CaltechAUTHORS
Published January 2024 | Version Published
Journal Article Open

The Galaxy Activity, Torus, and Outflow Survey (GATOS). III. Revealing the inner icy structure in local active galactic nuclei

Creators

  • 1. ROR icon University of Oxford
  • 2. ROR icon Centro de Astrobiología
  • 3. ROR icon European University Cyprus
  • 4. ROR icon Instituto de Física Fundamental
  • 5. ROR icon Max Planck Institute for Extraterrestrial Physics
  • 6. ROR icon National Autonomous University of Mexico
  • 7. ROR icon Instituto de Astrofísica de Canarias
  • 8. ROR icon University of La Laguna
  • 9. ROR icon Complutense University of Madrid
  • 10. ROR icon California Institute of Technology
  • 11. ROR icon French National Centre for Scientific Research
  • 12. ROR icon Spanish National Observatory
  • 13. ROR icon University of Alcalá
  • 14. ROR icon University of Alaska Anchorage
  • 15. ROR icon University of Southampton
  • 16. ROR icon European Space Astronomy Centre
  • 17. ROR icon Space Telescope Science Institute
  • 18. ROR icon Stanford University
  • 19. ROR icon Diego Portales University
  • 20. ROR icon The University of Texas at San Antonio
  • 21. ROR icon Astronomical Observatory
  • 22. ROR icon Durham University

Abstract

We use JWST/MIRI MRS spectroscopy of a sample of six local obscured type 1.9/2 active galactic nuclei (AGN) to compare their nuclear mid-IR absorption bands with the level of nuclear obscuration traced by X-rays. This study is the first to use subarcsecond angular resolution data of local obscured AGN to investigate the nuclear mid-IR absorption bands with a wide wavelength coverage (4.9–28.1 μm). All the nuclei show the 9.7 μm silicate band in absorption. We compare the strength of the 9.7 and 18 μm silicate features with torus model predictions. The observed silicate features are generally well explained by clumpy and smooth torus models. We report the detection of the 6 μm dirty water ice band (i.e., a mix of water and other molecules such as CO and CO2) at subarcsecond scales (∼0.26″ at 6 μm; inner ∼50 pc) in a sample of local AGN with different levels of nuclear obscuration in the range log NHX-Ray (cm−2)∼22 − 25. We find good correlation between the 6 μm water ice optical depths and NHX-Ray. This result indicates that the water ice absorption might be a reliable tracer of the nuclear intrinsic obscuration in AGN. The weak water ice absorption in less obscured AGN (log NHX-ray (cm−2)≲23.0 cm−2) might be related to the hotter dust temperature (> TsubH2O ∼ 110 K) expected to be reached in the outer layers of the torus due to their more inhomogeneous medium. Our results suggest it might be necessary to include the molecular content, such as H2O, aliphatic hydrocarbons (CH−), and more complex polycyclic aromatic hydrocarbon (PAH) molecules, in torus models to better constrain key parameters such as the torus covering factor (i.e., nuclear obscuration).

Copyright and License

© The Authors 2023. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Acknowledgement

The authors thank E. Dartois for useful discussions, and H.W.W. Spoon for providing laboratory spectra. I.G.B. and D.R. acknowledge support from STFC through grant ST/S000488/1 and ST/W000903/1. A.A.H. acknowledges support from grant PID2021-124665NB-I00 funded by MCIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe. M.P.S. acknowledges funding support from the Ramón y Cajal programme of the Spanish Ministerio de Ciencia e Innovación (RYC2021-033094-I). O.G.M. acknowledges PAPIIT UNAM IN109123 and to the Ciencia de Frontera project CF-2023-G-100 from CONHACYT. C.R.A. acknowledges the projects “Feeding and feedback in active galaxies”, with reference PID2019-106027GB-C42, funded by MICINN-AEI/10.13039/501100011033 and “Quantifying the impact of quasar feedback on galaxy evolution”, with reference EUR2020-112266, funded by MICINN-AEI/10.13039/501100011033 and the European Union NextGenerationEU/PRTR. E.B. acknowledges the María Zambrano program of the Spanish Ministerio de Universidades funded by the Next Generation European Union and is also partly supported by grant RTI2018-096188-B-I00 funded by the Spanish Ministry of Science and Innovation/State Agency of Research MCIN/AEI/10.13039/501100011033. S.G.B. acknowledges support from the research project PID2019-106027GA-C44 of the Spanish Ministerio de Ciencia e Innovación. E.G.-A. thanks the Spanish MICINN for support under projects PID2019-105552RB-C41 and PID2022-137779OB-C41. C.R. acknowledges support from Fondecyt Regular grant 1230345 and ANID BASAL project FB210003. M.J.W. acknowledges the award of a Leverhulme Emeritus Fellowship. his work is based on observations made with the JWST. The authors acknowledge the ERO team for developing their observing program with a zero-exclusive-access period. The authors are extremely grateful to the JWST helpdesk for their constant and enthusiastic support. Finally, we thank the anonymous referee for their useful comments.

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Additional details

Related works

Is new version of
Discussion Paper: arXiv:2310.09093 (arXiv)

Funding

Science and Technology Facilities Council
ST/S000488/1
Science and Technology Facilities Council
ST/W000903/1
Ministerio de Ciencia, Innovación y Universidades
PID2021-124665NB-I00
Ministerio de Ciencia, Innovación y Universidades
RYC2021-033094-I
Universidad Nacional Autónoma de México
IN109123
Consejo Nacional de Humanidades, Ciencias y Tecnologías
CF-2023-G-100
Ministerio de Ciencia, Innovación y Universidades
PID2019-106027GB-C42
Ministerio de Ciencia, Innovación y Universidades
EUR2020-112266
Ministerio de Ciencia, Innovación y Universidades
RTI2018-096188-B-I00
Ministerio de Ciencia, Innovación y Universidades
PID2019-105552RB-C41
Ministerio de Ciencia, Innovación y Universidades
PID2022-137779OB-C41
Fondo Nacional de Desarrollo Científico y Tecnológico
1230345
Agencia Nacional de Investigación y Desarrollo
FB210003
Leverhulme Trust

Dates

Accepted
2023-12-01
Available
2023-12-25
Published online

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Caltech groups
Division of Physics, Mathematics and Astronomy (PMA)
Publication Status
Published