The enormous increase in mid-IR sensitivity and spatial and spectral resolution provided by the JWST spectrographs enables, for the first time, detailed extragalactic studies of molecular vibrational bands. This opens an entirely new window for the study of the molecular interstellar medium in luminous infrared galaxies (LIRGs). We present a detailed analysis of rovibrational bands of gas-phase CO, H2O, C2H2, and HCN toward the heavily obscured eastern nucleus of the LIRG VV 114, as observed by NIRSpec and the medium resolution spectrograph on the Mid-InfraRed Instrument (MIRI MRS). Spectra extracted from apertures of 130 pc in radius show a clear dichotomy between the obscured active galactic nucleus (AGN) and two intense starburst regions. We detect the 2.3 μm CO bandheads, characteristic of cool stellar atmospheres, in the star-forming regions, but not toward the AGN. Surprisingly, at 4.7 μm, we find highly excited CO (Tex ≈ 700–800 K out to at least rotational level J = 27) toward the star-forming regions, but only cooler gas (Tex ≈ 200 K) toward the AGN. We conclude that only mid-infrared pumping through the rovibrational lines can account for the equilibrium conditions found for CO and H2O in the deeply embedded starbursts. Here, the CO bands probe regions with an intense local radiation field inside dusty young massive star clusters or near the most massive young stars. The lack of high-excitation molecular gas toward the AGN is attributed to geometric dilution of the intense radiation from the bright point source. An overview of the relevant excitation and radiative transfer physics is provided in an appendix.
GOALS-JWST: Mid-infrared Molecular Gas Excitation Probes the Local Conditions of Nuclear Star Clusters and the Active Galactic Nucleus in the LIRG VV 114
- Creators
- Buiten, Victorine A.
- van der Werf, Paul P.
- Viti, Serena
- Armus, Lee1
- Barr, Andrew G.
- Barcos-Muñoz, Loreto
- Evans, Aaron S.
- Inami, Hanae
- Linden, Sean T.
- Privon, George C.
- Song, Yiqing
- Rich, Jeffrey A.
- Aalto, Susanne
- Appleton, Philip N.
- Böker, Torsten
- Charmandaris, Vassilis
- Diaz-Santos, Tanio
- Hayward, Christopher C.
- Lai, Thomas S.-Y.
- Medling, Anne M.
- Ricci, Claudio
- U, Vivian
Abstract
Copyright and License
© 2024. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Acknowledgement
We thanks the anonymous referee for the constructive comments and suggestions. We thank Ewine van Dishoeck for useful discussions.
This work is based on observations made with the NASA/ ESA/CSA James Webb Space Telescope. The research was supported in part by NASA grant JWST-ERS-01328. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. The observations analyzed here can be accessed via doi:10.17909/yqk1-jr92.
S.V. acknowledges support from the European Research Council (ERC) Advanced grant MOPPEX 833460. H.I. acknowledges support from JSPS KAKENHI grant No. JP21H01129. The Flatiron Institute is supported by the Simons Foundation. A.M.M. acknowledges support from the National Science Foundation under AAG No. 2009416 and CAREER No. 2239807 and the NASA Astrophysics Data Analysis Program (ADAP) grant No. 80NSSC23K0750. C.R. acknowledges support from the Fondecyt Regular grant 1230345 and ANID BASAL project FB210003. V.U. acknowledges funding support from No. JWST-GO-01717.001-A, No. HST-AR-17065.005-A, No. HST-GO-17285.001-A, and NASA ADAP grant No. 80NSSC20K0450.
Facilities
JWST (NIRSpec and MIRI) -
Software References
Astropy (Astropy Collaboration et al. 2013, 2018, 2022), APLpy (Robitaille & Bressert 2012), NumPy (Harris et al. 2020), SciPy (Virtanen et al. 2020)
Files
Name | Size | Download all |
---|---|---|
md5:4738fcae7d0824c228830b5640819788
|
6.1 MB | Preview Download |
Additional details
- ISSN
- 1538-4357
- National Aeronautics and Space Administration
- JWST-ERS-01328
- National Aeronautics and Space Administration
- NAS 5-03127
- European Research Council
- 833460
- Japan Society for the Promotion of Science
- JP21H01129
- Simons Foundation
- National Science Foundation
- AST-2009416
- National Science Foundation
- AST-2239807
- National Aeronautics and Space Administration
- 80NSSC23K0750
- Fondo Nacional de Desarrollo Científico y Tecnológico
- 1230345
- Agencia Nacional de Investigación y Desarrollo
- FB210003
- National Aeronautics and Space Administration
- JWST-GO-01717.001-A
- National Aeronautics and Space Administration
- HST-AR-17065.005-A
- National Aeronautics and Space Administration
- HST-GO-17285.001-A
- National Aeronautics and Space Administration
- 80NSSC20K0450
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)