Structures Of Dust and gAs (SODA): Constraining the innermost dust properties of II Zw96 with JWST observations of H₂O and CO

Journal article

12 pags., 10 figs., 2 tabs.We analyze JWST NIRSpec+MIRI/MRS observations of the infrared (IR) gas-phase molecular bands of the most enshrouded source (D1) within the interacting system and luminous IR galaxy II Zw 096. We report the detection of rovibrational lines of HO ν = 1-0 (~4;5.3-7.2 μm) and CO ν = 1-0 (~4;4.45-4.95 μm) in D1. The CO band shows the R- and P-branches in emission and the spectrum of the HO band shows the P-branch in emission and the R-branch in absorption. The HO R-branch in absorption unveils an IR-bright embedded compact source in D1 and the CO broad component features a highly turbulent environment. From both bands, we also identified extended intense star-forming (SF) activity associated with circumnuclear photodissociation regions (PDRs), consistent with the strong emission of the ionised 7.7 μm polycyclic aromatic hydrocarbon band in this source. By including the 4.5-7.0 μm continuum information derived from the HO and CO analysis, we modelled the IR emission of D1 with a dusty torus and SF component. The torus is very compact (diameter of ~4;3 pc at 5 μm) and characterised by warm dust (~4;370 K), giving an IR surface brightness of ~4;3.6 × 10 L pc. This result suggests the presence of a dust-obscured active galactic nucleus (AGN) in D1, which has an exceptionally high covering factor that prevents the direct detection of AGN emission. Our results open a new way to investigate the physical conditions of inner dusty tori via modelling the observed IR molecular bands.I.G.B. and D.R. acknowledge support from STFC through grants ST/S000488/1 and ST/W000903/1. E.G.-A. acknowledges grants PID2019-105552RB-C4 and PID2022-137779OB-C41 funded by the Spanish MCIN/AEI/10.13039/501100011033. M.P.S. acknowledges support from grant RYC2021-033094-I funded by MCIN/AEI/10.13039/501100011033 and the EU NextGenerationEU/PRTR

Authors: García-Bernete, I; Pereira-Santaella, M; González-Alfonso, E; Rigopoulou, D; Efstathiou, A

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: EDP Sciences
• Journal: Astronomy & Astrophysics
• Volume: 682
• Pages: L5-L5
• Publication date: 2024-02-01
• Acceptance date: 2023-12-27
• DOI: 10.1051/0004-6361/202348744
• EISSN: 1432-0746
• ISSN: 0004-6361
• Language: English
• Keywords: Luminous infrared galaxy; Infrared; Surface brightness; Spectral line; Astrophysics; Emission spectrum; Brightness; Torus; Active galactic nucleus; Physics; Astronomy; Interstellar medium; Galaxy