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CAIRNS: The Cluster and Infall Region Nearby Survey. II. Environmental Dependence of Infrared Mass-to-Light Ratios
CAIRNS (Cluster and Infall Region Nearby Survey) is a spectroscopicsurvey of the infall regions surrounding nine nearby rich clusters ofgalaxies. In our previous paper, we used redshifts within ~10h-1 Mpc of the centers of the clusters to determine the massprofiles of the clusters based on the phase-space distribution of thegalaxies. Here, we use Two Micron All Sky Survey photometry and anadditional 515 redshifts to investigate the environmental dependence ofnear-infrared mass-to-light ratios. In the virial regions, the halooccupation function is nonlinear; the number of bright galaxies per haloincreases more slowly than the mass of the halo. On larger scales, thelight contained in galaxies is less clustered than the mass in richclusters. Specifically, the mass-to-light ratio inside the virial radiusis a factor of 1.8+/-0.3 larger than that outside the virial radius.This difference could result from changing fractions of baryonic tototal matter or from variations in the efficiency of galaxy formation ordisruption with environment. The average mass-to-light ratioM/LK=53+/-5h implies Ωm=0.18+/-0.03(statistical) using the luminosity density based on Two Degree FieldGalaxy Redshift Survey data. These results are difficult to reconcilewith independent methods that suggest higher Ωm.Reconciling these values by invoking bias requires that the typicalvalue of M/LK changes significantly at densities of<~3ρc.
| Galaxy coordinates. II. Accurate equatorial coordinates for 17298 galaxies
Using images of the Digitized Sky Survey we measured coodinates for17298 galaxies having poorly defined coordinates. As a control, wemeasured with the same method 1522 galaxies having accurate coordinates.The comparison with our own measurements shows that the accuracy of themethod is about 6 arcsec on each axis (RA and DEC).
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
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