The Optical Redshift Survey

Basilio Santiago , Michael Strauss, Ofer Lahav, John Huchra

Marc Davis, Alan Dressler, Harold Corwin

The Optical Redshift Survey (ORS) contains 8457 galaxies covering a solid angle of 8.09 sterad (about 2/3 of the sky). It is a compilation of previous wide-angle redshift surveys plus about 1300 new redshift measurements. The figure above shows on-sky projections of the sample galaxies with a grid in Galactic coordinates. The upper panel shows hemispheric projections whereas the lower one shows an Aitoff projection. The diagonal lines across both panels indicate the ESGC strip (see below). The sample avoids a 40 degrees strip in the Plane of the Galaxy plus regions where the B band absorption coefficient is A_B > 0.7 mag (these latter are shown as dark areas in the figure).

The sample is 98% complete in redshift and was defined according to the following selection criteria:

- Galaxies whose apparent B band magnitudes are brighter than 14.5. We call this subset ORS-m.


- Galaxies whose apparent B band diameters are larger than 1.9'. This subset we call ORS-d.

The ORS sample was drawn by applying these selection criteria to 3 major galaxy catalogs: the ESO-Uppsala Survey of the ESO(B) Atlas in declinations south of -17.5 degrees; the Uppsala General Catalogue (UGC) for declinations north of -2.5 degrees; the Extension to the Southern Galaxies Catalogue (ESGC) for the [-17.5, -2.5] declination strip.

The new redshifts were obtained in several observatories and telescopes: the 3m telescope at Lick Observatory (Univ. of California), the 1.5m telescope and the Multiple Mirror Telescope at Mt Hopkins Observatory (SAO and Univ. of Arizona), the 1.5m CTIO telescope, the 1.5m telescope at Palomar Observatory (Caltech, OCIW and Cornell Univ.) and the 2.1m telescope at Las Campanas (OCIW).

ORS provides a dense sampling of the galaxy distribution out to redshift velocities of about 8000 km/s. It is thus ideal for studying the properties of the galaxy distribution in the Local Universe, its clustering properties, galaxy segregation, main large scale structures, their shape, size and density contrast, etc. A list of ORS papers , both published and in preparation is also available.

  • Retrieve the ORS data in different formats (just press the shift button on your keyboard at the same time you click with the mouse buttom on the desired link).

    • Master files containing the ESO , UGC and ESGC galaxy catalogues with the ORS redshifts in them.

    • ORSd + ORSm sample files again separated in the three regions: ESO , UGC and ESGC .

    Basilio Santiago,