5. THE NEARER GROUPS WITHIN 10 MEGAPARSECS

The nearer groups are the groups whose distance moduli µ₀ 30 ( 10 Mpc) can be derived from secondary distance criteria (H II regions, bright stars, luminosity class). These groups in turn serve to calibrate the tertiary distance criteria (magnitudes, diameters) which are used to derive the distances of more distant groups or of southern hemisphere groups for which the secondary criteria are still missing. The apparent distribution of the nearer groups in supergalactic coordinates is shown in figure 3. Available data on each group taken mainly from the Reference Catalogue of Bright Galaxies (abbreviated BGC) are presented in tabular form (Tables 2 and 3). A brief description of individual groups follows.

Figure 3. Apparent distribution of nearer group (µ0 30.0) in supergalactic coordinates.

TABLE 2
ELEMENTS OF 54 NEARBY GROUPS

	Group,	lII	SGL	µ	µ0	D x d	V0	X
No.	Cluster,	bII	SGB	AB		(°)	n	Y
	Cloud	(°)	(°)	(mag)	(Mpc)	(Mpc)	A.D.	Z
G1	Scl	5	265	27.1	26.9	25x20	220	+0.1
		-80	-3	0.2	2.4	1.0x0.8	6	-2.4
							102	-0.2
G2	M81 (NGC 3031)	142	42	27.3	27.0	40x20	160	+1.8
		+41	+1	0.3	2.5	1.8x0.9	9	+1.7
							66	+0.0
G3	CVn I	162	82	28.1	27.9	28x14	342	+0.5
		+80	+5	0.2	3.8	1.9x0.9	9	+3.8
							69	+0.2
G4	NGC 5128	310	155	28.5	28.0	30x	319	-3.8
		+20	-5	0.5	4.0	2.1x	5	+1.3
							55	-0.4
G5	M101 (NGC 5457)	102	64	28.5	28.3	23x16	508	+1.8
		+60	+23	0.2	4.6	1.8x1.3	8	+3.8
							85	+1.7
G6	NGC 2841	170	45	29.2	28.9	15x7	589	+3.7
		+34	-20	0.3	6.0	1.6x0.8	4	+4.4
							122	-1.6
G7	NGC 1023	145	341	29.6	29.0	20x10	625	+5.9
		-20	-8	0.6	6.3	2.2x1.1	8	-1.9
							102	-1.0
G8	NGC 2997	250	133	30.0	29.4	14x8	534	-3.0
		+19	-53	0.6	7.6	1.9x1.1	2	+3.1
								-6.3
G9	M66 (NGC 3627)	241	97	29.6	29.4	7x4	592	-0.9
		+64	-19	0.2	7.6	1.0x0.6	5	+7.1
							74	-2.4
G10	CVn II	138	73	29.7	29.5	22x12	747	+2.4
		+75	+3	0.2	8.0	3.0x1.6	15	+7.7
							71	+0.3
G11	M96 (NGC 3368)	231	93	29.8	29.6	11x7	741	-0.7
		+58	-26	0.2	8.3	1.6x1.0	9	+7.4
							80	-3.6
G12	NGC 3184	176	67	30.1	29.9	10x5	629	+4.0
		+60	-13	0.2	9.6	1.7x0.8	4	+8.4
							122	-2.7
G13	Coma I	198	89	30.1	29.9	11x5	944	+0.1
		+86	+3	0.2	9.6	1.8x0.8	15	+9.5
							170	+0.5
G14	NGC 6300	329	195	31.0	30.0	10x3	1270	-9.5
		-15	+10	1.0	10.0	1.7x0.6	3	-2.7
							100	+1.6
G15	Cet I	178	300	30.5	30.2	12x9	1513	+4.7
		-56	-27	0.3	11.0	2.2x1.7	7	-8.6
							200	-5.0
G16	NGC 1566	265	235	30.6	30.3	5x5	999	-4.9
		-43	-40	0.3	11.5	1.0x1.0	5	-7.2
							156	-7.5
G17	UMa I(Z)	165	77	30.5	30.3	10x4	979	+2.3
		+75	-1	0.2	11.5	1.8x0.7	2	+10.2
								-0.2
G18	Vir S	284	103	30.5	30.3	12x12	1087	-2.7
		+75	-3	0.2	11.5	2.3x2.3	21	+11.2
							780	-0.6
G19	Vir E	284	103	30.5	30.3	12x12	1013	-2.7
		+75	-3	0.2	11.5	2.5x2.5	38	+11.2
							413	-0.5
G20	Vir Y	304	127	30.7	30.4	14x7	1307	-7.2
		+52	-2	0.3	12.0	2.9x1.4	13	+9.6
							322	-0.6
G21	NGC 1433	253	248	30.7	30.5	7x5	665	-3.6
		-49	-42	0.2	12.5	1.5x1.1	2	-9.0
								-7.9
G22	NGC 1672	270	226	30.8	30.5	5x?	?	-6.3
		-38	-39	0.3	12.5	1.0x?		-7.1
								-8.1
G23	NGC 3672	273	121	30.8	30.5	8x6	1583	-5.9
		+49	-22	0.3	12.5	1.8x1.3	2	+9.9
								-5.2
G24	UMa I(Y)	162	66	30.7	30.5	9x4	998	+4.9
		+64	-5	0.2	12.5	20.x0.8	1	+11.5
								-1.0
G25	Vir S'	287	107	30.7	30.5	3x2	1541	-3.6
		+70	-4	0.2	12.5	0.6x0.4	3	+11.9
							277	-0.8
G26	Vir X	293	113	30.7	30.5	13x7	1272	-5.0
		+65	-3	0.2	12.5	2.8x1.5	18	+11.4
							365	-0.5
G27	Grus	348	250	30.8	30.6	8x6	1561	-4.4
		-65	+8	0.2	13.2	1.9x1.5	8	-12.0
							112	+2.6
G28	UMa I(X)	150	56	30.8	30.6	7x5	1090	+7.5
		+54	-2	0.2	13.2	1.6x1.1	1	+10.8
								-0.5
G29	Vir III	352	122	30.9	30.6	15x11	1729	-6.1
		+55	+24	0.3	13.2	3.5x2.5	11	+10.4
							149	+5.3
G30	NGC 5866	90	62	31.0	30.7	6x3	920	+5.8
		+52	+32	0.3	13.8	1.4x0.7	3	+10.3
							130	+7.2
G31	Eri	212	282	30.9	30.7	15x12	1574	+2.5
		-55	-40	0.2	13.8	3.6x2.9	19	-10.8
							160	-8.2
G32	UMa I(S)	143	70	30.9	30.7	9x7	1016	+4.8
		+69	+3	0.2	13.8	2.2x1.7	5	+12.9
							63	+0.9
G33	Get II	160	292	31.0	30.8	9x8	1929	+5.1
		-68	-15	0.2	14.5	2.3x2.0	6	-13.0
							95	-4.0
G34	UMa I(N)	141	61	31.0	30.8	8x5	1074	+7.1
		+60	+3	0.2	14.5	2.0x1.3	8	+12.6
							95	+0.5
G35	Vir V	298	121	31.0	30.8	8x5	879	-7.1
		+57	-6	0.2	14.5	2.0x1.2	1	+12.6
								-1.5
G36	NGC 2207	230	264	31.4	30.9	6x5	1827	-0.3
		-18	-78	0.5	15.	1.5x1.2	3	-2.8
							419	-14.7
G37	NGC 5676	88	70	31.1	30.9	6x2	2411	+4.7
		+60	+28	0.2	15.	1.5x0.5	3	+12.4
							49	+7.0
G38	NGC 6876	324	214	31.3	30.9	6x2	?	-12.5
		-32	+3	0.4	15.	1.5x0.5		-8.3
								+0.6
G39	NGC 134	340	265	31.2	31.0	6x5	1786	-1.8
		-84	-4	0.2	16.	1.6x1.4	2	-15.9
								-1.0
G40	NGC 488	138	302	31.2	31.0	4x2	2336	+8.9
		-58	-6	0.2	16.	1.0x0.5	3	-13.2
							46	-1.4
G41	NGC 2768	154	43	31.3	31.0	7x4	1681	+11.3
		+40	-8	0.3	16.	1.9x1.1	7	+10.8
							160	-2.6
G42	NGC 2964	194	66	31.2	31.0	9x4	1463	+5.5
		+50	-27	0.2	16.	2.5x1.1	5	+13.1
							89	-7.4
G43	NGC 3396	193	75	31.2	31.0	1x1	1599	+3.9
		+63	-16	0.2	16.	0.3x0.3	4	+14.9
							73	-4.3
G44	NGC 3923	287	142	31.3	31.0	6x3	1635	-11.7
		+33	-20	0.3	16.	1.6x0.8	4	+9.0
							172	-5.7
G45	Pavo-Indus	344	230	31.3	31.0	13x8	2224	-9.9
		-45	+14	0.3	16.	3.6x2.2	9	-11.7
							472	+3.8
G46	Vir W	283	108	31.2	31.0	3x2.5	2168	-5.1
		+69	-6	0.2	16.	0.8x0.7	5	+14.9
							187	-1.9
G47	NGC 3190	213	82	31.3	31.1	4x3	1198	+2.1
		+55	-28	0.2	16.5	1.2x0.9	7	+14.5
							94	-7.7
G48	NGC 3504	204	80	31.3	31.1	5x2	1437	+2.4
		+64	-17	0.2	16.5	1.4x0.5	3	+15.7
							30	-4.5
G49	NGC 3607	232	93	31.3	31.1	4x2	1057	-0.8
		+67	-17	0.2	16.5	1.1x0.5	7	+15.4
							229	-4.6
G50	NGC 5846	0	125	31.4	31.1	2.5x2.5	1806	-8.1
		+48	+32	0.3	16.5	0.7x0.7	8	+11.4
							290	+8.7
G51	NGC 6643	105	31	31.5	31.1	7x3.5	1938	+12.3
		+28	+31	0.4	16.5	2.0x1.0	5	+7.0
							262	+8.5
G52	NGC 6861	355	223	31.4	31.1	7x4	2909	-11.5
		-33	+25	0.3	16.5	2.0x1.2	2	-9.7
								+6.7
G53	For I	237	263	31.3	31.1	7x7	1464	-1.5
		-55	-42	0.2	16.5	2.0x2.0	12	-12.2
							260	-10.1
G54	NGC 3245	202	71	31.4	31.2	2x1	1256	+3.9
		+58	-22	0.2	17.5	0.5x0.2	3	+15.8
							96	-6.7

G1. Sculptor Group (µ = 26.9, = 2.4, V₀ = 220). This nearest of all nearby groups is a loose association of six or seven late-type spirals Sc to Sm (NGC 0045, NGC 0055, NGC 0247, NGC 0253, NGC 0300, NGC 7793, and perhaps IC 5332) distributed at the rim of a 20° ring near the south galactic pole (de Vaucouleurs 1956a, 1959).

The fainter, smaller member NGC 0045 also has the largest velocity, and it may be on the far side of the group. If the group had a depth along the line of sight equal to its apparent diameter, the individual distance moduli could have a range of up to µ = 0.7 mag from, say, 26.7 to 27.4. However, the nearly circular outline suggests a flat structure seen face-on. The group has not merely no central concentration, but actually an empty region in its center. This peculiar structure is apparent in several other loose groups of spirals. It suggests the possibility that such groups are the galactic equivalent of old expanding stellar associations (de Vaucouleurs 1959).

The maximum dimensions of the group, 25° x 20° = 1.0 x 0.8 Mpc (or 20° x 20° if IC 5332 is excluded), are of the same order as the Local Group limited to its brighter members. The velocity range is about 400 km s^-1 (+95 to +489 km/sec), or 160 km/sec (+95 to +258 km/sec) if NGC 0045 is excluded. Detailed photometry, continuum, and HI radio data, optical and radio rotation curves, and mass estimates are available for several of the brighter members (de Vaucouleurs 1961b; de Vaucouleurs and Page 1962; Epstein 1964; Robinson and van Damme 1964; and chap. 3 of this volume). An HI cloud sharing the velocity of NGC 300 has been reported by Shobbrook and Robinson (1967) in a position several degrees from the galaxy where no optical luminosity can be seen.

G2. M81 Group (µ₀ = 27.0, = 2.5, V₀ = 160 km/sec). This well-known group centered on the M81-M82 pair in Ursa Major includes several late-type spirals and dwarf irregular satellites: NGC 2976, NGC 3077, IC 2574 (= DDO 81), A0936 (Ho I = DDO 63), and A0814 (Ho II = DDO 50) (Holmberg 1950). Several large nearby spirals including NGC 2366, NGC 2403, and possibly NGC 4236 have comparably low velocities and may be outlying members of the group. NGC 2403, NGC 2366, A0814, and two or three other dwarfs (DDO 44, 51, 53) may in fact form a subgroup in a larger cloud extending into Camelopardalis and including also the low-latitude, obscured group formed by NGC 1560, NGC 1569, IC 342, IC 356, Maffei 1 and 2, ⁽¹⁾ and possibly several dwarfs (DDO 33, 38, 39). This cloud may be interrupted by the galactic absorption belt. The overall dimensions of the cloud 40° x 20° = 1.8 x 0.9 Mpc are typical of these formations (compare UMa I, Virgo II, Leo II, etc.); the restricted M81 group is only 13° x 7° = 0.6 x 0.3 Mpc, or somewhat smaller than the Local Group.

Because of the large range of galactic latitudes covered by the UMa-Cam Cloud the apparent modulus varies from 27.3 (A = 0.3 mag) for M81 to 28.3 (A = 1.2 mag) for IC 342. The velocity range is about 350 km s^-1 (-26 to +322 km/sec).

The M81 group includes two examples of the rare I0 (or Irr II) galaxy type, NGC 3034 and NGC 3077. Both display well-known optical and/or radio peculiarities (see BGC for references). Radio continuum and HI emission, optical and radio rotation curves, and mass estimates are available for several of the brighter members (Epstein 1964, Heeschen and Wade 1964). (See chap. 3 of this volume by E. and G. Burbidge for detailed references on rotation curves.)

G3. Canes Venatici I Cloud (µ₀ = 27.9, = 3.8, V₀ = 342 km/sec). A loose cloud of low-velocity objects may be isolated in the foreground of several more distant, overlapping groups and clouds in the UMa-CVn-Coma area. This whole region is described as the CVn cluster or M94 group by van den Bergh (1960d), who points out that many dwarfs are concentrated in this area (van den Bergh 1959); Sersic (1960) describes a subset as the UMa I group and another as the UMa II group (both of which, however, are all within the boundaries of CVn). A detailed comparison of luminosities, diameters, velocities, H II regions, and brightest stars supports the latter interpretation. After much searching and with some hesitation in borderline cases, the following objects were isolated as members of the foreground CVn I cloud (or restricted M94 group): NGC 4136, NGC 4150, NGC 4214, NGC 4244, NGC 4258, NGC 4395, NGC 4449, NGC 4736 (M94), IC 4182, A1157 (= DDO 105), and possibly NGC 4826 (M64). Other possible dwarf members include DDO 99, 125, 126, 129, 133, 141, 143, and 156. All members are spirals of type Sb or later and Magellanic irregulars. The overall dimensions of the cloud are 28° x 14° = 1.9 x 0.9 Mpc (including NGC 4826), and the velocity range is about 300 km s^-1 (236-530). Radio continuum and HI emission has been detected in several members, including NGC 4214, NGC 4244, NGC 4258, NGC 4449, NGC 4736 (Heeschen and Wade 1964; Epstein 1964), and optical rotation curves and mass estimates are available for NGC 4258, NGC 4736, etc. (see chap. 3).

G4. NGC 5128 Group (µ₀ = 28.0, = 4.0, V₀ = 319). Several large southern galaxies having low velocities (range 271-410) may form a loose group or chain centered on NGC 5128, and including NGC 4945, NGC 5102, NGC 5236, NGC 5253, and possibly NGC 5068 (de Vaucouleurs 1956a, Sersic 1960b). Two (NGC 5102 and perhaps NGC 5128 = Cen A) are lenticulars, three are late-type spirals Sc-Scd, and one (NGC 5253) is peculiar, possibly an I0 irregular (the BGC classification Imp is incorrect). The overall length of the chain is 30° = 2.1 Mpc or 20° = 1.4 Mpc (excluding NGC 5068 which has the highest velocity). The velocity range is, however, only 140 km/sec (271-410 km/sec). Even if this chain does not form a physical (bound) group, it is useful to obtain some estimate of the distance of NGC 5128. Because of the large range of galactic latitudes covered the apparent modulus varies from 28.2 (A = 0.3) for NGC 5068 to 28.8 (A = 0.8) for NGC 4945. In addition to the extensive literature on NGC 5128 (see BGC for references), some optical and radio emission data are available for NGC 4945 and NGC 5236 (de Vaucouleurs 1964; Epstein 1964).

G5. M101 Group (µ₀ = 28.3, = 4.6, V₀ = 508 km/sec). This is a traditional group, but its membership is somewhat uncertain. It is included by van den Bergh (1960d) in his extended M94 group, but Holmberg (1950) and Sersic (1960a) make it a separate group. An analysis of luminosities, diameters, HII regions, and velocities, as well as the distribution on the sphere, supports the latter view. The major members, then, are M101 (NGC 5457) and its satellites NGC 5204, NGC 5474, NGC 5585 , and the wide pair formed by M51 (NGC 5194 and companion NGC 5195) and M63 (NGC 5055); a probable member is NGC 5949 and possibly some outlying systems including NGC 4605, NGC 5907, NGC 6503, A1353 (Ho IV), and A1339 (Ho V). Many dwarfs are concentrated in this region including DDO 175, 185, 186, 191, 193, and 194 around M101, and DDO 167, 168, 169, 172, 176, 177, 178, 181, 182 and 183 around M51-M63. Except for NGC 5195 (type I0), all bright members of the group are spirals of type later than Sb and dwarf Magellanic irregulars. The velocity range is 240 km s^-1 (395-634). The overall dimensions of the group are 23° x 16° = 1.8 x 1.3 Mpc, and again there is no central condensation. In fact, the group consists mainly of two subgroups centered on M101 and M51, each about 10° x 7° = 0.8 x 0.6 Mpc and are separated by some 10° = 0.8 Mpc. The separation between the M31-M33 and Galaxy-LMC subgroups in the Local Group is about 0.7 Mpc. Detailed photometric, spectroscopic, and radio data are available for M51, M63, and M101 (Holmberg 1950; Epstein 1964).

G6. NGC 2841 Group (µ₀ = 28.9, = 6.0, V₀ = 589). Several large spirals near the border of Ursa Major and Lynx have low velocities (range 422-751) and may form a loose group including NGC 2841 and NGC 2681 as the brightest members; the loose triplet of late-type spirals NGC 2500, NGC 2541, NGC 2552; and the close pair formed by NGC 2537, a peculiar Magellanic irregular, and IC 2233, an edge-on Sd (the L classification in BGC is an error). Several dwarf systems in the area, including DDO 040, DDO 041, DDO 043, DDO 046, DDO 048, DDO 049, DDO 052, DDO 055, and DDO 059, are possible members.

The overall dimensions 15° x 7° = 1.6 x 0.8 Mpc are normal. If the adopted modulus is correct, only one member (NGC 2841) is brighter than -18, but NGC 2681 is at M_G = -17.9. Little detailed i