| Title: |
Characterising the molecular line emission in the asymmetric Oph-IRS 48 dust trap: Temperatures, timescales, and sub-thermal excitation |
| Authors: |
Temmink, M.; Booth, A.S.; Leemker, M.; van der Marel, N.; van Dishoeck, E.F.; Evans, L.; Keyte, L.; Law, C.J.; Notsu, S.; Öberg, K.; Walsh, C. |
| Publisher Information: |
EDP Sciences |
| Publication Year: |
2025 |
| Collection: |
White Rose Research Online (Universities of Leeds, Sheffield & York) |
| Description: |
Context. The ongoing physical and chemical processes in planet-forming disks set the stage for planet (and comet) formation. The asymmetric disk around the young star Oph-IRS 48 has one of the most well-characterised chemical inventories, showing molecular emission from a wide variety of species at the dust trap: from simple molecules, such as CO, SO, SO₂, and H₂CO, to large complex organics, such as CH₂OH, CH₃OCHO, and CH₃OCH₃. One of the explanations for the asymmetric structure in the disk is dust trapping by a perturbation-induced vortex. Aims. We aimed to constrain the excitation properties of the molecular species SO₂, CH₃OH, and H₂CO, for which we have used 13, 22, and 7 transitions of each species, respectively. We further characterised the extent of the molecular emission, which differs among molecules, through the determination of important physical and chemical timescales at the location of the dust trap. We also investigated whether the anticyclonic motion of the potential vortex influences the observable temperature structure of the gas. Methods. Through a pixel-by-pixel rotational diagram analysis, we created maps of the rotational temperatures and column densities of SO₂ and CH₃OH. To determine the temperature structure of H₂CO, we have used line ratios of the various transitions in combination with non-local thermal equilibrium (LTE) RADEX calculations. The timescales for freeze-out, desorption, photodissociation, and turbulent mixing at the location of the dust trap were determined using an existing thermochemical model. Results. Our rotational diagram analysis yields temperatures of T = 54.8±1.4 K (SO₂) and T = 125.5−3.5+3.7 K (CH₃OH) at the emission peak positions of the respective lines. As the SO₂rotational diagram is well characterised and points towards thermalised emission, the emission must originate from a layer close to the midplane where the gas densities are high enough. The rotational diagram of CH₃OH is, in contrast, dominated by scatter and subsequent non-LTE RADEX calculations ... |
| Document Type: |
article in journal/newspaper |
| File Description: |
text |
| Language: |
English |
| ISSN: |
0004-6361 |
| Relation: |
https://eprints.whiterose.ac.uk/id/eprint/221674/1/aa52175-24.pdf; Temmink, M., Booth, A.S., Leemker, M. et al. (8 more authors) (2025) Characterising the molecular line emission in the asymmetric Oph-IRS 48 dust trap: Temperatures, timescales, and sub-thermal excitation. Astronomy & Astrophysics, 693. A101. ISSN: 0004-6361 |
| Availability: |
https://eprints.whiterose.ac.uk/id/eprint/221674/ |
| Rights: |
cc_by_4 |
| Accession Number: |
edsbas.2C2BFA2B |
| Database: |
BASE |