An Evolving and Mass-dependent σsSFR–M_⋆ Relation for Galaxies

Abstract

The scatter (σ sSFR ) of the specific star formation rates (sSFRs) of galaxies is a measure of the diversity in their star formation histories (SFHs) at a given mass. In this paper we employ the 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-shape form for the σ sSFR -M ⋆ relation with the scatter being minimal at a characteristic mass M ⋆ of 10 9.5 M ⊙ and increasing both at lower and higher masses. This implication is that the diversity of SFHs increases towards both at the low-and high-mass ends. We find that active galactic nuclei feedback is important for increasing the σ sSFR for high mass objects. On the other hand, we suggest that SNe feedback 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 combination of the EAGLE simulations 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.

Reproducing the Universe: a comparison between the EAGLE simulations and the nearby DustPedia galaxy sample

“…The new constraint minimally affects the EAGLE-SKIRT sample, because almost all galaxies in the selected mass bin already have the sSFRs above −10.8 yr −1 . This is in agreement with Katsianis et al (2019), who found the fraction of only ≈ 0.1 early-type galaxies at similar M star and sSFRs, for the whole EAGLE reference simulation, at z = 0. The results are shown in bottom panels of Fig.…”

Deep Extragalactic VIsible Legacy Survey (DEVILS): evolution of the σSFR–M⋆ relation and implications for self-regulated star formation

“…We present a detailed comparison to previous observations (Noeske et al 2007 ;Guo, Zheng & Fu 2013 ;Guo et al 2015 ;Ilbert et al 2015 ;Schreiber et al 2015 ;Willett et al 2015 ;Boogaard et al 2018 ), the EAGLE hydrodynamical simulations (Matthee & Schaye 2018 ;Katsianis et al 2019 ) and Shark semi-analytic model (Lagos et al 2018 ) in the Appendix, which is summarized in Fig. 8 .…”

“…Sparre et al ( 2015 ) use the Illustris simulation (Vogelsberger et al 2014 ) to explore the SFS and at z ∼ 0 find a relatively flat σ SFR -M at 9 < log 10 [ M * /M ] < 10.5 and increasing dispersion to higher masses, roughly consistent with observations. Katsianis et al ( 2019 ) applied a similar approach to EAGLE (Crain et al 2015 ;Schaye et al 2015 ;McAlpine et al 2016 ;Matthee & Schaye 2018 ) and find a 'U-shaped' σ SFR -M relation similar to that of Willett et al ( 2015 ). Conversely, Matthee & Schaye ( 2018 ) undertake a similar study with EAGLE but find a linearly decreasing σ SFR -M with stellar mass.…”

“…One of the key diagnostics in the variation of SFHs that leads to the distribution of galaxy properties is the dispersion along the SFR-M relation ( σ SFR -M ; Guo et al 2015 ;Willett et al 2015 ;Davies et al 2019a ;Katsianis et al 2019 ). At a given stellar mass, this dispersion essentially encodes the variation in galaxy SFHs -caused by the processes outlined abo v e. Recently, numerous studies have explored the shape of the σ SFR -M relation, finding v aried observ ational measurements of the dispersion at a given stellar mass and redshift (Elbaz et al 2007 ;Noeske et al 2007 ;Rodighiero et al 2010 ;Whitaker et al 2012 ;Guo et al 2015 ;Schreiber et al 2015 ;Santini et al 2017 ).…”

The high-redshift SFR–M* relation is sensitive to the employed star formation rate and stellar mass indicators: towards addressing the tension between observations and simulations

“…To infer stellar masses from the EAGLE+SKIRT galaxies, we use the Fitting and Assessment of Synthetic Templates (FAST) code (Kriek et al 2009) to fit the mock SEDs, following a similar procedure as various observational studies (González et al 2012;Botticella et al 2017;Aird et al 2018). Following the same procedure as in Katsianis et al (2019) we use the Bruzual & Charlot (2003) stellar population synthesis models and assume an exponentially declining SFH [SFR = exp(−t/tau)] (Fumagalli et al 2016;Abdurro'uf 2018), the Chabrier IMF (Chabrier 2003), the Calzetti et al (2000) dust attenuation law (Cullen et al 2018;McLure et al 2018b) and a metallicity Z = 0.2 Z⊙ (Chan et al 2016;McLure et al 2018a). We note that these assumptions are motivated by observational studies but not necessarily stand neither for the real/observed nor the EAGLE+SKIRT simulated galaxies (in table 1 we sumarize the SED fitting assumptions used by different authors).…”