SRED1991 (G0): Southern Redshifts Catalog, Dec <= 0, 1993 (19950131)
FILE: sred1991.g0 (12844 galaxies)
CONTENTS: Southern Redshifts Catalog; Fairall & Jones, 1991
DATASET: This file comes in HyperSky dataset G-19, version 19950131. Availability on HyperSky CD-ROM: Vol. 2 (1995)
DESCRIPTION: This file contains 12844 galaxies from the Southern Redshifts Catalog, maintained by A. Fairall et al at the University of Cape Town, South Africa. The catalog provides a "best-estimate" of the heliocentric radial velocities of galaxies south of Declination about 0 degrees. It is based on over 17000 redshift measurements, from over 200 sources, either published or otherwise made public.
The catalog was first published in 1981. The 1991 work is an update and extension of the 4th version, completed in January 1988. After the 1988 version, the northern Declination limit was shifted from -17.5 degrees to the equator, and radio velocities were added. The 1991 version, including updated references, has just over double the number of galaxies in the 1988 version.
The 1991 version is based on literature searches of the main journals up to April-June 1991. While the aim was to obtain all available redshifts, no claim to completeness is made. This is particularly applicable to the Declination zone 0 to -17.5 degrees, into which the catalog was most recently extended.
The HyperSky file is based on a version of the database available through the U.S. National Space Sciences Data Center (NSSDC) as Astronomical Data Center (ADC) catalog #7142. It is also available from the Stellar Data Center (CDS), Strasbourg, France, as catalog VII/142.
DATA: The HyperSky datafile contains the following data from the catalog:
POSITION: Right Ascension and Declination are based on the catalog 1950 coordinates, precessed to equinox 2000. In earlier versions of the catalog, declinations were rounded off to the nearest 15 arcsec - this remains for many entries under some references. Other entries (from Ref 131 onwards) were entered from files having declinations rounded off to the nearest 6 arcsec. Where galaxies are reported by multiple observers, small differences in coordinates sometimes occur, but usually these are less than 3s in R.A. and 30 arecsec in Declination.
MAG: No magnitudes are provided in the catalog. For this reason, galaxies in this datafile will cease to appear on your display field if you set the limiting faint magnitude for ".g0" objects brighter than the default. (This is possible only when other galaxy datafiles containing magnitudes are also used.)
IDENTIFICATION: Catalog designations were entirely picked up from the quoted references. Thus, if references chose to ignore recognized designations (such as NGC or ESO) they may also be absent in the catalog. In general, ESO designations were contracted to an "E" prefix. When multiple designations caused space problems, further contractions, such as NGC to an "N' prefix, were made.
COMMENTS: The comment lines following the identification contain the following information, if available, for each galaxy:
* A line giving the helicentric velocity (cz), or a brief note explaining why it is not provided. The velocity provided is a "best estimate" of the Heliocentric velocity. If only a single reference was available, then the value quoted was straight from that reference.
Experience shows that, in general, about one or two percent of the redshift velocities from a given source are completely erroneous (and sometimes the percentage is higher). This is apparently unavoidable, given the nature of optical galaxy spectra or radio confusion, and even the most careful investigators are sometimes fooled by spurious features or detections. Similarly, cross correlations on optical spectra can sometimes latch on to the wrong values. Since the bulk of the catalog concerns single reference redshifts, it is possible that 1 percent or so are erroneous.
When two or more redshift references are found for a galaxy, the catalog velocity is a form of mean value, rounded off to the nearest 10 km/s (except if the velocities agreed to within 20 km/s, when it is rounded to 1 km/s). In deciding this mean value, extra weighting was given to certain references known to be more accurate.
In general, optical velocities from higher dispersion spectra (with external errors better than 50 km/s) had triple weight. Radio redshifts were given still higher weight, but only when supported by optical observations. The maximum acceptable differences between optical velocities was considered to be 400 km/s, that between radio velocities was 100 km/s. If only two references were available, and there was no indication as to which is likely to be correct, then, rather than enter an uncertain value, the comment "large Difference" is substituted when the difference is greater than the above. Other cases where comments occur in place of a velocity include:
"superposed star": Superposed foreground star with near zero velocity.
"no emission lines"; No strong emission lines. The quality of the spectrogram did not permit redshift determination, but strong emission lines can be excluded.
"too faint": Too faint. The galaxy is of low surface brightness and only a tentative redshift (not given) could be obtained, or no redshift was obtained from the spectrogram.
"ESO4": (Reference 048) Observed spectroscopically at the European Southern Observatory, but no accurate redshift apparently yet available.
"not yet available" Observed spectroscopically but no velocity yet available. Worth including because of types such as Seyfert (see below).
* A line indicating certain galaxy classification types, including:
"Seyfert 1"
"Seyfert 2"
"Seyfert?"
"BL Lac object"
"emission" Generally implies low-excitation emission, [O II] 3727 and/or H-alpha, or unspecified emission.
"HII emission" H II emission, generally implying strong emission lines of relatively high excitation, including [O III] 5007 + 4959 emission.
REFERENCES
Southern Redshifts Catalogue and Plots A.P. Fairall and A. Jones Publications of the Department of Astronomy, University of Cape Town 1991, No. 11
"Large-Scale Structure in the Universe: Plots from the Updated Catalogue of Radial Velocities of Galaxies and the Southern Redshift Catalogue" A.P. Fairall, G.G.C. Palumbo, G. Vettolani, G. Kauffmann, A. Jones and G. Baiesi-Pillastrini, Mon. Not. R. astr. Soc., 247, 21P. 1990