Next Contents Previous

7.4 Luminosity Function

The mode of formation of the Reference Catalogue prevents the derivation of a meaningful luminosity function for groups other than the Local Group, (Section 4) except for the very brightest galaxies. Table 7 gives the numbers N18 and N17 of systems with MG < -18 and MG < -17 in the B(0) system (remember that MT is about 0.5 mag brighter on the average) for 38 groups (including the Local Group) and 17 clouds or clusters. The counts appear to be complete to -17 for µ0 < 30.0 only, and to -18 for µ0 < 31.0. The average population is Nbar18 = 4.3 for groups and Nbar18 appeq 15 for clouds and clusters. On the average a cloud or cluster (as defined here) comprises three or four groups. This is consistent with the ratio of average diameters (2.5/1.5)3 and the statistical relation between volume and average density in nearby space (de Vaucouleurs 1960a, 1961d).

TABLE 7
LUMINOSITY FUNCTION AND POPULATION-TYPE INDICES OF 55 NEARBY GROUPS

Group N18 N17* tbar Range St n

00 Local Group 2-3 3-4 +6.4 (+3,+9) 2.1 5
01 Sculptor 3 4 +7.3 (+5,+9) 1.0 6
02 M81 2 3 +4.6 (-1,+9) 3.7 5
03 CVn I 4 6 +5.6 (+2,+10) 3.5 5
04 NGC 5128 3 6 +3.3 (-4,+10) 4.7 6
05 M101 3 4 +4.0 (-1,+7) 2.0 5
06 NGC 2841 1 3 +5.8 (0,+10) 2.9 6
07 NGC 1023 2 4 +3.8 (-4,+7) 3.0 6
08 NGC 2997 3 5 +3.6 (-3,+6) 2.6 5
09 M66 3 4 +1.0 (-2,+3) 1.6 5
10 CVn II 5 11 +6.0 (+3,+9) 2.0 5
11 M96 2 5 -2.0 (-6,+3) 3.6 5
12 NGC 3184 4 4 +6.3 (+5,+9) 1.4 4
13 Coma I 10 12 +2.0 (-6,+5) 3.2 5
14 NGC 6300 3 (3) (+4.3) (+3,+5) (0.9) 3
15 Cet I 10 (16) +2.8 (-2,+5) 1.9 5
16 NGC 1566 9 (13) -1.6 (-6,+4) 3.3 5
17 UMa I (Z) 3 (5) +2.0 (-3,+7) 2.4 5
18 Virgo S 27 (45) +3.4 (+2,+5) 0.9 5
19 Virgo E 32 (51) -5.0 (-6,-2) 1.2 5
20 Virgo Y 16 (22) +1.4 (-6,+6) 3.5 5
21 NGC 1433 8 (8) +1.6 (-3,+6) 3.5 5
22 NGC 1672 3 (4) +4.0 (+3,+6) 1.2 5
23 NGC 3672 2 (6) -1.5 (-6,+5) 3.2 4
24 UMa I (Y) 3 (6) (+4.3) (+3,+5) (0.9) 3
25 Virgo S' 5 (10) +3.2 (0,+7) 2.2 5
26 Virgo X 24 (37) +1.8 (-5,+6) 3.4 5
27 Grus 17 (24) +1.6 (-2,+6) 2.1 5
28 UMa I (X) 3 (6) +2.8 (-3,+9) 3.8 5
29 Virgo III 15 (23) +3.0 (+2,+6) 1.6 5
30 NGC 5866 5 (5) +2.6 (-2,+5) 1.8 5
31 Eri 19 (24) +2.2 (-5,+5) 3.0 5
32 UMa I (S) 15 (20) +4.2 (+3,+5) 1.0 5
33 Cet II 6 (8) -2.4 (-6,+3) 4.3 5
34 UMa I (N) 15 (18) +3.2 (+1,+5) 1.4 5
35 Virgo V 9 (12) +2.2 (-4,+6) 3.4 5
36 NGC 2207 6 (7) +3.4 (-2,+6) 2.3 5
37 NGC 5676 3 (4) +3.0 (0,+5) 1.2 4
38 NGC 6876 3 (4) +2.0 (-6,+7) 4.5 4
39 NGC 0134 (5) (5) +0.8 (-3,+4) 3.0 5
40 NGC 0488 5 (6) +1.8 (-3,+4) 2.3 4
41 NGC 2768 5 (6) +0.8 (-5,+7) 4.2 5
42 NGC 2964 4 (8) +1.0 (-3,+4) 2.8 5
43 NGC 3396 3 (3) +4.2 (-3,+10) 3.4 5
44 NGC 3923 8 (8) -2.8 (-6,+5) 3.4 5
45 Pavo-Indus 24 (24) 0.0 (-6,+4) 3.6 5
46 Virgo W 6 (14) -0.2 (-6,+5) 3.1 5
47 NGC 3190 6 (8) -1.0 (-6,+4) 3.6 5
48 NGC 3504 3 (3) +0.5 (-3,+5) 3.0 4
49 NGC 3607 6 (10) -0.2 (-6,+6) 4.2 5
50 NGC 5846 8 (10) -1.8 (-6,+3) 3.8 5
51 NGC 6643 (5) (5) +2.8 (0,+5) 2.2 5
52 NGC 6861 9 (12) -3.2 (-6,0) 1.4 5
53 For I 15 (15) -2.6 (-6,+4) 2.9 5
54 NGC 3245 4 (4) +1.5 (-3,+4) 2.2 4

* Parentheses indicate incomplete data.

Next Contents Previous