Résumé / Abstract Journal-club_Galaxies

Séminaire/Seminar Galaxies

« Probing the timescale of the 1.4 GHz radio emissions as a star formation tracer »

Rafael Arango-Toro
Lab. Astroph. Marseille (LAM) (Marseille, France)

Radio used as tracer of the star formation rate (SFR) presents enormous advantages because it is not affected by dust as well as sources can be pinpoint at the subarcsecond level. The interpretation of the low-frequency 1.4 GHz luminosity is hampered by the difficulty of modeling the paths of cosmic rays in the interstellar medium, however, and by their interactions with the magnetic field. In this work We compare the SFR derived from radio observations, and the SFRs derived from spectral energy distribution (SED) modeling. We aim at better understanding the behavior of the SFR radio tracer, with a specific emphasis on the link to star formation histories (SFHs). The analysis is based on a subsample of 1584 star-forming galaxies extracted from the COSMOS VLA 3 GHz survey project. We used the SED modeling Code Investigating GALaxy Emission, CIGALE, with a nonparametric model for the SFH and fit the data over the wavelength range from the ultraviolet (UV) to the mid-infrared. We interpret difference between radio and SED-based SFR tracers in the light of recent gradients in the derived SFH. To validate the robustness of the results, we searched for any remaining contribution of active galaxy nuclei and tested the impact of our SFH modeling approach. Approximately 27% of our galaxies present a radio SFR that is at least ten times higher tan the instantaneous SFR from SED fitting. This trend primarily affects galaxies whose SFH activity decreased over the last 300 Myr. Both SFR indicators converge towards a consistent value when the SFHs are averaged over a period longer than 150 Myrs to derive the SFR indicator from the SED fitting. Although the radio emission at a low frequency of 1.4 GHz is a good tracer of star formation activity of galaxies with a constant or increasing SFH, our results indicate that is not the case for quenched galaxies. Our Analysis suggest that the star formation time sensitivity of low radio frequency might be longer than 150 Myrs. Interestingly, the discrepancy between the radio SFR and the SED SFR can be used as diagnostic to select post-starburst galaxies.
jeudi 11 mai 2023 - 11:30
Salle des séminaires Évry Schatzman
Institut d'Astrophysique de Paris
Page web du séminaire / Seminar's webpage