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Radial variations in nitrogen, carbon, and hydrogen fractionation in the PDS 70 planet-hosting disk

Luna, Rampinelli

Publisher
Zenodo
DOI
10.5281/zenodo.17108813
Repository
zenodo.org
Language
en

Abstract

Recent exoplanetary studies revealed a broad diversity in the exoplanetary population, suggesting that the outcomes of planet formation are similarly diverse. Footprints of the journey of building blocks of planets are stored in exoplanetary atmospheres, which are the result of a complex chemical evolution from the parental cloud down to protoplanetary disks. In particular, isotopic ratios of the main elements (hydrogen, carbon, nitrogen, oxygen) are powerful tracers of the formation history of planetary material. While isotopic ratios have been measured for a variety of astronomical objects along the timeline of planet formation, a complete study of isotope fractionation at the protoplanetary disk stage is still missing. I will present ALMA high resolution line emission observations of the PDS 70 disk, which is the best source where to test the chemical link between forming planets and their natal environment, as it is the only disk with two multi-wavelength directly detected protoplanets. Thanks to the unprecedented spatial resolution, I will show radially resolved 14N/15N, 12C/13C, and H/D ratios extracted from HCN isotopologues observations. In particular, radial variations of fractionation levels reveal how different fractionation processes dominate at different planet-forming scales. In this context, I will show how the presence of two giant protoplanets affects the radial profiles of isotopic ratios in a planet-hosting disk.

Full text

Radial variations in nitrogen, carbon, and hydrogen fractionation in the PDS 70 planet-hosting disk Towards New Frontiers: The Astrochemical Journey from Young Stellar Nurseries to Exoplanets Luna Rampinelli –ESO 2025 2° year PhD student –Università degli Studi di Milano Collaborators: Facchini S., Leemker M., Andrews S., Bae J., Benisty M., Curone P., Cridland A., Law C.J., Öberg K., Portilla-Revelo B., Teague R. ERC project UNVEIL, G.A. no. 101076613 Multiwavelength direct detection of two forming planets in the large cavity Astrochemistry in the PDS 70 disk as benchmark 1 Benisty+2021 Haffert+2019 Rampinelli+2024 Planet formation shaping molecular emission in the PDS 70 disk Chemical link between planets and disk Rampinelli+2024, Benisty+2021 2 Isotope fractionation of HCN from high spatial resolution ALMA observations Chemical link between planets and disk Rampinelli+2024, Benisty+2021 3 Chemical link between planets and disk Isotopic ratios as direct tracers of volatiles history Nomura+2022 Zhang+2021, Gandhi+2023 Barrado+2023 4 Chemical link between planets and disk Isotopic ratios as direct tracers of volatiles history 5 Complex picture: •Different environmental conditions •Different molecular tracers •Gas vs ices •Radial variations in the same object Nomura+2022 Isotopologue fractionation in disks Radial variations reveal local fractionation pathways 6 Hily-Blant+2019, Nomura+2023, Guzman+(in prep.) TW Hya V4046 Sgr Isotopologue fractionation in disks Radial variations reveal local fractionation pathways 7 Hily-Blant+2019, Nomura+2023, Guzman+(in prep.) Isotope selective photodissociation TW Hya V4046 Sgr Nitrogen fractionation of HCN Formation and fractionation of HCN depend on the UV field 8 Visser+2018 HCN formed from UV-pumped H2 Radial profile of HCN/HC15N assuming a radially constant 12C/13C = 69 15 Rampinelli+(subm.) Isotope fractionation of HCN in PDS 70 Assuming N(HCN) = 69 x N(H13CN) HCN/HC15N in PDS 70 Rampinelli+(subm.), Hily-Blant+2019, Nomura+2023 Decreasing 14N/15N profile for HCN beyond the dust cavity 16 Visser+2018 HCN/HC15N in PDS 70 Decreasing trend in the outer disk: N2isotope selective photodissociation 17 Prediction from thermochemical models of typical T Tauri disks Visser+2018 HCN/HC15N in PDS 70 Decreasing trend in the outer disk: N2isotope selective photodissociation 18 Deuteration of HCN in PDS 70 Radial profile of N(DCN) by assuming Tex(DCN)=Tex(H13CN) 19 Rampinelli+(subm.) Deuteration of HCN in PDS 70 Radial profile of N(DCN) consistent with N(H13CN) 20 Rampinelli+(subm.) Deuteration of HCN in PDS 70 Deuteration and nitrogen fractionation profiles do not correlate 21 Rampinelli+(subm.) Deuteration of HCN in PDS 70 22 Rampinelli+(subm.) Isotope selective photodissociation Deuteration and nitrogen fractionation profiles do not correlate Deuteration of HCN in PDS 70 23 Rampinelli+(subm.) Gas phase isotope exchange reactions Deuteration and nitrogen fractionation profiles do not correlate HCN/H13CN in PDS 70 24 Rampinelli+(subm.) HCN column density is needed to extract the radial profile of 12C/13C •Assumption of radially constant 12C/13C has to be verified HCN/H13CN in PDS 70 LB observations cover the hyperfine but half of the main HCN component 31 Double-Gaussian fit to extract the hyperfine flux Rampinelli+(subm.) HCN/H13CN in PDS 70 Extract HCN column density from the optically thin hyperfine component 32 Rampinelli+(subm.) HCN/H13CN consistent with ISM value 33 HCN/H13CN in PDS 70 Rampinelli+(subm.) HCN/H13CN consistent with ISM value 34 Huge uncertainties at small and large radii HCN/H13CN in PDS 70 Rampinelli+(subm.) HCN/H13CN consistent with ISM value 35 HCN/H13CN in PDS 70 Rampinelli+(subm.) HCN fractionation in disks Radial variations reveal local fractionation processes in disks 36 Rampinelli+(subm.)Hily-Blant+2019, Guzman+(in prep.), Cataldi+2021 HCN fractionation in astronomical objects HCN fractionation along timeline of star and planet formation 37 Rampinelli+ (subm.) Conclusions HCN fractionation in PDS 70: 1.Radial profiles of HCN/H13CN, HCN/HC15N, and DCN/HCN in the PDS 70 disk 2.PDS 70 results consistent with other disks suggesting similar fractionation processes in disks 3.Radial variations of isotope ratios reveal how fractionation pathways act at different spatial scales 38 Back-up Nitrogen fractionation •Low temperature isotope exchange reactions •Isotope selective photodissociation Efficient self-shielding of N2 Rampinelli+2024 Rampinelli+2024