Star formation Rate calibrations with infrared data of young star-forming regions in NGC6946 and M100: the effect of metallicity and IMF upper mass cutoff
Abstract
By means of the state-of-the-art radiative transfer code GRASIL (GRAphites and SILicates) in which the recently updated database of PARSEC's (PAdova TRieste Stellar Evolutionary Code) evolutionary tracks of massive stars has been implemented, we predict the panchromatic spectral energy distribution (including halpha emission lines) of star forming regions in the nearby and well studied starburst galaxy NGC6946 and that of the normal star-forming galaxy M100.We carry out a critical investigation of the effect of metallicity, IMF upper mass limit and star formation regime (star bursting versus normal star forming) on star formation rate (SFR) and dust attenuation properties of star forming galaxies. This allowed for the provision, from our best fit models, of a consistent set of SFR calibrations, that are explicitly dependent on metallicity and IMF upper mass limit and also on the age of the starburst, at wavelengths ranging from 3um to 1000um. We complement these with similar calibrations at radio wavelengths which do not suffer dust attenuation.We show that the upper mass limit can be well constrained by combining information from the observed far infrared, 24um, 33 GHz and Halpha luminosities. Another interesting property derived from the fits is that, while in normal galaxies the attenuation in the lines is significantly higher than that in the nearby continuum, in individual star bursting regions they are similar, supporting the notion that this effect is due to an age selective extinction. Since in these conditions the Balmer decrement method may not be accurate, we provide relations to estimate the attenuation from the observed 24um or 33GHz fluxes. These relations can be useful for the analysis of young high redshift galaxies.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E2489O