A PARAMETRIC MODELING APPROACH TO MEASURING THE GAS MASSES OF CIRCUMSTELLAR DISKS

By Jonathan P. Williams, W. Best. 2013

186 citations recorded by the source corpus.

The disks that surround young stars are mostly composed of molecular gas, which is harder to detect and interpret than the accompanying dust. Disk mass measurements have therefore relied on large and uncertain extrapolations from the dust to the gas. We have developed a grid of models to study the dependencies of isotopologue CO line strengths on disk structure and temperature parameters and find that a combination of 13CO and C18O observations provides a robust measure of the gas mass. We apply this technique to Submillimeter Array observations of nine circumstellar disks and published measurements of six well studied disks. We find evidence for selective photodissociation of C18O and determine masses to within a factor of about three. The inferred masses for the nine disks in our survey range from 0.7 to 6 MJup, and all are well below the extrapolation from the interstellar medium gas-to-dust ratio of 100. This is consistent with the low masses of planets found around such stars, and may be due to accretion or photoevaporation of a dust-poor upper atmosphere. However, the masses may be underestimated if there are more efficient CO depletion pathways than those known in molecular clouds and cold cores.

Subfields: Astronomy and Astrophysics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/35048d7248c59e00e5e713291eb5ac9874ae77f4

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Citations in the corpus

Observational Signatures of Planets in Protoplanetary Disks I: Gaps Opened by Single and Multiple Young Planets in Disks (2014, background): “We note that observational results have shown that the gas-todust mass ratio can be quite low (as low as ∼20) in some Class II disks (Williams & Best 2014).”
An ALMA Survey of Protoplanetary Disks in the σ Orionis Cluster (2017, methodology): “…2 01 7 2 Recent observations suggest that the inherited ISM ratio may actually decrease by an order of magnitude after just a few Myr of evolution (Williams & Best 2014; Ansdell et al. 2016), although these calculations may be underestimated due to carbon depletion (e.g., Miotello et al. 2016b).”
ALMA SURVEY OF LUPUS PROTOPLANETARY DISKS. I. DUST AND GAS MASSES (2016, methodology): “Surveys of the optically thick infrared (IR) emission across young stellar clusters have constrained the disk dispersal timescale to ∼10 Myr, providing important checks on planet formation theories (Haisch et al. 2001; Hernández et al. 2007; Evans et al. 2009).”
Gravitational Instabilities in Circumstellar Disks (2016, background): “Williams & Best (2014) used optically thick and thin CO isotopologues and conclude that most Class II disks have dust-to-gas ratios up to a factor of 10 below ISM values, implying that either planet formation is well underway, or total disk masses are even smaller.”
Accretion disks in luminous young stellar objects (2015, background): “Dust related processes such as grain growth and dust settling could result in a predominantly gaseous disk atmosphere that would be subject to photo-evaporation leading to gaseous disks winds or to the selective accretion of gas onto the central star (e.g., Williams & Best, 2014).”
A STEEPER THAN LINEAR DISK MASS–STELLAR MASS SCALING RELATION (2016, background): “…recent gas mass estimates using rotational lines from CO isotopologues have claimed gas-to-dust ratios well below the ISM value in young disks (Williams & Best 2014; Ansdell et al. 2016), detailed physico-chemical disk models need to be carried out to properly account for isotope-selective…”
WEAK TURBULENCE IN THE HD 163296 PROTOPLANETARY DISK REVEALED BY ALMA CO OBSERVATIONS (2015, methodology): “This model is based on the work of Rosenfeld et al. (2012, 2013), itself based on the structure laid out in Dartois et al. (2003), and has successfully been used to model CO emission from other disks (Andrews et al. 2012; Rosenfeld et al. 2012, 2013b, 2014; Williams & Best 2014).”
ALMA Survey of Lupus Protoplanetary Disks. II. Gas Disk Radii (2018, background): “Williams & Best (2014) and Ansdell et al. (2016).”
MAKE SUPER-EARTHS, NOT JUPITERS: ACCRETING NEBULAR GAS ONTO SOLID CORES AT 0.1 AU AND BEYOND (2014, methodology): “The protoplanetary disk TW Hydra is observed to have a dust-to-gas ratio that decreases radially outward (Andrews et al. 2012; see also Williams & Best 2014).”