Dust Emission as a Function of Stellar Population Age in the Nearby Galaxy M33

Abstract

Dust emission at 8 micron has been extensively calibrated as an indicator of current star formation rate for galaxies and ~kpc-size regions within galaxies. Yet, the exact link between the 8 micron emission and the young stellar populations in galaxies is still under question, as dust grains can be stochastically heated also by older field stars. In order to investigate this link, we have combined mid-infrared images from the Spitzer Space Telescope with a published star cluster candidates catalog for the Local Group galaxy M33. M33 is sufficiently close that the Spitzer's 8 micron images resolve individual regions of star formation. Star clusters represent almost-single-age stellar populations, which are significantly easier to model than more complex mixtures of stars. We find a decrease in the 8 micron luminosity per unit stellar mass as a function of age of the star clusters, with a large scatter that is consistent with varying fractions of stellar light absorbed by dust. The decrease and scatter both confirm findings based on more distant galaxies and are well described by simple models for the dust emission of a young stellar population. We conclude that the dust emission at 8 micron depends sensitively on the age of the stellar population, out to at least the oldest age analyzed here, ~400 Myr. This dependence complicates the use of the 8 micron emission as a star formation rate indicator, at least for small galactic regions and individual star forming regions. By leveraging the Spitzer legacy, this investigation paves the way for future explorations with the James Webb Space Telescope.

Accepted for publication on ApJ. Includes 5 figures

References in corpus (18)

• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• Metallicity Effects on Dust Properties in Starbursting Galaxies
• The Behavior of the Aromatic Features in M101 HII Regions: Evidence for Dust Processing
• Legacy ExtraGalactic UV Survey (LEGUS) with The Hubble Space Telescope. I. Survey Description
• Excitation of Polycyclic Aromatic Hydrocarbon (PAH) Emission: Dependence on Size Distribution, Ionization, and Starlight Spectrum and Intensity
• Star formation in M33: multiwavelength signatures across the disk
• Using H-alpha Morphology and Surface Brightness Fluctuations to Age-Date Star Clusters in M83
• Modeling Dust and Starlight in Galaxies Observed by Spitzer and Herschel: The KINGFISH Sample
• Radii of Young Star Clusters in Nearby Galaxies
• Investigating H$\alpha$, UV, and IR star-formation rate diagnostics for a large sample of z ~ 2 galaxies
• The M33 Variable Star Population Revealed by Spitzer
• A Catalog of Star Cluster Candidates in M33
• The MOSDEF Survey: Metallicity Dependence of the PAH Emission at High Redshift and Implications for 24 micron-inferred IR Luminosities and Star Formation Rates at z~2
• LEGUS and Halpha-LEGUS Observations of Star Clusters in NGC 4449: Improved Ages and the Fraction of Light in Clusters as a Function of Age
• Spitzer Analysis of HII Region Complexes in the Magellanic Clouds: Determining a Suitable Monochromatic Obscured Star Formation Indicator
• Quantifying the Heating Sources for Mid-infrared Dust Emissions in Galaxies: The Case of M 81
• The Age-Dependence of Mid-Infrared Emission Around Young Star Clusters
• Ages and Masses of Star Clusters in M33: a Multi-wavelength Study

Cited by in corpus (5)

• PHANGS-JWST First Results: Destruction of the PAH molecules in HII regions probed by JWST and MUSE
• Star Formation and Molecular Gas Diagnostics with Mid- and Far-Infrared Emission
• Empirical SED Templates for Star Clusters Observed with HST and JWST: No Strong PAH or IR Dust Emission after Five Myr
• Polycyclic aromatic hydrocarbons destruction in star-forming regions across 42 nearby galaxies
• The ISM scaling relations using inner HI and an application of estimating dust mass