# Probing the Timescale of the 1.4 GHz Radio emissions as a Star formation tracer

**Authors:** R. C. Arango-Toro, L. Ciesla, O. Ilbert, B. Magnelli, E. F. Jiménez-Andrade, V. Buat  
**arXiv:** [2304.13758](https://arxiv.org/abs/2304.13758)  
**Date:** 2023-04-26  
**Summary page:** https://www.summarizepaper.com/en/paper/2304.13758v1/

## Key points

- Radio emissions can be used as a tracer for star formation rate (SFR)
- Advantages of radio emissions over other SFR tracers include being unaffected by dust and pinpointing at sub-arc-second levels
- Interpreting low frequency 1.4 GHz luminosity is challenging due to difficulties in modeling cosmic ray paths in the interstellar medium and their interactions with magnetic fields
- The authors compare SFR derived from radio observations to those derived from spectral energy distribution (SED) modeling using Code Investigating GALaxy Emission (CIGALE) with a non-parametric star formation history model (SFH)
- Approximately 27% of galaxies present a radio SFR at least ten times larger than the instantaneous SFR from SED-fitting, primarily affecting galaxies that show declining SFH activity over the last 300 million years
- Both SFR indicators converge toward a consistent value when SFHs are averaged over periods longer than 150 million years to derive SED-based SFRs
- Low-frequency 1.4 GHz radio is an excellent tracer for star formation activity in galaxies with constant or increasing SFHs, but not reliable for quenching galaxies according to their results
- The sensitivity of low-frequency radio emission as an indicator of star formation time could be longer than 150 million years based on their analysis

## Summary

In the study "Probing the Timescale of the 1.4 GHz Radio emissions as a Star formation tracer," authors R. C. Arango-Toro, L. Ciesla, O. Ilbert, B. Magnelli, E. F. Jiménez-Andrade, and V. Buat investigate the use of radio emissions as a tracer for star formation rate (SFR). Radio emissions have advantages over other SFR tracers since they are unaffected by dust and can be pinpointed at sub-arc-second levels; however, interpreting low frequency 1.4 GHz luminosity is challenging due to difficulties in modeling cosmic ray paths in the interstellar medium and their interactions with magnetic fields. The authors compare SFR derived from radio observations to those derived from spectral energy distribution (SED) modeling using Code Investigating GALaxy Emission (CIGALE) with a non-parametric star formation history model (SFH). They fit data over a wavelength range from ultraviolet (UV) up to mid-infrared (mid-IR) to better understand the behavior of radio emission as an SFR tracer and its link with star-formation histories. Their analysis reveals that approximately 27% of galaxies present a radio SFR at least ten times larger than the instantaneous SFR from SED-fitting, primarily affecting galaxies that show declining SFH activity over the last 300 million years. Both SFR indicators converge toward a consistent value when SFHs are averaged over periods longer than 150 million years to derive SED-based SFRs. While low-frequency 1.4 GHz radio is an excellent tracer for star formation activity in galaxies with constant or increasing SFHs, it is not reliable for quenching galaxies according to their results. The authors suggest that the sensitivity of low-frequency radio emission as an indicator of star formation time could be longer than 150 million years based on their analysis. They validate their results by checking for any remaining active galaxy nuclei (AGN) contribution and testing the impact of their SFH modeling approach on their findings.