Metal content of the circumgalactic medium around star-forming galaxies at z $\sim$ 2.6 as revealed by the VIMOS Ultra-Deep Survey

TL;DR

This study investigates the distribution of metals in the circumgalactic medium around star-forming galaxies at z~2.6, revealing correlations with galaxy properties and potential redshift evolution, using composite spectra from the VIMOS Ultra Deep Survey.

Contribution

It provides new observational insights into the spatial distribution and properties of metals in the CGM at high redshift, highlighting correlations with galaxy characteristics and possible evolutionary trends.

Findings

Detection of metal absorption lines up to ~170 kpc from galaxies.

Correlation between metal absorption strength and galaxy star formation rate and mass.

Evidence for redshift evolution in CGM metal content.

Abstract

The circumgalactic medium (CGM) is the location where the interplay between large-scale outflows and accretion onto galaxies occurs. Metals in different ionization states flowing between the circumgalactic and intergalactic mediums are affected by large galactic outflows and low-ionization state inflowing gas. Observational studies on their spatial distribution and their relation with galaxy properties may provide important constraints on models of galaxy formation and evolution. To provide new insights into the spatial distribution of the circumgalactic of star-forming galaxies, we select a sample of 238 close pairs at $1.5 < z <4.5$ ($\langle z\rangle\sim$2.6) from the VIMOS Ultra Deep Survey. We then generate composite spectra by co-adding spectra of $background$ galaxies that provide different sight-lines across the CGM to examine the spatial distribution of the gas located around these galaxies and investigate possible correlations between the strength of the low- and high-ionization absorption features with different galaxy properties. We detect C II, Si II, Si IV and C IV) up to separations $\langle b \rangle=$ 172 kpc and 146 kpc. Our $W_{0}$ radial profiles suggest a potential redshift evolution for the CGM gas content producing these absorptions. We find a correlation between C II and C IV with star formation rate, stellar mass and trends with galaxy size estimated by the effective radius and azimuthal angle. Galaxies with high star formation rate show stronger C IV absorptions compared with star-forming galaxies with low SFR and low stellar mass. These results could be explained by stronger outflows, softer radiation fields unable to ionize high-ionization state lines or by the galactic fountain scenario where metal-rich gas ejected from previous star-formation episodes fall back to the galaxy.