Third Reference Catalogue of Bright Galaxies

This subdirectory contains the Third Reference Catalogue of Bright Galaxies (RC3). This file has details about this distribution of RC3.

The file rc3.10.0.txt contains the entire catalogue of 23,001 galaxies. Two previous versions of RC3 are also available here: rc39b.txt (no plus/minus symbols; also omitted in "rc3.10.0.txt") and rc39c.txt (with a few miscellaneous corrections, and with "±" (plus/minus) symbols as in the printed version; these "±" symbols may display in your browser, database manager, or other application with different characters depending on the file type).

These files are ASCII files containing only 7-bit ASCII characters (except the plus/minus symbols in "rc39c.txt"). bintro.tex, with LaTeX commands, is an earlier version of this file, and applies to "rc39[b|c].txt".

Finally, there is a comma-separated-variable version rc39b.csv for those who wish to import RC3 into a spreadsheet or DBMS. The contents of the CSV file are the same as "rc39b.txt"; the file is briefly described in rc3colscsv.txt. I'll be happy to prepare a CSV version of "rc3.10.0.txt" if I have requests for it.

1. Introduction

This is a brief description of the data entries in the Third Reference Catalogue of Bright Galaxies (RC3) by G. and A. de Vaucouleurs, H.G. Corwin, R.J. Buta, G. Paturel, and P. Fouque. It accompanies an ASCII version of RC3.10.0 (dated 1 June 2020) distributed on the World Wide Web. Any problems relating to this particular distribution should be addressed directly to me at

hcorwin1153@sbcglobal.net

Files included in this distribution are:

A text version of this file, a brief introduction to RC3.
The latest version of RC3, dated 1 June 2020).
The November 2019 version of RC3 with ± signs included (as in the printed version), and a few miscellaneous corrections.
The April 1994 version of RC3, currently also available at CDS (where it is catalogue VII/155); there are no plus/minus signs in this version.
A comma-separated-variable (CSV) version of "rc39b.txt".
A list of the columns (byte numbers) in RC3 and the information included in them.
A list of the columns (byte numbers) in the CSV version.
A list of known errors in the printed version of RC3, complete as of April 1994 (see also Corwin et al., AJ 108, 2128, 1994). All of these errors are corrected in "rc39[b|c].txt" and in "rc3.10.0.txt".
A short list of additional errors found in "rc39b.txt"; all of these errors are also corrected in RC3.10.0. Only miscellaneous errors are listed here; the file does not detail "bulk" changes in positions and/or identifications; or additional/revised classifications, diameters, photometry, and redshifts (see section 2 below for details).
A short Fortran 77 program to read the uncompressed RC3 file and check several aspects of the data. This program also has example read and format statements around which you can build your own RC3 reader. This old program can probably still be compiled with the "gfortran" option of "gcc", the freeware GNU compiler from the Free Software Foundation.

Please note that there are only 23,001 entries in RC3.10.0. Several Galactic objects, plate defects, and duplicate entries have been removed. Details are in the "rc3[new]bugs.txt" files (links above), and in Corwin et al., AJ 108, 2128, 1994.

Details of the reduction procedures, and Notes, References, and Appendices are in Volume 1 of the printed version of RC3, available from Springer-Verlag New York. References here to page numbers are to this first volume of RC3. Volumes 2 and 3 (included in the current distribution) are also available from Springer-Verlag should you wish to have a printed and bound version of the complete catalogue.

2. Revisions and Additions

This version of RC3 was inspired by my work on a forthcoming all-sky galaxy catalogue for amateur astronomers who might want a more compact and up-to-date list than the original RC3. (For preliminary examples of where that all-sky catalogue might be headed, see the SGC and SEGC sections of this web site.) I needed to use RC3 for its photometric systems of diameters and magnitudes, but -- with the two different precisions given for the positions, and with RC3's non-standard name formats -- I found the older versions of RC3 difficult to use. This new version addresses both of those shortcomings, and adds some significant new data as well.

The majority of the changes presented in RC3.10.0 are for the positions. All RC3 galaxies now have positions given to 0.1 seconds of time and 1 arcsecond. RMS accuracy for the updated positions is on the order of ±2 arcseconds; older positions, particularly in the south from ESO-B, still have accuracies of ±5-7 arcseconds. I'll replace these in a later version of RC3. Due to my thoughtless use of Fortran's "int" function (which truncates numbers) rather than "nint" (which rounds them) the declinations for about half the updated positions can read up to nearly one arcsecond too small. My apologies; I'll correct this too in a later release.

In the north, the old RC3 positions have been updated with a list of accurate positions for UGC galaxies (plus a few others). Almost all of these come from Cotton, Condon, and Arbizzani (ApJS 125, 409, 1999), though others from my personal collection of deep-sky-object positions (with sources given below) are also included. I used a 20-arcsecond search box; this pulled in most of the galaxies which already had more or less accurate positions. For the remainder, I used UGC name matching to assign the new positions to the galaxies.
For the entire sky, I updated RC3's NGC and IC galaxy positions and identifications to agree with those that I have collected (see the NGC/IC section of this web site for details). Here, I used a 10-arcsecond search box since the previous step matched most of the catalogue entries.
These steps still left over 1700 catalogued galaxies with poorly known (±0.2 minutes of time, ±2 arcminutes) positions, or positions that did not otherwise match within the search criteria. I updated these by hand, using primarily positions from Gaia DR2 (CDS catalogue number I/345), Pan-STARRS1 (II/349), SDSS DR12 (V/147), 2MASS PSC (II/246), URAT1 (I/329), UCAC (I/322A), CMC (I/327), 6dF (VII/259), 2MASS XSC (VII/233), NPM1G (I/200), GSC3 (I/305), GSCA (I/255), and UB10 (I/284) in roughly that order of preference. I accessed all of these catalogues through the versions currently online at VizieR.
For galaxies without nuclei, I estimated positions from Digitized Sky Survey images using HESARC's SkyView tools. For stellar objects such as galaxy nuclei, these positions have surprisingly small errors of less than ±2 arcseconds, though there is a +0.8 arcsecond offset in the declinations I measure using SkyView; I do not yet know if this is a general problem with the SkyView software (unlikely) or if it is a specific one arising through my particualar use of the SkyView tools on a Mac desktop computer (more likely in my opinion).
Barring typos, all of these positions will serve to unambiguously identify the RC3 galaxies. Please let me know about any bad positions you find! I'm sure a few remain.

Another major source of data came from the 1990 Photometric Atlas of Northern Bright Galaxies, (the "Kiso Atlas") edited by Keiichi Kodaira, Sadanori Okamura, and Shin-ichi Ichikawa; we received this just a few months too late to include it in the initial 1991 version of RC3. Recently, I determined impartial least squares relationships between the RC3 B-band data and the Kiso V-band photometry and diameters, and worked the reduced data into RC3 where needed. This provided V-band photometry and reduced diameters, axis ratios, and position angles for many bright galaxies previously without accurate data. I will be happy to send details of the reductions on request.
I have attempted to "rationalize" the names of all the galaxies in RC3 through the following steps:
- I have removed extra blank spaces between the name prefix and the following number. I have also padded out the numbers with leading zeros. Examples include "NGC 0001" instead of "NGC_____1", "PGC 00089" instead of "PGC____89", and so on.
- This has given the names a "standard" format within RC3 of a) the prefix followed by a single blank space, and b) the number padded with leading zeros. A major exception is "IRAS" which has no spaces between the prefix and the following number.
- The "ESO" names have the format "ESO FFF-NNN" (field-number), and MCG names are "MCG ±ZZ-FF-NNN" (zone-field-number).
- Almost all the object names with the prefix "A" are from RC2, though a few from RC1 remain. Those are recognizeable by having only the four digits of B1950 RA following the "A" (e.g. "A 0055"), while the RC2 names have six digits and a Dec sign (e.g. "A 0054+23").
- "A", "B", "C" etc. have traditionally been appended to the numbers to break ambiguities (e.g. "NGC 6027A", "NGC 6027B", and so on). Where confusion among these names in multiple systems is still possible, I have replaced the appended characters with directional notations, e.g. "n", "w", "se", "nw", etc. While these should help to identify component galaxies in multiple systems, I suggest using other names -- if available -- to refer to these objects.
- Finally, many UGC names have "a", "b", etc. appended. These were almost always assigned in right ascension order by Peter Nilson when he was building UGC, so I have retained them for ease of tracing them back to their origins, if needed.
I have also made other changes and additions, primarily to the classifications and diameters. Many additional and corrected classifications by Ron Buta will be given in a later version.

3. Use and Distribution

You may use any of the data in the electronic versions of RC3 in any way you wish. We do ask that you acknowledge RC3 and its authors in any publication that results from your use of the Catalogue. You may also freely distribute unaltered electromagnetic copies of RC3 to friends and colleagues as long as a copy of this documentation -- including this notice -- accompanies the Catalogue.

The printed version of RC3 is protected by copyright, and may not be reproduced in any manner without the written permission of the copyright holder, Springer-Verlag New York, Inc.

4. The Catalogue

The data for each galaxy are found on four successive lines. The entries are as follows:

Column 1 -- Positions

Line 1 -- RA and DEC = right ascension and declination for the equinox J2000.0, given to 0.1 second of time and 1 arcsec (Section 3.1.a, page 11). For "rc39[b|c].txt", the J2000 position is precessed from the B1950 position. For "rc3.10.0.txt", the J2000 position is the "base" position for RC3 and is precessed to B1950.

Line 2 -- l and b = Galactic longitude and latitude in the IAU 1958 system (Blaauw et al. 1960); both to 0.01 degrees.

Line 3 -- SGL and SGB = supergalactic longitude and latitude in the RC2 system (Section 3.1.b), both to 0.01 degrees.

Line 4 -- RA and DEC = right ascension and declination for the equinox B1950.0, precessed from the J2000.0 position in Column 1, Line 1 (Section 3.1.a, page 11). For "rc39[b|c].txt", the B1950 position is the "base" position for RC3, and is precessed to J2000.

Column 2 -- Names = commonly used designations for the galaxies (Section 3.2, page 12).

Line 1 -- Names (e.g. LMC, SMC) or NGC and IC designations.

Line 2 -- UGC (Nilson 1973), ESO (Lauberts 1982), MCG, Volumes 1-4 and MCG, Volume 5 (Vorontsov-Velyaminov et al. 1962-1974), UGCA (Nilson 1974), and CGCG (Zwicky et al. 1961-1968) designations, given in that order of preference. MCG designations not listed here are given in UGC, UGCA, and ESO.

Line 3 -- Other common designations (see Table 1, page 14, for a complete list).

Line 4 -- PGC (Paturel et al. 1989) designation. For cross identifications of various catalogues with PGC, see Appendix 10, page 561.

Column 3 -- Types and Luminosity Classes

Line 1 -- Type = mean revised morphological type in the RC2 system, coded as in RC2 (Section 3.3.a, page 13).

Line 2 -- S_T and n_L = sources of revised type estimates and number of luminosity class estimates. To those sources listed in Table 3, page 16, I have added "HC" meaning classifications by me, not otherwise published. I have arbitrarily assigned an error of 1.5 to these types.

Line 3 -- T = mean numerical index of stage along the Hubble sequence in the RC2 system (coded as explained in Section 3.3.c, page 16), and its mean error.

Line 4 -- L = mean numerical luminosity class in the RC2 system (coded as explained in Section 3.3.d, page 18), and its mean error. As with the types in Column 3, Line 1, my new luminosity classes carry an arbitrary error of 1.5.

Column 4 -- Optical Diameters and Axis Ratios

Line 1 -- logD₂₅ = mean decimal logarithm of the apparent major isophotal diameter measured at or reduced to surface brightness level μ_B = 25.0 B-mag/arcsec², and its mean error, as explained in Section 3.4.a, page 21. The unit of D is 0.1 arcminute to avoid negative entries. A few very uncertain diameters are flagged with question marks.

Line 2 -- logR₂₅ = mean decimal logarithm of the ratio of the major isophotal diameter, D₂₅, to the minor isophotal diameter, d₂₅, measured at or reduced to the surface brightness level μ_B = 25.0 B-mag/arcsec², and its mean error, as explained in Section 3.4.b, page 26. A few very uncertain axis ratios are flagged with question marks.

Line 3 -- logA_e = decimal logarithm of the apparent diameter (in 0.1 arcmin) of the "effective aperture," the circle centered on the nucleus within which one-half of the total B-band flux is emitted, and its mean error, both derived as explained in Section 3.4.c, page 28.

Line 4 -- logD₀ = decimal logarithm of the isophotal major diameter corrected to "face-on" (inclination = 0 degrees), and corrected for Galactic extinction to A_g = 0, but not for redshift, as explained in Section 3.4.d, page 29.

Column 5 -- Major Axis Position Angle, Galactic and Internal Extinctions

Line 1 -- p.a. = position angle, measured in degrees from north through east (all p.a. < 180 degrees), taken when available from UGC, ESO, and the Kiso Atlas (and in a few cases from HI data) (Section 3.5.a, page 30).

Line 2 -- A_g = Galactic extinction in B-band magnitudes, calculated following Burstein and Heiles (1978a), (1978b), (1982), and (1984), as explained in Section 3.5.b, page 30.

Line 3 -- A_i = internal extinction in B-band magnitudes (for correction to face-on), calculated from logR and T, as explained in Section 3.5.c, page 31.

Line 4 -- A₂₁ = HI line self-absorption in magnitudes (for correction to face-on), calculated from logR and T >= 1, as explained in section 3.5.d, page 32.

Column 6 -- Optical and Infrared Magnitudes

Line 1 -- B_T = total (asymptotic) magnitude in the B system, and its mean error, derived by extrapolation from photoelectric aperture-magnitude data, B_T^A, and from surface photometry with photoelectric zero point, B_T^S, as explained in Section 3.6.a, page 32. The magnitude is followed by an "M" when it is the weighted mean of B_T^A and B_T^S, by a "V" when it is a V-band magnitude rather than a B-band magnitude, and by a "v" when the nucleus of the galaxy is variable. The magnitude is replaced by an asterisk (*) when deriving B_T^A would have required an extrapolation in excess of 0.75 mag.

Line 2 -- m_B = photographic magnitude and its mean error from Ames (1930), Shapley and Ames (1932), CGCG, Buta and Corwin (1986), and/or Lauberts and Valentijn (1989) reduced to the B_T system, as explained in Section 3.6.b, page 37.

Line 3 -- m_FIR = far-infrared magnitude calculated from m_FIR = -20.0 - 2.5logFIR, where FIR is the far infrared continuum flux measured at 60 and 100 microns as listed in the IRAS Point Source Catalog (1987). For galaxies larger than 8 arcmin in RC2 and for the Virgo cluster area, resolved by the IRAS beam, integrated fluxes are taken from Rice et al. (1988) or Helou et al. (1988). See Section 3.6.c, page 43, for details.

Line 4 -- B_T⁰ = total "face-on" magnitude corrected for Galactic and internal extinction, and for redshift, as explained in Section 3.6.d, page 44.

Column 7 -- Total Color Indices

Line 1 -- (B-V)_T = total (asymptotic) color index in the Johnson B-V system, and its mean error, derived by extrapolation from photoelectric color-aperture data, and/or from surface photometry with photoelectric zero point, as explained in Section 3.7.a, page 45.

Line 2 -- (U-B)_T = total (asymptotic) color index in the Johnson U-B system, and its mean error, derived by extrapolation from photoelectric color-aperture data, and/or from surface photometry with photoelectric zero point, as explained in Section 3.7.a, page 45.

Line 3 -- (B-V)_T⁰ = total B-V color index corrected for Galactic and internal extinction, and for redshift, as explained in Section 3.7.b, page 47.

Line 4 -- (U-B)_T⁰ = total U-B color index corrected for Galactic and internal extinction, and for redshift, as explained in Section 3.7.b, page 47.

Column 8 -- Effective Color Indices and B-band Surface Brightness

Line 1 -- (B-V)_e = mean B-V color index, and its mean error, within the effective aperture A_e, derived by interpolation from photoelectric color-aperture data, as explained in Section 3.7.a, page 45.

Line 2 -- (U-B)_e = mean U-B color index, and its mean error, within the effective aperture A_e, derived by interpolation from photoelectric color-aperture data, as explained in Section 3.7.a, page 45.

Line 3 -- m'_e = mean B-band surface brightness in magnitudes per square arcmin (B-mag/arcmin²) within the effective aperture A_e, and its mean error, as given by the relation m'_e = B_T + 0.75 + 5logA_e - 5.26. m'_e is statistically related to the effective mean surface brightness, μ'_e (RC2, p. 31; Olson and de Vaucouleurs 1981), with which it coincides when log R = 0 (i = 0 degrees) (Section 3.8.a, page 49).

Line 4 -- m'₂₅ = the mean surface brightness in magnitudes per square arcmin (B-mag/arcmin²) within the μ_B = 25.0 B-mag/arcsec² elliptical isophote of major axis D₂₅ and axis ratio R_25, defined as in RC2 (Equation 21) by: m'₂₅= B_T + Delta m₂₅ + 5logD₂₅ - 2.5logR₂₅ - 5.26, where Delta m₂₅ = 2.5log(L_T/L_D₂₅) = B₂₅ - B_T is the magnitude increment contributed by the outer regions of a galaxy fainter than μ_B = 25.0 B-mag/arcsec². For details, see Section 3.8.b, page 50.

Column 9 -- 21-cm Magnitude and Linewidths, Hydrogen Index

Line 1 -- m₂₁ = 21-cm emission line magnitude, and its mean error, defined by m₂₁ = 21.6 - 2.5log(S_H), where S_H is the measured neutral hydrogen flux density in units of 10^-24 W/m². For details, see Section 3.9.a, page 51.

Line 2 -- W₂₀ = neutral hydrogen line full width (in km/s) measured at the 20% level (I₂₀/I_max), and its mean error, as explained in Section 3.9.b, page 51.

Line 3 -- W₅₀ = neutral hydrogen line full width (in km/s) measured at the 50% level (I₅₀/I_max), and its mean error, as explained in Section 3.9.b, page 51.

Line 4 -- HI = corrected neutral hydrogen index, which is the difference m₂₁⁰ - B_T⁰ between the corrected (face-on) 21-cm emission line magnitude and the similarly corrected magnitude in the B_T system. Details are given in Section 3.9.c, page 52. Since m₂₁ and B_T are listed separately in columns 6 and 9, line 1, there is no need to list the uncorrected index.

Column 10 -- Radial Velocities

Line 1 -- V₂₁ = cz is the mean heliocentric radial velocity, and its mean error, in km/s derived from neutral hydrogen observations, as explained in Section 3.10.a, page 52.

Line 2 -- V_opt = cz is the mean heliocentric radial velocity, and its mean error, in km/s derived from optical observations, as explained in Section 3.10.b, page 53.

Line 3 -- V_GSR = the weighted mean of the neutral hydrogen and optical velocities, corrected to the "Galactic standard of rest," as explained in Section 3.10.c, page 54.

Line 4 -- V_3K = the weighted mean velocity corrected to the reference frame defined by the 3 K microwave background radiation, as explained in Section 3.10.d, page 55.

hgcjr
hcorwin1153@sbcglobal.net

Latest revision of this file: 14 June 2020