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UZC - Updated Zwicky Catalog



The Zwicky Catalog of Galaxies, with a magnitude limit m_Zw <=15.5, has been the basis for the Center for Astrophysics (CfA) redshift surveys. To date, analyses of the Zwicky Catalog and redshift surveys based on it have relied on heterogeneous sets of galaxy coordinates and redshifts. In this Updated Zwicky Catalog (UZC), some of the inadequacies of previous catalogs are corrected by providing (1) coordinates with ~<2 arcsecond errors for all of the 19,369 catalog galaxies, (2) homogeneously estimated redshifts cz (radial velocities) for the majority (98%) of the data taken at the CfA (14,632 spectra), and (3) an estimate of the remaining "blunder" rate for both the CfA redshifts and for those compiled from the literature. For the reanalyzed CfA data a calibrated, uniformly determined error and an indication of the presence of emission lines in each spectrum are included. Redshifts (radial velocities) are provided for the 7257 galaxies in the CfA2 redshift survey that were not previously published; for another 5625 CfA redshifts (radial velocities), the remeasured or uniformly rereduced values are listed. Among the new measurements, 1807 are members of UZC "multiplets" associated with the original Zwicky catalog position in the coordinate range where the catalog is 98% complete. These multiplets provide new candidates for examination of tidal interaction among galaxies. All of the new redshifts (radial velocities) correspond to UZC galaxies with properties recorded in the CfA redshift compilation known as ZCAT. The redshift catalog included in the UZC is ~96% complete to m_Zw <=15.5 and ~98% complete (12,925 galaxies out of a total of 13,150) for the right ascension ranges 20 hr >= RA(1950) <= 4 hr and 8 hr <= RA(1950) <= 17 hr and the declination range -2.5 degrees <= Dec(1950) <= 50 degrees. This more complete region includes all of the CfA2 survey as analyzed to the date of the publication of the UZC (1999).

Catalog Bibcode



The updated Zwicky catalog (UZC).
       Falco E.E., Kurtz M.J., Geller M.J., Huchra J.P., Peters J., Berlind P.,
       Mink D.J., Tokarz S.P., Elwell B.
      <Publ. Astron. Soc. Pac. 111, 438 (1999)>
      =1999PASP..111..438F      (SIMBAD/NED BibCode)


This database was created by the HEASARC in October 2000 based on a machine-readable version obtained from the CDS (Catalog J/PASP/111/438). It was slightly revised in February 2001 (the 'redshift' parameters were renamed as 'radial velocity' parameters to conform with the usage in other similar HEASARC extragalactic catalogs).


The UZC Catalog designation based on the J2000 RA and declination.

The right ascension in the selected equinox. Notice that the RAs in the originating table were given in J2000 equatorial coordinates to a precision of 0.1 seconds of time.

The declination in the selected equinox. Notice that in the originating table, this was given in J2000 equatorial coordinates to a precision of 1 arcsecond.

The galactic longitude.

The galactic latitude.

The B-band magnitude m_Zw from the Zwicky-Nilson Catalog (ZNCAT: Tonry and Davis 1979, AJ, 84, 1511).

The heliocentric radial velocity, in km/s.

The RMS uncertainty in the radial velocity, in km/s.

The type of radial velocity for each galaxy, where E means it is derived from emission lines(s), A from absorption line(s), and B means from both emission and absorption lines.

The UZC class code for each galaxy, which is a number from 0 to 4 according to the quality of the match with Digital Sky Survey (DSS) galaxies:

  0: A "hit", where the Guide Star Catalog (GSC) and Zwicky-Nilson Catalog
     (ZNCAT: Tonry and Davis 1979, AJ, 84, 1511) objects are separated in
     position by a positional difference {DELTA}{theta} <= 180 arcseconds,
     are comparable in brightness as determined visually, and there is no
     other object within the field that could be the Zwicky Catalog galaxy.
     Note that the ZNCAT B-band (m_Zw) and the GSC V- or J-band magnitudes
     can differ significantly, because the expected colors for these galaxies
     are in the range ~0.3 - 1.0 mags.

  1: A "hit" with positional difference {DELTA}{theta} <= 180 arcseconds,
     again with a GSC brightness in the vicinity of the ZNCAT value. However,
     the field is centered on a GSC "star" rather than on a "nonstar", but
     there is only one possible Zwicky Catalog galaxy nearby, within the field.
     Thus, index 1 merely indicates that the nearest GSC object to the
     ZCAT coordinates is a star rather than the appropriate galaxy.

  2: A near "hit" with positional difference {DELTA}{theta} <= 180 arcseconds.
     However, there is confusion because there are at least two galaxies with
     an estimated spread in magnitudes |{DELTA}m| within the expected range,
     either of which could be a Zwicky Catalog galaxy.

  3: A near "hit" with positional difference {DELTA}{theta} <= 180 arcseconds,
     but with |{DELTA}m| outside the expected range, raising suspicions about
     the match of the GSC object to the Zwicky Catalog galaxy.

  4: No "hit" at all for positional difference {DELTA}{theta} <= 180 arcseconds;
     i.e., there is no match for a Zwicky Catalog galaxy.

The number of UZC neighboring galaxies to this galaxy, within 3 arcminutes.

The ZNCAT or Zwicky label, based on the 1950 equatorial position; multiplets generally share a single such label.

A reference code indicating the origin of the radial velocity measurement, for data taken at the CfA: Z for Z-machine, M for the MMT, and F for FAST spectra taken from the authors' own and other projects. The label X flags a low-S/N spectrum for Z-machine (FAST) measurements and indicates a low S/N match with a spectrum at a radial velocity < 100 km/s, an indication that no radial velocity could be determined.

This is the ZCAT literature reference number (the table listing these codes and corresponding references is Table 2 of the published (1999, PASP, v.111, p.438) paper and is available at the CDS: or a blank, for CfA unpublished data.

An alternative name which may be associated with a galaxy, such as an NGC number, as listed in ZCAT.

This flag is set to Y if the galaxy is a member of a Zwicky multiplet, or N otherwise.

This flag list the multiplicity information in the NASA Extragalactic Database (NED) for the galaxy: P for pairs, T for triples, G for groups, and blank otherwise.

Contact Person

Questions regarding the UZC database table can be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Monday, 14-Jan-2008 19:21:56 EST