2001MNRAS.325..385T

Query : 2001MNRAS.325..385T

2001MNRAS.325..385T - Mon. Not. R. Astron. Soc., 325, 385-404 (2001/July-3)

The Ursa Major cluster of galaxies - III. Optical observations of dwarf galaxies and the luminosity function down to MR=-11.

TRENTHAM N., TULLY R.B. and VERHEIJEN M.A.W.

Abstract (from CDS):

Result. are presented of a deep optical survey of the Ursa Major cluster, a spiral-rich cluster of galaxies at a distance of 18.6Mpc which contains about 30 per cent of the light but only 5 per cent of the mass of the nearby Virgo cluster. Fields around known cluster members and a pattern of blind fields along the major and minor axes of the cluster were studied with mosaic CCD cameras on the Canada-France-Hawaii Telescope. The dynamical crossing time for the Ursa Major cluster is only slightly less than a Hubble time. Most galaxies in the local Universe exist in similar moderate-density environments. The Ursa Major cluster is therefore a good place to study the statistical properties of dwarf galaxies, since this structure is at an evolutionary stage representative of typical environments, yet has enough galaxies that reasonable counting statistics can be accumulated. The main observational results of our survey are as follows.

(i) The galaxy luminosity function is flat, with a logarithmic slope α=-1.1 for -17<MR←11 from a power-law fit. The error in α is likely to be less than 0.2 and is dominated by systematic errors, primarily associated with uncertainties in assigning membership to specific galaxies. This faint-end slope is quite different from what was seen in the Virgo cluster, where α=-2.26±0.14.

(ii) Dwarf galaxies are as frequently found to be blue dwarf irregulars as red dwarf spheroidals in the blind cluster fields. The density of red dwarfs is significantly higher in the fields around luminous members than in the blind fields.

The most important result is the failure to detect many dwarfs. If the steep luminosity function claimed for the Virgo cluster were valid for Ursa Major, then in our blind fields we should have found ∼103 galaxies with -17<MR←11 whereas we have found two dozen. There is a clear deficiency of dwarfs compared with the expectations of hierarchical clustering theory. It is speculated that the critical difference between the Virgo and Ursa Major clusters is the very different dynamical collapse times, which probably straddle the time-scale for reionization of the Universe. Dwarf galaxies in the proto-Virgo environment probably formed before the epoch of reionization. The equivalent dwarf haloes in the proto-Ursa Major environment probably formed only after the epoch of reionization, when the conditions for star formation were inhospitable.


Abstract Copyright: The Royal Astronomical Society

Journal keyword(s): galaxies: clusters: individual: Ursa Major - galaxies: luminosity function, mass function - galaxies: photometry

Nomenclature: Table 2: [TTV2001] NN (Nos 1-65). Paragr.4: [TTV2001] JHHMM.m+DDMM N=9.

Simbad objects: 114

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Number of rows : 114
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 Malin 2 LIN 10 39 52.4820927048 +20 50 49.375560660   14.20       ~ 104 0
2 [TTV2001] 01 G 11 36 04.7 +47 31 14           ~ 1 0
3 [RDS2004] UMa 5 LSB 11 39 26.9 +47 34 03           ~ 3 0
4 NGC 3811 H2G 11 41 16.6113724536 +47 41 26.982320640   13.0       ~ 182 0
5 [TTV2001] 03 G 11 44 10.9 +48 02 24           ~ 1 0
6 [TTV2001] 04 GiC 11 45 16.3 +55 34 31           ~ 1 0
7 NGC 3850 GiC 11 45 35.6792908103 +55 53 12.850289447   14.4       ~ 78 0
8 2MASX J11455143+5605188 GiC 11 45 51.438 +56 05 18.82           ~ 8 0
9 [TTV2001] 05 G 11 45 57.9 +47 37 16           ~ 1 0
10 LEDA 2523325 G 11 46 19.0 +56 02 16           ~ 2 0
11 LEDA 2515483 GiC 11 46 34.074 +55 49 16.98           ~ 15 0
12 [TTV2001] 08 G 11 46 35.9 +54 47 55           ~ 1 0
13 [TTV2001] 09 GiC 11 46 49.6 +48 05 33           ~ 1 0
14 [TTV2001] 10 GiC 11 46 53.4 +54 40 10           ~ 1 0
15 [TTV2001] 11 GiC 11 47 13.9 +54 35 57           ~ 1 0
16 SMDG J1147219+552611 LSB 11 47 21.94 +55 26 11.3           ~ 3 0
17 [PYY2023] J114733+551101 GiC 11 47 33.5 +55 11 03           ~ 2 0
18 NGC 3888 H2G 11 47 34.33227 +55 58 02.1290   12.6       ~ 146 1
19 SMDG J1148128+551024 LSB 11 48 12.6 +55 10 26           ~ 3 0
20 [TTV2001] 15 LSB 11 48 43.585 +55 55 45.35           ~ 5 0
21 [TTV2001] 16 GiC 11 48 45.4 +56 01 56           ~ 1 0
22 NGC 3898 LIN 11 49 15.370 +56 05 03.66   11.7       ~ 329 1
23 [TTV2001] 17 G 11 49 18.7 +54 58 15           ~ 1 0
24 [TTV2001] 18 G 11 49 26.3 +55 15 13           ~ 1 0
25 SMDG J1150456+550645 LSB 11 50 45.6 +55 06 45           ~ 3 0
26 Mrk 1460 EmG 11 50 50.1094537992 +48 15 04.844817792   17.0       ~ 32 0
27 [TTV2001] 20 G 11 50 50.7 +54 46 00           ~ 1 0
28 Z 268-97 LIN 11 51 22.6953521976 +53 26 39.005023452   15.5       ~ 29 0
29 LEDA 2431790 GiC 11 51 53.666 +53 05 58.23           ~ 11 0
30 Z 269-12 GiP 11 52 07.07728 +52 06 28.5595   15.6       ~ 63 0
31 [TTV2001] J1152.9+4754 G 11 52.9 +47 54           ~ 1 0
32 MCG+09-20-023 GiC 11 53 09.4 +52 11 23   17       ~ 2 0
33 [TTV2001] 23 GiC 11 53 11.13816 +48 11 18.5460           ~ 2 0
34 NGC 3953 GiG 11 53 49.0086582552 +52 19 36.475395312   11.08   9.71   ~ 380 0
35 LEDA 3401153 AG? 11 53 52.348 +51 29 37.73           ~ 9 0
36 [TTV2001] J1154.2+5053 G 11 54.2 +50 53           ~ 1 0
37 [TTV2001] 25 GiC 11 54 27.6 +51 20 05           ~ 1 0
38 [TTV2001] 26 G 11 54 40.8 +48 13 49           ~ 1 0
39 [TTV2001] J1154.7+5053 G 11 54.7 +50 53           ~ 1 0
40 [TTV2001] J1155.5+4846 G 11 55.5 +48 46           ~ 1 0
41 [TTV2001] 27 GiC 11 55 38.2 +55 22 04           ~ 1 0
42 NGC 3972 GiG 11 55 45.09048 +55 19 14.6460   13.14   11.94   ~ 242 1
43 [TTV2001] 28 G 11 55 53.3 +50 31 12           ~ 1 0
44 SMDG J1155591+481200 LSB 11 55 59.1 +48 12 02           ~ 3 0
45 MATLAS-1124 LSB 11 56 09.4 +55 15 55           ~ 5 0
46 Z 269-18 GiG 11 56 28.76784 +50 25 42.0132   14.0       ~ 148 0
47 NGC 3985 GiG 11 56 42.1288367760 +48 20 03.129462132   13.0       ~ 122 0
48 Z 269-22 GiC 11 56 49.526 +53 09 37.21   13.90   12.96   ~ 155 0
49 Z 269-21 AG? 11 56 52.142 +50 49 01.16   15.4       ~ 63 0
50 LEDA 2501414 GiC 11 57 01.860 +55 25 11.18   16.53   15.37   ~ 14 0
51 [TTV2001] 32 GiC 11 57 03.1 +55 25 12           ~ 1 0
52 SMDG J1157038+531802 LSB 11 57 03.8 +53 18 03           ~ 4 0
53 SMDG J1157056+532627 LSB 11 57 05.6 +53 26 28           ~ 3 0
54 Z 243-32 EmG 11 57 17.3777198280 +49 17 00.669514488   14.2       ~ 140 0
55 [TTV2001] 35 GiC 11 57 21.0 +53 13 35           ~ 1 0
56 NGC 3990 GiP 11 57 35.5746104280 +55 27 31.486195296   13.57   12.10   ~ 124 0
57 M 109 GiG 11 57 35.9631479640 +53 22 29.006082336   10.94   9.57   ~ 483 0
58 SMDG J1157366+530959 LSB 11 57 36.6 +53 10 01           ~ 3 0
59 MCG+09-20-045 AG? 11 57 47.584 +53 14 04.03   16.27   15.59   ~ 40 0
60 NGC 3998 Sy2 11 57 56.1334044408 +55 27 12.922443432   11.64 12.10 10.09   ~ 682 2
61 SDSS J115802.77+551446.5 LSB 11 58 02.77740 +55 14 46.5118           ~ 5 0
62 MCG+08-22-048 GiC 11 58 11.556 +48 52 49.79   16       ~ 15 0
63 LEDA 213915 AG? 11 58 13.689 +55 23 16.54   16.61   15.41   ~ 16 0
64 MCG+09-20-050 AG? 11 58 25.96 +50 55 03.4   17       ~ 67 0
65 SMDG J1158259+485737 LSB 11 58 26.0 +48 57 36           ~ 3 0
66 LEDA 2832098 GiP 11 58 34.346 +53 20 43.68   17.27   16.05   ~ 14 0
67 Z 269-26 LSB 11 58 47.248 +53 25 32.55   15.07   14.23   ~ 70 0
68 [TTV2001] 42 G 11 58 47.9 +53 27 14           ~ 1 0
69 MCG+08-22-051 GiC 11 59 57.6822171528 +49 33 49.859931492   16       ~ 18 0
70 UGCA 262 GiC 12 00 35.422 +47 46 26.14   16.5       ~ 11 0
71 [TTV2001] 45 G 12 00 35.6 +47 58 10           ~ 1 0
72 [TTV2001] 46 G 12 02 21.3 +47 07 36           ~ 1 0
73 MCG+08-22-057 GiC 12 02 43.7191356096 +45 11 27.808631088   16.0       ~ 14 0
74 NGC 4047 AG? 12 02 50.6855747352 +48 38 10.300035480   12.8       ~ 110 1
75 LEDA 3096090 AGN 12 02 58.331 +47 39 11.13   17.3 18.99 17.4   ~ 10 0
76 NGC 4051 Sy1 12 03 09.6101337312 +44 31 52.682601288   11.08 12.92 9.94   ~ 2270 1
77 [TTV2001] 48 GiC 12 04 10.3 +43 39 17           ~ 1 0
78 [TTV2001] 49 GiC 12 04 49.9 +44 26 34           ~ 1 0
79 Z 215-20 EmG 12 04 57.905 +43 08 59.03   15.7       ~ 30 0
80 Z 215-22 LIN 12 05 15.5647127952 +43 10 08.472569952   15.2       ~ 25 0
81 LEDA 166120 LSB 12 05 24.5 +43 42 28           ~ 12 0
82 [TTV2001] 51 GiC 12 05 45.5 +49 42 54           ~ 1 0
83 Z 215-23 GiP 12 05 57.746 +43 08 36.08   14.40       ~ 123 1
84 SMDG J1206052+492849 LSB 12 06 05.2 +49 28 47           ~ 4 0
85 [PYY2023] J120605+492536 GiC 12 06 05.8 +49 25 37           ~ 2 0
86 NGC 4100 GiG 12 06 08.602 +49 34 56.32   11.7       ~ 269 0
87 Z 215-25 LSB 12 06 10.774 +42 57 20.85   15.6       ~ 66 0
88 SDSS J120625.42+422607.2 AG? 12 06 25.428 +42 26 07.20           ~ 8 0
89 [TTV2001] 54 G 12 06 26.0 +42 54 33           ~ 1 0
90 [TTV2001] 55 G 12 06 26.7 +49 33 24           ~ 1 0
91 MATLAS-1182 LSB 12 06 28.1 +43 01 12           ~ 5 0
92 NGC 4111 LIN 12 07 03.1334091672 +43 03 56.345868252 12.07 11.63 10.74     ~ 350 1
93 [TTV2001] J1207.1+4259 G 12 07.1 +42 59           ~ 1 0
94 [TTV2001] 57 GiC 12 07 09.4 +43 59 15           ~ 1 0
95 [TTV2001] 58 G 12 07 44.7 +48 51 23           ~ 1 0
96 NGC 4117 Sy2 12 07 46.1195809200 +43 07 34.818483864   14.04       ~ 178 1
97 NGC 4118 EmG 12 07 52.844 +43 06 40.26   15.7       ~ 26 0
98 [TTV2001] 59 G 12 09 28.1 +50 12 42           ~ 1 0
99 [TTV2001] 60 GiC 12 09 34.4 +50 26 02           ~ 1 0
100 [TTV2001] J1209.6+4201 G 12 09.6 +42 01           ~ 1 0
101 NGC 4143 LIN 12 09 36.0679174440 +42 32 03.031963368   13.04 12.08     ~ 251 0
102 [TTV2001] 61 G 12 09 47.8 +50 03 51           ~ 1 0
103 MCG+08-22-081 AG? 12 10 55.230 +50 17 15.19 16.44 16.60 15.81     ~ 30 1
104 NGC 4157 GiC 12 11 04.365 +50 29 04.85 12.48 12.15 11.35     ~ 373 2
105 [TTV2001] 62 GiC 12 11 13.3 +50 06 41           ~ 1 0
106 MCG+08-22-082 GiP 12 11 22.566 +50 16 10.28   16       ~ 13 0
107 SMDG J1211348+502613 LSB 12 11 34.9 +50 26 13           ~ 4 0
108 [TTV2001] J1213.4+4901 G 12 13.4 +49 01           ~ 1 0
109 [TTV2001] 65 G 12 14 43.7 +49 01 28           ~ 1 0
110 Z 243-68 AG? 12 19 12.2467997544 +49 21 17.286997140   14.3       ~ 56 0
111 Malin 1 LSB 12 36 59.3463193464 +14 19 49.164305988   17.80       ~ 224 0
112 NAME Ursa Major Cluster ClG 15 08.8 +67 07           ~ 424 1
113 NAME Local Group GrG ~ ~           ~ 9325 0
114 [GP82] 1444 GiC ~ ~           ~ 6 0

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