1997A&A...321...84B


Query : 1997A&A...321...84B

1997A&A...321...84B - Astronomy and Astrophysics, volume 321, 84-104 (1997/5-1)

The ESO Nearby Abell Cluster Survey. III. Distribution and kinematics of emission-line galaxies.

BIVIANO A., KATGERT P., MAZURE A., MOLES M., DEN HARTOG R., PEREA J. and FOCARDI P.

Abstract (from CDS):

We have used the ESO Nearby Abell Cluster Survey (ENACS) data, to investigate the frequency of occurrence of Emission-Line Galaxies (ELG) in clusters, as well as their kinematics and spatial distribution. Well over 90% of the ELG in the ENACS appear to be spirals; however, we estimate that the detected ELG represent only about one-third of the total spiral population. The apparent fraction of ELG increases towards fainter magnitude, as redshifts are more easily obtained from emission lines than from absorption lines. From the ELG that have an absorption-line redshift as well, we derive a true ELG fraction in clusters of 0.10, while the apparent fraction is 0.16. The apparent ELG fraction in the field is 0.42, while the true fraction is 0.21. The true ELG fractions in field and clusters are consistent if the differences in morphological mix are taken into account. Thus, it is not necessary to assume that ELG in and outside clusters have different emission-line properties. The average ELG fraction in clusters depends on global velocity dispersion σv: the true fraction decreases from 0.12 for σv≲600km/s to 0.08 for σv>900km/s. In only 12 out of 57 clusters, the average velocity of the ELG differs by more than 2σ from that of the other galaxies, and in only 3 out of 18 clusters σvof the ELG differs by more than 2σ from that of the other galaxies. Yet, combining the data for 75 clusters, we find that σvof the ELG is, on average, 20% larger than that of the other galaxies. It is unlikely that this is primarily due to velocity offsets of the ELG with regard to the other galaxies; instead, the larger σvfor the ELG must be largely intrinsic. The spatial distribution of the ELG is significantly less peaked towards the centre than that of the other galaxies. This causes the average projected density around ELG to be ∼30% lower than it is around the other galaxies. In combination with the inevitable magnitude bias against galaxies without detectable emission lines, this can lead to serious systematic effects in the study of distant clusters. From an analysis of the distributions of projected pair distances and velocity differences we conclude that at most 25% of the ELG are in compact substructures, while the majority of the ELG are distributed more or less smoothly. The virial estimates of the cluster masses based on the ELG only are, on average, about 50% higher than those derived from the other galaxies. This indicates that the ELG are either on orbits that are significantly different from those of the other galaxies, or that the ELG are not in virial equilibrium with the other galaxies, or both. The velocity dispersion profile of the ELG is found to be consistent with the ELG being on more radial orbits than the other galaxies. For the ELG, a ratio between tangential and radial velocity dispersion of 0.3 to 0.8 seems most likely, while for the other galaxies the data are consistent with isotropic orbits. The lower amount of central concentration, the larger value of σvand the possible orbital anisotropy of the ELG, as well as their content of line-emitting gas would be consistent with a picture in which possibly all spirals (but certainly the late-type ones) have not yet traversed the virialized cluster core, and may even be on a first (infall) approach towards the central, high-density region.

Abstract Copyright:

Journal keyword(s): galaxies: clusters of - galaxies: ISM galaxies: kinematics and dynamics - cosmology: observations

Simbad objects: 56

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Number of rows : 56
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 ACO 2717 ClG 00 03 12.9 -35 56 13           ~ 129 0
2 ACO 2715 ClG 00 03 20.67 -34 26 59.3           ~ 26 0
3 ACO 2734 ClG 00 11 21.60 -28 51 16.6           ~ 133 0
4 ACO 13 ClG 00 13 38.5 -19 30 19           ~ 97 1
5 ACO 2755 ClG 00 17 41.14 -35 12 01.0           ~ 37 1
6 ACO 2764 ClG 00 20 27 -49 13.3           ~ 25 0
7 ACO 2765 ClG 00 21 32.29 -20 45 25.3           ~ 13 0
8 ACO 2778 ClG 00 29 46.29 -30 15 24.2           ~ 21 0
9 ACO 2799 ClG 00 37 28.1 -39 08 59           ~ 40 0
10 ACO 2800 ClG 00 37 58 -25 05.5           ~ 41 0
11 ACO 87 ClG 00 43 01 -09 47.6           ~ 45 0
12 ACO 118 ClG 00 55 43.9 -26 24 46           ~ 44 0
13 ACO 119 ClG 00 56 16.8 -01 15 00           ~ 534 2
14 ACO 151 ClG 01 08 52.3 -15 25 01           ~ 183 1
15 ACO 168 ClG 01 15 09.8 +00 14 51           ~ 344 2
16 ACO 229 ClG 01 39 25 -03 37.8           ~ 25 0
17 ACO 295 ClG 02 02 27 -01 04.6           ~ 64 0
18 ACO 367 ClG 02 36 36.0 -19 22 16           ~ 49 0
19 ACO 380 ClG 02 45 19.44 -26 24 58.1           ~ 24 0
20 ACO 420 ClG 03 09 17 -11 31.6           ~ 25 0
21 ACO 514 ClG 04 47 40.0 -20 25 44           ~ 137 0
22 ACO 524 ClG 04 57.8 -19 43           ~ 25 0
23 ACO 543 ClG 05 30 36.1584 -22 27 33.665           ~ 27 0
24 ACO 548 ClG 05 47 01.7 -25 36 59           B8 200 2
25 ACO 754 ClG 09 08 50.1 -09 38 12           ~ 643 1
26 ACO 957 ClG 10 13 38.42 -00 55 32.6           ~ 200 2
27 ACO 978 ClG 10 20 26.66 -06 31 37.5           ~ 125 1
28 ACO 1069 ClG 10 39 54.3 -08 36 40           ~ 106 1
29 ACO 1809 ClG 13 53 03.72 +05 08 17.7           ~ 159 0
30 ACO 2040 ClG 15 12 45.2 +07 25 48           ~ 138 1
31 ACO 2048 ClG 15 15 16.52 +04 22 46.5           ~ 93 0
32 ACO 2052 ClG 15 16 45.5 +07 00 01           ~ 700 1
33 ACO 2353 ClG 21 34 22 -01 35.6           ~ 24 0
34 ACO 2361 ClG 21 39 07 -14 19.4           ~ 34 0
35 ACO 2362 ClG 21 40 43 -14 16.3           ~ 37 0
36 ACO 3799 ClG 21 41 38 -72 43.3           ~ 10 0
37 ACO 3806 ClG 21 46 37.9 -57 17 07           ~ 49 0
38 ACO 3809 ClG 21 46 57.5 -43 54 06           ~ 86 0
39 ACO 3822 ClG 21 54 06.2 -57 50 49           ~ 82 0
40 ACO 3825 ClG 21 58 22.4 -60 23 39           ~ 57 0
41 ACO 2401 ClG 21 58 52 -20 05.6           ~ 67 0
42 ACO 3827 ClG 22 01 49.1 -59 57 15           ~ 143 0
43 ACO 2426 ClG 22 14 27.3 -10 22 05           ~ 70 0
44 ACO 3864 ClG 22 20 09.1 -52 28 01           ~ 33 0
45 ACO 2436 ClG 22 20 29 -02 47.9           ~ 14 0
46 ACO 3879 ClG 22 27.8 -69 02           ~ 29 0
47 2MASX J22274915-6901238 BiC 22 27 49.1188452360 -69 01 24.191317272   16.42       ~ 18 0
48 ACO 2462 ClG 22 39 17.3 -17 22 23           ~ 93 0
49 ACO 2480 ClG 22 46 04 -17 41.2           ~ 36 0
50 ACO 3921 ClG 22 49 38.6 -64 23 15           ~ 140 1
51 ACO 2500 ClG 22 53 46.37 -25 30 00.0           ~ 24 0
52 ACO 2569 ClG 23 17 54 -12 51.6           ~ 30 0
53 ACO 4008 ClG 23 30 17 -39 19.4           ~ 26 0
54 ACO 4010 ClG 23 31 10.3 -36 30 26           ~ 55 0
55 ACO 2644 ClG 23 41 05 +00 05.3           ~ 41 0
56 ACO 4053 ClG 23 54 45.43 -27 40 52.6           ~ 39 0

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2022.05.22-15:39:25

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