Cosmology

Abstract:

We present a catalogue comprising over 10 000 QSOs covering an effective area of 289.6 deg2, based on spectroscopic observations with the 2-degree Field (2dF) instrument at the Anglo-Australian Telescope. This catalogue forms the first release of the 2dF QSO Redshift Survey. QSO candidates with 18.25 < bJ < 20.85 were obtained from a single homogeneous colour-selected catalogue based on APM measurements of UK Schmidt photographic material. The final catalogue will contain approximately 25 000 QSOs and will be released to the public at the end of 2002, one year after the observational phase is concluded.

Abstract:

We explore the origin of the color-magnitude relation (CMR) of early-type galaxies in the Virgo Cluster using spectra of very high signal-to-noise ratio for six elliptical galaxies selected along the CMR. The data are analyzed using a new evolutionary stellar population synthesis model to generate galaxy spectra at the resolution given by their velocity dispersions. In particular, we use a new age indicator that is virtually free of the effects of metallicity. We find that the luminosity-weighted mean ages of Virgo ellipticals are greater than ∼8 Gyr and show no clear trend with galaxy luminosity. We also find a positive correlation of metallicity with luminosity, color, and velocity dispersion. We conclude that the CMR is driven primarily by a luminosity-metallicity correlation. However, not all elements increase equally with the total metallicity, and we speculate that the CMR may be driven by both a total metallicity increase and a systematic departure from solar abundance ratios of some elements along the CMR. A full understanding of the role played by the total metallicity, abundance ratios, and age in generating the CMR requires the analysis of spectra of very high quality, such as those reported here, for a larger number of galaxies in Virgo and other clusters.

Abstract:

Using a new radio sample, 6C* designed to find radio galaxies at z > 4 along with the complete 3CRR and 6CE sample we extend the radio galaxy K-z relation to z~4.5. The 6C* K-z data significantly improve delineation of the K-z relation for radio galaxies at high redshift (z > 2). Accounting for non-stellar contamination, and for correlations between radio luminosity and estimates of stellar mass, we find little support for previous claims that the underlying scatter in the stellar luminosity of radio galaxies increases significantly at z > 2. This indicates that we are not probing into the formation epoch until at least z > 3.