4 Properties of the Canes Venatici I cloud

Figure 3 presents the distribution of 223 galaxies within an area of $\alpha = 11^{\rm h} 30^{\rm m}$ to $13^{\rm h} 40^{\rm m}$ ,

$\begin{figure} \par\setcounter{figure}{2} \includegraphics[angle=-90,width=15.2cm,clip]{Fig3.ps}\end{figure}$

Figure 3: Radial velocity distribution of 223 galaxies in the CVn I region.

$\delta = 25\hbox{$^\circ$ }$ to $55\hbox{$^\circ$ }$ according to their radial velocities with respect to the LG centroid. The data are taken from the latest version of the Lyon Extragalactic Database (LEDA) prepared by Paturel et al. (1996). The histogram shows a rather isolated peak at $V_{\rm LG} = 200 {-} 350$ km s^-1, which is caused by galaxies in the CVn I cloud. Another peak is seen in the range of 500-650 km s^-1 and may correspond to a more distant galaxy group aligned along the Supergalactic equator (data on distances of these galaxies are yet unknown). The distribution of 72 galaxies with $V_{\rm LG} < 550$ km s^-1 is given in equatorial coordinates in Fig. 4.

$\begin{figure} \par\includegraphics[angle=-90,width=15cm,clip]{Fig4.ps}\end{figure}$

Figure 4: The distribution of 72 galaxies with corrected radial velocities $V_{\rm LG} < 550$ km s^-1 in the Canes Venatici constellation in equatorial coordinates. The galaxies with $V_{\rm LG} < 400$ km s^-1 and >400 km s^-1 are indicated by filled circles and crosses, respectively. The two brightest galaxies, NGC 4736 and NGC 4449, are shown by filled squares.

The galaxies with $V_{\rm LG} < 400$ km s^-1are shown by filled circles. Two brightest members of the CVn I cloud, NGC 4736 and NGC 4449, are indicated by filled squares. Probable background galaxies with $400 < V_{\rm LG} < 550$ km s^-1 are shown by crosses. The complete list of the galaxies is given in Table 2.

Table 2: Galaxies in the Canes Venatici region with $V_{\rm LG} < 550$ km s^-1.
Name RA (B1950) Dec $B_{\rm t}$ T $V_{\rm LG}$ Distance Reference

U6541 113045.9 493052 14.23 10 304 3.89 RGB present paper

N3738 113304.4 544758 12.13 10 305 4.90 RGB present paper

N3741 113325.2 453343 14.3 10 264 3.03 RGB present paper

KK109 114433.5 435659 18.62 10 241 4.51 RGB present paper

U6817 114816.8 390931 13.44 10 248 2.64 RGB Karachentsev et al. (2002c)

N4068 120129.7 525201 13.19 10 290 5.2 BS Makarova et al. (1997)

N4080 120218.6 271616 14.28 10 519

Mrk757 120242.9 310801 14.80 0: 551

P38286 120250.2 283839 15.36 10 527

U7131 120639.4 311106 15.50 8 226 14. BS Makarova et al. (1998)

P38685 120724.5 364248 15.5 9: 341

N4144 120728.2 464407 12.16 6 319 9.7 BS Karachentsev et al. (1998)

N4150 120801.4 304047 12.45 -2 198 20: GCLF present paper

N4163 120937.5 362651 13.93 10 164 3.6 BS Tikhonov et al. (1998)

KK127 121051.0 301159 15.61 10 105

N4190 121113.5 365440 13.52 10 234 3.5 BS Tikhonov & Karachentsev (1998)

KDG90 121227.1 362948 15.40 -1 283 2.86 RGB Karachentsev et al. (2002c)

N4214 121308.2 363619 10.24 10 295 2.94 RGB Maiz-Apellaniz et al. (2002)

P39228 121318.5 523955 15.3 10 245

U7298 121400.6 523018 15.95 10 255 4.21 RGB present paper

N4244 121459.8 380506 10.67 6 255 4.49 RGB present paper

N4248 121523.0 474109 13.12 9: 544

N4258 121629.4 473453 9.10 4 507 7.28 SBF Tonry et al. (2001)

U7356 121641.0 472202 15.10 10 330: (HI flux confusion?)

U7369 121708.1 300938 14.70 -1 198

U7408 121847.5 460520 13.35 10 515

IC3247 122043.8 291015 15.25 8 539

IC3308 122247.7 265929 15.17 7 277

KK144 122258.0 284533 16.5 10 453

N4395 122320.8 334922 10.61 9 315 4.61 RGB present paper

UA281 122350.5 484607 15.15 10 349 5.7 BS Makarova et al. (1997)

U7559 122437.1 372509 14.12 10 231 4.87 RGB present paper

U7577 122515.4 434613 12.84 10 240 2.54 RGB Karachentsev et al. (2002c)

N4449 122545.1 442215 9.83 10 249 4.21 RGB present paper

U7599 122600.8 373035 14.98 9 291 6.9 BS Makarova et al. (1998)

U7605 122611.0 355940 14.76 10 317 4.43 RGB present paper

**Table 2:** Galaxies in the Canes Venatici region with $V_{\rm LG} < 550$ km s^-1.
Name	RA (B1950) Dec	$B_{\rm t}$	T	$V_{\rm LG}$	Distance	Reference
U6541	113045.9 493052	14.23	10	304	3.89 RGB	present paper
N3738	113304.4 544758	12.13	10	305	4.90 RGB	present paper
N3741	113325.2 453343	14.3	10	264	3.03 RGB	present paper
KK109	114433.5 435659	18.62	10	241	4.51 RGB	present paper
U6817	114816.8 390931	13.44	10	248	2.64 RGB	Karachentsev et al. (2002c)
N4068	120129.7 525201	13.19	10	290	5.2 BS	Makarova et al. (1997)
N4080	120218.6 271616	14.28	10	519
Mrk757	120242.9 310801	14.80	0:	551
P38286	120250.2 283839	15.36	10	527
U7131	120639.4 311106	15.50	8	226	14. BS	Makarova et al. (1998)
P38685	120724.5 364248	15.5	9:	341
N4144	120728.2 464407	12.16	6	319	9.7 BS	Karachentsev et al. (1998)
N4150	120801.4 304047	12.45	-2	198	20: GCLF	present paper
N4163	120937.5 362651	13.93	10	164	3.6 BS	Tikhonov et al. (1998)
KK127	121051.0 301159	15.61	10	105
N4190	121113.5 365440	13.52	10	234	3.5 BS	Tikhonov & Karachentsev (1998)
KDG90	121227.1 362948	15.40	-1	283	2.86 RGB	Karachentsev et al. (2002c)
N4214	121308.2 363619	10.24	10	295	2.94 RGB	Maiz-Apellaniz et al. (2002)
P39228	121318.5 523955	15.3	10	245
U7298	121400.6 523018	15.95	10	255	4.21 RGB	present paper
N4244	121459.8 380506	10.67	6	255	4.49 RGB	present paper
N4248	121523.0 474109	13.12	9:	544
N4258	121629.4 473453	9.10	4	507	7.28 SBF	Tonry et al. (2001)
U7356	121641.0 472202	15.10	10	330:		(HI flux confusion?)
U7369	121708.1 300938	14.70	-1	198
U7408	121847.5 460520	13.35	10	515
IC3247	122043.8 291015	15.25	8	539
IC3308	122247.7 265929	15.17	7	277
KK144	122258.0 284533	16.5	10	453
N4395	122320.8 334922	10.61	9	315	4.61 RGB	present paper
UA281	122350.5 484607	15.15	10	349	5.7 BS	Makarova et al. (1997)
U7559	122437.1 372509	14.12	10	231	4.87 RGB	present paper
U7577	122515.4 434613	12.84	10	240	2.54 RGB	Karachentsev et al. (2002c)
N4449	122545.1 442215	9.83	10	249	4.21 RGB	present paper
U7599	122600.8 373035	14.98	9	291	6.9 BS	Makarova et al. (1998)
U7605	122611.0 355940	14.76	10	317	4.43 RGB	present paper

Table 2: continued.
Name RA (B1950) Dec $B_{\rm t}$ T $V_{\rm LG}$ Distance Reference

N4460 122620.0 450827 12.26 -1 542 9.59 SBF Tonry et al. (2001)

KK149 122625.8 422715 15.01 10 446

U7639 122728.4 474822 14.13 10 446 8.0 BS Makarova et al. (1998)

KK151 122758.0 431039 15.8 9 479

N4485 122805.1 415833 12.32 10 530

U7699 123021.5 375352 13.17 8 514

U7698 123024.9 314853 13.15 10 321 6.1 BS Makarova et al. (1998)

UA290 123456.0 390112 15.74 10 484 6.70 RGB Crone et al. (2002)

UA292 123613.3 330229 16.1 10 306 3.1 BS Makarova et al. (1998)

IC3687 123950.8 384633 13.75 10 385 4.57 RGB present paper

KK160 124135.0 435615 17. 10 346

FGC1497 124435.2 325521 16. 9 521

U7949 124435.9 364457 15.12 10 351 10. BS Makarova et al. (1998)

KK166 124649.5 355305 17.62 -3 4.74 RGB present paper

U7990 124801.0 283726 16.2 10 495

N4736 124832.3 412328 8.74 2 353 4.66 RGB present paper

U8024 125139.3 272510 14.17 10 355 4.3 BS Makarova et al. (1998)

IC4182 130329.9 375223 12.41 9 356 4.70 Cep Sandage & Tammann (1982)

U8215 130550.4 470524 16.07 10 297 5.6 BS Makarova et al. (1997)

N5023 130957.9 441813 12.82 6 476 5.4 BS Sharina et al. (1999)

U8308 131110.8 463504 15.53 10 243 4.19 RGB present paper

KK191 131124.0 421831 18.2 10 429

U8320 131216.6 461101 12.73 10 273 4.33 RGB present paper

U8331 131320.3 474537 14.61 10 345 8.2 BS Karachentsev & Drozdovsky (1998)

N5204 132743.8 584032 11.73 9 341 4.65 RGB present paper

N5194 132749.7 472932 8.57 5 555 7.7 mem pair with N5195

N5195 132752.4 473132 10.45 -1 558 7.66 SBF Tonry et al. (2001)

U8508 132847.1 551002 14.40 10 186 2.56 RGB Karachentsev et al. (2002c)

N5229 133158.5 481016 14.51 7 460 5.1 BS Sharina et al. (1999)

N5238 133242.6 515209 13.8 8 345 5.2 BS Karachentsev & Tikhonov (1994)

U8638 133658.5 250144 14.47 10 273 2.3: BS Makarova et al. (1998)

U8651 133744.2 405931 14.7 10 272 3.01 RGB Karachentsev et al. (2002c)

U8833 135236.0 360500 15.15 10 285 3.19 RGB present paper

KK230 140501.5 351809 17.9 10 125 1.90 RGB Grebel et al. (2001)

DDO187 141338.6 231713 14.38 10 174 2.50 RGB Aparicio et al. (2000)

DDO190 142248.7 444506 13.25 10 266 2.79 RGB Karachentsev et al. (2002c)

**Table 2:** continued.
Name	RA (B1950) Dec	$B_{\rm t}$	T	$V_{\rm LG}$	Distance	Reference
N4460	122620.0 450827	12.26	-1	542	9.59 SBF	Tonry et al. (2001)
KK149	122625.8 422715	15.01	10	446
U7639	122728.4 474822	14.13	10	446	8.0 BS	Makarova et al. (1998)
KK151	122758.0 431039	15.8	9	479
N4485	122805.1 415833	12.32	10	530
U7699	123021.5 375352	13.17	8	514
U7698	123024.9 314853	13.15	10	321	6.1 BS	Makarova et al. (1998)
UA290	123456.0 390112	15.74	10	484	6.70 RGB	Crone et al. (2002)
UA292	123613.3 330229	16.1	10	306	3.1 BS	Makarova et al. (1998)
IC3687	123950.8 384633	13.75	10	385	4.57 RGB	present paper
KK160	124135.0 435615	17.	10	346
FGC1497	124435.2 325521	16.	9	521
U7949	124435.9 364457	15.12	10	351	10. BS	Makarova et al. (1998)
KK166	124649.5 355305	17.62	-3		4.74 RGB	present paper
U7990	124801.0 283726	16.2	10	495
N4736	124832.3 412328	8.74	2	353	4.66 RGB	present paper
U8024	125139.3 272510	14.17	10	355	4.3 BS	Makarova et al. (1998)
IC4182	130329.9 375223	12.41	9	356	4.70 Cep	Sandage & Tammann (1982)
U8215	130550.4 470524	16.07	10	297	5.6 BS	Makarova et al. (1997)
N5023	130957.9 441813	12.82	6	476	5.4 BS	Sharina et al. (1999)
U8308	131110.8 463504	15.53	10	243	4.19 RGB	present paper
KK191	131124.0 421831	18.2	10	429
U8320	131216.6 461101	12.73	10	273	4.33 RGB	present paper
U8331	131320.3 474537	14.61	10	345	8.2 BS	Karachentsev & Drozdovsky (1998)
N5204	132743.8 584032	11.73	9	341	4.65 RGB	present paper
N5194	132749.7 472932	8.57	5	555	7.7 mem	pair with N5195
N5195	132752.4 473132	10.45	-1	558	7.66 SBF	Tonry et al. (2001)
U8508	132847.1 551002	14.40	10	186	2.56 RGB	Karachentsev et al. (2002c)
N5229	133158.5 481016	14.51	7	460	5.1 BS	Sharina et al. (1999)
N5238	133242.6 515209	13.8	8	345	5.2 BS	Karachentsev & Tikhonov (1994)
U8638	133658.5 250144	14.47	10	273	2.3: BS	Makarova et al. (1998)
U8651	133744.2 405931	14.7	10	272	3.01 RGB	Karachentsev et al. (2002c)
U8833	135236.0 360500	15.15	10	285	3.19 RGB	present paper
KK230	140501.5 351809	17.9	10	125	1.90 RGB	Grebel et al. (2001)
DDO187	141338.6 231713	14.38	10	174	2.50 RGB	Aparicio et al. (2000)
DDO190	142248.7 444506	13.25	10	266	2.79 RGB	Karachentsev et al. (2002c)

Its columns contain: (1) galaxy name, (2) equatorial coordinates (1950.0), (3) apparent blue magnitude from the NED (uncorrected for Galactic extinction), (4) morphological type, (5) radial velocity with respect to the LG centroid, (6) distance to the galaxy with indication of the used method: "Cep'' - via cepheids, "RGB'' - via the tip of red giant branch stars, "SBF'' - via surface brightness fluctuations, "BS'' - from the luminosity of the brightest stars, and "GCLF'' - via the globular cluster luminosity function. The last column presents the source of data on the distance. In addition, we included in Table 2 an interacting galaxy pair NGC 5194/5195 with an accurate distance estimate and three nearby dwarf galaxies: DDO 187, DDO 190, and KK 230, situated slightly to the east of the above indicated boundary of the cloud. The data given in Figs. 3 and 4, and Table 2 permit us to infer properties of the structure and kinematics of the CVn I cloud.

Judging from their distances and radial velocities, 34 galaxies may be CVn I members. We distinguish their names in Table 2 with bold print. Among them there are 24 galaxies whose distances have been measured with an accuracy of $\sim$ (10-15)%. For the other 10 probable members of CVn I only rough distance estimates via the brightest stars are known so far. Karachentsev & Tikhonov (1994) claimed the typical error of distance modulus for the "BS''-method to be 0.4 mag. However, Rozanski & Rowan-Robinson (1994) and some others considered the uncertainties of this method to be greater than 0.5 mag. In Table 2 there are 19 galaxies whose distances have been measured at first via the brightest stars and then via TRGB. Their distance moduli are given in Table 3.

Table 3: Distance moduli for 19 galaxies in Canes Venatici derived from their brightest stars (BS) and RGB stars.
Galaxy $(m-M)_{\rm BS}$ $(m-M)_{\rm RGB}$ difference

UGC 6541 27.73 27.95 -0.22

NGC 3738 27.73 28.45 -0.72

NGC 3741 27.70 27.41 0.29

UGC 6817 27.97 27.11 0.86

NGC 4214 28.06 27.34 0.72

UGC 7298 29.67 28.12 (1.55)

NGC 4244 28.28 28.26 0.02

NGC 4395 28.13 28.32 -0.20

UGC 7559 27.97 28.44 -0.47

UGC 7559 28.53 28.44 0.09

UGC 7577 28.42 27.02 (1.40)

NGC 4449 27.33 28.12 -0.79

UGC 7605 28.24 28.23 0.01

UGCA 290 27.20 29.13 (-1.93)

IC 3687 27.37 28.30 -0.93

UGC 8308 27.85 28.11 -0.26

UGC 8320 28.01 28.18 -0.17

NGC 5204 28.46 28.34 0.12

UGC 8651 27.66 27.39 0.27

UGC 8833 27.53 27.52 0.01

**Table 3:** Distance moduli for 19 galaxies in Canes Venatici derived from their brightest stars (BS) and RGB stars.
Galaxy	$(m-M)_{\rm BS}$	$(m-M)_{\rm RGB}$	difference
UGC 6541	27.73	27.95	-0.22
NGC 3738	27.73	28.45	-0.72
NGC 3741	27.70	27.41	0.29
UGC 6817	27.97	27.11	0.86
NGC 4214	28.06	27.34	0.72
UGC 7298	29.67	28.12	(1.55)
NGC 4244	28.28	28.26	0.02
NGC 4395	28.13	28.32	-0.20
UGC 7559	27.97	28.44	-0.47
UGC 7559	28.53	28.44	0.09
UGC 7577	28.42	27.02	(1.40)
NGC 4449	27.33	28.12	-0.79
UGC 7605	28.24	28.23	0.01
UGCA 290	27.20	29.13	(-1.93)
IC 3687	27.37	28.30	-0.93
UGC 8308	27.85	28.11	-0.26
UGC 8320	28.01	28.18	-0.17
NGC 5204	28.46	28.34	0.12
UGC 8651	27.66	27.39	0.27
UGC 8833	27.53	27.52	0.01

Apart from three cases (UGC 7298, UGC 7577, and UGCA 290) with $\Delta (m-M)$ larger than 1.0 mag, the mean difference of distance moduli for the remaining 16 galaxies is ${<(m-M)_{\rm BS} - (m-M)_{\rm RGB}>} = -0.08 \pm 0.12$ mag, and the rms difference is 0.48 mag. As can be seen from Table 2, apart from galaxies with rough distance estimates there are also many galaxies whose distances have not yet been measured at all. For some objects (PGC 38277, PGC 38685, PGC 91228) their unreliable velocity estimates need to be checked. Due to the incompleteness of the present set of observational data, our conclusions about the structure of the CVn I cloud will have a preliminary character.

Unlike the Local Group and the nearest groups around M81 and Cen A, the galaxy complex in CVn I has no distinct dynamical center usually designated by a giant early-type galaxy. We assume that the dynamical center of CVn I lies between the two brightest cloud members, NGC 4736 and NGC 4449. Their absolute magnitudes, -19.69 and -18.37 mag, are substantially fainter than those of the Milky Way, M 31, M 81, and Centaurus A. As was mentioned above, around the Sa galaxy NGC 4736 there is not any known dwarf galaxy within 230 kpc. Such isolateness of NGC 4736 distinguishes it from the brightest members of other groups. If the luminosity of the brightest member of any group depends on the merging process of surrounding dwarf galaxies, then the rate of the merging process in the CVn I cloud was slow.

The amorphous cloud CVn I differs essentially from more compact nearby groups by its very sparse population of dSph galaxies. Only one CVn I member, KK 166, may currently be considered to be a definitive dSph galaxy. Another reddish LSB dwarf galaxy of regular shape, KDG 90, shows a strong H I flux, not typical of the dSphs. However, KDG 90 is situated near the bright irregular galaxy NGC 4214, which may lead to H I flux confusion. Anyhow, the relative number of dSphs in CVn I does not exceed 6%, which also gives evidence of low rate of interaction between the cloud galaxies if dSphs are primarily the result of stripping in interactions.

Comparing the luminosity function (LF) for field galaxies with the LF for members of three nearest groups (LG + M 81 + Cen A), Karachentsev et al. (2002c) noted an excess of very faint (M_B > -12 mag), as well as giant (M_B < -20 mag) galaxies in the groups. The excess of galaxies of extreme luminosities may be understood if the primordial LF grows on its bright and faint ends owing to "cannibalism'' and "debris'' left by galaxy interactions. In Fig. 5 we present the LF for 34 members of the CVn I cloud together with the LFs for 38 field galaxies and 96 members of the three groups. As it follows from Fig. 5, the LF of the CVn I seems to resemble the field LF more closely than the group LF. This feature indicates once again that galaxy interactions do not necessarily exercise significant influence on the dynamical evolution of galaxies in the CVn I cloud.

$\begin{figure} \par\includegraphics[angle=-90,width=15.6cm,clip]{Fig5.ps}\end{figure}$

Figure 5: The luminosity function of 34 CVn I cloud galaxies (middle histogram), 38 nearby field galaxies (upper histogram) and 96 galaxies situated in the LG, the M81 group, and the CenA group. E and dSph galaxies are shaded.

As was mentioned above, the boundary and the center position of the CVn I cloud still remain uncertain. Based on the data of Fig. 4 and Table 2, one can speculate that the cloud is a superposition of several groups populated by almost entirely irregular dwarf galaxies. In that sense, the CVn I complex resembles another loose cluster of late-type galaxies in Cancer (Bicay & Giovanelli 1987) and nearby cloud of dIrr galaxies in Ursa Major (Tully et al. 1996). Some groups in CVn I, for instance, [NGC 4244, NGC 4395, UGC 7559, UGC 7605, IC 3687], [UGC 8215, UGC 8308, UGC 8320, UGC 8331], and [UGC 8651, UGC 8760, UGC 8833] fit the definition of groups of "squelched'' galaxies introduced by Tully et al. (2002). Luminous matter in such groups plays a negligible role in their dynamical evolution.

Up: Galaxy flow in the cloud