The Mass-Dependent Star Formation Histories of Disk Galaxies: Infall Model Versus Observations

Abstract

We introduce a simple model to explore the star formation histories of disk galaxies. We assume that the disk origins and grows by continuous gas infall. The gas infall rate is parametrized by the Gaussian formula with one free parameter: infall-peak time t p . The Kennicutt star formation law is adopted to describe how much cold gas turns into stars. The gas outflow process is also considered in our model. We find that, at given galactic stellar mass M * , model adopting late infall-peak time t p results in blue colors, low metallicity, high specific star formation rate and high gas fraction, while gas outflow rate mainly influences the gas-phase metallicity and star formation efficiency mainly influences the gas fraction. Motivated by the local observed scaling relations, we construct a mass-dependent model by assuming low mass galaxy has later infall-peak time t p and larger gas outflow rate than massive systems. It is shown that this model can be in agreement with not only the local observations, but also the observed correlations between specific star formation rate and galactic stellar mass SF R/M * ∼ M * at intermediate redshift z < 1. Comparison between the Gaussian-infall model and exponential-infall model is also presented. It shows that the exponential-infall model predicts higher star formation rate at early stage and lower star formation rate later than that of Gaussian-infall. Our results suggest that the Gaussian infall rate may be more reasonable to describe the gas cooling process than the exponential infall rate, especially for low-mass systems.

The star formation history of low-mass disk galaxies: A case study of NGC 300

“…Indeed, both analytical (Erb 2008) and hydrodynamic (Finlator & Davé 2008) models showed that galactic outflows are important to reproduce the stellar mass-metallicity relation of galaxies. Moreover, for galaxies with stellar mass M * ≤ 10 10.5 M , the outflow process plays a crucial role during their evolution histories (Tremonti et al 2004;Spitoni et al 2010;Chang et al 2010). Finally, galaxies with rotation speed V rot ≤ 100-150 km s −1 may expel a large part of their supernova ejecta to the circumgalactic medium (Garnett 2002).…”

“…Since NGC 300 is a fairly low-mass disk galaxy (M * ≈ 10 9.29 M , Muñoz-Mateos et al 2007) with a rotation speed about V rot ≈ 91 km s −1 (Garnett 2002), the gas-outflow process has a significant influence on the chemical enrichment during its evolution history. We assume that the outflowing gas has the same metallicity as the ISM at the time the outflow is launched, and the outflowing gas does not fall to the disk again (Chang et al 2010;Kang et al 2012;Ho et al 2015). We follow the approach of Recchi et al (2008), i.e., the gas outflow rate f out (r, t) (in units of M pc −2 Gyr −1 ) is proportional to SFR surface density Ψ(r, t).…”

“…The parameter R is the return fraction and we obtain R = 0.43 after adopting stellar initial mass function (IMF) between 0.1 M and 100 M from Chabrier (2003). The parameter y is the nucleosynthesis yield and we set y = 1 Z throughout this work (Fu et al 2009;Chang et al 2010;Kang et al 2012). The parameter Z in is the metallicity of the infalling gas and we assume the infalling gas is metal-free, i.e., Z in = 0.…”

“…The parameter Z in is the metallicity of the infalling gas and we assume the infalling gas is metal-free, i.e., Z in = 0. Z out (r, t) is the metallicity of the outflowing gas and we assume that the outflow gas has the same metallicity as the ISM at the time the outflows are launched, e.g., Z out (r, t) = Z(r, t) (Chang et al 2010;Ho et al 2015). In summary, the infall timescale τ and the outflow coefficient b out are two free parameters in our model.…”

Long-slit Spectroscopy of Edge-on Low Surface Brightness Galaxies

“…Additionally, judging from the offset between the two closed-box lines in Figure 6, we find evidence that our LSBGs retain up to ∼ 3 times as much of their metals compared with dwarf irregulars (green squares), consistent with metal retention being related to galaxy mass. In any case, although the closed-box scenario cannot be completely ruled out for our LSBG sample, there is still substantial room for considering other, more complicated chemical evolution models with outflow or even infall (e.g., Edmunds 1990;Chang et al 2010) for our LSBG sample.…”