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LCRSCAT - Las Campanas Redshift Survey Catalog

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Overview

The Las Campanas Redshift Survey (LCRS) consists of 26,418 redshifts of galaxies selected from a CCD-based catalog obtained in the R band. The survey covers over 700 deg2 in six strips, each 1.5 x 80 degrees, three each in the north and south Galactic caps. The median redshift in the survey is about 30,000 km s-1. Essential features of the galaxy selection and redshift measurement methods are described and tabulated in the reference paper. These details are important for subsequent analysis of the LCRS data. Two-dimensional representations of the redshift distributions reveal many repetitions of voids, on the scale of about 5000 km s-1, sharply bounded by large walls of galaxies as seen in nearby surveys. Statistical investigations of the mean galaxy properties and of clustering on the large scale are reported elsewhere. These include studies of the luminosity function, power spectrum in two and three dimensions, correlation function, pairwise velocity distribution, identification of large-scale structures, and a group catalog.

This table contains entries for 94959 objects from the LCRS for which photometric data were obtained and which were initially classified as galaxies on the basis of this photometric information, although subsequent spectroscopy indicated that a small fracton of them are actually stars. There are 27021 objects out of this total which have spectroscopic redshift information (either of themselves or of a nearby object).

See also the LCRS home pages at: http://qold.astro.utoronto.ca/~lin/lcrs.html .


Catalog Bibcode

1996ApJ...470..172S

References

The Las Campanas Redshift Survey
    Shectman S.A., Landy S.D., Oemler A., Tucker D.L., Lin H., Kirshner R.P.,
    Schechter P.L.
   <Astrophys. J. 470, 172 (1996)>
   =1996ApJ...470..172S

Provenance

This table was created by the HEASARC in May 2010 based on the electronic version of Table 3 from the above reference which was obtained from the CDS (their catalog VII/203 file catalog.dat).

Parameters

Field_Name
The spectroscopic field designation: this is of the form HHMM-DDL, where the field equatorial coordinates (in B1950.0) are RA = HHMM and Dec = -DD, and the letter suffix L stands for 'E' (east), 'W' (west) or 'M' (middle). The complete parameters of the spectroscopic fields are specified in Table 2 of the reference paper.

Phot_Cat_Obj_Num
The photometric catalog object number of the object in the field specified by the field_name parameter.

Isophotal_Mag
The isophotal magnitude of the object in a hybrid red band which the authors call R_G;K-C, since though the observations were made in the Gunn r band, they were calibrated relative to standards in the Kron-Cousins R band. The zero-point difference between the R_G;K-C and true Kron-Cousins R is small, i.e., < 0.1 magnitudes. The isophotal magnitude corresponds to the sum of the background-corrected flux in all pixels within the object.

Drift_Scan
The B1950 position-based (HHMM-DDMM) designation of the drift scan which was used to obtain the object's photometry.

Central_Mag
The central magnitude of the object in a hybrid red band which the authors call R_G;K-C, since though the observations were made in the Gunn r band, they were calibrated relative to standards in the Kron-Cousins R band. The zero-point difference between the R_G;K-C and true Kron-Cousins R is small, i.e., < 0.1 magnitudes. The central magnitude corresponds to the flux within a 2 pixel radius of the object center.

Name
The LCRS catalog-based source designation of the object, constructed by the HEASARC based on the precepts of the catalog authors, namely: "In referencing individual galaxies within the LCRS, it is recommended that investigators adhere to the IAU-registered LCRS naming convention, as listed in the online "Dictionary of Nomenclature of Celestial Objects" (http://astro.u-strasbg.fr/cgi-bin/Dic), which is: LCRS BHHMMSS.s-DDMMSS, in which the coordinates are equinox 1950.0, RA is truncated (* not rounded *) to a tenth of a second, and DEC is truncated (* not rounded *) to a whole arcsecond."

RA
The Right Ascension of the object in the selected equinox. This was given in B1950.0 equatorial coordinates to a precision of 0.01 seconds of time in the original reference version. The positional calibration was done using the coordinate system defined by the HST Guide Star Catalog. Because of systematic zero-point uncertainties, however, the absosulte ccordinates should not be trusted to better than 1 arcsecond.

Dec
The Declination of the object in the selected equinox. This was given in B1950.0 equatorial coordinates to a precision of 0.1 arcseconds in the original reference version. The positional calibration was done using the coordinate system defined by the HST Guide Star Catalog. Because of systematic zero-point uncertainties, however, the absosulte ccordinates should not be trusted to better than 1 arcsecond.

LII
The Galactic Longitude of the object.

BII
The Galactic Latitude of the object.

Spect_Fiber
The name of the spectroscopic fiber which was used to obtain spectroscopy for the object.

Broad_Type
A broad description of the object's spectrum, as follows:

       c, e, b: galaxy
           - c: velocity from cross-correlation only
           - e: velocity from emission-line fitting only
           - b: velocity from both c and e

             s: star
            ?: spectrum failed to yield redshift
   nh, tc, bl: same as no spectrum attempted (intended spectrum not observed)
           QS: QSO
           PN: planetary nebula
  

Radial_Velocity
The heliocentric radial velocity of the object, in km/s, determined by cross-correlating the object's spectrum against a set of template spectra.

Radial_Velocity_Error
The RMS uncertainty in the heliocentric radial velocity of the object, in km/s.

SF_Product
The product sf of the sampling fraction, apparent magnitude completeness and central surface brightness completeness factors for the object. See Lin et al. (1996, ApJ, 464, 60) for more information; sf = f * F * G in the notation of that paper. Objects should be weighted by 1/sf in statistical analyses. Only those galaxies meeting the photometric selection limits have an entry.

GSF_Product
This parameter is similar to sf, but this sampling fraction gsf is computed only in a 1000-arcsecond radius nieghborhood of the galaxy. It attempts to account for any variable geometric sampling effects, e.g. the reduced spectroscopic success at field corners (Shectman et al. 1995, in Wide-Field Spectroscopy and the Distant Universe, proceedings of the 35th Herstmonceux Conference (July 1994), eds. S. J. Maddox & A. Aragon-Salamanca (Singapore: World Scientific), p. 98.). Experience with the galaxy power spectrum (Lin et al. 1996, ApJ, 471, 617) shows that using gsf instead of sf makes little difference, but 'it does not hurt to check this for your own analyses'.

Nearby_Radial_Velocity
For an object without a redshift, this field contains the radial velocity of its closest neighbor within 55 arcseconds, if one exists, that has a measured velocity. Only objects within the photometric limits have an entry. To assess the significance of this selection effect for your particular analysis, you can try assigning fake velocities as described in Lin et al. (1996, ApJ, 471, 617).

Class
The HEASARC Browse object classification, based on the value of the broad_type parameter, if available.


Contact Person

Questions regarding the LCRSCAT database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 5-May-2010