PDRs4All VII. The 3.3 $\mu$m aromatic infrared band as a tracer of physical properties of the ISM in galaxies

Abstract

Aromatic infrared bands (AIBs) are a set of broad emission bands at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 $\mu$m, seen in the infrared spectra of most galaxies. With JWST, the 3.3 $\mu$m AIB can in principle be detected up to a redshift of $\sim$ 7. Relating the evolution of the 3.3 $\mu$m AIB to local physical properties of the ISM is thus of paramount importance. By applying a dedicated machine learning algorithm to JWST NIRSpec observations of the Orion Bar photodissociation region obtained as part of the PDRs4All Early Release Science (ERS) program, we extracted two template spectra capturing the evolution of the AIB-related emission in the 3.2-3.6 $\mu$m range, which includes the AIB at 3.3 $\mu$m and its main satellite band at 3.4 $\mu$m. In the Orion Bar, we analyze the spatial distribution of the templates and their relationship with the fluorescent emission of H${}_2$ in the near infrared. We find that one template ("AIB${}_{\mathrm{Irrad}}$") traces regions of neutral atomic gas with strong far-UV fields, while the other template ("AIB${}_{\mathrm{Shielded}}$") corresponds to shielded regions with lower FUV fields and a higher molecular gas fraction. We then show that these two templates can be used to fit the NIRSpec AIB-related spectra of nearby galaxies. The relative weight of the two templates (AIB${}_{Irrad/Shielded}$) is a tracer of the radiative feedback from massive stars on the ISM. We derive an estimate of AIB${}_{Irrad/Shielded}$ in a $z$ = 4.22 lensed galaxy, and find that it has a lower value than for local galaxies. This pilot study illustrates how a detailed analysis of AIB emission in nearby regions can be used to probe the physical conditions of the extragalactic ISM.

10 pages, 7 figures, accepted for publication in A&A

References in corpus (30)

• Dust Masses, PAH Abundances, and Starlight Intensities in the SINGS Galaxy Sample
• PDRs4All IV. An embarrassment of riches: Aromatic infrared bands in the Orion Bar
• Winds, Clumps, and Interacting Cosmic Rays in M82
• PDRs4All III: JWST's NIR spectroscopic view of the Orion Bar
• A Luminous Infrared Merger with Two Bipolar Molecular Outflows: ALMA and SMA Observations of NGC 3256
• Formation of the Methyl Cation by Photochemistry in a Protoplanetary Disk
• PDRs4All: A JWST Early Release Science Program on radiative feedback from massive stars
• Mixed aliphatic and aromatic composition of evaporating very small grains in NGC 7023 revealed by the 3.4/3.3 $\mu$m ratio
• All the PAHs: an AKARI-Spitzer Cross Archival Spectroscopic Survey of Aromatic Emission in Galaxies
• GOALS-JWST: Tracing AGN Feedback on the Star-Forming ISM in NGC 7469
• GOALS-JWST: Mid-Infrared Spectroscopy of the Nucleus of NGC 7469
• Spatial variations in aromatic hydrocarbon emission in a dust-rich galaxy
• The properties of Polycyclic Aromatic Hydrocarbons in galaxies: constraints on PAH sizes, charge and radiation fields
• PHANGS-JWST First Results: Tracing the Diffuse ISM with JWST Imaging of Polycyclic Aromatic Hydrocarbon Emission in Nearby Galaxies
• PDRs4All II: JWST's NIR and MIR imaging view of the Orion Nebula
• GOALS-JWST: Resolving the Circumnuclear Gas Dynamics in NGC 7469 in the Mid-Infrared
• The C--H Stretching Features at 3.2--3.5 Micrometer of Polycyclic Aromatic Hydrocarbons with Aliphatic Sidegroups
• GOALS-JWST: Hidden Star Formation and Extended PAH Emission in the Luminous Infrared Galaxy VV 114
• Superhydrogenated Polycyclic Aromatic Hydrocarbon Molecules: Vibrational Spectra in the Infrared
• GOALS-JWST: Revealing the Buried Star Clusters in the Luminous Infrared Galaxy VV 114
• The 3.3 micron PAH Emission as a Star Formation Rate Indicator
• GOALS-JWST: Gas Dynamics and Excitation in NGC7469 revealed by NIRSpec
• GOALS-JWST: Pulling Back the Curtain on the AGN and Star Formation in VV 114
• Photodissociation of aliphatic PAH derivatives under relevant astrophysical conditions
• Discovery of Carbon Radio Recombination Lines in M82
• Contribution of polycyclic aromatic hydrocarbon ionization to neutral gas heating in galaxies: model versus observations
• GOALS-JWST: Unveiling Dusty Compact Sources in the Merging Galaxy IIZw096
• Measuring the Heating and Cooling of the Interstellar Medium at High redshift: PAH and [C II] Observations of the Same Star Forming Galaxies at z~2
• Unmixing methods based on nonnegativity and weakly mixed pixels for astronomical hyperspectral datasets
• GOALS-JWST: NIRCam and MIRI Imaging of the Circumnuclear Starburst Ring in NGC 7469

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• Acenaphthene Derivatives as Signatures of C${}_{11}$H${}_9^{+}$ Reactivity with Methylated Naphthalenes
• PDRs4All XIX. The 6 to 9 $\mu$m region as a probe of PAH charge and size in the Orion Bar