Distance Indicators and Peculiar Velocities Status of the 6dFGS V-survey Lachlan Campbell, RSAA/AAO 6dFGS Workshop April 2005

To map in detail the density and peculiar velocity fields over half the local volume out to 15,000 km/s. To provide additional constraints on cosmological models, and better measurements of fundamental parameters, from statistics of these fields. To achieve these goals the aim was to calculate D n -  distances for approximately bright early type galaxies. V-survey goals

Distance Indicators Present day ellipticals obey scaling relations involving their structural and dynamical properties. Populate the fundamental plane in 3D space defined by r e, e, . D n -  is a projection of the FP, where D n is defined as the diameter which encloses a chosen mean surface brightness level.

Calibration Sample Sample with 272 galaxies in common with the SMAC survey, and 450 with ENEAR, both of which provide photometric parameters and velocity dispersions. Provide a basis for estimating external errors and understanding any systematic biases.

Corrections for extinction, K corrections & surface brightness dimming, and most importantly seeing effects (using the prescription of Saglia et al. 1993). Work by Hogg suggests there should be a small statistically insignificant offset between 2MASS and literature K band photometry. 2MASS photometry K=12.75 z=0.05 K=9.5 z=0.013

Differences in FP parameter 2MASS appear to give a semi-major axis half-light radii. SMAC give circular half-light radii. 2MASS psf circularises small galaxies. Colour gradients between wavelengths.

Summary of Photometry 2MASS photometry internally consistent to 0.01dex or ~2% External comparison with both Optical and NIR photometry gives errors of 0.03 dex or ~7%

Galaxy velocity dispersions are calculated using the two standard Fourier methods of cross-correlation (Tonry & Davis 1979) and Fourier quotient (Sargent et al. 1979). Use synthetic SSP galaxy template spectra (Vazdekis 1999) to estimate the broadening of absorption lines, most significantly in the Mg II and Fe lines. The Fourier quotient pipeline is being managed at Durham University to provide an independent check on the pipeline at RSAA/AAO. Velocity Dispersions

Instrumental dispersion 580V (VPH Grating) 600V (Reflection Grating)

Summary of Velocity Dispersions 6dFGS sigmas internally consistent to better than 6% based on comparisons between the pipelines. External comparison with both SMAC and ENEAR gives an error of ~8%.

 Total120K % % none35% %15000 V-survey Size Initial estimates of final numbers based on the minimum cuts listed for each parameter. All of the cuts assume a minimum R value of 5, and an initial total of 35% of the galaxies passing the z-quality and distance cuts.

Conclusions 2MASS photometry appears very reliable. 6dFGS velocity dispersions are as accurate as the best previous results. Therefore, we expect to at least match the standard previous distance accuracy of the FP of ~20%, and for the hoped for numbers of galaxies.