Final Activity Report Summary - EHIG (Evolution of highly ionised gas over cosmic time)
As galaxy formation has proceeded across cosmic time, the collapse of matter into galactic potential wells together with supernova-driven galactic outflows has led to the generation of large volumes of interstellar plasma in and around galaxies.
In this project, the observational properties of these plasma halos were studied using optical absorption line spectroscopy of background quasars. The spectra were obtained using the UVES spectrograph mounted on the Very Large Telescope at Cerro Paranal, Chile. Absorption features from five-times-ionised oxygen atoms, four-times-ionised nitrogen atoms, and three-times-ionised carbon atoms were observed at the precise redshift where galactic structures where known to reside, based on prior analysis of the lines of neutral hydrogen. Analysis of the absorption line profiles has led to quantitative measurements of the properties of highly ionised gas: its mass, phase structure, and kinematics. In this dataset we found evidence for galactic winds, in the form of ionised outflows driven at speeds of up to 1000 km/s.
The most important scientific achievement is the first detection of hot interstellar gas (at temperatures above 100 000 Kelvin) in high-redshift galaxies. This plasma phase may harbour a significant fraction of all the metals produced by star formation in the early Universe.
In this project, the observational properties of these plasma halos were studied using optical absorption line spectroscopy of background quasars. The spectra were obtained using the UVES spectrograph mounted on the Very Large Telescope at Cerro Paranal, Chile. Absorption features from five-times-ionised oxygen atoms, four-times-ionised nitrogen atoms, and three-times-ionised carbon atoms were observed at the precise redshift where galactic structures where known to reside, based on prior analysis of the lines of neutral hydrogen. Analysis of the absorption line profiles has led to quantitative measurements of the properties of highly ionised gas: its mass, phase structure, and kinematics. In this dataset we found evidence for galactic winds, in the form of ionised outflows driven at speeds of up to 1000 km/s.
The most important scientific achievement is the first detection of hot interstellar gas (at temperatures above 100 000 Kelvin) in high-redshift galaxies. This plasma phase may harbour a significant fraction of all the metals produced by star formation in the early Universe.