Investigating the asymmetric chemistry in the disk around the young star HD 142527

Abstract

The atmospheric composition of planets is determined by the chemistry of the disks in which they form. Studying the gas-phase molecular composition of disks thus allows us to infer what the atmospheric composition of forming planets might be. Recent observations of the IRS 48 disk have shown that (asymmetric) dust traps can directly impact the observable chemistry through (radial and vertical) transport and the sublimation of ices. The asymmetric HD 142527 disk provides another good opportunity to investigate the role of dust traps in setting the disk’s chemical composition. In this work we use archival ALMA observations of the HD 142527 disk to obtain a molecular inventory that is as large as possible in order to investigate the possible influence of the asymmetric dust trap on the disk’s chemistry. We present the first ALMA detections of [C I], 13C18O, DCO+, H2CO, and additional transitions of HCO+ and CS in this disk. In addition, we present upper limits for non-detected species such as SO and CH3OH. For the majority of the observed molecules, a decrement in the emission at the location of the dust trap is found. For the main CO isotopologues, continuum oversubtraction is the likely cause of the observed asymmetry, while for CS and HCN we propose that the observed asymmetries are likely due to shadows cast by the misaligned inner disk. As the emission of the observed molecules is not co-spatial with the dust trap, and no SO or CH3OH is found, thermal sublimation of icy mantles does not appear to play a major role in changing the gas-phase composition of the outer disk in HD 142527 disk. Using our observations of 13C18O and DCO+ and a RADMC-3D model, we determine the CO snowline to be located beyond the dust traps, favouring cold gas-phase formation of H2CO rather than the hydrogenation of CO-ice and subsequent sublimation.

CI Traces the Disk Atmosphere in the IM Lup Protoplanetary Disk

“…Although IM Lup and HD 142527 are both disks around T Tauri stars, they show more than one order of magnitude difference in their C I column densities. The IM Lup disk is also one order of magnitude more massive (Zhang et al 2021;Lodato et al 2023) than that of HD 142527 (Temmink et al 2023), which implies that the inferred C I column density is not particularly sensitive to the total disk mass, as previously indicated in the models of Pascucci et al (2023). The large millimeter dust cavity (≈100 au) of the HD 142527 disk leads to increased UV transparency, and thus also likely contributes to its larger C I column density.…”

“…For the sake of comparison with other disks, we also computed a disk-averaged N col ≈ 2 × 10 16 cm −2 . Among disks with spatially resolved C I, this is approximately one order of magnitude lower than that of HD 142527 (Temmink et al 2023) and HD 163296 (Alarcón et al 2022) and a factor of a few less than the HD 169142 disk (Booth et al 2023).…”

“…However, the majority of existing C I detections are spatially unresolved. Even for those few existing spatially resolved observations, most are at modest angular resolutions (0 5-1″; e.g., Alarcón et al 2022;Booth et al 2023;Temmink et al 2023). This has prohibited a detailed understanding of the C I emission structure, namely, while it is widely assumed that C I traces the disk upper layers, no observations to date have directly confirmed this or pinpointed the exact location of the transition region between C I and the CO molecular layer.…”

An ALMA Molecular Inventory of Warm Herbig Ae Disks. I. Molecular Rings, Asymmetries, and Complexity in the HD 100546 Disk

“…The only other chemically well-studied transition disk around a Herbig source is HD 142527. Observations so far do not show bright CH 3 OH or SO emission, however, the millimeter dust (and ice) trap is located further from the star where it remains too cold for thermal ice sublimation (Temmink et al 2023).…”

An ALMA Molecular Inventory of Warm Herbig Ae Disks. II. Abundant Complex Organics and Volatile Sulphur in the IRS 48 Disk

“…The HCO + abundance in the IRS 48 disk is similarly low as found in HD 100546 and HD 142527, which is 2 orders of magnitude lower than found in the HD 163296 and MWC 480 disks (see Table 4; Aikawa et al 2021;Temmink et al 2023;Booth et al 2024, priv. comm.…”