PHANGS-JWST First Results: Tracing the Diffuse ISM with JWST Imaging of Polycyclic Aromatic Hydrocarbon Emission in Nearby Galaxies

Abstract

JWST observations of polycyclic aromatic hydrocarbon (PAH) emission provide some of the deepest and highest resolution views of the cold interstellar medium (ISM) in nearby galaxies. If PAHs are well mixed with the atomic and molecular gas and illuminated by the average diffuse interstellar radiation field, PAH emission may provide an approximately linear, high resolution, high sensitivity tracer of diffuse gas surface density. We present a pilot study that explores using PAH emission in this way based on MIRI observations of IC 5332, NGC 628, NGC 1365, and NGC 7496 from the PHANGS-JWST Treasury. Using scaling relationships calibrated in Leroy et al. (2022), scaled F1130W provides 10--40 pc resolution and 3$\sigma$ sensitivity of ${\Sigma }_{\mathrm{gas}}\sim 2$ M${}_{\odot }$ pc${}^{-2}$. We characterize the surface densities of structures seen at $<7$ M${}_{\odot }$ pc${}^{-2}$ in our targets, where we expect the gas to be HI-dominated. We highlight the existence of filaments, inter-arm emission, and holes in the diffuse ISM at these low surface densities. Below $\sim 10$ M${}_{\odot }$ pc${}^{-2}$ for NGC 628, NGC 1365, and NGC 7496 the gas distribution shows a ``Swiss cheese''-like topology due to holes and bubbles pervading the relatively smooth distribution of diffuse ISM. Comparing to recent galaxy simulations, we observe similar topology for the low surface density gas, though with notable variations between simulations with different setups and resolution. Such a comparison of high resolution, low surface density gas with simulations is not possible with existing atomic and molecular gas maps, highlighting the unique power of JWST maps of PAH emission.

arXiv comment18 pages, 6 figures, accepted as part of a PHANGS-JWST Focus Issue to appear in ApJ

References in corpus (86)

• Astropy: A Community Python Package for Astronomy
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• E pur si muove: Galiliean-invariant cosmological hydrodynamical simulations on a moving mesh
• The CO-to-H2 Conversion Factor
• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• Cosmological Hydrodynamics with Adaptive Mesh Refinement: a new high resolution code called RAMSES
• Infrared Emission from Interstellar Dust. II. The Diffuse Interstellar Medium
• THINGS: The HI Nearby Galaxy Survey
• The Neutral Atomic Phases of the ISM in the Galaxy
• Dust Masses, PAH Abundances, and Starlight Intensities in the SINGS Galaxy Sample
• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• The Dark Molecular Gas
• The CO-to-H2 Conversion Factor and Dust-to-Gas Ratio on Kiloparsec Scales in Nearby Galaxies
• The CO-to-H2 Conversion Factor From Infrared Dust Emission Across the Local Group
• Andromeda's Dust
• The Atomic to Molecular Transition in Galaxies. II: HI and H_2 Column Densities
• The initial conditions of stellar protocluster formation. I. A catalogue of Spitzer dark clouds
• New calibrations for abundance determinations in HII regions
• Simulating the formation of molecular clouds. II. Rapid formation from turbulent initial conditions
• The Evolution of ISM Mass Probed by Dust Emission -- ALMA Observations at z = 0.3 to 2
• The Interstellar dust properties of nearby galaxies
• Detection and Characterization of Cold Interstellar Dust and PAH Emission from COBE Observations
• Magnetically Aligned HI Fibers and the Rolling Hough Transform
• HI-to-H2 Transitions and H I Column Densities in Galaxy Star-Forming Regions
• Distances to PHANGS Galaxies: New Tip of the Red Giant Branch Measurements and Adopted Distances
• On the nature of star-forming filaments: I. Filament morphologies
• Tracing the total molecular gas in galaxies: [CII] and the CO-dark gas
• PHANGS CO kinematics: disk orientations and rotation curves at 150 pc resolution
• Giant Molecular Filaments in the Milky Way
• Oxygen Depletion in the Interstellar Medium: Implications for Grain Models and the Distribution of Elemental Oxygen
• Characterizing Magnetohydrodynamic Turbulence in the Small Magellanic Cloud
• Dust and Gas in the Magellanic Clouds from the HERITAGE Herschel Key Project. II. Gas-to-Dust Ratio Variations across ISM Phases
• The PHANGS-JWST Treasury Survey: Star Formation, Feedback, and Dust Physics at High Angular resolution in Nearby GalaxieS
• Star formation in metal-poor gas clouds
• New Constraints on the ${}^{12}$CO(2-1)/(1-0) Line Ratio Across Nearby Disc Galaxies
• Modeling Dust and Starlight in Galaxies Observed by Spitzer and Herschel: NGC 628 and NGC 6946
• Dust continuum emission as a tracer of gas mass in galaxies
• Low-J CO Line Ratios From Single Dish CO Mapping Surveys and PHANGS-ALMA
• The Physical Properties of Large-Scale Galactic Filaments
• Simulations of the star-forming molecular gas in an interacting M51-like galaxy
• Can dust emission be used to map the interstellar medium in high-redshift galaxies? Results from the Herschel Reference Survey
• Modeling Dust and Starlight in Galaxies Observed by Spitzer and Herschel: The KINGFISH Sample
• HI shells in the outer Milky Way
• Cold and Warm Atomic Gas around the Perseus Molecular Cloud. II. The Impact of High Optical Depth on the HI Column Density Distribution and Its Implication for the HI-to-H2 Transition
• Analytic HI-to-H2 Photodissociation Transition Profiles
• Scaling Relations of Compressible MHD Turbulence
• The Polycyclic Aromatic Hydrocarbon Mass Fraction on a 10 pc scale in the Magellanic Clouds
• PHANGS-JWST First Results: A statistical view on bubble evolution in NGC628
• The Relationship Between Molecular Gas, HI, and Star Formation in the Low-Mass, Low-Metallicity Magellanic Clouds
• ROHSA: Regularized Optimization for Hyper-Spectral Analysis - Application to phase separation of 21 cm data
• Cold and warm atomic gas around the Perseus molecular cloud I: Basic Properties
• Properties of cold and warm HI gas phases derived from a Gaussian decomposition of HI4PI data
• PHANGS-JWST First Results: Destruction of the PAH molecules in HII regions probed by JWST and MUSE
• PHANGS-JWST First Results: Multi-wavelength view of feedback-driven bubbles (The Phantom Voids) across NGC 628
• Clumping and the Interpretation of kpc-Scale Maps of the Interstellar Medium: Smooth HI and Clumpy, Variable H2 Surface Density
• Dust in the diffuse emission of the galactic plane - The Herschel/Spitzer SED fitting
• PHANGS-JWST First Results: Mid-infrared emission traces both gas column density and heating at 100 pc scales
• Molecular Gas Properties and CO-to-H2 Conversion Factors in the Central Kiloparsec of NGC 3351
• PHANGS-JWST First Results: Variations in PAH Fraction as a Function of ISM Phase and Metallicity
• First Results from the $Herschel$ and ALMA Spectroscopic Surveys of the SMC: The Relationship Between [CII]-bright Gas and CO-bright Gas at Low Metallicity
• CO-dark gas and molecular filaments in Milky Way-type galaxies - II: The temperature distribution of the gas
• Spitzer Analysis of HII Region Complexes in the Magellanic Clouds: Determining a Suitable Monochromatic Obscured Star Formation Indicator
• The Galactic Dust-Up: Modeling Dust Evolution in FIRE
• The Spatially Resolved Dust-to-Metals Ratio in M101
• Metals and dust content across the galaxies M101 and NGC 628
• The CO-dark molecular gas mass in 30 Doradus
• METAL: The Metal Evolution, Transport, and Abundance in the Large Magellanic Cloud Hubble program. II. Variations of interstellar depletions and dust-to-gas ratio within the LMC
• GASKAP-HI Pilot Survey Science I: ASKAP Zoom Observations of HI Emission in the Small Magellanic Cloud
• Topology of Neutral Hydrogen Within the Small Magellanic Cloud
• The history of dynamics and stellar feedback revealed by the HI filamentary structure in the disk of the Milky Way
• The Galactic dynamics revealed by the filamentary structure in atomic hydrogen emission
• TurbuStat: Turbulence Statistics in Python
• PHANGS-JWST First Results: The Dust Filament Network of NGC 628 and its Relation to Star Formation Activity
• PHANGS--JWST First Results: ISM structure on the turbulent Jeans scale in four disk galaxies observed by JWST and ALMA
• Simulations of the star-forming molecular gas in an interacting M51-like galaxy: cloud population statistics
• PHANGS-JWST First Results: The 21 $\mu$m Compact Source Population
• Polycyclic Aromatic Hydrocarbons, the Anomalous Microwave Emission, and Their Connection to the Cold Neutral Medium
• A new catalog of HI supershell candidates in the outer part of the Galaxy
• The Metallicity Dependence of the HI Shielding Layers in Nearby Galaxies
• A lack of constraints on the cold opaque HI mass: HI spectra in M31 and M33 prefer multi-component models over a single cold opaque component
• Identifying Tools for Comparing Simulations and Observations of Spectral-line Data Cubes
• The "Maggie" filament: Physical properties of a giant atomic cloud
• PHANGS-JWST First Results: A combined HST and JWST analysis of the nuclear star cluster in NGC 628
• The discovery of the largest gas filament in our Galaxy, or a new spiral arm?
• Diagnosing Turbulence in the Neutral and Molecular Interstellar Medium of Galaxies

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