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RED SEQUENCE DWARF GALAXIES IN CLUSTERS F. G. Kopylova and A.I. Kopylov
Special astrophysical observatory, Russian Academy of Sciences Red sequence galaxies in clusters are an important population for understanding galaxy formation and evolution in general. They represent systems with very little or no on-going star formation and thus are a unique tracer of past activity of galaxies. The origin of red sequence galaxies and how the faint end of the red sequence builds up are still not clear. To study the red sequence luminosity function and dwarf-to-giant ratio (DGR), we select 10 clusters of galaxies of the Leo Supercluster (z 0.035, D 150 · h-1 M pc) (Fig.1). The total masses and K-band 70 luminosities in comparable physical regions (within R200 close to the virial radius) were determined for them using observational data from the SDSS-DR6 and 2MASS (Table). We isolate and analyze red sequence galaxies in color-magnitude diagrams (CMD) of these clusters. Galaxies are selected if they are within ±3 of the fit to the average CMD for the cluster members with r < 17.8 mag (Fig.2). We use color cuts: (u - r) -0.24, -0.1 (g - r) 0.1, -0.075 (r - i) 0.075), and photometric redshifts from the SDSS database (PhotoZ) for galaxies with r = 17.8 - 20 mag. We define as dwarfs the galaxies in the magnitude range Mr -19 В -16. We construct the composite luminosity function of spectroscopically confirmed members of clusters to Mr = -18 (Schechter function parameters are Mr = -21.53 ± 0.23, = -1.02 ± 0.09) and the composite luminosity function of red sequence galaxies to Mr = -16 (Mr = -22.26 ± 0.26, = -1.16 ± 0.04). We study how the DGR for red sequence galaxies depends on global cluster properties (richness, velocity dispersion, mass, optical luminosity) and find no correlation between them. The average DGR for the red galaxies as a function of clustercentric radius slightly decreases in the central cluster regi on .

50

A1314

40

A1257 A1228A A1228B
30

A1185

20

A1177

10

A1142 A1016

A0999

A1139

0

13 h 12 h

cz = 8400 - 9799

09 h

Fig.1

11 h

Leo Supercluster

10 h

cz = 9800 - 11199 cz = 11200 - 12599

Clust. A0999 A1016 A1139 A1142 A1177 A1185 A1228A A1228B A1257 A1314

RA (2000) DEC 10 23 23.8+12 50 06 10 27 07.8+11 00 30 10 58 11.0+01 36 16 11 00 51.4+10 31 46 11 09 44.4+21 45 32 11 10 41.4+28 42 20 11 22 09.4+34 20 56 11 22 56.5+34 06 41 11 26 17.3+35 20 25 11 34 49.3+49 04 39

cz

N200 23 26 70 58 26 180 25 28 18 115

248 267 437 526 337 695 232 347 357 644

R200 0.60 0.65 1.06 1.28 0.82 1.69 0.56 0.84 0.87 1.57

M200 0.26 0.32 1.42 2.48 0.65 5.73 0.21 0.71 0.77 4.56

M /LK


Lx /10

44

km / s
9553 9647 11797 10610 9641 9852 10486 12859 10226 9938

km/s Mpc 1014 M M /L

erg/s
0.17 0.28 0.22 0.27 0.12 0.27

25 26 58 34 22 91 14 41 77 115