| Name: | Shridharan Baskaran |
| Affiliation: | Tata Institute of Fundamental Research |
| Conference ID: | ASI2025_318 |
| Title: | A New Look at Protoplanetary Disk Accretion: Mid-Infrared HI Line Analysis from JWST-MIRI |
| Authors: | B. Shridharan 1, P. Manoj 1, Vinod Pathak 1, Bihan Banerjee 1, H. Tyagi 1, Mayank Narang 2, Blesson Mathew 3, R. Arun 4, Sujay Jadhav 1 |
| Authors Affiliation: | 1 B. Shridharan, P. Manoj, Vinod Pathak, Bihan Banerjee, H. Tyagi, Sujay Jadhav Tata Institute of Fundamental Research, Mumbai, India
2 Mayank Narang Academia Sinica Institute of Astronomy & Astrophysics, Taipei 10617, Taiwan
3 Blesson Mathew CHRIST (Deemed to be University), India
4 R. Arun Indian Institute of Astrophysics |
| Mode of Presentation: | Oral |
| Abstract Category: | Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Abstract: | The balance between accretion and ejection of material in protoplanetary disks regulates the mass reservoir available for planet formation. Traditionally, optical and near-infrared (NIR) HI lines, such as Hα, Paβ, and Brγ, have been used to estimate accretion in young stellar objects (YSOs). However, these lines suffer from opacity effects to varying degrees and may originate from different regions, such as winds and jets, complicating their use as reliable accretion indicators. Higher-order HI lines with Nup > 6, originating from dense regions in magnetospheric accretion columns, offer a more reliable alternative. We undertake a large, homogeneous analysis of over 80 JWST/MIRI archival spectra of Class II disks, focusing on HI (Nup = 6–14) emission lines in the MIR range, taking advantage of MIRI’s high sensitivity and broad wavelength coverage (5–28 µm). We present our detections of MIR HI lines and identify lines that can serve as accretion indicators. The MIR spectra of Class II disks are also known to be rich in molecular features. We discuss the molecular contamination affecting each HI line and remove their contributions by LTE modeling of the molecular features. We provide calibrated empirical relations to convert MIR HI line luminosities into mass accretion rates, improving upon available optical/NIR proxies. This enables the community to estimate accretion rates directly from JWST/MIRI spectra. Additionally, we compare observed HI line ratios with theoretical models by Kwan & Fischer (2011) to estimate accretion column densities more accurately, extending upon previous studies using Balmer and Paschen series lines. Finally, we explore the correlation between HI lines and fine-structure lines, such as [NeII], [FeII] and [ArII], which trace photoevaporation from the inner disk, allowing for simultaneous measurements of accretion and disk dispersal in Class II disks. |
