Models of Chemistry, Thermal Balance, and Infrared Spectra from Intermediate‐Aged Disks around G and K Stars

Gorti, Uma; Hollenbach, D. J.

doi:10.1086/422406

Cited by 139 publications

(183 citation statements)

References 79 publications

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“…In a somewhat complementary approach, the work by Gorti & Hollenbach (2004) addresses mostly the disk midplane of evolved ("transitional") disks with low gas and dust densities and inner holes. These disks are optically thin (τ V ∼ < 5) in the continuum although gas lines may be optically thick.…”

Section: Summer School "Protoplanetary Disks: Theory and Modeling Meementioning

confidence: 99%

Ionization and heating by X-rays and cosmic rays

Güdel

2015

EPJ Web of Conferences

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Abstract. High-energy radiation from the central T Tauri and protostars plays an important role in shaping protoplanetary disks and influences their evolution. Such radiation, in particular X-rays and extreme-ultraviolet (EUV) radiation, is predominantly generated in unstable stellar magnetic fields (e.g., the stellar corona), but also in accretion hot spots. Even jets may produce X-ray emission. Cosmic rays, i.e., high-energy particles either from the interstellar space or from the star itself, are of crucial importance. Both highenergy photons and particles ionize disk gas and lead to heating. Ionization and heating subsequently drive chemical networks, and the products of these processes are accessible through observations of molecular line emission. Furthermore, ionization supports the magnetorotational instability and therefore drives disk accretion, while heating of the disk surface layers induces photoevaporative flows. Both processes are crucial for the dispersal of protoplanetary disks and therefore critical for the time scales of planet formation. This chapter introduces the basic physics of ionization and heating starting from a quantum mechanical viewpoint, then discusses relevant processes in astrophysical gases and their applications to protoplanetary disks, and finally summarizes some properties of the most important high-energy sources for protoplanetary disks.

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Section: Summer School "Protoplanetary Disks: Theory and Modeling Meementioning

confidence: 99%

Ionization and heating by X-rays and cosmic rays

Güdel

2015

EPJ Web of Conferences

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“…For protoplanetary disks, physical-chemical models have been applied by e.g. Kamp & van Zadelhoff (2001), Glassgold et al (2004), Kamp & Dullemond (2004), Gorti & Hollenbach (2004), Nomura & Millar (2005), Aikawa & Nomura (2006), Jonkheid et al (2004), Jonkheid et al (2006), Jonkheid et al (2007), Gorti & Hollenbach (2008), Woitke et al (2009a), Woods & Willacy (2009), and Ercolano et al (2009a).…”

Section: Introductionmentioning

confidence: 99%

The warm gas atmosphere of the HD 100546 disk seen byHerschel

Bruderer

Dishoeck

Doty

et al. 2012

A&A

256

454

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Context. With the Herschel Space Observatory, lines of simple molecules (C + , O, and high-J lines of CO, J up 14) have been observed in the atmosphere of protoplanetary disks. When combined with ground-based data on [C i], all principle forms of carbon can be studied. These data allow us to test model predictions for the main carbon-bearing species and verify the presence of a warm surface layer. The absence of neutral carbon [C i], which is predicted by models to be strong, can then be interpreted together with ionized carbon [C ii] and carbon monoxide. Aims. We study the gas temperature, excitation, and chemical abundance of the simple carbon-bearing species C, C + , and CO, as well as O by the method of chemical-physical modeling. Using the models, we explore the sensitivity of the lines to the entering parameters and constrain the region from which the line radiation emerges. Methods. Numerical models of the radiative transfer in the lines and dust are used together with a chemical network simulation and a calculation of the gas energetics to obtain the gas temperature. We present our new model, which is based on our previous models but includes several improvements that we report in detail, together with the results of benchmark tests. Results. A model of the disk around the Herbig Be star HD 100546 is able to reproduce the CO ladder together with the atomic finestructure lines of [O i] and either [C i] or [C ii]. We find that the high-J lines of CO can only be reproduced by a warm atmosphere with T gas T dust . The low-J lines of CO, observable from the ground, are dominated by the outer disk with a radius of several 100 AU, while the high-J CO observable with Herschel-PACS are dominated from regions within some tens of AU. The spectral profiles of high-J lines of CO are predicted to be broader than those of the low-J lines. We study the effect of several parameters including the size of the disk, the gas mass of the disk, the PAH abundance and distribution, and the amount of carbon in the gas phase. Conclusions. The main conclusions of our work are (i) only a warm atmosphere with T gas T dust can reproduce the CO ladder. (ii) The CO ladder together with [O i] and the upper limit to [C i] can be reproduced by models with a high gas/dust ratio and a low abundance of volatile carbon. These models however produce too small amounts of [C ii]. Models with a low gas/dust ratio and more volatile carbon also reproduce CO and [O i], are in closer agreement with observations of [C ii], but overproduce [C i]. Owing to the uncertain origin of the [C ii] emission, we prefer the high gas/dust ratio models, indicating a low abundance of volatile carbon.

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“…Ercolano et al (2008) and others focused on the X-ray role in causing the photo-evaporation of the surface layers of the disk. Gorti & Hollenbach (2004 Woods & Willacy (2009) studied carbon isotope fractionation using the same method as Gorti & Hollenbach (2004) to calculate the X-ray ionization rates. Henning et al (2010) studied the role of UV and X-rays on C 2 H column densities and the excitation conditions in disks around T Tauri stars.…”

Section: Introductionmentioning

confidence: 99%

X-ray impact on the protoplanetary disks around T Tauri stars

Aresu¹,

Kamp²,

Meijerink³

et al. 2011

A&A

122

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Context. T Tauri stars have X-ray luminosities in the range L X = 10 28 − 10 32 erg s −1 . These luminosities are similar to their UV luminosities (L UV ∼ 10 30 −10 31 erg s −1 ) and therefore X-rays are expected to affect the physics and chemistry of the upper layers of their surrounding protoplanetary disks. Methods. We implemented X-ray physics and chemistry into the chemo-physical disk code ProDiMo. We include Coulomb heating and H 2 ionization as heating processes and both primary and secondary ionization due to X-rays in the chemistry. Results. X-rays heat the gas causing it to expand in the optically thin surface layers. Neutral molecular species are not significantly affected in terms of their abundance and spatial distribution, but charged species such as N + , OH + , H 2 O + , and H 3 O + display enhanced abundances in the disk surface.

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Models of Chemistry, Thermal Balance, and Infrared Spectra from Intermediate‐Aged Disks around G and K Stars

Cited by 139 publications

References 79 publications

Ionization and heating by X-rays and cosmic rays

Ionization and heating by X-rays and cosmic rays

The warm gas atmosphere of the HD 100546 disk seen byHerschel

X-ray impact on the protoplanetary disks around T Tauri stars

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