Spectral Energy Distributions of Passive T Tauri and Herbig Ae Disks: Grain Mineralogy, Parameter Dependences, and Comparison with Infrared Space Observatory LWS Observations

By E. Chiang, M. K. Joung, M. Creech-Eakman, C. Qi, J. Kessler, G. Blake, E. V. van Dishoeck. 2000

245 citations recorded by the source corpus.

We improve upon the radiative, hydrostatic equilibrium models of passive circumstellar disks constructed by Chiang & Goldreich. New features include (1) an account for a range of particle sizes, (2) employment of laboratory-based optical constants of representative grain materials, and (3) numerical solution of the equations of radiative and hydrostatic equilibrium within the original two-layer (disk surface plus disk interior) approximation. We systematically explore how the spectral energy distribution (SED) of a face-on disk depends on grain size distributions, disk geometries and surface densities, and stellar photospheric temperatures. Observed SEDs of three Herbig Ae and two T Tauri stars, including spectra from the Long Wavelength Spectrometer (LWS) aboard the Infrared Space Observatory (ISO), are fitted with our models. Silicate emission bands from optically thin, superheated disk surface layers appear in nearly all systems. Water ice emission bands appear in LWS spectra of two of the coolest stars. Infrared excesses in several sources are consistent with significant vertical settling of photospheric grains. While this work furnishes further evidence that passive reprocessing of starlight by flared disks adequately explains the origin of infrared-to-millimeter wavelength excesses of young stars, we emphasize by explicit calculations how the SED alone does not provide sufficient information to constrain particle sizes and disk masses uniquely.

Subfields: Astronomy and Astrophysics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/5491dd72f4c71396b4d3836fc579c22b2653453b

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Citations in the corpus

STRUCTURE AND EVOLUTION OF PRE-MAIN-SEQUENCE CIRCUMSTELLAR DISKS (2009, unknown): “…Rd Rin { 1 − exp [−Σ(R)kiν cos i ]} × Bν [Ti(R)] R d2 dR (11) and F sν = 2π ∫ Rd Rin { 1 + exp [−Σ(R)kiν cos i ]} × Bν [Ts(R)] ∆Σ(R) ksν R d2 dR (12) (Dullemond et al. 2001; Chiang et al. 2001), where ν is the frequency, d is the distance to the source, i is the disk inclination with respect to…”
Gas in the Terrestrial Planet Region of Disks: CO Fundamental Emission from T Tauri Stars (2003, background): “…has been studied theoretically by several groups, for both actively accreting (Calvet et al. 1991; Malbet & Bertout 1991; D’Alessio et al. 1998; Malbet, Lachaume, & Monin 2001) and passive circumstellar disks (Chiang & Goldreich 1997; Chiang et al. 2001; Dullemond, van Zadelhoff, & Natta 2002).”
High-Resolution Submillimeter Constraints on Circumstellar Disk Structure (2006, background): “With only the unresolved SED, it is not possible to uniquely determine most of these parameters (Thamm et al. 1994; see also Chiang et al. 2001 for a similar discussion with more sophisticated models).”
Organic molecules in protoplanetary disks around T Tauri and Herbig Ae stars (2004, background): “Detailed modeling of the SED of these objects suggests that the disks are in a state of dust settling, especially LkCa 15 (Chiang et al. 2001).”
Particle Pileups and Planetesimal Formation (2003, methodology): “To date, q-values near 0.5 seem difficult to avoid (see, e.g., Chiang et al. 2001; D’Alessio, Calvet, & Hartmann 2001), while estimates for p-values via dust continuum observations are traditionally hampered by lack of spatial resolution and ignorance concerning the dust opacity and the dust-to-gas…”
Large grains in the disk of CQ Tau (2003, methodology): “This is likely to be the case, since both the shape of the SED at shorter wavelengths (Chiang et al. 2001; Natta et al. 2001) and the characteristic polarimetric variability of CQ Tau (Natta & Whitney 2000) are well fitted by flared disks.”
Dust Dynamics, Surface Brightness Profiles, and Thermal Spectra of Debris Disks: The Case of AU Microscopii (2005, result): “We model the emissivity of the dust as a broken power law: Qemis = { 1 for 2πs > λ 2πs/λ otherwise , (72) in approximate agreement with the model of Chiang et al. (2001) for ice-mantled silicate grains.”
RESOLVED IMAGES OF LARGE CAVITIES IN PROTOPLANETARY TRANSITION DISKS (2011, background): “…for optically thin emission (e.g., Beckwith & Sargent 1991; Andrews & Williams 2005b) and the intricate relationship between irradiation, heating, and grain properties in the disk atmosphere (D’Alessio et al. 1999, 2001, 2006; Chiang et al. 2001) are important, but will not be reviewed again here.”
c2d Spitzer IRS Spectra of Disks around T Tauri Stars. I. Silicate Emission and Grain Growth (2005, background): “Dust settling and growth affect disk temperatures and vertical structures, resulting in dust photospheres that are flatter rather than flared (e.g., D’Alessio et al. 1999; Chiang et al. 2001; Dullemond & Dominik 2004).”
PROTOPLANETARY DISK STRUCTURES IN OPHIUCHUS (2009, background): “For many disks, there is compelling evidence that dust grains have settled toward the disk midplane (Chiang et al. 2001; Dullemond & Dominik 2004b; D’Alessio et al. 2006).”
Magnetospheres and Disk Accretion in Herbig Ae/Be Stars (2004, background): “Dusty disk models can in principle explain the infrared excess emission of many HAe/Be stars (Hillenbrand et al. 1992, hereafter HSVK92; Chiang et al. 2001; Natta et al. 2001; Dullemond et al. 2001, hereafter DDN01).”
Passive Irradiated Circumstellar Disks with an Inner Hole (2001, methodology): “Comparison with the Observations Disk models where the irradiation from the star dominates the heating provide a good Ðt to most properties of preÈmain-sequence stars over a large range of masses (see, e.g., DÏAlessio et al. 1998, 1999 ; CG97 ; Chiang et al. 2001).”
The Far-Ultraviolet Spectrum of TW Hydrae. I. Observations of H2 Fluorescence (2002, background): “The H2 fluorescence typically occurs in warm regions (T 2000 3500 K), which may pose certain problems in comparing this conclusion with disk models (e.g., D’Alessio, Calvet, &Hartmann 2001; Chiang et al. 2001; Glassgold & Najita 2001).”
Protoplanetary Disks and Their Evolution (2011, background): “Observed disk SEDs have less mid-infrared emission than expected for this degree of flaring due to settling of dust grains toward the midplane (Chiang et al. 2001, D’Alessio et al. 1999).”
Observations of the Icy Universe (2015, background): “These observations do show unequivocally the sensitivity of the modes to the thermal history of the ice (Malfait et al., 1999; Dartois et al., 1998; Omont et al., 1990; Sylvester et al., 1999; Demyk et al., 2000; Chiang et al., 2001).”
Size-sorting dust grains in the surface layers of protoplanetary disks (2008, unknown): “In addition to the feature-boosting effect described here, dust sedimentation is also known to reduce the mid- to far-infrared flux of a disk (Miyake & Nakagawa 1995; Chiang et al. 2001; Dullemond & Dominik 2004b; D’Alessio et al. 2006).”