TY - JOUR
T1 - Galaxy population in a cluster of galaxies around the radio galaxy 3C 324 at z = 1.2 1
AU - Nakata, Fumiaki
AU - Kajisawa, Masaru
AU - Yamada, Toru
AU - Kodama, Tadayuki
AU - Shimasaku, Kazuhiro
AU - Tanaka, Ichi
AU - Doi, Mamoru
AU - Furusawa, Hisanori
AU - Hamabe, Masaru
AU - Iye, Masanori
AU - Kimura, Masahiko
AU - Komiyama, Yutaka
AU - Miyazaki, Satoshi
AU - Okamura, Sadanori
AU - Ouchi, Masami
AU - Sasaki, Toshiyuki
AU - Sekiguchi, Maki
AU - Yagi, Masafumi
AU - Yasuda, Naoki
PY - 2001
Y1 - 2001
N2 - We discuss the properties of galaxies around the radio galaxy 3C 324 at z = 1.2 based on BV RIK′ multi-band imaging data. We have applied a photometric-redshift technique to objects in the 3C 324 field, and identified 35 objects as plausible cluster members. We have found that red and luminous members are concentrated in a small region enclosed by a circle of 40″ radius (0.33 Mpc at z= 1.2 for Ω0 = 0.3, λ0 = 0.7, H0 = 70kmS-1 MpC-1 cosmology) from the 3C 324 galaxy. The 3C 324 cluster is probably much more compact in size compared with the local clusters. We constructed a K′-band luminosity function of the cluster members and fitted a Schechter function, and found the characteristic magnitude to be K′*AB = 20.2 ± 0.6. This value is consistent with the extrapolation of the pure passive evolution seen for z < 1 clusters. We have identified eight bright galaxies which form a red color-magnitude sequence. The slope of the sequence is consistent with the passive evolution model down to K′AB < 22; we also found that there is no clear age variation in these bright red galaxies. However, seven out of these eight galaxies exhibit a significant excess in the rest UV light with respect to the passive evolution model. This may suggest that the massive early-type galaxies in this high-redshift cluster are still forming stars to some extent. We have confirmed a truncation of the color-magnitude sequence at K′AB ∼ 22; faint passively-evolving galaxies may not yet be present in this cluster at z ∼ 1.2. The overall color distribution of the cluster members, selected by the photometric redshift technique, is found to be very broad. We derived the fraction of blue galaxies in this cluster following a definition of Butcher and Oemler (1984, AAA 038.160.068), and obtained fB = 0.39 ± 0.28, which is higher than that for z < 1 clusters. This indicates that the star-formation activity of this cluster is, on the average, higher than that of lower redshift counterparts.
AB - We discuss the properties of galaxies around the radio galaxy 3C 324 at z = 1.2 based on BV RIK′ multi-band imaging data. We have applied a photometric-redshift technique to objects in the 3C 324 field, and identified 35 objects as plausible cluster members. We have found that red and luminous members are concentrated in a small region enclosed by a circle of 40″ radius (0.33 Mpc at z= 1.2 for Ω0 = 0.3, λ0 = 0.7, H0 = 70kmS-1 MpC-1 cosmology) from the 3C 324 galaxy. The 3C 324 cluster is probably much more compact in size compared with the local clusters. We constructed a K′-band luminosity function of the cluster members and fitted a Schechter function, and found the characteristic magnitude to be K′*AB = 20.2 ± 0.6. This value is consistent with the extrapolation of the pure passive evolution seen for z < 1 clusters. We have identified eight bright galaxies which form a red color-magnitude sequence. The slope of the sequence is consistent with the passive evolution model down to K′AB < 22; we also found that there is no clear age variation in these bright red galaxies. However, seven out of these eight galaxies exhibit a significant excess in the rest UV light with respect to the passive evolution model. This may suggest that the massive early-type galaxies in this high-redshift cluster are still forming stars to some extent. We have confirmed a truncation of the color-magnitude sequence at K′AB ∼ 22; faint passively-evolving galaxies may not yet be present in this cluster at z ∼ 1.2. The overall color distribution of the cluster members, selected by the photometric redshift technique, is found to be very broad. We derived the fraction of blue galaxies in this cluster following a definition of Butcher and Oemler (1984, AAA 038.160.068), and obtained fB = 0.39 ± 0.28, which is higher than that for z < 1 clusters. This indicates that the star-formation activity of this cluster is, on the average, higher than that of lower redshift counterparts.
KW - Galaxies: Clusters: Individual (3C 324)
KW - Galaxies: Elliptical and lenticular, cD
KW - Galaxies: Evolution
KW - Galaxies: Formation
KW - Galaxies: Luminosity function, mass function
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U2 - 10.1093/pasj/53.6.1139
DO - 10.1093/pasj/53.6.1139
M3 - Article
AN - SCOPUS:0035624763
SN - 0004-6264
VL - 53
SP - 1139
EP - 1152
JO - Publication of the Astronomical Society of Japan
JF - Publication of the Astronomical Society of Japan
IS - 6
ER -