Calibrating mid-infrared emission as a tracer of obscured star formation on HII-region scales in the era of JWST

Abstract

Measurements of the star formation activity on cloud scales are fundamental to uncovering the physics of the molecular cloud, star formation, and stellar feedback cycle in galaxies. Infrared (IR) emission from small dust grains and polycyclic aromatic hydrocarbons (PAHs) are widely used to trace the obscured component of star formation. However, the relation between these emission features and dust attenuation is complicated by the combined effects of dust heating from old stellar populations and an uncertain dust geometry with respect to heating sources. We use images obtained with NIRCam and MIRI as part of the PHANGS--JWST survey to calibrate dust emission at 21$\mu \mathrm{m}$, and the emission in the PAH-tracing bands at 3.3, 7.7, 10, and 11.3$\mu \mathrm{m}$ as tracers of obscured star formation. We analyse $\sim$ 20000 optically selected HII regions across 19 nearby star-forming galaxies, and benchmark their IR emission against dust attenuation measured from the Balmer decrement. We model the extinction-corrected H$\alpha$ flux as the sum of the observed H$\alpha$ emission and a term proportional to the IR emission, with $a_{IR}$ as the proportionality coefficient. A constant $a_{IR}$ leads to extinction-corrected H$\alpha$ estimates which agree with those obtained with the Balmer decrement with a scatter of $\sim$ 0.1 dex for all bands considered. Among these bands, 21$\mu \mathrm{m}$ emission is demonstrated to be the best tracer of dust attenuation. The PAH-tracing bands underestimate the correction for bright HII regions, since in these environments the ratio of PAH-tracing bands to 21$\mu \mathrm{m}$ decreases, signalling destruction of the PAH molecules. For fainter HII regions all bands suffer from an increasing contamination from the diffuse infrared background.

accepted for publication in A&A

References in corpus (37)

• Cosmic Star Formation History
• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• Some Aspects of Measurement Error in Linear Regression of Astronomical Data
• A z=0 Multi-wavelength Galaxy Synthesis I: A WISE and GALEX Atlas of Local Galaxies
• The PHANGS-MUSE survey -- Probing the chemo-dynamical evolution of disc galaxies
• SDSS-IV MaNGA: The Impact of Diffuse Ionized Gas on Emission-line Ratios, Interpretation of Diagnostic Diagrams, and Gas Metallicity Measurements
• Distances to PHANGS Galaxies: New Tip of the Red Giant Branch Measurements and Adopted Distances
• PHANGS-ALMA Data Processing and Pipeline
• PHANGS CO kinematics: disk orientations and rotation curves at 150 pc resolution
• UV Dust Attenuation in Star-forming Galaxies: II Calibrating the A(UV) vs. L_TIR/L_UV relation
• Excitation of Polycyclic Aromatic Hydrocarbon (PAH) Emission: Dependence on Size Distribution, Ionization, and Starlight Spectrum and Intensity
• The PHANGS-JWST Treasury Survey: Star Formation, Feedback, and Dust Physics at High Angular resolution in Nearby GalaxieS
• New Constraints on the ${}^{12}$CO(2-1)/(1-0) Line Ratio Across Nearby Disc Galaxies
• A tale of two DIGs: The relative role of HII regions and low-mass hot evolved stars in powering the diffuse ionised gas (DIG) in PHANGS-MUSE galaxies
• Old and young stellar populations in DustPedia galaxies and their role in dust heating
• High-resolution, 3D radiative transfer modeling : I. The grand-design spiral galaxy M51
• The PHANGS-MUSE Nebula Catalogue
• All the PAHs: an AKARI-Spitzer Cross Archival Spectroscopic Survey of Aromatic Emission in Galaxies
• Environmental dependence of the molecular cloud lifecycle in 54 main sequence galaxies
• The Polycyclic Aromatic Hydrocarbon Mass Fraction on a 10 pc scale in the Magellanic Clouds
• The quenching of galaxies, bulges, and disks since cosmic noon: A machine learning approach for identifying causality in astronomical data
• The ALMaQUEST Survey IX: The nature of the resolved star forming main sequence
• PHANGS-JWST First Results: Destruction of the PAH molecules in HII regions probed by JWST and MUSE
• PHANGS-JWST First Results: Mid-infrared emission traces both gas column density and heating at 100 pc scales
• PHANGS-JWST First Results: Mapping the 3.3 micron Polycyclic Aromatic Hydrocarbon Vibrational Band in Nearby Galaxies with NIRCam Medium Bands
• PHANGS-JWST First Results: Variations in PAH Fraction as a Function of ISM Phase and Metallicity
• PHANGS-JWST First Results: Tracing the Diffuse ISM with JWST Imaging of Polycyclic Aromatic Hydrocarbon Emission in Nearby Galaxies
• Calibration of hybrid resolved star formation rate recipes based on PHANGS-MUSE H$\alpha$ and H$\beta$ maps
• High-Resolution Radiative Transfer Modelling of M33
• A new estimator of resolved molecular gas in nearby galaxies
• Star Formation and Molecular Gas Diagnostics with Mid- and Far-Infrared Emission
• PHANGS-JWST First Results: The 21 $\mu$m Compact Source Population
• PHANGS-JWST First Results: A Global and Moderately Resolved View of Mid-Infrared and CO Line Emission from Galaxies at the Start of the JWST Era
• MUSE stares into the shadows: the high-resolution dust attenuation curve of NGC 5626
• Star-formation rate and stellar mass calibrations based on infrared photometry and their dependence on stellar population age and extinction
• The Contribution of Evolved Stars to PAH Heating and Implications for Estimating Star Formation Rates
• A Comparative Study of Mid-Infrared Star-Formation Rate Tracers and Their Metallicity Dependence

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