Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 498, Issue 1, Pages 235-257Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/staa2430
Keywords
HII regions; galaxies: evolution; galaxies: ISM; galaxies: star formation; galaxies: stellar content
Categories
Funding
- state of Baden-Wurttemberg through bwHPC
- German Research Foundation (DFG) [INST 35/1134-1 FUGG, INST 37/935-1 FUGG, KR4801/1-1]
- European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme via the ERC Starting Grant MUSTANG [714907]
- DFG Sachbeihilfe [KR4801/2-1]
- Australia Research Council [DP160100695, FT180100375]
- Australia-Germany Joint Research Cooperation Scheme (UA-DAAD) [57387355]
- STFC [ST/R000484/1, ST/L00061X/1] Funding Source: UKRI
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We recently presented a new statistical method to constrain the physics of star formation and feedback on the cloud scale by reconstructing the underlying evolutionary timeline. However, by itself this new method only recovers the relative durations of different evolutionary phases. To enable observational applications, it therefore requires knowledge of an absolute 'reference time-scale' to convert relative time-scales into absolute values. The logical choice for this reference time-scale is the duration over which the star formation rate (SFR) tracer is visible because it can be characterized using stellar population synthesis (SPS) models. In this paper, we calibrate this reference time-scale using synthetic emission maps of several SFR tracers, generated by combining the output from a hydrodynamical disc galaxy simulation with the SPS model SLUG2. We apply our statistical method to obtain self-consistent measurements of each tracer's reference time-scale. These include Ha and 12 ultraviolet (UV) filters (from GALEX, Swift, and HST), which cover a wavelength range 150-350 nm. At solar metallicity, the measured reference time-scales of H alpha are 4.32(-0.23)(+0.09) Myr with continuum subtraction, and 6-16 Myr without, where the time-scale increases with filter width. For the UV filters we find 17-33 Myr, nearly monotonically increasing with wavelength. The characteristic time-scale decreases towards higher metallicities, as well as to lower star formation rate surface densities, owing to stellar initial mass function sampling effects. We provide fitting functions for the reference time-scale as a function of metallicity, filter width, or wavelength, to enable observational applications of our statistical method across a wide variety of galaxies.
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