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ZCAT_REF: Description of the CFA redshift catalogue

Introduction

The CFA REDSHIFT CATALOGUE incorporates much of the latest velocity data from the Whipple Observatory and other sources as well as velocities from earlier compilations such as the Second Reference Catalogue of de Vaucouleurs, de Vaucouleurs and Corwin, the Index of Galaxy Spectra of Gisler and Friel, and the Catalogue of Radial Velocities of Galaxies of Palumbo, Tanzella Nitti and Vettolani. It includes BT magnitudes, some UGC numbers and increased "accuracy" in the velocity source information. (Note that in this release, we have not yet completed the cross-reference with the UGC and updating of all the velocity sources. Patience .)

The format for the catalogue looks like: 

  e:g:   (A11; I2; I2; F 4:1; A1; I2; I2; I2; F 5:2; I5; I3; A1; ::::::::::)
A more detailed description of the format can be found in Table 1. By definition, we are continually adding information and updates of the catalogue will be made available at reasonable intervals.

The data presented here have primarily been assembled for the purpose of studying the large scale structure of the universe, and, as such, are nearly complete in redshift information, but are not necessarily complete in such categories as diameter, magnitude and cross-references to other catalogues. Additional information of that type will be added in later editions.

Velocities

Please note that the velocities quoted are heliocentric and that redshifts (z's) have been converted to velocity via v = z x c, where c = 299; 792 km s-1 . Redshift is defined as 
		     ((lam )  - (lam )O )
		z  =  ___________________
			   (lam )O
We quote heliocentric velocites to allow individual users to correct to their own favorite galactocentric or "local groupocentric" or "Virgocentric" or even the (mu )-wave background frame. We have endeavored to properly remove such corrections before entering data into the catalogue, but confusion still remains in those cases where the authors do not explicitly state what corrections were made. In those cases we assume 300 x sin(l)cos(b) km s-1 to be the galactocentric correction. Note also that now that velocites of precisions less than 30 km/sec are commonplace, the correction to heliocentic is mandatory.

Basic radial velocity sources are listed in Table 2. Velocities with negative source designations are still in the private domain and cannot be used without the appropriate owner's consent. The additional source information in columns 43 and 44 is the number of the paper under the broader source categorization. Initially this was alphabetic, but as more recent papers are added, the numbering scheme has become chronological. Again, beware of blanks, which may signify source zero, but most likely indicates that this information has not yet been updated. In any case, the zero/blank paper for each source is likely to represent the largest number of velocities available from that source (e.g. the Second Reference Catalogue).

Objects listed in the catalog that have no velocity and no listed velocity source (in the northern hemisphere) will be observed as part of the CfA survey extension. Give us time! (in particular, telescope time....)

Errors: Velocity errors

In general, the errors listed for velocities are the errors quoted by the original source. (i.e., random errors are quoted and systematic ones are neglected.) The only exceptions are where multiple measurements have significantly improved the velocity precision. Many sources quote errors that are really the internal mean error - e.g. the variance in the velocities measured from multiple lines in a single spectrum of a galaxy. These often do not include errors in zero points, errors caused by mis-centering the galaxy in the slit, other instrumental offsets, etc., and are always underestimates of the true external error in the velocity estimate. Some sources are better than others; velocity errors from the CfA survey and most 21-cm sources are nearly within unity of the true external error (CfA errors are only about 10-20% low), while the uncertainties quoted in some older works, such as the RC2 and the RSA, are underestimates by more than a factor of two (see, for example, Sandage 1978). For several more detailed analyses of velocity uncertainties, see Lewis (1983), Rood (1982) and references therein.

A small number of our velocities are listed with the notation "poor velocity." These are weak cross-correlation velocities or velocities from single emission lines that need to be checked. We will do that. In general, there is enough information in the spectra to suggest that they are nearly correct (but I wouldn't stake my first born child on them).

Magnitudes

Magnitudes for galaxies are a persistent and pesky problem. We have tried to do our best to adopt a more or less uniform system for the largest number of galaxies. That system is the B(0)-Zwicky system (Huchra 1976). Magnitude sources for quoted values are given in Table 3. BT magnitudes, when available, are given in a separate column of the catalogue. These are generally about 0.4 magnitude brighter than magnitudes on the B(0)-Zw system. Some additional galaxy magnitudes, especially for objects in deeper surveys, come from digital scans of photographic plates - mostly in the photographic J and R bands. These magnitudes, by definition, are rarely easily converted into the more standard isophotal or total photographic B systems; each observer requires different zero point and color corrections.

Temporarily, we have derived very approximate corrections from other systems to the B(0)-Zwicky system. These are given for sources 3-7 as:

                      3   B(0) = M + 1.38       
                      4   B(0) = M + 0.34        
                      5   B(0) = M + 0.5          
                      6   B(0) = M + 0.4           
                      7   B(0) = M + 0.5            
                      R   B(0) = M + 1.6 for T < 1   
                          B(0) = M + 1.2 for 0 < T < 6
                          B(0) = M + 0.9 for 5 < T     
                      J   B(0) = M + 0.4 (approximately)
Note that these corrections are NOT in ZCAT, but rather represent suggested corrections for future and further use. BT magnitudes are given for those galaxies that have them in columns 59-63.

Magnitudes are taken preferentially from the 1st Reference Catalogue of de Vaucouleurs - B(0), Harvard Corrected - and then from the Zwicky Catalog. B(0) magnitudes are given the source designation "0," Harvard Corrected are "2," and Zwicky catalogue magnitudes are "1." Magnitudes from other sources are used only when necessary and/or available. As mentioned above, this choice of system maximizes the number of galaxy magnitudes available and will allow for easy conversion to other systems given diameter and morphological type information (e.g. the BT system).

                   0 blank b(0) 1st ref cat                       
                   1 zwicky                                      
                   2 shapley ames                               
                   3 tully and fisher                          
                   4 graham                                   
                   5 markarian, russian estimates            
                   6 bt - 2nd ref cat                       
                   7 mcg (vorontsov-velyaminov)            
                   8 photoelectric or photographic blue   
                   9 observers eye estimates             
                   r photographic r iiia-f, o-98 or 103ae + red filter
                   j photographic j iiia-j  
                   b photographic b
PHOTOGRAPHIC magnitudes from sources 8, R, J and B are calibrated via PDS or other micro-densitometer scans.

Morphological-Types

Morphological types are de Vaucouleurs' T types from the RC2, Uppsala Catalog and the Revised Shapley-Ames Catalog. Some additional types have been defined for peculiar and un-typed objects and for objects that are in catalogues of extragalactic objects but are really galactic in nature:

      33 REFLECTION NEBULA misclassified elsewhere as a galaxy
      32 HII REGION misclassified elsewhere as a galaxy    
      31 HII REGION PART OF ANOTHER GALAXY                  
      30 PLANETARY NEBULA misclassified elsewhere as a galaxy    
      25 PLATE FLAW, STAR ETC. misclassified elsewhere as a galaxy
      20 SPIRAL (GENERAL)                   
      16 IRR II                              
      15 PECULIAR OR UNTYPED                  
      11 COMPACT IM (EXTRAGALACTIC HII REGIONS)
      -6 COMPACT ELLIPTICAL (SAME AS DV)        
      -7_ELLIPTICAL_(GENERAL)
We decided to retain galactic objects, HII regions that are parts of other galaxies, and other such objects to prevent their inclusion in future lists of galaxies. Users should remove objects of type greater than 20 before using this catalogue as a simple galaxy catalogue _ otherwise you'll get all the HII regions in M101 listed separately as well a few plate flaws, stars and other assorted junk!

The format for the morphological type designations is: I2, A1, I1, A1, where the first two digits are the numerically coded T type, the next letter is the Bar type, the next digit is the numericaly coded luminosity class, and the final letter denotes morphological perculiarities. The types are explained in more detail in Table 4.

Additional types for galaxies in the CfA Redshift Survey region (described below) have been estimated by J. Huchra from glass copies of the Palomar Sky Survey. Types for southern galaxies come from both the ESO catalog and the Vorontsov-Velyaminov Catalogues.

!!! BEWARE Remember that types as well as source designations should be read in alphanumeric format to not confuse blanks with zeros.

Diameters

Diameters are in arc minutes from the blue Palomar Sky Survey or the ESO quick blue survey a la Nilson, ESO, VV or the RC2. The input format is given below as F4.1, but be forewarned that several galaxies have diameters that exceed 99.9 arc-minutes (e.g. M31 and M33) and are stored as F4.0, and many, especially faint, galaxies have diameters smaller than 1 arc-minute that have been measured with precisions of two decimal places (e.g. 0.35'). As it stands, an input format of F4.n is sufficient to handle all the diameters in the catalog, but an output format of F6.2 is required to reproduce the catalog entries properly (without either overflow or truncation).

Subset-Catalogs

There are several subset catalogues that represent "complete" samples of galaxies. One, published in the Ap. J. Supplements in June of 1983 is called "North Zwicky Forty" or NZ40.DAT for short (fans of bad Burt Reynolds movies take note). It contains all galaxies in the merged Zwicky-Nilson catalog with the following properties:

             B     14:5       and
             bII     40 deg;  AN D  (del)     0:0 deg       or
             bII     -30 deg;  AN D  (del)     -2:5 deg
The velocities for this sample are complete - it contains one star III ZW 92 (Zwicky wasn't perfect, but awfully close!) and ~ 2400 galaxies.

The other, large area, complete, magnitude limited catalogue is called the "Bright Galaxy Redshift Catalogue" or BGRC.DAT for short and contains all known galaxies brighter than B(0) = 13.21 in our adopted magnitude system. It is a whole sky catalogue and the velocites are 99% complete. It contains ~ 1350 galaxies. This sub-catalogue has only been circulated as a private communication. This catalogue is also extremely close to the Revised Shapley-Ames Catalogue of Sandage and Tammann.

ZCAT contains the data from the Southern Galaxy Redshift Survey (da Costa et al. 1987), which is an almost complete diameter limited sample of ~ 1900 galaxies which also contains information on (but not yet the velocites for) the IRAS galaxy survey of M. Davis, J. Huchra, M. Strauss, J. Tonry and A. Yahil _ all objects above an absolute galactic latitude of 10 degrees with IR colors like galaxies and with F60 > 1.95 Jy. ZCAT also contains all the data from the Nearby Galaxy Catalogue of Tully and Fisher (1987), and is being continually updated with the data for the UGC catalogue survey of Bothun (1986). Many (but not all) of the sources from the IRAS survey are designated by "IRnnnnn" in the comment field.

In addition, ZCAT contains (but without complete velocity information) all the Zwicky catalogue galaxies with mB 15.5 in the CfA survey region. Lastly, this version of ZCAT does contain the velocity and type information for the first slice of the deeper CfA survey:

             26:O5     (del)     32:O5
             8h     (alp) <=  17h

Nomenclature

In this catalogue, we rely as much as possible on good positions for proper identifcation of the galaxies listed. In many cases, several authors have published velocities for the same galaxy with different ID's and discrepant positions. We have done our best to remove such degeneracies, but know that some such duplicates still exist in the catalogue.

Many galaxies are listed in more than one catalogue _ it is not unusual for a galaxy to be in Zwicky, Nilson, the MCG, Markarian's lists, etc. We have tried to include complete identifications from the UGC and Markarian lists, but other identifcations are given for only a small fraction of the galaxies in the catalogue. (Usually they have been entered when the measurers provide machine readable catalogues of their data with all the other names listed). When they exist, MCG designations will be found in the comment field and will generally look like "nn-mm-ppp," where nn is the declination zone (negative zones are preceeded by "-"), mm is the sky survey field in the zone running from 0h, and ppp is the galaxy number. ESO designations will look like "ESOnnn-Gmm," where nnn is the ESO field number and mm is the galaxy number on the plate. Interacting galaxies in ESO are often designated "IGmm."

Even though all coordinates in this list are quoted to 0.s1 and 1", the actual precision of positions for galaxies varies considerably. In general, coordinates from the Zwicky or Nilson catalogs are quoted to 1' and are precise to a little better than that. Coordinates from the MCG are often off by more than 2'. Galaxies from the above catalogues have coordinates quoted to only the nearest 1' and 6s. Coordinates precise to 5"-6" have been taken from the RC2, Spellman, Madore and Helou (1989), the ESO Catalogue and similar lists. In some small number of cases, usually in the inner regions of clusters of galaxies, coordinates to this precision have been measured by us or our collaborators. A growing subset of galaxies in this catalogue have coordinates measured to arc-second precision via measuring engine or plate scanner. This is particularly true for Seyfert galaxies, Markarian galaxies, radio sources and other AGN, and also for data sets that come from multiple-fiber observations or new, deep small area surveys. Coordinates for IRAS sources extracted from the PSC are accurate to 20"-30", while strong sources that have been add-scanned will have more precise coordinates.

Notes

In a very few instances we have listed discrepant velocites (where two velocity measures disagree by more than double their combined external errors) found by other sources in the comment field - e.g. 1234(9) indicates a velocity of 1234 from source 9. Effort is being made to clear these up by remeasuring the galaxies.

In general, the velocities listed are the best available in terms of the quoted measurement errors and the reliablity of the source (some people persist in quoting errors considerably smaller than their true external errors). In only a few cases have we attempted to average high quality data to produce slightly better values. For almost all objects only one velocity is available. We do not think it appropriate to average low quality data with the newer, significantly better velocites available from 21-cm work and relatively high dispersion optical work. The purpose of this catalogue is to be a complete list of galaxies with radial velocities for mapping and statistical studies. (Observers who feel that their velocites have been slighted for poorer velocities should get in touch with J.P.H.) In several cases, we have omitted velocities derived from detailed HI maps of galaxies - primarily because a single dish measurment of sufficient quality is usually extant. The best quality optical and HI observations have velocity errors < 10 km sec-1 , which are well below the internal velocity dispersions of the galaxies. By definition, there is some question as to what such high "precision" velocities really mean relative to the centers of "mass" of galaxies.

Radial velocites greater than 100,000 km/sec will be found in the companion catalogue ZBIG.DAT. We have not been as assiduous in our efforts to maintain that catalogue (interested parties should contact Hy Spinrad for more information.) Averaged radial velocities for Abell clusters will also be found in another catalogue ABELL.DAT.

THE CATALOGUERS MAKE NO CLAIM THAT THIS ISSUE IS COMPLETE OR FREE FROM ERRORS.

All galaxies brighter than B(0)=13.2 have been included, even when no velocity is available, but otherwise there is no homogeneous magnitude limit to the catalogue. Some galaxies are listed despite their lack of velocity. These are objects in complete samples that we are currently trying to observe, DDO dwarves without velocites, "DOUBLE" galaxies that have been split up for the production of North Zwicky Forty or galaxies from other interesting catalogs (e.g. Binggeli et al.'s work on the Virgo Cluster dwarves - Ref 0109). Magnitudes on systems 0, 1 and 2 are more or less equivalent but other systems have not been well calibrated and are meant only to serve as a guide to the galaxy's brightness. Some of this data is unpublished, so authors are warned against making reference until this list is formally published.

We are constantly updating this list as new velocites, particularly better velocities, become available. We do not guarantee that what you see one day will be there the next! Present plans are to publish in some form (SAO Special Report?) the version we have (cleaned of zero velocity objects, etc.) this year.

A fairly large number of FORTRAN based utility programs now exists for sorting and searching in ZCAT including routines to do circle searches around annuli, cuts in galactic or equatorial coordinates, etc. See John Huchra for a more detailed description of these.

!!!!!! IF ERRORS ARE FOUND, AS SOME ARE SURE TO IN A COMPILATION THIS LARGE, PLEASE REPORT THEM TO THE AUTHOR (JPH). IF YOU WISH TO MAKE ADDITIONS, THESE WILL BE GRATEFULLY ACCEPTED - EVEN MORE SO IF LISTINGS GIVE ACCURATE 1950 COORDINATES AND HELIO- CENTRIC VELOCITIES.

In this day and age, there is no need to present data in unusable formats, so we humbly request that all authors henceforth quote heliocentric velocities (or redshifts = delta-lambda/lambda) and reasonably accurate 1950 coordinates in publications of data and that all editors not accept papers presenting velocities in unusable forms. An HP-25 program to calculate the correction from geocentric to heliocentric velocity to a precision of 1 km/sec is available from JPH. Presentation of velocities in undefined or poorly defined inertial reference frames (e.g. Local Groupocentric or the (mu )-wave background frame) should be avoided at all costs. Editors please take note!

Special thanks are in order for all the people who have worked on this catalog over the years - Dinah Danby, Bob Davis, Marc Davis, Peggy Geller, Ed Horine, Dave Latham, April Michel, Jon Morse, Jim Peters, Suzanne Rapp, Susan Tokarz and John Tonry. Thanks are also extended to those other observers who have sent in redshifts (particularly those who send heliocentric z's and good, 1950 coordinates!) like Tony Fairall, Riccardo Giovanelli, Martha Haynes, George Helou, Lyle Hoffman, Nathan Krumm, Otto Richter and Ed Salpeter. This work has been supported by the Smithsonian Institution and by NASA grant NAGW-201. Some computer support has also been provided by the Digital Equipment Corporation.

John Huchra IAU Working Group on Galaxy Redshifts Center for Astrophysics 60 Garden Street Cambridge, MA 02138 U.S.A. (617-495-7375)

References

Tables

Magnitudes : Photometric and Magnitude Sources

         PHOTOMETRY AND MAGNITUDE SOURCES

  __________________________________________________________
  |  0  |BLANK B(0) 1ST REF CAT                            |
  |  1  |ZWICKY                                            |
  |  2  |SHAPLEY AMES                                      |
  |  3  |TULLY AND FISHER                                  |
  |  4  |GRAHAM                                            |
  |  5  |MARKARIAN, RUSSIAN ESTIMATES                      |
  |  6  |BT - 2ND REF CAT                                  |
  |  7  |MCG (VORONTSOV-VELYAMINOV)                        |
  |  8  |PHOTOELECTRIC or PHOTOGRAPHIC BLUE                |
  |  9  |OBSERVERS EYE ESTIMATE (BLUE)                     |
  |  R  |PHOTOGRAPHIC R IIIa-F, O-98 or 103aE + red filter |
  |  J  |PHOTOGRAPHIC J IIIa-J                             |
  |__V__|PHOTOGRAPHIC_or_PHOTOELECTRIC_V___________________|
PHOTOGRAPHIC magnitudes from sources 8, B, V, J and R, are calibrated via PDS or other microdensitometer scans.

Morphology : Morphologic Types in zCat

         MORPHOLOGICAL TYPES IN ZCAT

  _________________________________________________________
  |  -7 U|nclassified Elliptical                          |
  |  -6 C|ompact Elliptical                               |
  |  -5 E|, and  dwarf E                                  |
  |  -4 E|/S0                                             |
  |  -3 L|-, SO-                                          |
  |  -2 L|, SO                                            |
  |  -1 L|+, SO+                                          |
  |   0  |SO/a, SO-a                                      |
  |   1  |Sa                                              |
  |   2  |Sab                                             |
  |   3  |Sb                                              |
  |   4  |Sbc                                             |
  |   5  |Sc                                              |
  |   6  |Scd                                             |
  |   7  |Sd                                              |
  |   8  |Sdm                                             |
  |   9  |Sm, Magellanic Spiral                           |
  |  10 I|m, Irr I, Magellanic Irregular, Dwarf Irregular |
  |  11 C|ompact Irregular, Extragalactic HII Region      |
  |  15 P|eculiar, Unclassifiable                         |
  |  16 I|rr II                                           |
  |  20 S|..., Sc-Irr, Unclassified Spiral                |
  |  25 P|late Flaw, Star, etc. misclassified as galaxy!  |
  |  26 T|Tauri star (from IRAS Surveys)                  |
  |  30 P|anetary Nebula                                  |
  |  31 D|ark Cloud (no object visible on POSS)           |
  |  33 R|efelection Nebulosity                           |
  |  32 H|II region in external galaxy                    |
  |  40 I|ndiv. Comp. of Multiple Nucleus Galaxy          |
  |______|________________________________________________|

         Bar Types (B)
  ___________________________________________________
  |  A  | A, unbarred                               |
  |  X  | X, AB, mixed type                         |
  |  B  | B, Barred                                 |
  |_____|___________________________________________|

         Peculiarities (P)
  ___________________________________________________
  |  P  |Peculiar                                   |
  |  S  |No inner ring                              |
  |  R  |Ringed (outer)                             |
  |  T  |Pseudo inner ring                          |
  |  D  |Double or Multiple                         |
  |_____|___________________________________________|

   
  Luminosity Classes (L) (for Spirals and Irregulars)
  ________________________________________________
  |  1 I      |6  III-IV                         |
  |  2 I-II   |7  IV                             |
  |  3 II     |8  IV-V                           |
  |  4 II-III |9  V                              |
  |  5 III    |                                  |
  |___________|__________________________________|

Sources : The Source Listing For ZCAT