DEVILS/MIGHTEE/GAMA/DINGO: The Impact of SFR Timescales on the SFR-Radio Luminosity Correlation
arxiv(2024)
摘要
The tight relationship between infrared luminosity (L_TIR) and 1.4
GHz radio continuum luminosity (L_1.4GHz) has proven useful for
understanding star formation free from dust obscuration. Infrared emission in
star-forming galaxies typically arises from recently formed, dust-enshrouded
stars, whereas radio synchrotron emission is expected from subsequent
supernovae. By leveraging the wealth of ancillary far-ultraviolet -
far-infrared photometry from the Deep Extragalactic VIsible Legacy Survey
(DEVILS) and Galaxy and Mass Assembly (GAMA) surveys, combined with 1.4 GHz
observations from the MeerKAT International GHz Tiered Extragalactic
Exploration (MIGHTEE) survey and Deep Investigation of Neutral Gas Origins
(DINGO) projects, we investigate the impact of timescale differences between
far-ultraviolet - far-infrared and radio-derived star formation rate (SFR)
tracers. We examine how the SED-derived star formation histories (SFH) of
galaxies can be used to explain discrepancies in these SFR tracers, which are
sensitive to different timescales. Galaxies exhibiting an increasing SFH have
systematically higher L_TIR and SED-derived SFRs than predicted from
their 1.4 GHz radio luminosity. This indicates that insufficient time has
passed for subsequent supernovae-driven radio emission to accumulate. We show
that backtracking the SFR(t) of galaxies along their SED-derived SFHs to a time
several hundred megayears prior to their observed epoch will both linearise the
SFR-L_1.4GHz relation and reduce the overall scatter. The minimum
scatter in the SFR(t)-L_1.4GHz is reached at 200 - 300 Myr prior,
consistent with theoretical predictions for the timescales required to disperse
the cosmic ray electrons responsible for the synchrotron emission.
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