The peculiar motions of early-type galaxies in two distant regions -- III. The photometric data

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Abstract
We present R-band CCD photometry for 776 galaxies observed in the EFAR project. The photometry is compared with photoelectric data, showing that a common zero-point good to better than 1 per cent and a precision of 0.03 mag per zero-point have been achieved. We give the circularly averaged surface brightness profiles and the photometric parameters of the 762 programme galaxies, Dn diameters (at 20.5 mag arcsec−2), half-luminosity radii Re, total magnitudes mT and average effective surface brightnesses ‹SBe›. The photometric parameters are derived using the seeing-convolved, R1/4-plus-exponential fitting algorithm described in Paper IV which optimally combines multiple profiles and corrects for sky subtraction errors. The parameters of the two-component fits are also given. We find that the diameters Dn span the range 4.8–90 arcsec, with ‹logDn› = 1.30 or 20 arcsec. The run of the effective radii Re is 1.6–71.2 arcsec, with ‹logRe› = 0.84 or 6.9 arcsec. The total magnitudes mT extend from 10.57 to 15.97 mag, with a mean of 13.85 mag. The effective surface brightnesses ‹SBe› span the range 17.78–22.35 mag arcsec−2 with a mean of 19.89 mag arcsec−2 . The mean photometric precisions of Dn diameters, magnitudes and surface brightnesses are 0.9 per cent, 0.017 mag and 0.017 mag arcsec−2 respectively. In addition, the fitting scheme quantifies and minimizes the many systematic biases affecting the determination of galaxy photometric parameters. We find simple R1/4 fits for only 14 per cent of the total, and simple exponential fits for ≈ 1 per cent of the total. The spread in sky values measured from the different profiles of the same object is less than 1 per cent in 85 per cent of the cases. In 80 per cent of the fits a reduced χ2 of less than 12 is obtained. More than 90 per cent of the galaxies have at least one profile extending to more than 4 half-luminosity radii. More than 90 per cent of the galaxies are well resolved, having at least one profile where Re > 2Г, where Г is the FWHM of the point-spread function. More than 80 per cent of the profiles have a global signal-to-noise ratio larger than 300. The extrapolation needed to derive total magnitudes is less than 10 per cent for 80 per cent of the fits. More than 80 per cent of the galaxies have mean effective surface brightness larger than the observed sky brightness. In 90 per cent of the profiles the estimate of the contamination of the sky by the galaxy light is less than 1 per cent. Summarizing, the extensive internal comparisons, together with Monte Carlo simulations (see Paper IV), show that we derive total magnitudes and half-luminosity radii to better than 0.15 mag and 25 per cent respectively for 90 per cent of our sample. In contrast, external comparisons show that data in the literature can be strongly affected by systematic errors due to large extrapolations, small radial range, sky subtraction errors, seeing effects, and the use of a simple R1/4 fit. The resulting errors can easily amount to more than 0.5 mag in the total magnitudes and 50 per cent in the half-luminosity radii. The errors on the combined quantity FP = log Re − 0.3 ‹SBe› which enters the Fundamental Plane equation remain, however, always smaller than 0.03 dex. The galaxy type classification, based on all of the information available to us, shows that 31 per cent of the sample objects, visually selected from photographic images to be of early type, are in fact spiral or barred galaxies. The 69 per cent of galaxies classified as early-type can be subdivided into cD (8 per cent), E (12 per cent with a simple R1/4 law best fit), and E/SO (48 per cent with a disc-plus-bulge best fit). The photographic diameters Dw measured in Paper I correlate with Dn diameters or, equivalently, with the Fundamental Plane quantity FP = log Re — 0.3 ‹SBe›, with 23 per cent scatter for the early-type sample.

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