Insights from Synthetic Star-forming Regions: III. Calibration of Measurement Techniques of Star-formation Rates

TL;DR

This paper evaluates and improves methods for measuring star-formation rates in star-forming regions using synthetic observations, highlighting the limitations of existing infrared tracers at local scales and proposing new calibration strategies.

Contribution

It systematically assesses the accuracy of common SFR measurement techniques and introduces improved calibration methods tailored for individual star-forming regions.

Findings

Infrared SFR tracers calibrated for galaxies are unreliable at local scales.

Adjusting characteristic timescales improves calibration accuracy.

High-mass stellar feedback causes rapid infrared emission decline.

Abstract

Through an extensive set of realistic synthetic observations (produced in Paper I), we assess in this part of the paper series (Paper III) how the choice of observational techniques affects the measurement of star-formation rates (SFRs) in star-forming regions. We test the accuracy of commonly used techniques and construct new methods to extract the SFR, so that these findings can be applied to measure the SFR in real regions throughout the Milky Way. We investigate diffuse infrared SFR tracers such as those using 24 {\mu}m, 70 {\mu}m and total infrared emission, which have been previously calibrated for global galaxy scales. We set up a toy model of a galaxy and show that the infrared emission is consistent with the intrinsic SFR using extra-galactic calibrated laws (although the consistency does not prove their reliability). For local scales, we show that these techniques produce completely unreliable results for single star-forming regions, which are governed by different characteristic timescales. We show how calibration of these techniques can be improved for single star-forming regions by adjusting the characteristic timescale and the scaling factor and give suggestions of new calibrations of the diffuse star-formation tracers. We show that star-forming regions that are dominated by high-mass stellar feedback experience a rapid drop in infrared emission once high-mass stellar feedback is turned on, which implies different characteristic timescales. Moreover, we explore the measured SFRs calculated directly from the observed young stellar population. We find that the measured point sources follow the evolutionary pace of star formation more directly than diffuse star-formation tracers.