Submillimeter lines from circumstellar disks around pre-main sequence stars

By G. V. Zadelhoff, E. Dishoeck, W. Thi, Geoffrey A. Blake Leiden Observatory, C. I. O. Technology.. 2001

144 citations recorded by the source corpus.

Observations of submillimeter lines of CO, HCO^+, HCN and their isotopes from circumstellar disks around low mass pre-main sequence stars are presented. CO lines up to J = 6 → 5, and HCO^+ and HCN lines up to J = 4 → 3, are detected from the disks around LkCa 15 and TW Hya. These lines originate from levels with higher excitation temperatures and critical densities than studied before. Combined with interferometer data on lower excitation lines, the line ratios can be used to constrain the physical structure of the disk. The different line ratios and optical depths indicate that most of the observed line emission arises from an intermediate disk layer with high densities of 10^6−10^8 cm^(−3) and moderately warm temperatures in the outer regions. The data are compared with three different disk models from the literature using a full 2D Monte Carlo radiative transfer code. The abundances of the molecules are constrained from the more optically thin ^(13)C species and indicate depletions of ≈1−30 for LkCa 15 and very high depletions of >100 for TW Hya with respect to dark cloud abundances. Evidence for significant freeze-out (factors of 10 or larger) of CO and HCO+ onto grain surfaces at temperatures below 22 K is found, but the abundances of these molecules must also be low in the warmer upper layer, most likely as a result of photodissociation. A warm upper layer near the surface of a flaring disk heated by stellar and interstellar radiation is an appropriate description of the observations of TW Hya. LkCa 15 seems to be cooler at the surface, perhaps due to dust settling. The density constraints are also well fitted by the flared disk models.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/77f124d2877101e7f9e446ffb31a75c4b5e8685f

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Instrumentation

Citations in the corpus

A SPATIALLY RESOLVED VERTICAL TEMPERATURE GRADIENT IN THE HD 163296 DISK (2013, background): “Furthermore, the angle that the cone makes with the disk midplane (ψ ∼ 15◦) is fairly large (but not abnormally so; van Zadelhoff et al. 2001) and suggests that the disk cannot be treated as geometrically thin.”
Imaging the Disk around TW Hydrae with the Submillimeter Array (2004, background): “…calculated with the constant Dc, the one below includes additional jump depletion (Dj) by a factor of 10 where the kinetic temperature falls below 22 K (the critical temperature of CO desorption, van Zadelhoff et al. 2001), and the bottom one includes Dj of 100 at that same temperature threshold.”
Our astrochemical heritage (2012, background): “…isotopologues with evidence of depletion (Dutrey et al. 1996, 2007a; Qi et al. 2004), CN, HCN, HNC, CS, HCO+, C2H and H2CO (Dutrey et al. 1997; van Zadelhoff et al. 2001; Thi et al. 2004; Chapillon et al. 2012b), N2H+ (Dutrey et al. 2007b), SO (Fuente et al. 2010), CS (Dutrey et al. 2011), DCO+…”
Gas density drops inside dust cavities of transitional disks around young stars observed with ALMA (2015, background): “…inside the dust cavity: the CO abundance is not constant throughout the disk with respect to molecular hydrogen due to photodissociation by the UV radiation from the star and freeze out onto dust grains in colder regions close to the midplane (van Zadelhoff et al. 2001; Aikawa et al. 2002).”
Organic molecules in protoplanetary disks around T Tauri and Herbig Ae stars (2004, methodology): “The mean kinetic temperatures are less well constrained: the ratio 13CO J = 3 → 2 / 13CO J = 1 → 0 of 1.35 ± 0.4 suggests that Tkin ∼ 20–40 K for LkCa 15 in the region where the 13CO emission originates, assuming that both lines are optically thin (van Zadelhoff et al. 2001).”
Protoplanetary Disks and Their Evolution (2011, background): “…measuring the globally averaged properties, and showed that other molecules including HCO+ and H2CO were also strongly depleted as much as, if not more than, CO in classical T Tauri disks (Dutrey, Guilloteau & Guelin 1997; Thi, van Zadelhoff & van Dishoeck 2004; van Zadelhoff et al. 2001).”
Complex organic molecules in protoplanetary disks (2013, background): “The molecules detected at (sub)mm wavelengths include CO, HCO+, CN, HCN, CS, N2H +, SO and C2H (see, e.g., Kastner et al. 1997; Dutrey et al. 1997; van Zadelhoff et al. 2001; Thi et al. 2004; Fuente et al. 2010; Henning et al. 2010).”
2018 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules (2018, unknown): “…al. (2008) [31] Sargent & Beckwith (1987) [32] Smith et al. (2009) [33] Thi et al. (1999) [34] Thi et al. (2011) [35] Walsh et al. (2016) [36] van Zadelhoff et al. (2001) References: [1] Barman et al. (2011) [2] Barman et al. (2015) [3] Deming et al. (2013) [4] Haynes et al. (2015) [5] Kreidberg…”
Survival of molecular gas in cavities of transition disks - I. CO (2013, background): “The reason why optically thick lines still slightly increase with δgas is, that the line can broaden or get optically thick higher in the disk, thus tracing warmer regions (van Zadelhoff et al. 2001; Dartois et al. 2003).”
Young Stars Near the Sun (2004, background): “A modest suite of molecules (CO, HCN, HCO+, CN), including some with multiple isotopic species, has already been detected from the TW Hya disk (Kastner et al. 1997, van Zadelhoff et al. 2001, Bergin et al. 2003, Wilner et al. 2003, van Dishoeck et al. 2003).”
The Far-Ultraviolet Spectrum of TW Hydrae. I. Observations of H2 Fluorescence (2002, unknown): “On the basis of submillimeter CO emission and estimates for the disk mass, Thi et al. (2001) and van Zadelhoff et al. (2001) determined that CO is underabundant by a factor of 500 around TWHya, with respect to a typical interstellar medium (ISM) H2/CO ratio of 104.”
Radiation thermo-chemical models of protoplanetary disks I. Hydrostatic disk structure and inner rim (2009, background): “…(e.g. Beckwith et al., 1990), gas observations are intrinsically more difficult and have focused until recently on rotational lines of abundant molecules such as CO, HCN, HCO+ (e.g. Beckwith et al., 1986; Koerner et al., 1993; Dutrey et al., 1997; van Zadelhoff et al., 2001; Thi et al., 2004).”
CO emission from discs around isolated HAeBe and Vega-excess stars (2005, unknown): “In the case of a face-on disc, comparison of the temperatures at the τ=1 surface (see van Zadelhoff et al., 2001, their Figure 6) with the temperatures assumed in our present model indicates that we may be underestimating the temperature at a given radius by a factor of between 1.0 and 2.0.”
Circumstellar Dust Disks in Taurus-Auriga: The Submillimeter Perspective (2005, background): “Interpretation of these lines and those from trace molecular species require sophisticated models of the disk structure (e.g., Dartois, Dutrey, & Guilloteau 2003; Kamp & Dullemond 2004) and chemistry (e.g., van Zadelhoff et al. 2001, 2003; Aikawa et al. 2002; Qi et al. 2003).”
A PARAMETRIC MODELING APPROACH TO MEASURING THE GAS MASSES OF CIRCUMSTELLAR DISKS (2013, background): “Even 13CO lines may have significant optical depth (Dutrey et al. 1996; van Zadelhoff et al. 2001) but are less saturated and, together with constraints on C18O, provide a means to more accurately measure the total number of molecules, as has been previously carried out for molecular clouds and…”
Volatile carbon locking and release in protoplanetary disks. A study of TW Hya and HD 100546 (2016, background): “This is generally understood to result from the freezeout of molecules in the midplane and from CO photodissociation in the disk atmosphere (Dutrey et al. 1996, 1997, 2003; van Zadelhoff et al. 2001; Chapillon et al. 2008, 2010).”
Resolved gas cavities in transitional disks inferred from CO isotopologs with ALMA (2015, background): “…CO emission into density is not trivial either: the CO abundance with respect to H2 varies throughout the disk due to photodissociation by the stellar UV radiation and freeze-out onto dust grains in the cold regions in the midplane and outer disk (van Zadelhoff et al. 2001; Aikawa et al. 2002).”
THE TW Hya DISK AT 870 μm: COMPARISON OF CO AND DUST RADIAL STRUCTURES (2011, background): “…account for the effects that X-ray heating, chemical differentiation, and gas-dust temperature departures have on the vertical structure of the disk (e.g., van Zadelhoff et al. 2001; Jonkheid et al. 2004; Kamp & Dullemond 2004; Kamp et al. 2010; Woitke et al. 2009, 2010; Aresu et al. 2011).”
CHEMICAL PROCESSES IN PROTOPLANETARY DISKS (2010, background): “…2006, 2008), DM Tauri (Dutrey et al. 1997; Ceccarelli et al. 2004, 2005; Guilloteau et al. 2006; catherine.walsh@qub.ac.uk Dutrey et al. 2007; Piétu et al. 2007) and LkCa 15 (van Zadelhoff et al. 2001; Aikawa et al. 2003; Qi et al. 2003; Thi et al. 2004; Dutrey et al. 2007; Piétu et al. 2007).”