The molecular composition of the planet-forming regions of protoplanetary disks across the luminosity regime

Abstract

(Abridged) Near- to mid-IR observations of protoplanetary disks show that the inner regions (<10AU) are rich in small organic volatiles (e.g., C2H2 and HCN). Trends in the data suggest that disks around cooler stars (~3000K) are potentially more carbon- and molecule-rich than their hotter counterparts. Our aims are to explore the composition of the planet-forming region of disks around stars from M dwarf to Herbig Ae and compare with the observed trends. Models of the disk physical structure are coupled with a gas-grain chemical network to map the abundances in the planet-forming zone. N2 self shielding, X-ray-induced chemistry, and initial abundances, are investigated. The composition in the 'observable' atmosphere is compared with that in the midplane where the planet-building reservoir resides. M dwarf disk atmospheres are relatively more molecule rich than those for T Tauri or Herbig Ae disks. The weak far-UV flux helps retain this complexity which is enhanced by X-ray-induced ion-molecule chemistry. N2 self shielding has only a small effect and does not explain the higher C2H2/HCN ratios observed towards cooler stars. The models underproduce the OH/H2O column density ratios constrained in Herbig Ae disks, despite reproducing the absolute value for OH: H2O self shielding only increases this discrepency. The disk midplane content is sensitive to the initial main elemental reservoirs. The gas in the inner disk is generally more carbon rich than the midplane ices and is most significant for disks around cooler stars. The atmospheric C/O ratio appears larger than it actually is when calculated using observable tracers only because gas-phase O2 is predicted to be a significant oxygen reservoir. The models suggest that the gas in the inner regions of disks around cooler stars is more carbon rich; however, calculations of the molecular emission are necessary to confirm the observed trends.

28 pages (including the Appendix); 23 figures (including 6 in the Appendix); accepted for publication in Astronomy & Astrophysics; Figure 1 axes labels fixed and small typos corrected

References in corpus (26)

• The James Webb Space Telescope
• Complex Chemistry in Star-Forming Regions: An Expanded Gas-Grain Warm-up Chemical Model
• UV excess measures of accretion onto young very low-mass stars and brown dwarfs
• Interstellar water chemistry: from laboratory to observations
• Towards Chemical Constraints on Hot Jupiter Migration
• Complex organic molecules in protoplanetary disks
• Laboratory evidence for efficient water formation in interstellar ices
• Photoprocesses in protoplanetary disks
• H2O and OH gas in the terrestrial planet-forming zones of protoplanetary disks
• Formation of hydrogen peroxide and water from the reaction of cold hydrogen atoms with solid oxygen at 10K
• Molecular oxygen in the rho Ophiuchi cloud
• Formation of Water in the Warm Atmospheres of Protoplanetary Disks
• Gas-grain chemistry in cold interstellar cloud cores with a microscopic Monte Carlo approach to surface chemistry
• Isotope selective photodissociation of N2 by the interstellar radiation field and cosmic rays
• Formation of simple organic molecules in inner T Tauri disks
• Water vapor distribution in protoplanetary disks
• Gas composition of main volatile elements in protoplanetary discs and its implication for planet formation
• High-resolution Ultraviolet Radiation Fields of Classical T Tauri Stars
• Exploring the Origins of Carbon in Terrestrial Worlds
• Medium-separation binaries do not affect the first steps of planet formation
• Ro-vibrational excitation of an organic molecule (HCN) in protoplanetary disks
• Warm HCN, C2H2, and CO in the disk of GV Tau
• Shielding by Water and OH in FUV and X-ray Irradiated Protoplanetary Disks
• The Effects of Initial Abundances on Nitrogen in Protoplanetary Disks
• The Mid-infrared E-ELT Imager and Spectrograph (METIS)
• Effects of Reagent Rotation and Vibration on H + OH (v,j) $\to$ O + H2

Cited by in corpus (122)

• Photodissociation and photoionisation of atoms and molecules of astrophysical interest
• Astrochemistry and compositions of planetary systems
• First detection of gas-phase methanol in a protoplanetary disk
• Volatile carbon locking and release in protoplanetary disks. A study of TW Hya and HD 100546
• Lupus disks with faint CO isotopologues: low gas/dust or large carbon depletion?
• Setting the volatile composition of (exo)planet-building material. Does chemical evolution in disk midplanes matter?
• Molecular abundances and C/O ratios in chemically evolving planet-forming disk midplanes
• Water in star-forming regions (WISH): Physics and chemistry from clouds to disks as probed by Herschel spectroscopy
• Planet-forming material in a protoplanetary disc: the interplay between chemical evolution and pebble drift
• Peering into the formation history of beta Pictoris b with VLTI/GRAVITY long baseline interferometry
• CO destruction in protoplanetary disk midplanes: inside versus outside the CO snow surface
• Sensitivity analysis of grain surface chemistry to binding energies of ice species
• G11.92-0.61 MM1: A Keplerian disc around a massive young proto-O star
• HCN/HNC intensity ratio: a new chemical thermometer for the molecular ISM
• MINDS. The detection of ${}^{13}$CO${}_2$ with JWST-MIRI indicates abundant CO${}_2$ in a protoplanetary disk
• Robustness of N2H+ as tracer of the CO snowline
• Hints for icy pebble migration feeding an oxygen-rich chemistry in the inner planet-forming region of disks
• An ALMA survey of DCN/H${}^{13}$CN and DCO${}^{+}$/H${}^{13}$CO${}^{+}$ in protoplanetary disks
• Cometary ices in forming protoplanetary disc midplanes
• Molecules with ALMA at Planet-forming Scales (MAPS). VII. Sub-stellar O/H and C/H and super-stellar C/O in planet feeding gas
• A primordial origin for molecular oxygen in comets: A chemical kinetics study of the formation and survival of O${}_2$ ice from clouds to disks
• The depletion of water during dispersal of planet-forming disk regions
• First detection of gas-phase ammonia in a planet-forming disk
• CO2 infrared emission as a diagnostic of planet-forming regions of disks
• Abundant hydrocarbons in the disk around a very-low-mass star
• Unveiling the physical conditions of the youngest disks: A warm embedded disk in L1527
• Modelling mid-infrared molecular emission lines from T Tauri stars
• MINDS. Abundant water and varying C/O across the disk of Sz 98 as seen by JWST/MIRI
• Connecting planet formation and astrochemistry: Refractory carbon depletion leading to super-stellar C/O in giant planetary atmospheres
• Origin of molecular oxygen in Comet 67P/Churyumov-Gerasimenko
• CO emission tracing a warp or radial flow within $\lesssim$ 100 au in the HD 100546 protoplanetary disk
• OH mid-infrared emission as a diagnostic of H${}_2$O UV photodissociation. I. Model and application to the HH 211 shock
• Close-in ice lines and the super-stellar C/O ratio in discs around very low-mass stars
• The chemistry of disks around T Tauri and Herbig Ae/Be stars
• The diverse chemistry of protoplanetary disks as revealed by JWST
• Upper limits on CH${}_3$OH in the HD 163296 protoplanetary disk: evidence for a low gas-phase CH${}_3$OH/H${}_2$CO ratio
• Grand challenges in protoplanetary disc modelling
• X-ray photodesorption from water ice in protoplanetary disks and X-ray dominated regions
• The Chemical Inventory of the Inner Regions of Planet-forming Disks -- The JWST/MINDS Program
• The kinematics and excitation of infrared water vapor emission from planet-forming disks: results from spectrally-resolved surveys and guidelines for JWST spectra
• A Subarcsecond ALMA Molecular Line Imaging Survey of the Circumbinary, Protoplanetary Disk Orbiting V4046 Sgr
• The composition of hot Jupiter atmospheres assembled within chemically evolved protoplanetary discs
• Candidate Water Vapor Lines to Locate the H${}_2$O Snowline through High-Dispersion Spectroscopic Observations II. The Case of a Herbig Ae Star
• MINDS. Hydrocarbons detected by JWST/MIRI in the inner disk of Sz28 consistent with a high C/O gas-phase chemistry
• Observing Carbon & Oxygen Carriers in Protoplanetary Disks at Mid-infrared Wavelengths
• Candidate Water Vapor Lines to Locate the H${}_2$O Snowline through High-Dispersion Spectroscopic Observations I. The Case of a T Tauri Star
• Efficiency of radial transport of ices in protoplanetary disks probed with infrared observations: the case of CO${}_2$
• Cometary compositions compared with protoplanetary disk midplane chemical evolution. An emerging chemical evolution taxonomy for comets
• JWST Observations of Young protoStars (JOYS): overview of program and early results
• The carbon-to-oxygen ratio: implications for the spectra of hydrogen-dominated exoplanet atmospheres
• exoALMA V: Gaseous Emission Surfaces and Temperature Structures
• Dust continuum emission and the upper limit fluxes of sub-millimeter water lines of the protoplanetary disk around HD 163296 observed by ALMA
• The gas-phase reaction of NH2 with formaldehyde (CH2O) is not a source of formamide (NH2CHO) in interstellar environments
• X-ray induced chemistry of water and related molecules in low-mass protostellar envelopes
• Herbig Stars: A Quarter Century of Progress
• Chemical Feedbacks of Pebble Growth: Impacts on CO depletion and C/O ratios
• Methanol ice co-desorption as a mechanism to explain cold methanol in the gas-phase
• ALMA 870 $\mu$m continuum observations of HD 100546. Evidence of a giant planet on a wide orbit
• Exploring the link between star and planet formation with Ariel
• Missing water in Class I protostellar disks
• The dry and carbon poor inner disk of TW Hya: evidence for a massive icy dust trap
• Chemical evolution in ices on drifting, planet-forming pebbles
• CO2-rich protoplanetary discs as a probe of dust radial drift & trapping
• OH mid-infrared emission as a diagnostic of H${}_2$O UV photodissociation. III. Application to planet-forming disks
• The nitrogen carrier in protoplanetary disks
• Hydrocarbon chemistry in inner regions of planet forming disks
• Burned to ashes: How the thermal decomposition of refractory organics in the inner protoplanetary disc impacts the gas-phase C/O ratio
• Observing substructure in circumstellar discs around massive young stellar objects
• Imaging the water snowline in a protostellar envelope with H${}^{13}$CO${}^{+}$
• The effects of dust evolution on disks in the mid-IR
• MINDS. JWST-MIRI reveals a peculiar CO${}_2$-rich chemistry in the drift-dominated disk CX Tau
• A JWST/MIRI analysis of the ice distribution and PAH emission in the protoplanetary disk HH 48 NE
• Complex organic molecules in protoplanetary disks : X-ray photodesorption from methanol-containing ices. Part I -- Pure methanol ices
• Measuring elemental abundance ratios in protoplanetary disks at millimeter wavelengths
• Candidate Water Vapor Lines to Locate the ${\mathrm{H}}_2\mathrm{O}$ Snowline through High-dispersion Spectroscopic Observations. III. Submillimeter ${\mathrm{H}}_2$${}^{16}\mathrm{O}$ and ${\mathrm{H}}_2$${}^{18}\mathrm{O}$ Lines
• An ALMA Survey of Chemistry in Disks around M4-M5 Stars
• The edge-on protoplanetary disk HH 48 NE I. Modeling the geometry and stellar parameters
• The impact of pre-main sequence stellar evolution on midplane snowline locations and C/O in planet forming discs
• Formation of cometary O${}_2$ ice and related ice species on grain surfaces in the midplane of the pre-Solar nebula
• Chemical signatures of a warped protoplanetary disc
• Exploring HNC and HCN line emission as probes of the protoplanetary disk temperature
• Electric heating and angular momentum transport in laminar models of protoplanetary disks
• A major asymmetric ice trap in a planet-forming disk IV. Nitric oxide gas and a lack of CN tracing sublimating ices and a C/O ratio $<1$
• Catching the Birth of a Dark Molecular Cloud for the First Time
• The infrared line-emitting regions of T Tauri protoplanetary disks
• Inside-Out Planet Formation. VII. Astrochemical Models of Protoplanetary Disks and Implications for Planetary Compositions
• High-Resolution Mid-Infrared Spectroscopy of GV Tau N: Surface Accretion and Detection of Ammonia in a Young Protoplanetary Disk
• Complex organic molecules in protoplanetary disks: X-ray photodesorption from methanol-containing ices. Part II -- Mixed methanol-CO and methanol-H2O ices
• The Molecular Composition of Shadowed Protosolar Disk Midplanes beyond the Water Snowline
• First detections of H13CO+ and HC15N in the disk around HD 97048: Evidence for a cold gas reservoir in the outer disk
• Planck Cold Clumps in the lambda Orionis Complex. III. A chemical probe of stellar feedback on cores in the lambda Orionis cloud
• Radial and vertical constraints on the icy origin of H${}_2$CO in the HD 163296 Protoplanetary Disk
• ALMA reveals thermal and non-thermal desorption of methanol ice in the HD 100546 protoplanetary disk
• Water shielding in the terrestrial planet-forming zone: Implication for inner disk organics
• Astrochemical modelling of infrared dark clouds
• Thermochemical modelling of brown dwarf discs
• Probing UV-Sensitive Pathways for CN and HCN Formation in Protoplanetary Disks with the Hubble Space Telescope
• Complex cyanides as chemical clocks in hot cores
• Modeling snowline locations in protostars: The impact of the structure of protostellar cloud cores
• Connecting Planetary Composition with Formation
• Signatures of Hot Molecular Hydrogen Absorption from Protoplanetary Disks: I. Non-thermal Populations
• Using HCO${}^{+}$ isotopologues as tracers of gas depletion in protoplanetary disk gaps
• Chemical transformation of CO in evolving protoplanetary discs across stellar masses: a route to C-rich inner regions
• An inherited complex organic molecule reservoir in a warm planet-hosting disk
• Deuterium Chemodynamics of Massive Pre-Stellar Cores
• An SMA Survey of Chemistry in Disks around Herbig AeBe Stars
• Lyman-alpha Scattering Models Trace Accretion and Outflow Kinematics in T Tauri Systems
• Chemical evolution in planet-forming regions with growing grains
• Understanding JWST water spectra: what can thermochemical models tell us about the (cold) water in protoplanetary disks?
• Planet formation in chemically diverse and evolving discs -- I. Composition of planetary building blocks
• Water and OH Emission from the inner disk of a Herbig Ae/Be star
• MINDS. Strong oxygen depletion in the inner regions of a very low-mass star disk?
• Connecting planet formation and astrochemistry: C/O and N/O of warm giant planets and Jupiter-analogs
• Gas dynamics around a Jupiter mass planet: II. Chemical evolution of circumplanetary material
• Radii, masses, and transit-timing variations of the three-planet system orbiting the naked-eye star TOI-396
• C/O ratios in self-gravitating protoplanetary discs with dust evolution
• Tree-based solvers for adaptive mesh refinement code FLASH -- IV: An X-ray radiation scheme to couple discrete and diffuse X-ray emission sources to the thermochemistry of the interstellar medium
• The effect of carbon grain destruction on the chemical structure of protoplanetary disks
• Protoplanetary Disk Chemistry
• Water UV-shielding in the terrestrial planet-forming zone: Implications from water emission
• Chemical complexity in protoplanetary disks in the era of ALMA and Rosetta
• Linking Outer Disk Pebble Dynamics and Gaps to Inner Disk Water Enrichment