Redshift surveys and cosmology: A summary of the Dunk Island Conference

Redshift surveys constitute one of the prime tools of observational cosmology. Imaging surveys of the whole sky are now available at a wide range of wavelengths, and provide a basis for the new generation of massive redshift surveys currently in progress. The very large datasets produced by these surveys call for new and sophisticated approaches to the analysis of large-scale structure and the galaxy population. These issues, and some preliminary results from the new redshift surveys, were discussed at the second Coral Sea Cosmology Conference, held at Dunk Island on 24-28 August 1999. This is a summary of the conference; the full conference proceedings are on the WWW at http://www.mso.anu.edu.au/DunkIsland/Proceedings

Measuring H0 from the 6dF Galaxy Survey and future low-redshift surveys

Baryon acoustic oscillations (BAO) at low redshift provide a precise and largely model-independent way to measure the Hubble constant, H0. The 6dF Galaxy Survey measurement of the BAO scale gives a value of H0 = 67 +/- 3.2 km/s/Mpc, achieving a 1-sigma precision of 5%. With improved analysis techniques, the planned WALLABY (HI) and TAIPAN (optical) redshift surveys are predicted to measure H0 to 1-3% precision.Comment: Proceedings of IAU Symposium 289, "Advancing the Physics of Cosmic Distances", Richard de Grijs & Giuseppe Bono (eds), 2012, 4p

The Stellar Populations of Low-redshift Clusters

We present some preliminary results from an on-going study of the evolution of stellar populations in rich clusters of galaxies. This sample contains core line-strength measurements from 183 galaxies with b_J <= 19.5 from four clusters with ~0.04. Using predictions from stellar population models to compare with our measured line strengths we can derive relative luminosity-weighted mean ages and metallicities for the stellar populations in each of our clusters. We also investigate the Mgb'-sigma and Hbeta_G'-sigma scaling relations. We find that, consistent with previous results, Mgb' is correlated with sigma, the likely explanation being that larger galaxies are better at retaining their heavier elements due to their larger potentials. Hbeta', on the other hand, we find to be anti-correlated with sigma. This result implies that the stellar populations in larger galaxies are older than in smaller galaxies.Comment: 3 pages, 2 figures, to appear in the Proceedings of IAU Colloquium 195: "Outskirts of Galaxy Clusters: intense life in the suburbs", Torino Italy, March 12-16 200

Measurement of Star-Formation Rate from H-alpha in field galaxies at z=1

We report the results of J-band infrared spectroscopy of a sample of 13 z=1 field galaxies drawn from the Canada-France Redshift Survey, targeting galaxies whose redshifts place the rest frame H-alpha line emission from HII regions in between the bright night sky OH lines. As a result we detect emission down to a flux limit of ~10^{-16} ergs cm^{-2} s^{-1} corresponding to a luminosity limit of ~10^{41} ergs at this redshift for a H_0=50 km s^{-1} Mpc,^{-1} q_0=0.5 cosmology. From these luminosities we derive estimates of the star-formation rates in these galaxies which are independent of previous estimates based upon their rest-frame ultraviolet (2800A) luminosity. The mean star-formation rate at z=1, from this sample, is found to be at least three times as high as the ultraviolet estimates. The standard dust extinction in these galaxies is inferred to be A_V=0.5-1.0 mags, comparable to local field galaxies, suggesting that the bulk of star-formation is not heavily obscured unless one uses greyer extinction laws. Star-forming galaxies have the bluest colours and a preponderance of disturbed/interacting morphologies. We also investigate the effects of particular star-formation histories, in particular the role of bursts vs continuous star-formation in changing the detailed distribution of UV to H-alpha emission. Generally we find that models dominated by short, overlapping, bursts at typically 0.2 Gyr intervals provide a better model for the data than a constant rate of star-formation. The star-formation history of the Universe from Balmer lines is compiled and found to be typically 2--3\times higher than that inferred from the UV {\em at all redshifts}. It can not yet be clearly established whether the star-formation rate falls off or remains constant at high-redshift.Comment: 15 pages including 8 figures. MNRAS in pres

Extended stellar kinematics of elliptical galaxies in the Fornax cluster

We present extended stellar kinematics for a sample of 13 elliptical galaxies in the Fornax cluster. Major-axis velocity dispersion profiles (VDPs) and rotation curves (RCs) are given for 12 of the galaxies. A major feature of this data is the spatial extension: for 8 galaxies the data extends beyond 1 R_e, and for 5 it extends beyond 2 R_e. Compared to the previously available data, this corresponds to an increase in spatial coverage by a factor from 1 to 5. Five of the ellipticals in the sample turn out to be rotationally-supported systems, having positive rotation parameter log (V/sigma)*. One of these five, and another 3 galaxies from the remaining sample, display evidence for bar-like kinematics. The data indicate that the true number of `dynamically hot' stellar systems, is much lower than previously thought: of the Es in the present sample only 1/4 are confirmed as `pressure-supported' systems. The data reveal a host of individual peculiarities, like: wiggles, strong gradients, and asymmetries in the rotation curve and/or in the velocity dispersion profile, thus showing that the presence of kinematically distinct components and/or triaxiality is a common characteristic of this class of object.Comment: 27 pages, includes 15 eps figures. Accepted for publication in A&A Sup

Autofib Redshift Survey: II -- The Evolution of the Galaxy Luminosity Function by Spectral Type

We determine the evolution of the galaxy luminosity function (LF) as a function of spectral type using the Autofib redshift survey, a compendium of over 1700 galaxy redshifts in various magnitude-limited samples spanning b_J=11.5-24.0. To carry out this analysis we have developed a cross-correlation technique which classifies faint galaxy spectra into one of six types based on local galaxy templates. Tests and simulations show that this technique yields classifications correct to within one type for more than 90% of the galaxies in our sample. We have also developed extensions of the step-wise maximum likelihood method and the STY parametric method for estimating LFs which are applicable to recovering an evolving LF from multiple samples. We find that: (i) The spectra and LF of E/S0 galaxies show no appreciable evolution out to at least z ~ 0.5. (ii) Early-type spirals show modest evolution, characterised by a gradual steepening of the faint end of their LF with redshift. (iii) Out to z ~ 0.5, the overall evolution of the galaxy population is dominated by changes seen in late-type spirals. The characteristic luminosity (L^*) of these galaxies appears to brighten with redshift and there are signs of strong density evolution (a rapid increase in \phi^*). These effects appear to be luminosity dependent so that the LF steepens at higher redshift. These trends are accompanied by a steep increase in the median [OII] equivalent width, implying a rapid increase in the star-formation rate with redshift at fixed luminosity---a given star-formation rate is found at higher redshift in galaxies of higher luminosity. We find that these conclusions are robust with respect to spectral classification errors and the luminosity function estimator.Comment: LaTeX, 22 pages, 22 figure