The text and material for this chapter were prepared during the summer of 1965 and based, on data in the Reference Catalogue of Bright Galaxies (BGC). (A supplementary survey of more distant groups was prepared by Corwin [1967], giving a total of 109 groups with estimated distances and mean velocities.) This material has been used for studies of the motion of the Sun with respect to galaxies (Stewart and Sciama 1967; de Vaucouleurs and Peters 1968) and of the velocity dispersion in groups (Rood, Rothman, and Turnrose 1970; Chamaraux, Montmerle, and Tadokoro 1972; Geller and Peebles 1973; Turner and Sargent 1974). A disturbing feature of the distance scale derived for the groups in this chapter was the implied nonlinearity of the velocity-distance relation at small distances (de Vaucouleurs 1972).
In the meantime better data have become available: (1) systematic errors in estimates of galaxy diameters have been thoroughly investigated (Heidmann, Heidmann, and de Vaucouleurs 1971); (2) additional redshift determinations have accumulated (G. and A. de Vaucouleurs 1967 and other sources), leading to some revisions of group membership; and, especially, (3) much progress has been made in the derivation of isophotal diameters and integrated magnitudes of galaxies (revision of BGC in preparation).
Figure A1. Velocity-distance ratio for revised distances of 72 nearby groups in northern and southern galactic hemispheres. Note absence of correlation in SGH (cf. fig. 1 in de Vaucouleurs 1972). |
Recently an application of this new material was made (with the collaboration of H. Corwin) to the derivation of revised distances for 77 groups having the best current data, including the 54 groups discussed in this chapter. The revised distances are listed in Table A1. From various statistical tests these new distances appear to have very small errors, on the order of 0.1-0.2 mag in the distance moduli. A satisfactory feature of this new distance scale is that it removes almost completely the nonlinearity of the Hubble diagram for nearby groups, at least in the southern galactic hemisphere; a slight non-linearity persists in the northern hemisphere, however, where the ideal velocity field is apparently perturbed by the local density excess associated with the Local Supercluster (fig. A1). Furthermore, the average value of the Hubble constant indicated by the groups is still about 100 km s-1 Mpc-1, in agreement with independent estimates by van den Bergh (1970 and this volume) and Roberts (1972), but in disagreement with the low values of ~ 50 preferred by Sandage (1972 and this volume) and Abell (1972). This persistent discrepancy between different methods all relying on the same basic calibration (Local Group and nearest groups) indicates a continuing need for further critical analysis of all approaches to this fundamental problem of the distance scale.
Group | V | V0 | µc | µ0c | ``H'' | |
G01 Sculptor | 230 | 194 | 27.16 | 26.96 | 2.5 | 78.7 |
G02 M81 | 25 | 160 | 27.68 | 27.38 | 3.0 | 53.4 |
G03 CVn I | 280 | 342 | 28.47 | 28.27 | 4.5 | 75.9 |
G04 NGC 5128 | 530 | 319 | 28.49 | 27.99 | 4.0 | 80.3 |
G05 M101 | 360 | 508 | 28.91 | 28.71 | 5.5 | 91.8 |
G06 NGC 2841 | 550 | 589 | 29.83 | 29.53 | 8.0 | 73.2 |
G07 NGC 1023 | 472 | 619 | 29.07 | 28.47 | 4.9 | 125.2 |
G08 NGC 2997 | 820 | 534 | 30.47 | 29.87 | 9.4 | 56.6 |
G09 M66 | 705 | 592 | 29.33 | 29.13 | 6.7 | 88.3 |
G10 CVn II | 697 | 747 | 29.52 | 29.32 | 7.3 | 102.4 |
G11 M96 | 876 | 741 | 29.50 | 29.30 | 7.2 | 102.3 |
G12 NGC 3184 | 630 | 629 | 29.98 | 29.78 | 9.0 | 69.6 |
G13 Coma I | 954 | 944 | 29.75 | 29.55 | 8.1 | 115.9 |
G14 NGC 6300 | 1411 | 1270 | 31.27 | 30.27 | 11.3 | 112.1 |
G15 Cet I | 1500 | 1513 | 30.67 | 30.37 | 11.8 | 127.9 |
G16 NGC 1566 | 1220 | 999 | 31.22 | 30.92 | 15.3 | 65.5 |
G17 UMa I(Z) | 947 | 979 | 30.56 | 30.36 | 11.8 | 83.0 |
G18 Vir S | 1152 | 1087 | 30.51 | 30.31 | 11.5 | 94.2 |
G19 Vir E | 1093 | 1013 | 30.87 | 30.67 | 13.6 | 74.4 |
G20 Vir Y | 1442 | 1307 | 30.80 | 30.50 | 12.6 | 103.9 |
G21 NGC 1433 | 845 | 665 | 31.16 | 30.96 | 15.6 | 42.7 |
G22 NGC 1672 | 31.22 | 30.92 | 15.3 | |||
G23 NGC 3672 | 1783 | 1583 | 31.60 | 31.30 | 18.2 | 86.9 |
G24 UMa I(Y) | 948 | 998 | 31.04 | 30.84 | 14.7 | 67.8 |
G25 Vir S' | 1631 | 1541 | 31.16 | 30.96 | 15.5 | 99.1 |
G26 Vir X | 1375 | 1272 | 30.98 | 30.78 | 14.3 | 88.7 |
G27 Grus | 1583 | 1561 | 31.48 | 31.28 | 18.0 | 86.7 |
G28 UMa I(X) | 1025 | 1090 | 30.35 | 30.15 | 10.7 | 101.7 |
G29 Vir III | 1749 | 1729 | 30.90 | 30.60 | 13.2 | 131.2 |
G30 NGC 5866 | 740 | 920 | 30.99 | 30.69 | 13.7 | 67.1 |
G31 Eri I | 1680 | 1574 | 30.83 | 30.63 | 13.4 | 117.7 |
G32 UMa I(S) | 966 | 1016 | 31.11 | 30.91 | 15.2 | 66.7 |
G33 Cet II | 1880 | 1929 | 31.19 | 30.99 | 15.8 | 122.4 |
G34 UMa I(N) | 984 | 1074 | 30.73 | 30.53 | 12.8 | 84.1 |
G35 Vir V | 1015 | 879 | 31.45 | 31.25 | 17.8 | 49.3 |
G36 NGC 2207 | 2050 | 1827 | 30.54 | 30.04 | 10.2 | 179.6 |
G37 NGC 5676 | 2261 | 2411 | 31.44 | 31.24 | 17.7 | 136.1 |
G38 NGC 6876 | 31.10 | 30.70 | 13.8 | |||
G39 N0134 | 1800 | 1786 | 31.86 | 31.66 | 21.5 | 83.1 |
G40 N0488 | 2236 | 2336 | 30.91 | 30.71 | 13.9 | 168.4 |
G41 NGC 2768 | 1590 | 1681 | 30.98 | 30.68 | 13.7 | 122.8 |
G42 NGC 2964 | 1515 | 1463 | 31.36 | 31.16 | 17.1 | 85.7 |
G43 NGC 3396 | 1635 | 1599 | 31.48 | 31.28 | 18.0 | 88.7 |
G44 NGC 3923 | 1840 | 1635 | 31.97 | 31.67 | 21.6 | 75.7 |
G45 Pav-Ind | 2275 | 2224 | 32.20 | 31.90 | 24.0 | 92.6 |
G46 Vir W | 2280 | 2168 | 31.83 | 31.63 | 21.2 | 102.4 |
G47 NGC 3190 | 1295 | 1198 | 31.42 | 31.22 | 17.5 | 68.5 |
G48 NGC 3504 | 1490 | 1437 | 31.15 | 30.95 | 15.5 | 92.8 |
G49 NGC 3607 | 1150 | 1057 | 31.67 | 31.47 | 19.7 | 53.7 |
G50 NGC 5846 | 1793 | 1806 | 31.27 | 30.97 | 15.6 | 115.8 |
G51 NGC 6643 | 1690 | 1938 | 31.80 | 31.40 | 19.1 | 101.7 |
G52 NGC 6861 | 2940 | 2909 | 32.24 | 31.94 | 24.4 | 119.3 |
G53 For I | 1615 | 1464 | 31.59 | 31.39 | 18.9 | 77.3 |
G54 NGC 3245 | 1315 | 1256 | 31.82 | 31.62 | 21.1 | 59.5 |
* V = mean heliocentric velocity; V0 = mean galactocentric velocity; µc = revised apparent modulus; µ0c = revised modulus corrected for extinction in the Galaxy; = revised distance in megaparsecs; ``H'' = velocity-distance ratio V0/ in km s-1 Mpc-1.