Modeling Dust and Starlight in Galaxies Observed by Spitzer and Herschel: The KINGFISH Sample
Metadatos
Afficher la notice complèteEditorial
The American Astronomical Society
Materia
Astrophysical dust processes (99) Polycyclic aromatic hydrocarbons (1280) Interstellar medium (847) Infrared galaxies (790)
Date
2020-02Referencia bibliográfica
Aniano, G., Draine, B. T., Hunt, L. K., Sandstrom, K., Calzetti, D., Kennicutt, R. C., ... & Smith, J. D. (2020). Modeling Dust and Starlight in Galaxies Observed by Spitzer and Herschel: The KINGFISH Sample. The Astrophysical Journal, 889(2), 150. [https://doi.org/10.3847/1538-4357/ab5fdb]
Résumé
Interstellar dust and starlight are modeled for the galaxies of the project “Key Insights on Nearby Galaxies: A FarInfrared Survey with Herschel.” The galaxies were observed by the Infrared Array Camera and the Multiband
Imaging Photometer for Spitzer on Spitzer Space Telescope, and the Photodetector Array Camera and Spectrometer
and the Spectral and Photometric Imaging Receiver on Herschel Space Observatory. With data from 3.6 to
500 μm, dust models are strongly constrained. Using a physical dust model, for each pixel in each galaxy we
estimate (1) dust surface density, (2) dust mass fraction in polycyclic aromatic hydrocarbons (PAHs), (3)
distribution of starlight intensities heating the dust, (4) total infrared (IR) luminosity emitted by the dust, and (5) IR
luminosity originating in subregions with high starlight intensity. The dust models successfully reproduce the
observed global and resolved spectral energy distributions. With the angular resolution of Herschel, we obtain
well-resolved maps (available online) for the dust properties. As in previous studies, we find the PAH fraction qPAH
to be an increasing function of metallicity, with a threshold oxygen abundance Z/Ze ≈ 0.1, but we find the data to
be fitted best with qPAH increasing linearly with log O H ( ) above a threshold value of 0.15(O/H)e. We obtain total
dust masses for each galaxy by summing the dust mass over the individual map pixels; these “resolved” dust
masses are consistent with the masses inferred from a model fit to the global photometry. The global dust-to-gas
ratios obtained from this study are found to correlate with galaxy metallicities. Systems with Z/Ze 0.5 have
most of their refractory elements locked up in dust, whereas in systems with Z/Ze 0.3 most of these elements
tend to remain in the gas phase. Within galaxies, we find that qPAH is suppressed in regions with unusually warm
dust with nL L n ( ) 70 m 0.4 m dust. With knowledge of one long-wavelength flux density ratio (e.g., f160/f500), the
minimum starlight intensity heating the dust (Umin) can be estimated to within ∼50%, despite a variation in Umin of
more than two orders of magnitude. For the adopted dust model, dust masses can be estimated to within ∼0.2 dex
accuracy using the f160/f500 flux ratio and the integrated dust luminosity, and to ∼0.07 dex accuracy using the
500 μm luminosity nLn ( ) 500 mm alone. There are additional systematic errors arising from the choice of dust model, but these are hard to estimate. These calibrated prescriptions for estimating starlight heating intensity and
dust mass may be useful for studies of high-redshift galaxies.