Документ взят из кэша поисковой машины. Адрес оригинального документа : http://mavr.sao.ru/hq/katya/NDG/DVD/Posters/Karachentsev.pdf Дата изменения: Thu Oct 1 21:02:01 2009 Дата индексирования: Sat Oct 17 00:08:21 2009 Кодировка: Поисковые слова: virgo cluster

Blueshifted galaxies in the Virgo cluster
I. D. Karachentsev, O. G. Nasonova (Kashibadze), Special Astrophysical Observatory, Russia We consider a sample of 65 galaxies with negative radial velocities with respect to the Lo cal group in the Virgo cluster. According to the Virgo Cluster Catalogue (=VCC, Binggeli et al., 1985), the population of the cluster accounts more than 2000 members, most of them are dwarf urregular (dIr), elliptical (dE) and spheroidal (dSph) systems. Assuming that Virgo distance is 17.0 Mpc (Tonry et al. 2001), dwarfs galaxies (MB < -16.5m) make up 80% of the sample. There is only one elliptical galaxy (NGC 4406) among 13 galaxies of normal and high luminosity.

Some features of the blueshifted galaxy sample
·All the blueshifted galaxies are distributed compactly within virial radius V I R = 6.0 . ·The centroid of the sample is displaced significantly at 1.10 ± 0.35 towards NW from the dynamical cluster center, M87. ·Galaxies of early and late types demonstrate an appreciable difference in their positioning relative to the centroid: E and S0 galaxies are lo cated mainly at east side while ob jects with young stellar population tend to west and south sides. ·Surprisingly, dwarf galaxies of the sample (both early-type and late-type) exhibit a clumpiness on a scale of 10 arcmin (50 kpc). The median velo city difference in such pairs and triplets is about 70 km/s.
70
19

18

60
17

50

16

15

mB, mag

40

14

30

13

12

20
11 E, S0 S, Ir 10

10

0 -1000

9 -900

-800

-700

-600

-500

-500

0

500

1000

1500

2000

2500

3000

3500

4000

VLG, km s-1

-400

-300

-200

-100

0

The radial velo city distribution of 800 galaxies in the central part of the Virgo cluster. A sharp peak near Vh 0 is due to the effect of "stellar spam" pro duced by binary stars presented as galaxies in LEDA database.
E, S0
20
°

The radial velo city VLG ­ magnitude mB distribution of sample ob jects. Early-type galaxies (E, S0, dE, dSph) are marked with red circles and late-type galaxies(S, dIr, BCD) with blue ones.
VLG track
50(-193) 55(-219) 45(-172) 40(-151) 64(-282) 60(-248)

S, Ir

Virgo center

SG equator

18

°

14°00

13°00
16
°

30(-110)

35(-132)

NGC4406
13°30

14

°

12

°

13°00

12°45
NGC4406
20(-68)

25(-88)

10°

12°30
NGC4486

8

°

12°30
15(-51)

6

°

12°00

NGC4486

12h56m 12h48m 12h40m 12h32m 12h24m 12h16m 12h08m 12h00m 12h34m 12h32m 12h30m 12h28m 12h26m 12h24m 12h22m

12 33

h

m

12 32

h

m

12 31

h

m

12 30

h

m

12 29

h

m

12 28

h

m

12 27

h

m

12 26

h

m

Galaxies with ne The yellow circle The cross marks the inclined line

gative velo cities in equatorial co ordinates. is virial zone of the cluster (V I R = 6.0 ). M87 as the physical center of the cluster, represents the supergalactic equator.

The centroid drift for galaxies ranged by VLG from zero to the extremal negative velo city (-866 km/s). The number of averaged galaxies (and their mean radial velo city) are given near running centroid positions.

Conclusions
The observed NW asymmetry of the blueshifted galaxies may be interpreted as evidence for merging of the M86 subcluster with the main Virgo cluster bo dy (Binggeli et al., 1993). A new attempt is made by us to explain this phenomenon by the tangential motion of the Lo cal group regarding to the Virgo cluster caused by its pushing from the Lo cal void. The work was supported through grants of RFBR 07­02­00005 and RFBR-DFG 06­02­04017.