 rate depends slightly on the temperature through the variation of predissociation probabilities with rotational quantum number for some bands. Shielding functions are provided for a range of H 2 and H column densities, with H 2 being much more effective than H in reducing the N 2 rate inside a cloud. Shielding by CO is not effective. The new rates are 28% lower than the previously recommended values. Nevertheless, diffuse cloud models still fail to reproduce the possible detection of interstellar N 2 except for unusually high densities and/or low incident UV radiation fields. The transition of N → N 2 occurs at nearly the same depth into a cloud as that of C + → C → CO. The orders-of-magnitude lower N 2 photodissociation rates in clouds exposed to black-body radiation fields of only 4000 K can qualitatively explain the lack of active nitrogen chemistry observed in the inner disks around cool stars. Conclusions. Accurate photodissociation rates for N 2 as a function of depth into a cloud are now available that can be applied to a wide variety of astrophysical environments.

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The Different Evolution of Gas and Dust in Disks Around Sun-Like and Cool Stars

Cited by 185 publications

References 72 publications

Herschel/PACS view of disks around low-mass stars and brown dwarfs in the TW Hydrae association

Herschel/PACS view of disks around low-mass stars and brown dwarfs in the TW Hydrae association

DIGIT survey of far-infrared lines from protoplanetary disks

Photodissociation of interstellar N₂

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The Different Evolution of Gas and Dust in Disks Around Sun-Like and Cool Stars

Cited by 185 publications

References 72 publications

Herschel/PACS view of disks around low-mass stars and brown dwarfs in the TW Hydrae association

Herschel/PACS view of disks around low-mass stars and brown dwarfs in the TW Hydrae association

DIGIT survey of far-infrared lines from protoplanetary disks

Photodissociation of interstellar N2

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About

Photodissociation of interstellar N₂