The gas inflow and outflow rate in star-forming galaxies at $z\sim1.4$

TL;DR

This study estimates gas inflow and outflow rates in star-forming galaxies at redshift ~1.4 using a chemical evolution model, revealing a decline in these rates from higher to lower redshifts and comparing well with previous findings.

Contribution

It provides new constraints on gas flow rates at z~1.4 and demonstrates their evolution across cosmic time using a simple analytic model and observational data.

Findings

Inflow rate is approximately 1.8 times the SFR.

Outflow rate is approximately 0.6 times the SFR.

Both inflow and outflow rates decrease from z~2.2 to z~0.

Abstract

We try to constrain the gas inflow and outflow rate of star-forming galaxies at $z\sim1.4$ by employing a simple analytic model for the chemical evolution of galaxies. The sample is constructed based on a large near-infrared (NIR) spectroscopic sample observed with Subaru/FMOS. The gas-phase metallicity is measured from the [\ion{N}{2}]$\lambda$6584/H$\alpha$ emission line ratio and the gas mass is derived from the extinction corrected H$\alpha$ luminosity by assuming the Kennicutt-Schmidt law. We constrain the inflow and outflow rate from the least-$\chi^{2}$ fittings of the observed gas mass fraction, stellar mass, and metallicity with the analytic model. The joint $\chi^{2}$ fitting shows the best-fit inflow rate is $\sim1.8$ and the outflow rate is $\sim0.6$ in unit of star-formation rate (SFR). By applying the same analysis to the previous studies at $z\sim0$ and $z\sim2.2$, it is shown that the both inflow rate and outflow rate decrease with decreasing redshift, which implies the higher activity of gas flow process at higher redshift. The decreasing trend of the inflow rate from $z\sim2.2$ to $z\sim0$ agrees with that seen in the previous observational works with different methods, though the absolute value is generally larger than the previous works. The outflow rate and its evolution from $z\sim2.2$ to $z\sim0$ obtained in this work agree well with the independent estimations in the previous observational works.