The dependence of Galactic outflows on the properties and orientation of zCOSMOS galaxies at z ~ 1

TL;DR

This study investigates how the properties and orientation of zCOSMOS galaxies at z ~ 1 influence cool galactic outflows, revealing dependencies on stellar mass, star formation rate, galaxy color, and orientation.

Contribution

It provides new insights into the dependence of galactic outflow characteristics on galaxy properties and orientation at z ~ 1, using MgII absorption in stacked spectra.

Findings

Outflow equivalent width increases with stellar mass and star formation rate.

Face-on disk galaxies show higher outflow velocities than edge-on ones.

Irregular galaxies have outflow properties similar to face-on disks.

Abstract

We present an analysis of cool outflowing gas around galaxies, traced by MgII absorption lines in the co-added spectra of a sample of 486 zCOSMOS galaxies at 1 < z < 1.5. These galaxies span a range of stellar masses (9.45< log[M*/Msun]<10.7) and star formation rates (0.14 < log [SFR/Msun/yr] < 2.35). We identify the cool outflowing component in the MgII absorption and find that the equivalent width of the outflowing component increases with stellar mass. The outflow equivalent width also increases steadily with the increasing star formation rate of the galaxies. At similar stellar masses the blue galaxies exhibit a significantly higher outflow equivalent width as compared to red galaxies. The outflow equivalent width shows strong effect with star formation surface density ({\Sigma}SFR) of the sample. For the disk galaxies, the outflow equivalent width is higher for the face-on systems as compared to the edge-on ones, indicating that for the disk galaxies, the outflowing gas is primarily bipolar in geometry. Galaxies typically exhibit outflow velocities ranging from -200 km/s to -300 km/s and on average the face-on galaxies exhibit higher outflow velocity as compared to the edge-on ones. Galaxies with irregular morphologies exhibit outflow equivalent width as well as outflow velocities comparable to face on disk galaxies. These galaxies exhibit minimum mass outflow rates > 5-7 Msun/yr and a mass loading factor ({\eta} = dMout/dt /SFR) comparable to the star formation rates of the galaxies.