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arXiv · 2610.28795

FAUST XXXII. Chemically layered structures and ionisation in the disk and envelope of NGC 1333 IRAS 4C

Shota Notsu·Nami Sakai·Yichen Zhang·Ana Lopez-Sepulcre·Claire J. Chandler·Ziwei E. Zhang·Cecilia Ceccarelli·Claudio Codella·Yuri Aikawa·Jaime E. Pineda·Brian Svoboda·Felipe O. Alves·Nadia Balucani·Eleonora Bianchi·Mathilde Bouvier·Gemma Busquet·Paola Caselli·Emmanuel Caux·Steven Charnley·Spandan Choudhury·Nicol as Cuello·Marta De Simone·Francois Dulieu·Aurora Duran·Lucy Evans·Cecile Favre·Siyi Feng·Davide Fedele·Francesco Fontani·Tetsuya Hama·Tomoyuki Hanawa·Eric Herbst·Shingo Hirano·Tomoya Hirota·Andrea Isella·Izaskun Jimenez-Serra·Doug Johnstone·Claudine Kahane·Romane Le Gal·Bertrand Lefloch·Laurent Loinard·Hauyu Baobab Liu·Antonio Martinez-Henares·Luke T. Maud·Maria Jose Maureira·Francois Menard·Seyma Mercimek·Anna Miotello·George Moellenbrock·Shoji Mori·Nadia M. Murillo·Riouhei Nakatani·Hideko Nomura·Yasuhiro Oba·Ross O'Donoghue·Satoshi Ohashi·Yuki Okoda·Juan Ospina-Zamudio·Yoko Oya·Linda Podio·Albert Rimola·Giovanni Sabatini·Takeshi Sakai·Dominique M. Segura-Cox·Yancy Shirley·Leonardo Testi·Charlotte Vastel·Serena Viti·Naoki Watanabe·Yoshimasa Watanabe·Arezu Witzel·Ci Xue·Bo Zhao·Satoshi Yamamoto
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Abstract

Recent molecular line observations with high spatial resolutions have revealed vertical chemical stratification in Class I/II disks (i.e. chemical composition changing with height in the vertical direction of the disk), as well as a radial variation of ionisation rates. However, such chemical layered structures in Class 0 disk and envelope systems have been investigated only for limited objects, such as L1527. In the context of the ALMA Large Program FAUST, we report the results of molecular line observations toward the disk and envelope around the low-mass Class 0 protostar NGC 1333 IRAS 4C in the Perseus Molecular Cloud. Previous observations have shown that the disk rotation axis of this object is largely tilted to the line of sight, making it suitable for studying the molecular abundance distribution as a function of disk height. We found that the molecules known as gas density tracers such as C18O and H2CO are distributed around the disk midplane. In addition, molecules known as tracers of photochemical reactions such as CCH and c-C3H2 are distributed in the low-density upper layers of the disk, unlike the distribution in L1527. Moreover, the column density ratio of HCO+/CO derived from the H13CO+ and C18O line emission suggests that the ionisation degree and the ionisation rate vary with the disk radius and they are larger in the outer region of the disk and envelope.

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Shota Notsu, Nami Sakai, Yichen Zhang, Ana Lopez-Sepulcre, Claire J. Chandler, Ziwei E. Zhang, Cecilia Ceccarelli, Claudio Codella, Yuri Aikawa, Jaime E. Pineda, Brian Svoboda, Felipe O. Alves, Nadia Balucani, Eleonora Bianchi, Mathilde Bouvier, Gemma Busquet, Paola Caselli, Emmanuel Caux, Steven Charnley, Spandan Choudhury, Nicol as Cuello, Marta De Simone, Francois Dulieu, Aurora Duran, Lucy Evans, Cecile Favre, Siyi Feng, Davide Fedele, Francesco Fontani, Tetsuya Hama, Tomoyuki Hanawa, Eric Herbst, Shingo Hirano, Tomoya Hirota, Andrea Isella, Izaskun Jimenez-Serra, Doug Johnstone, Claudine Kahane, Romane Le Gal, Bertrand Lefloch, Laurent Loinard, Hauyu Baobab Liu, Antonio Martinez-Henares, Luke T. Maud, Maria Jose Maureira, Francois Menard, Seyma Mercimek, Anna Miotello, George Moellenbrock, Shoji Mori, Nadia M. Murillo, Riouhei Nakatani, Hideko Nomura, Yasuhiro Oba, Ross O'Donoghue, Satoshi Ohashi, Yuki Okoda, Juan Ospina-Zamudio, Yoko Oya, Linda Podio, Albert Rimola, Giovanni Sabatini, Takeshi Sakai, Dominique M. Segura-Cox, Yancy Shirley, Leonardo Testi, Charlotte Vastel, Serena Viti, Naoki Watanabe, Yoshimasa Watanabe, Arezu Witzel, Ci Xue, Bo Zhao, Satoshi Yamamoto. 2026-10-20. FAUST XXXII. Chemically layered structures and ionisation in the disk and envelope of NGC 1333 IRAS 4C. https://arxiv.org/abs/2610.28795

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