PRODIGE Envelope To Disk with NOEMA III. The Origin Of Complex Organic Molecule Emission In SVS13A

Complex Organic Molecules (COMs) have been found toward low-mass protostars but the origins of the COM emission are still unclear.

It can be associated with, for example, hot corinos, outflows, and/or accretion shock/disk atmosphere. We have conducted NOEMA observations toward SVS13A from the PROtostars & DIsks: Global Evolution (PRODIGE) program. Our previous DCN observations reveal a possible infalling streamer, which may affect the chemistry of the central protobinary by inducing accretion outbursts and/or shocked gas.

Here, we further analyze six O-bearing COMs: CH₃OH, aGg’-(CH₂OH)2, C₂H₅OH, CH₂(OH)CHO, CH₃CHO, and CH₃OCHO. Although the COM emission is not spatially resolved, we constrain the source sizes to ≲0.3−0.4 arcsec (90−120 au) by conducting uv-domain Gaussian fitting.

Interestingly, the high-spectral resolution data reveal complex line profiles with multiple peaks showing differences between these six O-bearing COMs. The LTE fitting unveils differences in excitation temperatures and emitting areas among these COMs. We further conduct multiple-velocity-component LTE fitting to decompose the line emission into different kinematic components. Up to 6 velocity components are found from the LTE modeling.

The temperature, column density, and source size of these components from each COM are obtained. We find a variety in excitation temperatures (100−500 K) and source sizes (D∼10−70 au) from these kinematic components from different COMs. The emission of each COM can trace several components and different COMs most likely trace different regions. Given this complex structure, we suggest that the central region is inhomogeneous and unlikely to be heated by only protostellar radiation. We conclude that accretion shocks induced by the large-scale infalling streamer likely exist and contribute to the complexity of the COM emission.

Central positions of selected COM transitions at different velocities. The top two panels show the integrated intensity map (left) and central positions (right) from CH3CN (Hsieh et al. 2023) as a reference for the O-bearing COMs. The contours show the 1.3 mm continuum emission from Tobin et al. (2018). Different line transitions are marked in different symbols (Tables B.1 to B.6). The scale bar is 0 ′′ . 1 for the bottom six panels. The beam sizes for these COM emissions are depending on the line frequency but is the same to as CH3CN (1 ′′. 2 × 0 ′′. 7) within 10%. — astro-ph.GA

T.-H. Hsieh, J. E. Pineda, D. M. Segura-Cox, P. Caselli, M. T. Valdivia-Mena, C. Gieser, M. J. Maureira, A. Lopez-Sepulcre, L. Bouscasse, R. Neri, Th. Möller, A. Dutrey, A. Fuente, D. Semenov, E. Chapillon, N. Cunningham, Th. Henning, V. Pietu, I. Jimenez-Serra, S. Marino, C. Ceccarelli

Comments: 29 pages, 18 figures, accepted to A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2403.16892 [astro-ph.GA] (or arXiv:2403.16892v1 [astro-ph.GA] for this version)
Submission history
From: Tien-Hao Hsieh
[v1] Mon, 25 Mar 2024 16:03:40 UTC (5,487 KB)
https://arxiv.org/abs/2403.16892
Astrobiology, Astrochemistry,