Predictions for the secondary CO, C and O gas content of debris discs from the destruction of volatile-rich planetesimals
Authors: Quentin Kral, Luca Matra, Mark Wyatt, Grant Kennedy
Abstract
This paper uses observations of dusty debris discs, including a growing number of gas detections in these systems, to test our understanding of the origin and evolution of this gaseous component. It is assumed that all debris discs with icy planetesimals create second generation CO, C and O gas at some level, and the aim of this paper is to predict that level and assess its observability. We present a new semi-analytical equivalent of the numerical model of Kral et al. (2016) allowing application to large numbers of systems.That model assumes CO is produced from volatile-rich solid bodies at a rate that can be predicted from the debris disc's fractional luminosity. CO photodissociates rapidly into C and O that then evolve by viscous spreading. This model provides a good qualitative explanation of all current observations, with a few exceptional systems that likely have primordial gas. The radial location of the debris and stellar luminosity explain some non-detections, e.g. close-in debris (like HD 172555) is too warm to retain CO, while high stellar luminosities (like $η$ Tel) result in short CO lifetimes. We list the most promising targets for gas detections, predicting $>15$ CO detections and $>30$ CI detections with ALMA, and tens of CII and OI detections with future far-IR missions. We find that CO, CI, CII and OI gas should be modelled in non-LTE for most stars, and that CO, CI and OI lines will be optically thick for the most gas-rich systems. Finally, we find that radiation pressure, which can blow out CI around early-type stars, can be suppressed by self-shielding.
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Closest papers
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Modelling the Spatial Distribution and Origin of CO Gas in Debris DisksAntonio Hales, Uma Gorti, John Carpenter et al. · 2019 · Solar and Stellar Astrophysics · cited 10 times · AI summary available
Abstract
The detection of gas in debris disks raises the question of whether this gas is a remnant from the primordial protoplanetary phase, or released by the collision of secondary bodies. In this paper we analyze ALMA observations at 1-1.5" resolution of three debris disks where the $^{12}$CO(2-1) rotational line was detected: HD131835, HD138813, and HD156623. We apply the iterative Lucy-Richardson deconvolution technique to the problem of circumstellar disks to derive disk geometries and surface brightness distributions of the gas. The derived disk parameters are used as input for thermochemical models to test both primordial and cometary scenarios for the origin of the gas. We favor a secondary …
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The search for gas in debris discs: ALMA detection of CO gas in HD 36546Isabel Rebollido, Álvaro Ribas, Itziar de Gregorio-Monsalvo et al. · 2021 · Earth and Planetary Astrophysics · cited 10 times · Not summarized yet
Abstract
Debris discs represent the last stages of planet formation and as such are expected to be depleted of primordial gas. Nonetheless, in the last few years the presence of cold gas has been reported in $\sim$ 20 debris discs from far-IR to (sub-)mm observations and hot gas has been observed in the optical spectra of debris discs for decades. While the origin of this gas is still uncertain, most evidences point towards a secondary origin, as a result of collisions and evaporation of small bodies in the disc. In this paper, we present ALMA observations aimed at the detection of CO gas in a sample of 8 debris discs with optical gas detections. We report the detection of CO ($^{12}$CO and $^{13}$CO…
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Thermochemical constraints on a primordial-origin of gas-rich debris disksH. Mitani, W. Ooyama, R. Nakatani et al. · 2026 · arXiv (Cornell University) preprint · AI summary available
In short
Thermochemical models support a primordial origin for CO-rich debris disks under dust-poor, weak-ionisation conditions, but predict neutral-carbon emission more extended than observed.
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Thermochemical constraints on a primordial-origin of gas-rich debris disksH. Mitani, W. Ooyama, R. Nakatani et al. · 2026 · Earth and Planetary Astrophysics · AI summary available
In short
Dust-poor primordial-remnant disks can reproduce substantial CO, low neutral-carbon/CO ratios, and weak HCO+ under suppressed cosmic-ray ionisation, but their predicted neutral-carbon emission is too extended.
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A self-consistent model for the evolution of the gas produced in the debris disc of $β$ PictorisQuentin Kral, Mark Wyatt, Robert Carswell et al. · 2016 · Earth and Planetary Astrophysics · cited 68 times · Not summarized yet
Abstract
This paper presents a self-consistent model for the evolution of gas produced in the debris disc of $\beta$ Pictoris. Our model proposes that atomic carbon and oxygen are created from the photodissociation of CO, which is itself released from volatile-rich bodies in the debris disc due to grain-grain collisions or photodesorption. While the CO lasts less than one orbit, the atomic gas evolves by viscous spreading resulting in an accretion disc inside the parent belt and a decretion disc outside. The temperature, ionisation fraction and population levels of carbon and oxygen are followed with the photodissociation region model Cloudy, which is coupled to a dynamical viscous $\alpha$ model. We…
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A Deep Search for Five Molecules in the 49 Ceti Debris DiskJessica Klusmeyer, A. Meredith Hughes, Luca Matra et al. · 2021 · Solar and Stellar Astrophysics · cited 5 times · AI summary available
In short
A deep ALMA search detected none of five molecules beyond CO in 49 Ceti, supporting selective carbon shielding rather than necessarily unusual exocometary ice composition.
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New millimeter CO observations of the gas-rich debris disks 49 Cet and HD 32297Attila Moór, Quentin Kral, Péter Ábrahám et al. · 2019 · Earth and Planetary Astrophysics · cited 30 times · AI summary available
Abstract
Previous observations revealed the existence of CO gas at nearly protoplanetary level in several dust-rich debris disks around young A-type stars. Here we used the ALMA 7m-array to measure $^{13}$CO and C$^{18}$O emission toward two debris disks, 49 Cet and HD 32297, and detected similarly high CO content ($>$0.01M$_\oplus$). These high CO masses imply a highly efficient shielding of CO molecules against stellar and interstellar ultraviolet photons. Adapting a recent secondary gas disk model that considers both shielding by carbon atoms and self-shielding of CO, we can explain the observed CO level in both systems. Based on the derived gas densities we suggest that, in the HD 32297 disk, dus…
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The hybrid disks: a search and study to better understand evolution of disksJ. Pericaud, E. Di Folco, A. Dutrey et al. · 2016 · A&A 600, A62 (2017) · cited 33 times · AI summary available
Abstract
The increased sensitivity of millimeter-wave facilities now makes possible the detection of low amounts of gas in debris disks. Some of the gas-rich debris disks harbor peculiar properties, with possible pristine gas and secondary generated dust. The origin of the gas in these hybrid disks is strongly debated and the current sample is too sparse to understand this phenomenon. More detections are necessary to increase the statistics on this population. Lying at the final stages of evolution of proto-planetary disks and at the beginning of the debris disk phase, these objects could provide new insight into the processes involved in the making of planetary systems. We carried out a deep survey …
Prior work it builds on
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The magnetorotational instability in debris-disc gasQuentin Kral, Henrik Latter · 2016 · Earth and Planetary Astrophysics · cited 26 times · Not summarized yet
Abstract
Debris discs are commonly swathed in gas which can be observed in UV, in fine structure lines in FIR, and in resolved maps of CO emission. Carbon and oxygen are overabundant in such gas, but it is severely depleted in hydrogen. As a consequence, its ionisation fraction is remarkably high, suggesting magnetohydrodynamic (MHD) processes may be important. In particular, the gas may be subject to the magnetorotational instability (MRI), and indeed recent modelling of $\beta$ Pictoris requires an anomalous viscosity to explain the gas's observed radial structure. In this paper we explore the possibility that the MRI is active in debris-disc gas and responsible for the observed mass transport. We …
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Exocometary gas structure, origin and physical properties around β Pictoris through ALMA CO multitransition observationsL. Matrá, W. Dent, M. Wyatt et al. · 2016 · Monthly Notices of the Royal Astronomical Society · cited 84 times · Not summarized yet
Abstract
Recent ALMA observations unveiled the structure of CO gas in the 23 Myr old β Pictoris planetary system, a component that has been discovered in many similarly young debris discs. We here present ALMA CO J = 2−1 observations, at an improved spectro-spatial resolution and sensitivity compared to previous CO J = 3−2 observations. We find that (1) the CO clump is radially broad, favouring the resonant migration over the giant impact scenario for its dynamical origin, (2) the CO disc is vertically tilted compared to the main dust disc, at an angle consistent with the scattered light warp. We then use position-velocity diagrams to trace Keplerian radii in the orbital plane of the disc. Assuming a…
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DISCOVERY OF MOLECULAR GAS AROUND HD 131835 IN AN APEX MOLECULAR LINE SURVEY OF BRIGHT DEBRIS DISKSA. Moór, T. Henning, A. Juhász et al. · 2015 · The Astrophysical Journal · cited 51 times · Not summarized yet
Abstract
Debris disks are considered to be gas-poor, but recent observations revealed molecular or atomic gas in several 10–40 Myr old systems. We used the APEX and IRAM 30 m radio telescopes to search for CO gas in 20 bright debris disks. In one case, around the 16 Myr old A-type star HD 131835, we discovered a new gas-bearing debris disk, where the CO 3–2 transition was successfully detected. No other individual system exhibited a measurable CO signal. Our Herschel Space Observatory far-infrared images of HD 131835 marginally resolved the disk at both 70 and 100 μm, with a characteristic radius of ∼170 AU. While in stellar properties HD 131835 resembles β Pic, its dust disk properties are similar t…
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GAS EMISSION FROM DEBRIS DISKS AROUND A AND F STARSK. Zagorovsky, A. Brandeker, Yan-Qin Wu · 2010 · The Astrophysical Journal · cited 19 times · Not summarized yet
Abstract
Gas has been detected in a number of debris disk systems. This gas may have arisen from grain sublimation or grain photodesorption. It interacts with the surrounding dust grains through a number of charge and heat exchanges. Studying the chemical composition and physical state of this gas can therefore reveal much about the dust component in these debris disks. We have produced a new code, ontario, to address gas emission from dusty gas-poor disks around A–F stars. This code computes the gas ionization and thermal balance self-consistently, with particular care taken of heating/cooling mechanisms. Line emission spectra are then produced for each species (up to zinc) by statistical equilibriu…
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CO mass upper limits in the Fomalhaut ring - the importance of NLTE excitation in debris discs and future prospects with ALMAL. Matrá, O. Panic, M. Wyatt et al. · 2014 · Monthly Notices of the Royal Astronomical Society · cited 69 times · Not summarized yet
Abstract
In recent years, gas has been observed in an increasing number of debris discs, though its nature remains to be determined. Here, we analyse CO molecular excitation in optically thin debris discs, and search ALMA Cycle-0 data for CO J=3-2 emission in the Fomalhaut ring. No signicant line emission is observed; we set a 3upper limit
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Updated on 31 October 2026.