Spatial variations in aromatic hydrocarbon emission in a dust

Nature (2023)Cite this article

176 Altmetric

Metrics details

Dust grains absorb half of the radiation emitted by stars throughout the history of the universe, re-emitting this energy at infrared wavelengths1,=1.2. Nature 458, 737–739 (2009)." href="#ref-CR2" id="ref-link-section-d59258243e1304_1">2,3. Polycyclic aromatic hydrocarbons (PAHs) are large organic molecules that trace millimetre-size dust grains and regulate the cooling of interstellar gas within galaxies4,5. Observations of PAH features in very distant galaxies have been difficult owing to the limited sensitivity and wavelength coverage of previous infrared telescopes6, 4 submillimeter galaxy. Astrophys. J. 786, 31 (2014)." href="/articles/s41586-023-05998-6#ref-CR7" id="ref-link-section-d59258243e1321">7. Here we present James Webb Space Telescope observations that detect the 3.3 μm PAH feature in a galaxy observed less than 1.5 billion years after the Big Bang. The high equivalent width of the PAH feature indicates that star formation, rather than black hole accretion, dominates infrared emission throughout the galaxy. The light from PAH molecules, hot dust and large dust grains and stars are spatially distinct from one another, leading to order-of-magnitude variations in PAH equivalent width and ratio of PAH to total infrared luminosity across the galaxy. The spatial variations we observe suggest either a physical offset between PAHs and large dust grains or wide variations in the local ultraviolet radiation field. Our observations demonstrate that differences in emission from PAH molecules and large dust grains are a complex result of localized processes within early galaxies.

This is a preview of subscription content, access via your institution

Access Nature and 54 other Nature Portfolio journals

Get Nature+, our best-value online-access subscription

$29.99 / 30 days

cancel any time

Subscribe to this journal

Receive 51 print issues and online access

$199.00 per year

only $3.90 per issue

Rent or buy this article

Get just this article for as long as you need it

$39.95

Prices may be subject to local taxes which are calculated during checkout

All JWST data are available from the Mikulski Archive for Space Telescopes (https://archive.stsci.edu/) under programme no. 1355. The reduced JWST data products used in this work are available from the TEMPLATES collaboration public data repository, https://github.com/jwst-templates. This paper makes use of ALMA data under project code nos. 2016.1.01374.S and 2016.1.01499.S, available from the ALMA science archive (https://almascience.nrao.edu/aq).

JWST and ALMA data were reduced using the publicly available pipeline software for both observatories. Our reduction and analysis scripts for MIRI/MRS data are available from the TEMPLATES collaboration public data repository, https://github.com/jwst-templates.

Dole, H. et al. The cosmic infrared background resolved by Spitzer: contributions of mid-infrared galaxies to the far-infrared background. Astron. Astrophys. 451, 417–429 (2006).

Article ADS CAS Google Scholar

Devlin, M. J. et al. Over half of the far-infrared background light comes from galaxies at z>=1.2. Nature 458, 737–739 (2009).

Article ADS CAS PubMed Google Scholar

Zavala, J. A. et al. The evolution of the IR luminosity function and dust-obscured star formation over the past 13 billion years. Astrophys. J. 909, 165 (2021).

Article ADS Google Scholar

Kwok, S. & Zhang, Y. Mixed aromatic-aliphatic organic nanoparticles as carriers of unidentified infrared emission features. Nature 479, 80–83 (2011).

Article ADS PubMed Google Scholar

Rigopoulou, D. et al. The properties of polycyclic aromatic hydrocarbons in galaxies: constraints on PAH sizes, charge and radiation fields. Mon. Not. R. Astron. Soc. 504, 5287–5300 (2021).

Article ADS CAS Google Scholar

Li, A. Spitzer's perspective of polycyclic aromatic hydrocarbons in galaxies. Nat. Astron. 4, 339–351 (2020).

Article ADS Google Scholar

Riechers, D. A. et al. Polycyclic aromatic hydrocarbon and mid-infrared continuum emission in a z > 4 submillimeter galaxy. Astrophys. J. 786, 31 (2014).

Article ADS Google Scholar

Carlstrom, J. E. et al. The 10 Meter South Pole Telescope. Publ. Astron. Soc. Pac. 123, 568 (2011).

Article ADS Google Scholar

Everett, W. B. et al. Millimeter-wave point sources from the 2500 Square Degree SPT-SZ Survey: catalog and population statistics. Astrophys. J. 900, 55 (2020).

Article ADS CAS Google Scholar

Weiß, A. et al. ALMA redshifts of millimeter-selected galaxies from the SPT Survey: the redshift distribution of dusty star-forming galaxies. Astrophys. J. 767, 88 (2013).

Article ADS Google Scholar

Spilker, J. S. et al. ALMA imaging and gravitational lens models of South Pole Telescope—selected dusty, star-forming galaxies at high redshifts. Astrophys. J. 826, 112 (2016).

Article ADS Google Scholar

Spilker, J. S. et al. Ubiquitous molecular outflows in z > 4 massive, dusty galaxies. I. Sample overview and clumpy structure in molecular outflows on 500 pc scales. Astrophys. J. 905, 85 (2020).

Article ADS CAS Google Scholar

Rizzo, F. et al. A dynamically cold disk galaxy in the early Universe. Nature 584, 201–204 (2020).

Article ADS CAS PubMed Google Scholar

Peng, B. et al. Discovery of a dusty, chemically mature companion to a z~4 starburst galaxy in JWST ERS data. Astrophys. J. 944, L36 (2023).

Article ADS Google Scholar

De Breuck, C. et al. A dense, solar metallicity ISM in the z=4.2 dusty star-forming galaxy SPT0418-47. Astron. Astrophys. 631, A167 (2019).

Article Google Scholar

Spilker, J. S. et al. Ubiquitous molecular outflows in z > 4 massive, dusty galaxies. II. Momentum-driven winds powered by star formation in the early Universe. Astrophys. J. 905, 86 (2020).

Article ADS CAS Google Scholar

Draine, B. T. et al. Excitation of polycyclic aromatic hydrocarbon emission: dependence on size distribution, ionization, and starlight spectrum and intensity. Astrophys. J. 917, 3 (2021).

Article ADS CAS Google Scholar

Schutte, W. A., Tielens, A. G. G. M. & Allamandola, L. J. Theoretical modeling of the infrared fluorescence from interstellar polycyclic aromatic hydrocarbons. Astrophys. J. 415, 397 (1993).

Article ADS Google Scholar

Joblin, C., Tielens, A. G. G. M., Allamandola, L. J. & Geballe, T. R. Spatial variation of the 3.29 and 3.40 micron emission bands within reflection nebulae and the photochemical evolution of methylated polycyclic aromatic hydrocarbons. Astrophys. J. 458, 610 (1996).

Article ADS CAS PubMed Google Scholar

Barker, J. R., Allamandola, L. J. & Tielens, A. G. G. M. Anharmonicity and the interstellar polycyclic aromatic hydrocarbon infrared emission spectrum. Astrophys. J. 315, L61 (1987).

Article ADS CAS Google Scholar

Maltseva, E. et al. High-resolution IR absorption spectroscopy of polycyclic aromatic hydrocarbons in the 3 μm region: role of hydrogenation and alkylation. Astron. Astrophys. 610, A65 (2018).

Article Google Scholar

Imanishi, M., Nakagawa, T., Shirahata, M., Ohyama, Y. & Onaka, T. AKARI IRC infrared 2.5-5 μm spectroscopy of a large sample of luminous infrared galaxies. Astrophys. J. 721, 1233–1261 (2010).

Article ADS CAS Google Scholar

Rich, J. et al. GOALS-JWST: pulling back the curtain on the AGN and star formation in VV 114. Astrophys. J. 944, L50 (2023).

Article ADS Google Scholar

Yamada, R. et al. A relation of the PAH 3.3 μm feature with star-forming activity for galaxies with a wide range of infrared luminosity. Publ. Astron. Soc. Jap. 65, 103 (2013).

Article ADS Google Scholar

Inami, H. et al. The AKARI 2.5-5 micron spectra of luminous infrared galaxies in the local Universe. Astron. Astrophys. 617, A130 (2018).

Article Google Scholar

Sajina, A. et al. Detections of water ice, hydrocarbons, and 3.3 μm PAH in z~2 ULIRGs. Astrophys. J. 703, 270–284 (2009).

Article ADS CAS Google Scholar

Siana, B. et al. Detection of far-infrared and polycyclic aromatic hydrocarbon emission from the cosmic eye: probing the dust and star formation of Lyman break galaxies. Astrophys. J. 698, 1273–1281 (2009).

Article ADS CAS Google Scholar

Smith, J. D. T. et al. The mid-infrared spectrum of star-forming galaxies: global properties of polycyclic aromatic hydrocarbon emission. Astrophys. J. 656, 770–791 (2007).

Article ADS CAS Google Scholar

Lai, T. S. Y., Smith, J. D. T., Baba, S., Spoon, H. W. W. & Imanishi, M. All the PAHs: an AKARI-Spitzer cross-archival spectroscopic survey of aromatic emission in galaxiies. Astrophys. J. 905, 55 (2020).

Article ADS CAS Google Scholar

Chabrier, G. Galactic stellar and substellar initial mass function. Publ. Astron. Soc. Pac. 115, 763–795 (2003).

Article ADS Google Scholar

Jakobsen, P. et al. The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope: I. Overview of the instrument and its capabilities. Astron. Astrophys. 661, A80 (2022).

Article CAS Google Scholar

Böker, T. et al. The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope: III. Integral-field spectroscopy. Astron. Astrophys. 661, A82 (2022).

Article Google Scholar

Rieke, G. H. et al. The Mid-infrared instrument for the James Webb Space Telescope, I: introduction. Publ. Astron. Soc. Pac. 127, 584 (2015).

Article ADS Google Scholar

Wells, M. et al. The mid-infrared instrument for the James Webb Space Telescope, VI: the Medium Resolution Spectrometer. Publ. Astron. Soc. Pac. 127, 646 (2015).

Article ADS Google Scholar

Labiano, A. et al. Wavelength calibration and resolving power of the JWST MIRI Medium Resolution Spectrometer. Astron. Astrophys. 656, A57 (2021).

Article CAS Google Scholar

JWST-Templates. GitHub https://github.com/jwst-templates.

Reuter, C. et al. The complete redshift distribution of dusty star-forming galaxies from the SPT-SZ Survey. Astrophys. J. 902, 78 (2020).

Article ADS CAS Google Scholar

Download references

JWST is operated by the Space Telescope Science Institute under the management of the Association of Universities for Research in Astronomy, Inc., under NASA contract no. NAS 5-03127. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan) and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Department of Physics and Astronomy and George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, College Station, TX, USA

Justin S. Spilker, Jack E. Birkin & Grace M. Olivier

Department of Astronomy, University of Illinois, Urbana, IL, USA

Kedar A. Phadke, Melanie Archipley, Seonwoo Kim, Cassie Reuter, Joaquin D. Vieira & David Vizgan

Center for AstroPhysical Surveys, National Center for Supercomputing Applications, Urbana, IL, USA

Kedar A. Phadke, Melanie Archipley, Cassie Reuter & Joaquin D. Vieira

Núcleo de Astronomía de la Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Santiago, Chile

Manuel Aravena & Manuel Solimano

Department of Physics, University of Cincinnati, Cincinnati, OH, USA

Matthew B. Bayliss, Keunho J. Kim & Alex Navarre

Aix Marseille Univ., CNRS, CNES, LAM, Marseille, France

Matthieu Béthermin & Gayathri Gururajan

Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada

James Burgoyne, Scott C. Chapman & Ryley Hill

Department of Astronomy, University of Florida, Gainesville, FL, USA

Jared Cathey, Anthony H. Gonzalez & Desika Narayanan

National Research Council, Herzberg Astronomy and Astrophysics, Victoria, British Columbia, Canada

Scott C. Chapman

Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada

Scott C. Chapman

Institute of Theoretical Astrophysics, University of Oslo, Oslo, Norway

Håkon Dahle

Department of Physics and Astronomy ‘Augusto Righi’, University of Bologna, Bologna, Italy

Gayathri Gururajan

INAF – Osservatorio di Astrofisica e Scienza dello Spazio, Bologna, Italy

Gayathri Gururajan

Center for Computational Astrophysics, Flatiron Institute, New York, NY, USA

Christopher C. Hayward, Yashar D. Hezaveh & Ronan Legin

Département de Physique, Université de Montréal, Montreal, Quebec, Canada

Yashar D. Hezaveh & Ronan Legin

Ciela – Montreal Institute for Astrophysical Data Analysis and Machine Learning, Montreal, Quebec, Canada

Yashar D. Hezaveh & Ronan Legin

Mila – Québec Artificial Intelligence Institute, Montreal, Quebec, Canada

Yashar D. Hezaveh & Ronan Legin

Observational Cosmology Lab, NASA Goddard Space Flight Center, Greenbelt, MD, USA

Taylor A. Hutchison, Jane R. Rigby & James E. Rhoads

Space Telescope Science Institute, Baltimore, MD, USA

David Law

Department of Physics and Astronomy, University of California, Los Angeles, CA, USA

Matthew A. Malkan

Steward Observatory, University of Arizona, Tucson, AZ, USA

Daniel P. Marrone

National Radio Astronomy Observatory, Charlottesville, VA, USA

Eric J. Murphy

University of Florida Informatics Institute, Gainesville, FL, USA

Desika Narayanan

Cosmic Dawn Center, DTU Space, Technical University of Denmark, Kongens Lyngby, Denmark

Desika Narayanan & Katherine E. Whitaker

The Observatories of the Carnegie Institution for Science, Pasadena, CA, USA

Jeffrey A. Rich

Department of Astronomy, University of Michigan, Ann Arbor, MI, USA

Keren Sharon

Ritter Astrophysical Research Center, Department of Physics and Astronomy, University of Toledo, Toledo, OH, USA

J. D. T. Smith

Max-Planck-Institut für Radioastronomie, Bonn, Germany

Nikolaus Sulzenauer & Axel Weiß

Department of Physics, University of Illinois, Urbana, IL, USA

Joaquin D. Vieira

Department of Astronomy, University of Massachusetts, Amherst, MA, USA

Katherine E. Whitaker

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

You can also search for this author in PubMed Google Scholar

J.S.S. led data analysis and drafted the main text. K.A.P. and D.L. contributed to data analysis. J.D.T.S. assisted in interpretation of data. J.R.R. and J.D.V. contributed to management of the TEMPLATES programme. All authors contributed to interpretation of the results and editing of the text, and are ordered alphabetically after K.A.P.

Correspondence to Justin S. Spilker.

The authors declare no competing interests.

Nature thanks the anonymous reviewers for their contribution to the peer review of this work. Peer reviewer reports are available.

Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Each column shows a 100-channel average from the MRS data cube corresponding to the wavelength ranges indicated at top. The top row shows the original pipeline-processed data. Horizontal stripe features are evident, a manifestation of the so-called ‘shower’ artifacts in MIRI data. The middle row shows the estimated background to be subtracted averaged over the same wavelength range. The bottom row shows the final background-subtracted image. The circles show the region of the cube that was masked during the background estimation due to the presence of real source emission from SPT0418-47. All images are on the same color scale. The 3.3 μm PAH feature is mostly contained within the wavelength range of the third column.

Using additional ALMA continuum data at rest-frame 120 μm, we calculate the implied changes in Tdust under standard assumptions about the shape of the dust spectral energy distribution. The 120 μm and 160 μm images are shown on a linear min/max color scale, masking pixels detected at S/N<5 in either band, to demonstrate their qualitative similarity. This similarity consequently implies only small changes in Tdust across the source. We use the resolved Tdust map to estimate the implied correction to our ‘default’ assumption of a constant conversion between LIR and 160 μm flux density; the right panel shows that only ≈10% variations are implied, subdominant to other sources of uncertainty in our analysis.

Using mock data with constant LPAH/LIR inserted into signal-free portions of the MRS data cube, we test the extent to which the faintness of the PAH feature and noise properties of the MRS data influence our conclusion that SPT0418-47 shows large variations in LPAH/LIR. Points show individual pixels from several of the mock realizations, while the black dashed line and grey shaded region illustrate the median and 16–84th percentile range of the distribution of all mock simulations. Even in the faintest regions, LPAH/LIR is still recovered to within a factor of ≈2, improving to ±25% in brighter regions.

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and Permissions

Spilker, J.S., Phadke, K.A., Aravena, M. et al. Spatial variations in aromatic hydrocarbon emission in a dust-rich galaxy. Nature (2023). https://doi.org/10.1038/s41586-023-05998-6

Download citation

Received: 14 January 2023

Accepted: 21 March 2023

Published: 05 June 2023

DOI: https://doi.org/10.1038/s41586-023-05998-6

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.