Professor Roger Davies

Abstract:

We describe the design of a 2nd generation instrument for the ESO VLT which uses 24 cryogenic pickoff arms linked to diamond-machined image slicing integral field units to deliver a unique multiple deployable integral field capability in the near-infrared (1-2.5 mu m). The science requirements for the instrument are presented and linked to the functional specification. The baseline instrument concept is described with emphasis on technological innovations. (c) 2006 Elsevier B.V. All rights reserved.

Abstract:

We present the fundamental plane (FP) for 38 early-type galaxies in the two rich galaxy clusters RX J0152.7-1357 (z = 0.83) and RX J1226.9+3332 (z = 0.89), reaching a limiting magnitude of MB = -19.8 in the rest frame of the clusters. While the zero-point offset of the FP for these high-redshift clusters relative to our low-redshift sample is consistent with passive evolution with a formation redshift of zform ≈ 3.2, the FP for the high-redshift clusters is not only shifted as expected for a mass-independent zform but rotated relative to the low-redshift sample. Expressed as a relation between the galaxy masses and the mass-to-light ratios, the FP is significantly steeper for the high-redshift clusters than for our low-redshift sample. We interpret this as a mass dependency of the star formation history, as has been suggested by other recent studies. The low-mass galaxies (10 ^10.3 M⊙) have experienced star formation as recently as z ≈ 1.35 (1.5 Gyr prior to their look-back time), while galaxies with masses larger than 10^11.3 M⊙ had their last major star formation episode at z > 4.5. © 2006, The American Astronomical Society. All rights reserved.