The Kinematics of CIV in Star-Forming Galaxies at z~1.2

TL;DR

This study analyzes the kinematics of CIV in star-forming galaxies at z~1.2, revealing blueshifted high-ionization gas linked to star formation and providing insights into the multi-phase circumgalactic medium.

Contribution

First statistical analysis of CIV kinematics in z~1.2 star-forming galaxies, distinguishing interstellar CIV from stellar wind profiles and linking absorption features to galaxy properties.

Findings

69% of CIV profiles are blueshifted, indicating outflows.

CIV shows a small but significant blueshift relative to FeII.

CIV blueshift correlates with star formation rate.

Abstract

We present the first statistical sample of rest-frame far-UV spectra of star-forming galaxies at z~1. These spectra are unique in that they cover the high-ionization CIV{\lambda}{\lambda}1548, 1550 doublet. We also detect low-ionization features such as SiII{\lambda}1527, FeII{\lambda}1608, AlII{\lambda}1670, NiII{\lambda}{\lambda}1741, 1751 and SiII{\lambda}1808, and intermediate-ionization features from AlIII{\lambda}{\lambda}1854, 1862. Comparing the properties of absorption lines of lower- and higher- ionization states provides a window into the multi-phase nature of circumgalactic gas. Our sample is drawn from the DEEP2 survey and spans the redshift range 1.01 < z < 1.35 (<z> = 1.25). By isolating the interstellar CIV absorption from the stellar P-Cygni wind profile we find that 69% of the CIV profiles are blueshifted with respect to the systemic velocity. Furthermore, CIV shows a small but significant blueshift relative to FeII (offset of the best-fit linear regression -76 $\pm$ 26 km/s). At the same time, the CIV blueshift is on average comparable to that of MgII{\lambda}{\lambda}2796, 2803. At this point, in explaining the larger blueshift of CIV absorption at the ~ 3-sigma level, we cannot distinguish between the faster motion of highly-ionized gas relative to gas traced by FeII, and filling in on the red side from resonant CIV emission. We investigate how far-UV interstellar absorption kinematics correlate with other galaxy properties using stacked spectra. These stacking results show a direct link between CIV absorption and the current SFR, though we only observe small velocity differences among different ionization states tracing the outflowing ISM.