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ADDENDUM TO CHAPTER 14 (JANUARY 1973)

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

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.

TABLE A1
REVISED DISTANCES OF 54 GROUPS*
Group V V0 µc µ0c Delta ``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; Delta = revised distance in megaparsecs; ``H'' = velocity-distance ratio V0/Delta in km s-1 Mpc-1.

REFERENCES

  1. Abell, G.O. 1972, in External Galaxies and Quasi-stellar Objects, IAU Symposium No. 44, ed. D.S. Evans (Dordrecht: Reidel), p. 350.
  2. Chamaraux, P., Montmerle, T., and Tadokoro, M. 1972, Ap. and Space Sci., 15, 383.
  3. Corwin, H.G. 1967, unpublished M.A. thesis, University of Kansas.
  4. de Vaucouleurs, G. 1972, in External Galaxies and Quasi-stellar Objects, IAU Symposium No. 44, ed. D.S. Evans (Dordrecht: Reidel), p. 353.
  5. de Vaucouleurs, G., and Peters, W.L. 1968, Nature, 220, 868.
  6. de Vaucouleurs, G., and de Vaucouleurs, A. 1967, A.J., 72, 730.
  7. Geller, M.J., and Peebles, P.J.E. 1973, Ap. J., 184, 329.
  8. Heidmann, J., Heidmann, N., and Vaucouleurs, G. de. 1971, Mem. R.A.S., 75, Parts 4-6, 85-104.
  9. Roberts, M. 1972, in External Galaxies and Quasi-stellar Objects, IAU Symposium No. 44, ed. D.S. Evans (Dordrecht; Reidel), p. 32.
  10. Rood, H.J., Rothman, V.C.A., and Turnrose, B.E. 1970, Ap. J., 162, 411.
  11. Sandage, A. 1972, Ap. J., 178, 1.
  12. Stewart, J.M., and Sciama, D.W. 1967, Nature, 216, 742.
  13. Turner, E.L., and Sargent, W.L.W. 1974, Ap. J., 194, 587.
  14. van den Bergh, S. 1970, Nature, 225, 503.

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