An evolving and mass-dependent σsSFR-M  relation for galaxies

Antonios Katsianis*, Xianzhong Zheng, Valentino Gonzalez, Guillermo Blanc, Claudia Del P. Lagos, Luke J. M. Davies, Peter Camps, Ana Trčka, Maarten Baes, Joop Schaye, James W. Trayford, Tom Theuns, Marko Stalevski

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The scatter (σ sSFR) of the specific star formation rates of galaxies is a measure of the diversity in their star formation histories (SFHs) at a given mass. In this paper, we employ the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations to study the dependence of the σ sSFR of galaxies on stellar mass (M ) through the σ sSFR-M relation in z ∼ 0-4. We find that the relation evolves with time, with the dispersion depending on both stellar mass and redshift. The models point to an evolving U-shaped form for the σ sSFR-M relation, with the scatter being minimal at a characteristic mass M of 109.5 M o and increasing both at lower and higher masses. This implies that the diversity of SFHs increases toward both the low- and high-mass ends. We find that feedback from active galactic nuclei is important for increasing the σ sSFR for high-mass objects. On the other hand, we suggest that feedback from supernovae increases the σ sSFR of galaxies at the low-mass end. We also find that excluding galaxies that have experienced recent mergers does not significantly affect the σ sSFR-M relation. Furthermore, we employ the EAGLE simulations in combination with the radiative transfer code SKIRT to evaluate the effect of SFR/stellar mass diagnostics in the σ sSFR-M relation, and find that the SFR/M methodologies (e.g., SED fitting, UV+IR, UV+IRX-β) widely used in the literature to obtain intrinsic properties of galaxies have a large effect on the derived shape and normalization of the σ sSFR-M relation.

Original languageEnglish
Article number11
Number of pages17
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 26 Jun 2019


  • Cosmology: Theory
  • Galaxies: Star Formation
  • Surveys
  • UKRI
  • STFC


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