The chemistry of protoplanetary disks

The chemistry of protoplanetary disks CNAP Assistant Astronomer at IPAG / IRAM / UGA [Credit: Pat Rawlings / NASA] Romane Le Gal Romane.Le-Gal [at] univ-grenoble-alpes.fr 1. Why studying protoplanetary disk chemistry? ! => What for? How?" 2. Can we probe the chemistry at planet-forming scales?! => Which facilities to use? Are there specific tracers?" 3. How to disentangle between chemical inheritance & chemical reprocessing in protoplanetary disks? ! => Can we detect signs of inheritance from earlier stages? Outline 1. Why studying protoplanetary disk chemistry? ! => What for? How?" 2. Can we probe the chemistry at planet-forming scales?! => Which facilities to use? Are there specific tracers?" 3. How to disentangle between chemical inheritance & chemical reprocessing in protoplanetary disks? ! => Can we detect signs of inheritance from earlier stages? Outline Most stars hosts his own planetary system [Credit: M. Kornmesse/ESO] Planet bestiary [Credit: M. Vargic] Planetary system Molecular cloud Protostar Protoplanetary disk Protoplanetary disks ~0.5-3 Myr ~0.1Myr ~3-10Myr > 10 Myr [Credit: Bill Saxton NSF/AUI/NRAO] •Pivotal stage in evolution from interstellar molecular clouds to planetary systems. Protoplanetary disks [Credit: Bill Saxton NSF/AUI/NRAO] ~0.5-3 Myr ~0.1Myr ~3-10Myr > 10 Myr Planetary system Molecular cloud Protostar Protoplanetary disk •Pivotal stage in evolution from interstellar molecular clouds to planetary systems. •How does their chemical compositions and structures influence the future compositions of forming planets? Chemistry in protoplanetary disks • Formation, excitation & destruction of molecules ? •Pivotal stage in evolution from interstellar molecular clouds to planetary systems. •How does their chemical compositions and structures influence the future compositions of forming planets? [Credit: Bill Saxton NSF/AUI/NRAO] ~0.5-3 Myr ~0.1Myr ~3-10Myr > 10 Myr Planetary system Molecular cloud Protostar Protoplanetary disk • Formation, excitation & destruction of molecules ? • Are molecules preserved from their initial formation in molecular clouds? • Are molecules preserved from their initial formation in molecular clouds? [Credit: Bill Saxton NSF/AUI/NRAO] ~0.5-3 Myr ~0.1Myr ~3-10Myr > 10 Myr Chemistry in protoplanetary disks Planetary system Molecular cloud Protostar Protoplanetary disk •Pivotal stage in evolution from interstellar molecular clouds to planetary systems. •How does their chemical compositions and structures influence the future compositions of forming planets? HS+ NS SO SO2 HCS+ CS HSCN C3S C2S OCS HS SO+ CS+ S+ S HNCSH+ H2CS+ HCS HSO2+ S H3+ O, OH C+, H+ OH, O2 C2 H C, C+ HO O CH2 C+ H3+, HCO+,! H3O+ C, C+ H+ CH3+ H2O N CH3 H H H H N He+ H2 H2CS C, N, O O, C, S C H2S NS+ N N NH HO C C+ C, C+ H+ C+ O CO He+ H3+, ! HCO+,! H3O+ C N H2S+ H2 H,O HNC S H3CS+ H3+, HCO+ CH2 S C+ C+ C2H C+ H3+, HCO+, H3O+ O C+ C NH C+, H+ C+ N * * * * * * HC3S+ HC2S+ solid state reactions gas-phase reactions electronic recombinations * prestellar core (L1544) PDR (Horsehead) protostellar envelope! (IRAS16293-2422) Intermediate species Schematic “simplified” view of the ISM sulfur chemical network Adapted from: Vastel, Quénard, Le Gal et al. 2018, MNRAS, 478, 5514 [Vastel, Quénard, Le Gal+ 2018] [Drozdovskaya+ 2018] [Rivière-Marichalar, …,! Le Gal+ 2019] Physical properties of the modeled source (Tgaz , n, AV , ζ, G0 , ...)" 0D / 1D / 2D Physical properties of interstellar dust ! (Tdust , r, …) Physical properties of molecules ! (m, Ebinding, ...) Code Chemical network" (pure gas phase, gas/grains, grains) Chemical composition (elemental & initial) Chemical species abundances as function of time Astrochemical modeling Proto-planetary disk structure Henning & Semenov, Chemical Reviews, 113, 9016, 2013 Proto-planetary disk structure Henning & Semenov, Chemical Reviews, 113, 9016, 2013 Cold mid-plane Photon-dominated layer Lukewarm molecular layer Proto-planetary disk structure Proto-planetary disk structure Photon-dominated layer Lukewarm molecular layer Cold mid-plane Proto-planetary disk structure Photon-dominated layer Lukewarm molecular layer Le Gal et al. 2019a, ApJ, 876, 72 Cold mid-plane Disk chemistry modelling results ALMA observation of CS gap Understanding of the observed abundance & spatial structure of the most accessible sulfur molecule in disks. Models versus Observations: CS case Modeling results First H2CS detection in disks [Le Gal et al. 2019a, ApJ, 876, 72] • Observations of 3 transitions of H2CS: ➡ detected in MWC 480 ➡ tentatively detected in LkCa15 •H2CS/CS 2/3 >> H2S/CS 1/20 ➡ part of the S-reservoir in disks is in organic form (i.e. CxHySz) ≈ ≈ Molecules with ALMA at Planet-forming Scales Team: 5 co-PIs: K. Öberg,"Y. Aikawa,"E. Bergin, V. Guzmán,C. Walsh + 39 co-Is!" http://alma-maps.info Zoom in on five of the brightest lines in one single disk: HD 163296 [ Öberg & MAPS collaboration, ApJS, 2021, 257, 1] Variety of emission morphologies and radial intensity profiles for a single line: HCN 3-2 [ Öberg & MAPS collaboration, ApJS, 2021, 257, 1] Molecules with ALMA at Planet-forming Scales [ Öberg & MAPS collaboration, ApJS, 2021, 257, 1] •5 discs with signs of ongoing planet formation" •4 spectral settings across B3 & B6 " •20 species including CS http://alma-maps.info [ Le Gal et al. 2019, ApJ, 876, 72 ] Disk-integrated column densities MAPS disks [ Le Gal & MAPS collaboration, 2021, ApJS, 257, 12] [ Le Gal et al. 2019, ApJ, 876, 72 ] CS column density is rather flat in disks. Disk-integrated column densities MAPS disks [ Le Gal & MAPS collaboration, 2021, ApJS, 257, 12] Disk chemistry modeling results => CS/SO ratio is a promising probe for the C/O ratio in disks [Bergin et al. 1997, Semenov et al. 2018] Modeling results vs observations in MWC 480 [ Le Gal & MAPS collaboration, 2021, ApJS, 257, 12] Disk chemistry modeling results CH3CN Column density (cm-2) Radius (au) Modeling results vs observations in MWC 480 [Le Gal et al. 2019b, ApJ, 876, 86] => CS/SO ratio is a promising probe for the C/O ratio in disks [Bergin et al. 1997, Semenov et al. 2018] [ Le Gal & MAPS collaboration, 2021, ApJS, 257, 12] CS/SO probe for the C/O elemental ratio Modeling results vs observations in MWC 480 CS/SO observed in all five MAPS disks C/O ratio 1 in most disks of our sample => What does this telling us? ≳ [ Le Gal & MAPS collaboration, 2021, ApJS, 257, 12] Why probing the C/O ratio? [Bergin & Cleeves 2018] [Öberg & Bergin 2021] 1. Why studying protoplanetary disk chemistry? ! => What for? How?" 2. Probing the chemistry at planet-forming scales ! => High angular resolution observations in disks" 3. Disentangling between chemical inheritance & chemical reprocessing in protoplanetary disks: ! => Observations of earlier evolutionary stage Outline 1. Why studying protoplanetary disk chemistry? ! => What for? How?" 2. Can we probe the chemistry at planet-forming scales?! => Which facilities to use? Are there specific tracers?" 3. How to disentangle between chemical inheritance & chemical reprocessing in protoplanetary disks? ! => Can we detect signs of inheritance from earlier stages? Chemical exploration of Class I YSOs [Adapted from: Bill Saxton NSF/AUI/NRAO] • Several spectral surveys probed the chemistry of: (1) the earliest stages of star formation: ‣TIMASSS (Caux+2011), ‣PILS (Jorgensen+2016), ‣ASAI (Lefloch+2018), ‣SOLIS (Ceccarelli+2017), ‣FAUST (Codella+2021) (2) and of late planetforming disks: ‣DISCS (Öberg+2010, 2011), ‣CID (Guilloteau+2016), ‣ALMA-MAPS (Öberg+2021) (ALMA Partnership 2015) HL Tau (Class I disk) Segura-cox+2020 (Nature) IRS 63 (Class I disk) Chemical exploration of Class I YSOs [Adapted from: Bill Saxton NSF/AUI/NRAO] [Le Gal, Öberg, Huang, Law, Ménard, Lefloch, Vastel, Lopez-Sepulcre, Favre, Bianchi, Ceccarelli et al. 2020, ApJ, 898,131] The CHEMYSO survey [PI: Le Gal, 140 hr / IRAM, 17 co-Is] • Several spectral surveys probed the chemistry of: (1) the earliest stages of star formation: ‣TIMASSS (Caux+2011), ‣PILS (Jorgensen+2016), ‣ASAI (Lefloch+2018), ‣SOLIS (Ceccarelli+2017), ‣FAUST (Codella+2021) (2) and of late planetforming disks: ‣DISCS (Öberg+2010, 2011), ‣CID (Guilloteau+2016), ‣ALMA-MAPS (Öberg+2021) • Highly deuterated gas, but opacity effects are observed for the brightest lines • N2D+ & 13C isotopologues are optically thin => pretty constant D/H ratio • ~ constant D/H ratio => similar thermal histories or thermal structures? [Huang& Öberg 2015;! Salinas et al. 2017] [Huang+2017] [Huang+2017] [Le Gal et al. 2020, ApJ, 898, 131] Class II Class II Class II Common diagnostics of chemical inheritance: D/H tracers •HCN/HC15N: span in evolutionary stage if the isotopic ratio is inherited! or span in physical properties of our sample, if the ratio is reset in situ •CN/HCN: highest in I-04365, second most luminous source of our sample [Guzman+2017] [Hily-Blant+2019] [Magalhaes+2018] The UV-field strength: a major chemical reprocessing agent? [Le Gal et al. 2020, ApJ, 898, 131] ❖Class I YSOs are molecule-rich! (at least our of 7 source sample…, Le Gal et al. 2020): ‣30 small (Natoms 3) molecules detected: C, N, O, and S carriers (e.g. small cyanides, hydrocarbons, etc.) and variety of D,13C, 15N, 18O, 17O and 34S isotopologues ‣Other organics (Natoms 3) & COMs: H2CO, C3H2, CH3OH, HC3N, CH3CHO, etc. ❖Statistical analysis: tracers of (i) dense cold gas, (i) shocked gas & dense ionized gas ❖Interferometric observations needed to distinguish between envelope & disk chemistry => NOEMA data (Tanious, Le Gal et al. 2024, A&A)! ! ! ❖Future plans: Extent the source sample & increase the statistics and demography ! ≤ > PHD of M. Tanious First results of the CHEMYSO survey From cloud to protostellar system From cloud to protoplanetary disk in prep ➢With the high spectral and spatial resolution of the last generation of telescopes (e.g. ALMA and now NOEMA!) we can now study in details the chemical compositions and structures of planet-forming disks: ✦Mapping out the vertical and radial distributions of the molecular gas, e.g. with CS, the most readily observed S-bearing molecule in disks ✦H2CS/CS ~ 2/3 => S-reservoir in disks could be more organic than thought! ✦Search for new species in disks predicted by models & obs. in astrophysical objects." ✦Synergy with JWST (GTO & GO programs) to probe the icy and warm gas disk composition! ➢Astrochemical modelling needed to interpret observations (chemical history & astrophysical probes)" ✦CS/SO is a promising probe for the elemental C/O ratio ✦C/O 0.9 in the MWC 480 disk, in agreement with nitriles observations (Le Gal et al. 2019b) & with independent disk model based on CO and C2H observations (MAPS coll.)" ✦S/H ratio in between the highly depleted value of dense molecular core and the Solar value => part of the sulfur is released from molecular cloud to protoplanetary disk stages (?)" ➢Identify what chemical abundances can be expected on nascent planets ≠ ≳ Summary and perspectives Backup slides