Andrew Bunker

Abstract:

The analysis of Lyman-break galaxies lying at z > 5 has greatly enhanced our understanding of star formation at this cosmologically important epoch. However the vast majority of candidate galaxies at these redshifts either lack spectroscopic confirmation or were selected for their extreme youth and strong Lyman-α emission. Spectroscopy is essential both to constrain the redshifts and properties of the candidate galaxies, and to eliminate lower-redshift interlopers. We discuss results from our recent spectroscopy of high-redshift, rest-UV selected sources using 8 and 10 m telescopes and the contribution of such observations to our overall understanding of the cosmological evolution of the galaxy population. © Società Italiana di Fisica.

Abstract:

We present the results of an optical and near-IR spectroscopic study of giant nebular emission-line halos associated with three z > 3 radio galaxies, 4C 41.17, 4C 60.07, and B2 0902+34. Previous deep narrowband Lyα imaging revealed complex morphologies with sizes up to 100 kpc, possibly connected to outflows and AGN feedback from the central regions. The outer regions of these halos show quiet kinematics with typical velocity dispersions of a few hundred km s-1 and velocity shears that can mostly be interpreted as being due to rotation. The inner regions show shocked cocoons of gas closely associated with the radio lobes. These display disturbed kinematics and have expansion velocities and/or velocity dispersions > 1000 km ss-:. The core region is chemically evolved, and we also find spectroscopic evidence for the ejection of enriched material in 4C 41.17 up to a distance of ≈60 kpc along the radio axis. The dynamical structures traced in the Lyα line are, in most cases, closely echoed in the carbon and oxygen lines. This shows that the Lyα line is produced in a highly clumped medium of small filling factor and can therefore be used as a tracer of the dynamics of high-redshift radio galaxies (HzRGs). We conclude that these HzRGs are under-going a final jet-induced phase of star formation with ejection of most of their interstellar medium before becoming "red and dead" elliptical galaxies. © 2007, The American Astronomical Society. All rights reserved.