Feedback in Emerging Extragalactic Star Clusters, FEAST: The Relation between 3.3 μm Polycyclic Aromatic Hydrocarbon Emission and Star Formation Rate Traced by Ionized Gas in NGC 628

• Published in: The Astrophysical journal Vol. 971; no. 1; pp. 115 - 136
• Main Authors: Gregg, Benjamin, Calzetti, Daniela, Adamo, Angela, Bajaj, Varun, Ryon, Jenna E., Linden, Sean T., Correnti, Matteo, Cignoni, Michele, Messa, Matteo, Sabbi, Elena, Gallagher, John S., Grasha, Kathryn, Pedrini, Alex, Gutermuth, Robert A., Melinder, Jens, Kotulla, Ralf, Pérez, Gustavo, Krumholz, Mark R., Bik, Arjan, Östlin, Göran, Johnson, Kelsey E., Bortolini, Giacomo, Smith, Linda J., Tosi, Monica, Maji, Subhransu, Faustino Vieira, Helena
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.08.2024; IOP Publishing
• Subjects: Aromatic hydrocarbons; Correlation coefficient; Correlation coefficients; Emission analysis; Emissions; Feedback; Galaxies; H alpha line; H II regions; Hydrocarbons; Hydrogen recombinations; Initial mass function; Interstellar dust; Interstellar medium; James Webb Space Telescope; Local interstellar medium; Luminosity; Metallicity; Polycyclic aromatic hydrocarbons; Spiral galaxies; Star & galaxy formation; Star clusters; Star formation; Star formation rate; Star forming regions; Stars; Young star clusters
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ad54b4

Abstract We present maps of ionized gas (traced by Pa α and Br α ) and 3.3 μ m polycyclic aromatic hydrocarbon (PAH) emission in the nearby spiral galaxy NGC 628, derived from new JWST/NIRCam data from the Feedback in Emerging extrAgalactic Star clusTers (FEAST) survey. With this data, we investigate and calibrate the relation between 3.3 μ m PAH emission and star formation rate (SFR) in and around emerging young star clusters (eYSCs) on a scale of ∼40 pc. We find a tight (correlation coefficient ρ ∼ 0.9) sublinear (power-law exponent α ∼ 0.75) relation between the 3.3 μ m PAH luminosity surface density and SFR traced by Br α for compact, cospatial (within 0.″16 or ∼7 pc) peaks in Pa α , Br α , and 3.3 μ m (eYSC–I). The scatter in the relationship does not correlate well with variations in local interstellar medium metallicity, due to a radial metallicity gradient, but rather is likely due to stochastic sampling of the stellar initial mass function (IMF) and variations in the PAH heating and age of our sources. The deviation from a linear relation may be explained by PAH destruction in more intense ionizing environments, variations in age, and IMF stochasticity at intermediate to low luminosities. We test our results with various continuum subtraction techniques using combinations of NIRCam bands and find that they remain robust with only minor differences in the derived slope and intercept. An unexpected discrepancy is identified between the relations of hydrogen recombination lines (Pa α versus Br α ; H α versus Br α ).