Multicolor Photometry of the Nearby Galaxy Cluster A119

Multicolor Photometry of the Nearby Galaxy Cluster A119

Jin-Tao Tian National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; tianjintao2010@gmail.com
Graduate University, Chinese Academy of Sciences, Beijing 100039, China Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
   Qi-Rong Yuan Department of Physics, Nanjing Normal University, Nanjing, China \vs\no    Xu Zhou National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; tianjintao2010@gmail.com
Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
   Zhao-Ji Jiang National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; tianjintao2010@gmail.com
Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
   Jun Ma National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; tianjintao2010@gmail.com
Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
   Jiang-Hua Wu National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; tianjintao2010@gmail.com
Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
   Zhen-Yu Wu National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; tianjintao2010@gmail.com
Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
   Zhou Fan National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; tianjintao2010@gmail.com
Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
   Tian-Meng Zhang National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; tianjintao2010@gmail.com
Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
   Hu Zou National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; tianjintao2010@gmail.com
Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
Abstract

This paper presents multicolor optical photometry of the nearby galaxy cluster Abell 119 () with the Beijing-Arizona-Taiwan-Connecticut (BATC) system of 15 intermediate bands. Within the BATC viewing field of 58\arcmin 58\arcmin, there are 368 galaxies with known spectroscopic redshifts, including 238 member galaxies (called sample I). Based on the spectral energy distributions (SEDs) of 1376 galaxies brighter than , photometric redshift technique and the color-magnitude relation of early-type galaxies are applied to select faint member galaxies. As a result, 117 faint galaxies were selected as new member galaxies. Combined with sample I, an enlarged sample (called sample II) of 355 member galaxies is obtained. Spatial distribution and localized velocity structure for two samples demonstrate that A119 is a dynamically complex cluster with at least three prominent substructures in the central region within 1 Mpc. A large velocity dispersion for the central clump indicates a merging along the line of sight. No significant evidences for morphology and luminosity segregations are found in both samples. With the evolutionary synthesis model PEGASE, environmental effect on the star formation properties is confirmed. Faint galaxies in low-density region tend to have longer time scales of star formation, smaller mean stellar ages, and lower metallicities of interstellar medium, which is in agreement with the context of hierarchical cosmological scenario.

galaxies: clusters: individual(A119) — galaxies: distances and redshifts — galaxies: evolution — galaxies: kinematics and dynamics — methods: data analysis
\volnopage

2011 Vol. X No. XX, 000–000

1 Introduction

As the most massive gravitationally bound structures in the universe, clusters of galaxies are not only the powerful probes tracing the large scale structure, but also the unique astrophysical laboratories for investigating evolution of galaxies and dark matter in dense environment (Bahcall et al. 1988; Pearce et al. 2000; Cortese et al. 2004; Mantz et al. 2008). The hierarchical formation scenario predicts that galaxy clusters are formed by continuous accreting subunits of smaller mass at the nodes of large-scale filaments (West et al. 1991; Katz & White 1993). Substructures in galaxy clusters have been intensively studied since the ROSAT era using the X-ray surface brightness distribution from observations and simulations (Jones & Forman 1984; Ventimiglia et al. 2008; Piffaretti & Valdarnini 2008; Zhang et al. 2009). Based on quantitative measure of substructure in nearby clusters, a significant fraction ( 50%) of clusters shows evidence of merging (Geller & Beers 1982; Dressler & Shectman 1988; Mohr et al. 1995; Buote & Tsai 1996), indicating that galaxy clusters are still dynamically young units, undergoing the process of formation (Dressler & Shectman 1988; O’Hara et al. 2006).

The Beijing-Arizona-Taiwan-Connecticut (BATC) galaxy cluster survey aims at obtaining the spectral energy distributions (SEDs) of galaxies in more than 30 nearby clusters at different dynamic statuses, with 15 intermediate-band filters in optical band (Yuan et al. 2001). The photometric redshift technique makes it possible to pick up faint cluster galaxies down to mag. With the enlarged sample of member galaxies, dynamical substructures, luminosity function, luminosity segregation, and star formation properties of these nearby clusters can be addressed (Yuan et al. 2003; Yang et al. 2004; Zhang et al. 2010; Liu et al 2011; Pan et al. 2011). As one of the brightest extended X-ray sources with multiple clumps, the galaxy cluster Abell 119 (hereafter A119) is included in the target list of the BATC cluster survey.

The nearby () cluster A119, located at 005621.4, -01\degr15\arcmin47\arcsec.0 (J2000.0), is of richness class 1 (Abell 1958), and is classified as Bautz-Morgan class II - III (Bautz & Morgan 1970). The most luminous member galaxy, UGC 579, is classified as a cD galaxy (Postman & Lauer 1995; Saglia et al. 1997). Peres et al. (1998) argued that there is no cooling flow in this cluster. What A119 appeals to people are its high X-ray luminosity and multiple substructures. Edge et al. (1990) derived a luminosity of erg s for A119. Fabricant (1993) argued that substructures in its core involves at least three clumps from inspection of X-ray maps and galaxy isopleths. However, Girardi et al. (1997) argued that A119 is a regularly shaped cluster, and no evidence of substructure is found on the basis of their own detection method. There are three discrete radio galaxies in A119, namely 0053-015, 0053-016, and 3C 29 (Feretti et al. 1999). There is no evidence for luminosity segregation in A119 (Pracy et al. 2005). Fig. 1 shows the ROSAT and NVSS smoothed contours superimposed on the -band image of 58\arcmin 58\arcmincentered on the cD galaxy UGC 579. The X-ray brightness contour shows a clear NE elongation in the central region, suggesting that A119 is not likely to be a well-relaxed regular cluster.

The structure of this paper is as follows. In Section 2 we describe the BATC multicolor photometric observations and data reduction. In Section 3, spatial distribution and dynamics of cluster galaxies with known spectroscopic redshifts are investigated. Photometric redshift technique and its application on selection of faint member galaxies are given in section 4. In section 5, based on enlarged sample of cluster galaxies, we unveil some observational properties of A119, such as spatial distribution, dynamics, morphology-density relation, and luminosity segregation. In section 6, star formation properties for the spectroscopically-confirmed member galaxies is presented. Finally, we summarize our work in Section 7. Throughout this paper, the CDM cosmology model with H=73 km s Mpc, =0.3, and =0.7 are assumed.

Figure 1: The smoothed contours of the ROSAT PSPC image in soft X-ray band (0.1-2.4keV) (solid lines) and the NVSS FIRST (Faint Images of the Radio Sky at Twenty-cm) map at wavelength of , overlaying on optical image of 58\arcmin 58\arcminin the BATC band.The sizes of gaussian smoothing windows are adopted as 30\arcsecand 4\arcminfor the radio and X-ray contours, respectively.

2 Observations and Data Reduction

The observation of A119 were carried out with the 60/90cm f/3 Schmidt Telescope of National Astronomical Observatories of China (NAOC), at the Xinglong station with an altitude of 900m. The BATC multicolor photometric system includes 15 intermediate-band filters, namely, , and , covering the whole optical wavelength range from about 3000 to 10000 Å. These filters are specially designed to avoid most of bright night-sky emission lines (Yan et al. 2000). The transmission curves can be seen in Yuan et al. (2003).

An 2048 2048 Ford CCD camera was equipped with the BATC system before October 2006. The field of view was 58\arcmin58\arcmin, with a scale of 1.7\arcsecper pixel. For pursuing better spatial resolution and higher sensitivity in blue bands, a new E2V 4096 4096 CCD is now put into service. This CCD has a quantum efficiency of 92.2% at 4000 Å  and the field of view is extended to 92\arcmin92\arcmin. The spatial scale becomes 1.36\arcsecper pixel since the pixel size is 12 m, exactly 4/5 of former pixel size (15 m). The details of the telescope, camera, and data-acquisition system can be found elsewhere (Zhou et al. 2001; Yan et al. 2000).

From September 2002 to November 2006, only 12 BATC filters, from d to p, were taken to target A119 with the old CCD, discontinuously. Since 2007, the exposures in a, b, c bands have been completed with new CCD camera. In total, we have about 54 hr of exposure (see more details in Table 1).

\bc
Table 1: Parameters of the BATC filters and the observational statistics of A119
No. Filter FWHM Exposure Number of Completeness Objects
Name (Å) (Å) (second) Images (arcsec) Magnitude Detected
1 a 3371 356 20760 19 4.18 21.0 7526
2 b 3894 294 4860 12 5.94 20.5 7471
3 c 4201 297 8880 11 4.36 20.5 7959
4 d 4546 367 24000 23 4.15 20.5 6079
5 e 4872 377 19800 19 4.95 20.5 7745
6 f 5247 338 12000 13 4.50 20.5 6813
7 g 5784 285 8400 10 3.51 20.0 7400
8 h 6073 310 8100 9 3.48 19.5 7730
9 i 6709 518 3960 5 3.65 19.5 8158
10 j 7010 168 6900 8 4.11 19.0 7254
11 k 7526 200 8400 10 3.78 19.0 6711
12 m 8024 256 15900 17 3.98 19.0 7250
13 n 8517 160 12000 13 4.77 19.0 7879
14 o 9173 255 25200 24 4.15 18.5 8219
15 p 9723 280 22079 22 4.25 18.5 7158
\ec\tablecomments

0.86 Effective wavelengths of the filters; This column lists the seeing of the combined images.

The standard procedures of bias substraction, dome flat-field correction, and position calibration were carried out with automatic data-processing software, PIPLINE I, developed specially for the BATC multicolor photometry (Fan et al. 1996; Zhou et al. 2001). The cosmic rays and bad pixels were corrected by comparing the multiple images during combination.

For detecting sources and measuring the fluxes within a given aperture in the combined BATC images, we use the photometry package, PIPELINE II, developed on the basis of DAOPHOT (Stetson 1987) kernel (Zhou et al. 2003a). The objects with signal-to-noise ratio greater than the threshold 3.5 in , , and bands are considered to be detected. Because the pixel size ratio between the old and the new CCD is 5:4, an aperture radius of 4 pixels (i.e.=1.\arcsec74=6.\arcsec8) is taken for the images in 12 redder bands ( to ), and a radius of 5 pixels (i.e., =1\arcsec.365=6.\arcsec8) is adopted for the images in bluer bands (a,b,c). Flux calibration in the BATC system is performed by using four Oke-Gunn standard stars (HD 19445, HD 84937, BD+262606, and BD+17 4708) (Gunn & Stryker 1983). The procedures of BATC flux calibration are slightly corrected by (Zhou et al. 2001). Model calibration on the basis of the stellar SED library are performed to check the results of flux calibration via standard stars (Zhou et al. 1999). The flux measurements derived by above these two calibration methods are in accordance with each other for most filters. As a result, the SEDs of 10,605 sources have been obtained.

Spatial scale at cluster redshift z=0.0442 is 0.834 kpc/arcsec, the typical seeing of combined images in the BATC bands is about 4.\arcsec2, corresponding to 3.5 kpc, which is smaller than the size of a typical spiral galaxy. For checking the completeness of the BATC detection of galaxies, we compare the SDSS galaxies down to within a central region with a radius of 0.5 degree. There are 1121 SDSS-detected galaxies among which 1017 galaxies are also detected by the BATC photometry, corresponding to a completeness of 90.7%.

3 Analysis of cluster galaxies with known spectroscopic redshifts

3.1 Sample of Spectroscopically-Confirmed Member Galaxies

For investigating the properties of galaxy cluster A119, 368 normal galaxies with have known spectroscopic redshifts () are extracted in our viewing field from the NASA/IPAC Extragalactic Database (NED). We cross-identified all these galaxies with the BATC-detected sources.

In order to eliminate foreground and background galaxies, we apply a standard iterative 3-clipping algorithm (Yahil & Vidal 1977) to the velocity distribution. For a galaxy cluster with complex dynamics, the velocity distribution is expected to be non-gaussian. Using the ROSTAT software, we can derive two resistant and robust estimators, the biweight location (C) and scale (S), analogous to the velocity mean and dispersion (Beers et al. 1990). The galaxies with velocities between (CC) and (CC) are selected as member galaxies. After reaching the convergence, we achieve C=13298 and S=854 . The errors of these two estimators correspond to confidence interval, and they are calculated by bootstrap resamplings of 10,000 subsamples of the velocity data. There are 238 member galaxies with 10736 15860 , and we refer to these galaxies as “sample I”. Based on 153 member galaxies of A119, Way et al. (1997) derived C=13228 and S=778 , slightly smaller than our estimation. Fabricant (1993) derived a mean radial velocity of and a velocity dispersion of based on 80 member galaxies, which is in good agreement with our statistics.

Fig. 2 shows the distribution of spectroscopic redshifts for those 368 galaxies. We take the NED-given cluster redshift of for A119. For testing normality of velocity distribution, we apply the Shapiro-Wilk W test to sample I, and obtain the statistic , corresponding a probability value of which is much greater than the critical value . This indicates that the velocity distribution for sample I prove to be consistent with Gaussian. The embedded panel of Fig. 2 shows the histogram of radial velocities with a Gaussian fit. With the velocities and positions of these member galaxies, mass of A119 can be derived by applying virial theorem, assuming this cluster is well virialized (Geller & Peebles 1973; Oegerle & Hill 1994). We obtain a virial mass of . Table 2 lists the spectroscopic redshifts of 238 member galaxies in sample I.

No. R.A. Decl. Ref. No. R.A. Decl Ref.
1 00 56 21.0 -01 13 33 0.036755 (1) 60 00 56 27.6 -01 23 15 0.042379 (1)
2 00 56 18.4 -01 08 04 0.036889 (2) 61 00 56 16.2 -01 18 50 0.042416 (1)
3 00 56 24.7 -01 16 42 0.037232 (1) 62 00 56 42.8 -01 13 26 0.042429 (1)
4 00 56 11.1 -01 19 42 0.037489 (1) 63 00 56 20.3 -01 14 33 0.042476 (1)
5 00 56 12.9 -01 15 48 0.037783 (1) 64 00 56 07.0 -01 28 28 0.042499 (1)
6 00 56 25.6 -01 15 45 0.038223 (3) 65 00 56 01.9 -01 32 59 0.042563 (2)
7 00 56 29.2 -01 13 36 0.038403 (1) 66 00 55 54.4 -01 03 50 0.042586 (1)
8 00 56 17.9 -01 15 43 0.038580 (1) 67 00 55 50.7 -01 11 20 0.042613 (1)
9 00 55 51.5 -01 14 04 0.038588 (4) 68 00 56 02.7 -01 20 04 0.042689 (3)
10 00 56 32.4 -01 11 15 0.038677 (2) 69 00 55 30.5 -01 24 51 0.042763 (2)
11 00 57 03.0 -01 20 42 0.038680 (1) 70 00 55 31.1 -01 13 24 0.042793 (8)
12 00 56 21.0 -01 10 36 0.039130 (2) 71 00 55 39.9 -01 29 21 0.042806 (1)
13 00 56 17.8 -01 15 37 0.039154 (2) 72 00 56 56.5 -00 56 37 0.042836 (2)
14 00 57 13.7 -01 00 44 0.039230 (2) 73 00 56 17.1 -01 23 07 0.042840 (2)
15 00 56 18.0 -01 16 22 0.039254 (1) 74 00 56 39.7 -01 28 29 0.042863 (2)
16 00 54 42.1 -01 29 22 0.039561 (5) 75 00 55 45.9 -01 12 27 0.043023 (1)
17 00 55 28.5 -01 19 25 0.039747 (1) 76 00 57 48.7 -01 00 15 0.043090 (2)
18 00 55 29.5 -01 07 58 0.039771 (2) 77 00 56 06.0 -01 03 26 0.043123 (2)
19 00 55 46.8 -01 17 08 0.039948 (1) 78 00 57 51.7 -01 08 10 0.043143 (4)
20 00 56 26.1 -01 09 25 0.040011 (1) 79 00 55 47.8 -01 42 10 0.043223 (2)
21 00 54 38.7 -01 10 11 0.040066 (4) 80 00 55 05.0 -01 15 09 0.043313 (2)
22 00 57 09.7 -01 22 49 0.040188 (2) 81 00 57 14.6 -01 17 09 0.043370 (2)
23 00 55 38.2 -01 11 00 0.040355 (1) 82 00 55 40.7 -01 18 44 0.043423 (3)
24 00 56 46.0 -01 32 39 0.040365 (2) 83 00 57 26.3 -01 20 37 0.043450 (2)
25 00 56 18.6 -01 13 07 0.040365 (1) 84 00 56 57.0 -01 23 20 0.043497 (2)
26 00 56 39.3 -01 04 37 0.040441 (1) 85 00 56 04.0 -01 13 03 0.043543 (4)
27 00 55 16.2 -01 30 50 0.040581 (2) 86 00 55 27.0 -01 13 23 0.043544 (4)
28 00 55 55.6 -01 14 50 0.040778 (2) 87 00 56 25.9 -01 16 30 0.043583 (2)
29 00 56 51.5 -01 16 21 0.041002 (2) 88 00 57 59.9 -01 25 09 0.043607 (5)
30 00 56 02.3 -01 29 46 0.041058 (1) 89 00 56 47.1 -00 52 41 0.043617 (2)
31 00 55 35.6 -01 14 08 0.041116 (4) 90 00 56 18.1 -01 14 31 0.043647 (2)
32 00 55 57.2 -01 30 50 0.041182 (1) 91 00 54 29.8 -01 10 17 0.043655 (4)
33 00 55 51.2 -00 48 50 0.041194 (4) 92 00 56 45.3 -00 56 27 0.043658 (4)
34 00 55 32.9 -01 11 33 0.041205 (1) 93 00 56 19.7 -01 17 10 0.043727 (1)
35 00 56 13.6 -01 13 38 0.041235 (1) 94 00 56 47.1 -01 16 57 0.043800 (1)
36 00 55 42.0 -01 03 31 0.041235 (1) 95 00 56 12.8 -00 50 02 0.043805 (4)
37 00 57 10.7 -01 01 08 0.041298 (2) 96 00 56 37.2 -01 32 24 0.043817 (1)
38 00 55 21.4 -01 21 08 0.041472 (2) 97 00 56 32.2 -01 21 04 0.043847 (1)
39 00 55 55.0 -01 02 59 0.041569 (1) 98 00 56 16.4 -01 32 36 0.043897 (2)
40 00 56 20.3 -01 15 02 0.041575 (1) 99 00 57 11.6 -01 37 11 0.043934 (8)
41 00 55 25.2 -01 18 32 0.041585 (2) 100 00 56 27.4 -00 47 33 0.043940 (2)
42 00 56 37.8 -01 20 41 0.041589 (1) 101 00 55 52.2 -01 30 06 0.043957 (2)
43 00 54 41.0 -01 34 29 0.041625 (6) 102 00 56 29.3 -01 20 25 0.044034 (2)
44 00 55 44.9 -01 12 57 0.041649 (4) 103 00 56 41.6 -01 19 33 0.044080 (1)
45 00 56 47.4 -00 55 12 0.041686 (4) 104 00 55 45.6 -01 03 17 0.044110 (1)
46 00 55 22.9 -01 12 40 0.041782 (2) 105 00 56 38.5 -01 23 26 0.044117 (2)
47 00 55 39.0 -01 25 15 0.041842 (1) 106 00 56 23.5 -00 59 13 0.044137 (2)
48 00 57 53.7 -00 48 53 0.041849 (6) 107 00 55 16.9 -00 55 05 0.044179 (4)
49 00 56 10.7 -01 07 01 0.041856 (2) 108 00 55 38.2 -01 16 46 0.044197 (1)
50 00 55 47.2 -01 13 53 0.041876 (1) 109 00 57 02.0 -00 52 31 0.044238 (4)
51 00 56 22.2 -01 06 43 0.041956 (1) 110 00 55 54.2 -00 55 21 0.044264 10)
52 00 56 38.2 -01 17 53 0.041972 (1) 111 00 55 12.9 -01 19 18 0.044274 (2)
53 00 56 46.4 -01 16 51 0.042060 (7) 112 00 56 40.9 -01 02 04 0.044277 (2)
54 00 55 45.6 -01 05 03 0.042139 (4) 113 00 56 01.7 -01 03 52 0.044284 (8)
55 00 54 38.8 -01 34 27 0.042216 (6) 114 00 55 16.4 -01 21 05 0.044291 (1)
56 00 55 43.2 -01 02 01 0.042266 (2) 115 00 56 35.7 -01 15 56 0.044354 (1)
57 00 56 30.7 -01 10 22 0.042273 (2) 116 00 55 53.6 -00 54 04 0.044357 (2)
58 00 54 26.1 -00 55 42 0.042321 (4) 117 00 55 05.5 -01 14 02 0.044407 (2)
59 00 56 31.5 -01 21 42 0.042359 (2) 118 00 56 58.5 -01 15 25 0.044434 (2)

Table 2: Catalog of 238 Spectroscopically Confirmed Member Galaxies in A119
No. R.A. Decl. Ref. No. R.A. Decl Ref.
119 00 55 51.2 -01 18 23 0.044444 (8) 179 00 55 19.1 -01 11 16 0.046149 (1)
120 00 56 16.1 -01 15 19 0.044464 (3) 180 00 56 15.8 -01 26 48 0.046182 (1)
121 00 56 03.3 -00 49 41 0.044464 (2) 181 00 56 21.8 -01 26 58 0.046205 (2)
122 00 58 02.1 -00 49 37 0.044503 (4) 182 00 55 16.3 -01 24 16 0.046232 (1)
123 00 57 08.5 -01 29 39 0.044591 (8) 183 00 56 07.1 -01 20 36 0.046272 (6)
124 00 55 57.9 -01 14 24 0.044597 (4) 184 00 54 50.6 -01 28 45 0.046295 (2)
125 00 56 39.6 -01 04 43 0.044602 (4) 185 00 56 25.1 -01 18 37 0.046299 (1)
126 00 55 59.6 -01 32 09 0.044624 (1) 186 00 54 54.6 -01 20 27 0.046305 (1)
127 00 56 38.7 -01 21 06 0.044627 (1) 187 00 56 56.7 -01 27 11 0.046319 (1)
128 00 56 00.0 -01 16 16 0.044637 (1) 188 00 56 07.8 -01 25 47 0.046365 (1)
129 00 56 12.8 -01 16 10 0.044671 (2) 189 00 56 25.6 -01 30 41 0.046432 (1)
130 00 55 55.1 -01 03 51 0.044694 (2) 190 00 57 03.0 -00 52 25 0.046472 (2)
131 00 55 49.6 -01 04 54 0.044716 (4) 191 00 56 27.7 -01 01 27 0.046525 (2)
132 00 56 18.1 -01 37 33 0.044771 (2) 192 00 56 41.0 -01 18 26 0.046542 (1)
133 00 55 40.8 -00 59 50 0.044779 (4) 193 00 57 02.0 -00 52 47 0.046585 (6)
134 00 57 07.8 -01 27 54 0.044781 (8) 194 00 56 26.6 -01 20 53 0.046615 (1)
135 00 56 31.4 -01 36 59 0.044801 (2) 195 00 55 03.6 -01 19 03 0.046689 (1)
136 00 55 51.6 -01 30 23 0.044814 (1) 196 00 56 18.8 -01 28 12 0.046812 (1)
137 00 56 04.9 -01 08 09 0.044830 (4) 197 00 56 44.5 -00 52 29 0.046842 (2)
138 00 56 53.2 -01 17 42 0.044858 (1) 198 00 54 49.4 -01 23 19 0.046972 (1)
139 00 55 18.8 -01 16 38 0.044888 (3) 199 00 56 17.6 -01 17 43 0.047176 (1)
140 00 56 39.3 -01 34 39 0.044931 (8) 200 00 57 41.6 -01 18 44 0.047186 (6)
141 00 57 04.9 -00 55 09 0.044951 (2) 201 00 55 58.6 -01 12 10 0.047206 (1)
142 00 56 14.3 -01 08 40 0.044961 (2) 202 00 54 53.4 -01 34 35 0.047266 (2)
143 00 55 54.5 -00 55 14 0.044964 (2) 203 00 56 11.2 -01 07 40 0.047299 (1)
144 00 55 57.3 -01 22 15 0.044971 (1) 204 00 56 11.3 -01 31 35 0.047373 (1)
145 00 55 45.4 -01 23 59 0.045008 (2) 205 00 55 18.5 -01 19 05 0.047549 (1)
146 00 57 34.9 -01 23 28 0.045031 (3) 206 00 57 15.5 -00 49 31 0.047688 (4)
147 00 56 27.9 -01 26 07 0.045061 (2) 207 00 56 33.7 -01 09 52 0.047746 (1)
148 00 56 23.0 -01 14 58 0.045118 (1) 208 00 55 13.6 -01 04 34 0.047773 (2)
149 00 57 31.8 -00 55 40 0.045154 (2) 209 00 56 51.6 -01 00 26 0.047796 (4)
150 00 56 00.7 -01 27 03 0.045181 (1) 210 00 55 51.1 -01 09 53 0.047810 (2)
151 00 56 46.6 -01 35 47 0.045211 (5) 211 00 56 52.7 -01 07 53 0.047880 (4)
152 00 56 13.3 -01 16 12 0.045318 (2) 212 00 56 30.0 -01 05 13 0.047916 (4)
153 00 56 38.4 -01 07 34 0.045358 (2) 213 00 56 15.0 -01 15 47 0.047936 (1)
154 00 55 55.0 -01 14 49 0.045368 (1) 214 00 55 39.7 -00 52 36 0.047954 (4)
155 00 57 22.7 -00 49 19 0.045376 (4) 215 00 56 57.8 -01 09 29 0.048092 (4)
156 00 55 17.9 -01 17 11 0.045421 (2) 216 00 56 30.4 -01 32 02 0.048167 (2)
157 00 55 03.2 -01 15 57 0.045508 (2) 217 00 56 26.8 -01 19 48 0.048383 (1)
158 00 55 53.3 -01 06 59 0.045520 (4) 218 00 56 10.4 -01 08 25 0.048393 (2)
159 00 55 11.2 -00 48 37 0.045623 (4) 219 00 56 11.9 -01 16 39 0.048523 (1)
160 00 56 16.2 -01 09 46 0.045635 (1) 220 00 55 43.7 -01 19 46 0.048614 (1)
161 00 55 08.9 -01 02 47 0.045655 (2) 221 00 56 13.4 -01 14 18 0.048662 (4)
162 00 56 15.4 -01 05 54 0.045748 (1) 222 00 57 06.9 -01 23 51 0.048707 (2)
163 00 55 45.3 -01 19 28 0.045755 (2) 223 00 55 19.2 -01 31 01 0.048707 (1)
164 00 56 26.5 -01 37 34 0.045765 (2) 224 00 57 11.1 -01 22 49 0.048827 (6)
165 00 57 39.8 -00 53 33 0.045789 (4) 225 00 57 00.3 -00 49 31 0.048850 (2)
166 00 56 52.7 -01 09 33 0.045812 (2) 226 00 56 11.3 -01 31 53 0.048947 (2)
167 00 55 08.8 -01 23 48 0.045825 (8) 227 00 55 59.1 -01 18 01 0.048977 (2)
168 00 56 10.2 -01 16 04 0.045838 (2) 228 00 55 38.2 -01 34 47 0.049030 (6)
169 00 55 25.8 -01 23 02 0.045908 (1) 229 00 56 58.3 -01 22 45 0.049101 (1)
170 00 56 43.2 -01 23 45 0.045958 (1) 230 00 56 48.7 -01 29 32 0.049564 (1)
171 00 55 32.3 -01 12 40 0.045967 (4) 231 00 56 22.8 -01 12 35 0.049918 (2)
172 00 55 59.2 -01 09 49 0.045993 (4) 232 00 56 56.9 -01 12 43 0.049991 (4)
173 00 56 56.0 -00 59 48 0.046020 (4) 233 00 56 39.0 -01 17 43 0.050155 (5)
174 00 57 06.4 -00 54 31 0.046032 (2) 234 00 55 57.6 -01 17 26 0.050628 (2)
175 00 55 14.7 -00 49 20 0.046037 (4) 235 00 56 39.1 -01 05 23 0.050902 (1)
176 00 55 30.8 -01 17 50 0.046052 (1) 236 00 56 54.2 -01 15 25 0.051325 (1)
177 00 55 42.9 -01 11 46 0.046132 (1) 237 00 56 34.5 -01 16 49 0.052399 (1)
178 00 56 11.3 -00 58 13 0.046139 (2) 238 00 55 31.2 -01 11 33 0.052850 (1)

References: (1) Cava et al. (2009); (2) Smith et al. (2004); (3)Wegner et al. (1999); (4) Abazajian et al. (2003); (5) Dale et al. (1998); (6) Rines et al. (2003); (7) Kinman & Hintzen (1981); (8) Katgert et al (1998)

Table 2: — Continued.
Figure 2: The histogram of spectroscopic redshifts between 0.0 and 0.4 for 368 galaxies detected by all multicolor surveys. The embedded panel shows the histogram of radial velocity (cz) distribution of 238 galaxies in A119 in bins of 400 .

3.2 Spatial Distribution and Localized Velocity Structure

Contour map of surface galaxy density is an intuitive tool in terms of knowing existence of substructures in galaxy clusters. Left panel of Fig. 3 shows contour maps of surface density with a smoothing Gaussian window of , superimposed on the projected positions of 238 galaxies in sample I. As shown by the contour map, A119 does not appear to be spherically asymmetric , and at least three clumps can be found. It seems to agree with the X-ray brightness map (see Fig. 1), which indicates the presence of substructures in A119.

The clumps in spatial distribution might be due to projection effect. For eliminating the ambiguity in substructure detection, we apply the -test to sample I for quantifying the localized variation in velocity distribution. The statistic is introduced by Colless & Dunn (1996) to quantify the local deviation on the scale of nearest neighbors:

where is the number of member galaxies, and represents probability of standard K-S statistic being greater than observed value . Thus a greater means a greater probability that the local velocity distribution differs from the overall distribution. The probability P() can be estimated by Monte Carlo simulations by randomly shuffling velocities. Table 4 gives the results of the -test for samples I and II (sample II will be defined in the next section). For the 238 member galaxies in sample I, the probability P() is found to be less than 15% for a range of neighbor sizes (), indicating a probable substructure presence in A119 .

Bubble plots in the case of 9 nearest neighbors are shown in the right panel of Fig. 3. Bubble size at the position of each galaxy is proportional to log[P(DD)]. Consequently, the larger bubbles indicate a greater difference between local and overall velocity distributions. For sample I, three remarkable bubble clumps, called A, B, and C, can be found. The southern ’clump’ shown in the contour map (see the left panel) is untrue, because no bubble clustering appears at the same location. Big bunch of bubbles in central region obviously indicates an anomalous velocity distribution at center. For observing the anomalous kinematics in bubble clumps, stripe densities of velocity distributions are presented in Fig. 4 . For clumps A and C, their velocity distributions have anomalous dispersions. Compared with the dispersion of overall sample I (S ), clump A has a very large dispersion (S ), while clump C has significantly small dispersion (S ). Clump B is found to have smaller mean velocity (C ). Keep in mind that the errors of above biweight estimators correspond to a 90% confidence interval. Above biweight estimators in clumps differ from those for whole sample at more than 3 significance level. It is interesting that 85% of the member galaxies with  are found in clump A, which unambiguously points to a merging along the line-of-sight direction in cluster core. Clump C seems to be a compact group of galaxies with a bulk velocity of 12966 . The classic Kolmogorov-Smirnov (K-S) test shows the difference for velocity distributions between each clump (A/B/C) and the overall sample I are very significant, corresponding to the probabilities of 91.4%, 96%, and 95.2%, respectively. This means three clumps are probably real substructures.

Figure 3: Left: Spatial distribution for 238 spectroscopic member galaxies of A119 in sample I(denoted by filled circles). The contour map of the surface density use the smoothing Gaussian window . Contour map is superposed with the surface density levels 0.11, 0.16, 0.21, 0.26, 0.31, 0.36, 0.41 and 0.46 arcmin. The dashed big circles show a typical region of rich clusters with a radius of Mpc of the cluster center. The region within dotted line represents BATC field. Right:Bubble plot showing the localized variation for groups of the 9 nearest neighbors for 238 member galaxies in sample I.
Figure 4: Stripe density plot of velocity of the spectroscopically confirmed galaxies in whole cluster, clumps A, B and C, respectively.

4 Photometric redshft technique and selection of faint member

4.1 Membership Selection by Photometric Redshift Technique

Although optical spectroscopy is a straightforward approach for the cluster membership determination, spectroscopy of faint galaxies remains a rather daunting task. Photometric redshift technique plays a crucial role in finding faint galaxies based on their spectral energy distributions (SEDs) (Pelló et al. 1999; Brunner & Lubin 2000).

Technique of photometric redshift has been applied extensively in deep photometric survey with large-field detectors (Lanzetta et al. 1996; Arnouts et al. 1999; Furusawa et al. 2000). A standard SED-fitting code, called HYPERZ (Bolzonella et al. 2000), is adopted for estimating the photometric redshifts. The procedure has been adapted especially for the BATC multicolor photometric system (Yuan et al. 2001; Xia et al. 2002; Zhou et al. 2003b). The SED templates for normal galaxies are generated through convolving the galaxy spectra in template library GISSEL98 (Galaxy Isochore Synthesis Spectral Evolution Library; Bruzual & Charlot (1993)) with transmission curves of the BATC filters. For a given source, the photometric redshift, , corresponds to the best fit (in the -sense) between photometric SED and template SED. The reddening law of Milky Way (Allen 1976) is adopted for dust extinction, and the A is flexible in a range from 0.0 to 0.2.

A cross-identification between SDSS photometric catalog and the BATC-detected sources, 1376 galaxies in our viewing field are extracted, including 1008 faint galaxies without spectroscopic redshifts. As a test, we firstly let the z vary in a wide range from 0.0 to 1.0, with steps of 0.01. Only small number of galaxies are found to have . We search the photometric redshifts for 1376 galaxies brighter than in a range from 0.0 to 0.4, with a step of 0.001.

To appraise the precision of our estimation, a comparison between and values for the galaxies brighter than =17.0 is given in fig. 5. The dashed lines indicate an average redshift deviation of 0.0103, and error bars of z correspond to 68% confidence level in photometric redshift determination. Our z estimate is basically in accordance with the z values. In Fig.5, there are five galaxies whose photo-z values are significantly deviated from the spectroscopic redshifts. We check images and SEDs of these galaxies, and find that the SEDs of some galaxies suffer from some satellite contamination within the aperture, and some galaxies locate at the edge of BATC field, which result in false SEDs.

An iterative 2-clipping algorithm is applied to the values of 238 member galaxies in sample I. We achieve C= 0.048 and S=0.09 for z estimate. Statistically, 137 of 144 member galaxies (about 95%) brighter than =17.0 are found to have their photometric redshifts within deviation, corresponding to a range from 0.030 to 0.066. Even for all 238 member galaxies in sample I, 192 galaxies (about 81%) are found to have . The range is taken as a selection criterion of faint member candidates. As a result, 144 galaxies with are regarded as new member candidates of A119. The distributions of photometric redshift for sample I and new member candidates are shown in Fig. 6. The dashed lines denote the range of selection criterion.

Figure 5: Comparison between photometric redshift (z) and spectroscopic redshift (z) for 157 galaxies brighter than with known spectroscopic redshifts in A119. The solid line corresponds to , and dashed lines indicate an average deviation of 0.0103.
Figure 6: The distribution of photometric redshifts, with a bin size of 0.002. The black histogram shows z 238 galaxies in sample I. The dashed lines represent the z range of selection criterion.

4.2 Color-Magnitude Correlation

A universal correlation between color and absolute magnitude for early-type galaxies, called CM relation, has been commonly found in rich galaxy clusters(Bower et al. 1992, and references therein). Brighter early-type galaxies tend to be redder. The SDSS photometric catalog provides a parameter, fracDeV, defined as fraction of the brightness contribution by de Vaucouleurs component. We take the galaxies with fracDeV 0.5 as early-types, and the remaining as late-type galaxies. The CM relation can be used to constrain the membership selection of early-type galaxies (Yuan et al. 2001).

Fig. 7 shows the relation between color index and magnitude for member galaxies in sample I and newly-selected member candidates. A linear fitting is performed for the 181 early-type galaxies in sample I: , and dashed lines denote deviation. A majority of early-type member galaxies in sample I follows a tight color-magnitude correlation. However, 27 early-type candidates of member galaxies are scattered beyond the deviation of intercept, and they are removed from our candidate list.

Finally, a list of 355 member galaxies is obtained by combining the 238 spectroscopically confirmed member galaxies in sample I (including 181 early-type galaxies and 57 late-type galaxies) with the 117 newly selected member galaxies (including 36 early-type galaxies and 81 late-type galaxies), to which we refer as sample II. SED information, the SDSS morphological parameter ‘fracDeV’, and photometric redshifts for the 117 newly selected member galaxies are catalogued in Table 3. The magnitude of 99.00 means non-detection in the specified band.

For estimating the percentage of object blending due to the seeing effect, a cross-identification of the 117 new candidates of member galaxies is performed with the photometric catalog of the SDSS galaxies. A searching circle with a radius of 4.\arcsec5 centered at BATC-detected galaxies is adopted, and 3 galaxies are found to have more than one counterpart within the searching region, corresponding to a small probability (2.6%) of object blending.

Figure 7: Color-magnitude relation for early-type galaxies in A119. Early-type member galaxies with known spectroscopic redshifts are denoted by filled circles, and newly selected early-type member candidates are denoted by open circles. The solid line shows the linear fit for 181 early-type galaxies in sample I. The dashed lines correspond to the deviation of intercept.
No. R.A. Decl. fracDeV
1 0 57 43.29 -1 30 40.00 0.030 0.080 19.50 20.13 18.84 99.00 19.32 19.49 19.18 19.12 18.66 18.80 18.55 18.80 18.48 18.64 18.52
2 0 56 17.74 -1 19 30.50 0.030 0.000 99.00 21.65 19.15 20.69 20.59 20.24 99.00 21.08 19.48 18.93 20.40 19.60 19.38 20.46 99.00
3 0 54 51.55 -1 13 24.20 0.030 0.376 21.65 21.02 19.58 19.38 18.76 18.66 18.34 18.27 18.11 18.02 17.86 17.85 17.68 17.67 17.88
4 0 56 48.50 -0 54 10.50 0.030 0.474 21.83 21.73 21.07 20.11 20.38 20.24 19.31 19.26 19.19 19.43 19.19 19.22 18.71 19.18 18.26
5 0 57 35.82 -1 23 13.30 0.030 1.000 21.27 19.98 19.44 19.06 18.50 18.47 18.33 18.05 17.75 17.62 17.52 17.49 17.22 17.08 17.59
6 0 58 02.94 -1 27 55.20 0.031 0.504 19.41 19.01 18.74 99.00 18.69 18.44 18.70 99.00 18.28 18.37 18.46 99.00 18.52 18.44 18.26
7 0 57 09.83 -1 11 31.10 0.031 1.000 21.62 20.13 19.84 18.91 19.09 18.79 18.32 18.45 18.11 18.20 18.00 17.84 17.61 17.54 17.36
8 0 56 31.40 -1 33 42.40 0.032 0.082 20.66 19.97 19.51 99.00 18.89 18.80 18.31 18.49 18.13 18.10 18.00 17.89 17.68 17.79 17.65
9 0 55 59.26 -1 16 11.90 0.032 0.000 21.85 20.46 20.60 20.52 20.24 19.73 20.68 19.53 19.30 99.00 19.17 19.45 18.85 18.76 18.53
10 0 56 25.61 -1 10 47.20 0.032 0.333 20.98 20.22 19.73 19.56 18.88 18.86 18.46 18.55 18.28 18.39 18.14 18.19 18.03 17.86 17.53
11 0 55 41.29 -0 56 30.70 0.032 0.358 19.49 18.87 18.62 18.47 18.22 18.23 18.20 18.03 17.81 17.99 17.86 18.00 17.69 17.56 17.45
12 0 56 30.90 -1 09 13.40 0.032 0.295 21.58 20.39 20.09 19.78 19.53 19.28 18.88 18.76 18.59 18.64 18.50 18.45 18.30 18.26 17.69
13 0 56 16.92 -1 32 28.70 0.033 0.384 20.61 19.51 19.23 99.00 18.43 18.35 18.11 17.97 17.88 17.88 17.63 17.59 17.41 17.35 17.73
14 0 55 45.99 -1 24 07.90 0.033 0.417 21.75 20.13 20.33 19.99 19.15 99.00 19.32 18.93 18.60 18.68 18.40 18.44 18.26 18.12 18.42
15 0 57 04.88 -1 10 59.90 0.033 0.275 20.60 19.21 18.73 18.57 17.80 18.00 17.80 17.86 17.67 17.57 17.42 17.41 17.02 17.01 99.00
16 0 55 26.52 -1 37 50.50 0.034 0.000 19.57 19.19 18.52 99.00 18.05 17.98 17.75 17.62 17.54 17.45 17.57 17.39 17.37 17.23 17.43
17 0 56 57.82 -1 33 16.80 0.034 0.011 20.25 19.82 19.08 99.00 18.66 18.45 18.41 18.07 18.07 17.93 17.91 17.84 17.62 17.64 17.68
18 0 56 14.31 -1 15 16.80 0.034 0.972 22.71 99.00 19.49 19.16 18.37 18.22 18.39 17.93 17.66 17.82 17.37 17.26 17.12 16.97 17.31
19 0 56 28.79 -1 20 30.50 0.035 0.179 24.51 20.77 20.23 20.09 19.37 99.00 19.06 19.10 18.61 18.94 18.74 18.55 17.98 18.27 18.50
20 0 56 28.82 -1 36 43.80 0.035 0.000 21.50 20.04 20.44 99.00 19.62 19.70 19.61 19.43 19.11 19.19 19.01 19.22 18.67 18.68 18.47
21 0 55 20.59 -1 12 31.60 0.036 0.154 21.75 20.10 20.10 19.56 19.34 19.06 18.71 18.82 18.55 18.59 99.00 18.51 18.00 17.95 18.60
22 0 55 38.94 -1 09 46.80 0.036 0.030 21.07 21.41 20.31 20.10 19.50 19.43 19.44 18.97 18.99 19.52 99.00 19.09 18.60 18.59 18.50
23 0 56 49.25 -1 01 15.80 0.036 0.076 21.84 20.51 20.21 19.86 19.63 99.00 19.03 19.22 18.74 18.49 18.77 18.56 18.29 18.32 18.30
24 0 57 08.77 -0 56 48.00 0.036 0.393 22.08 21.28 20.20 19.80 19.48 19.46 18.82 18.84 18.67 18.62 18.62 18.72 18.20 18.54 18.45
25 0 55 52.56 -1 21 31.60 0.038 0.725 20.59 20.32 19.40 18.98 18.61 18.52 18.44 17.97 17.89 18.02 17.87 17.65 17.56 17.32 17.95
26 0 57 21.38 -1 16 39.80 0.038 0.129 99.00 22.17 21.12 20.32 20.01 20.05 19.57 19.71 19.48 19.15 19.10 19.23 18.87 18.92 20.79
27 0 55 56.44 -1 36 46.80 0.039 0.209 19.98 19.20 18.61 18.14 17.78 17.69 17.36 17.17 17.06 16.95 16.94 16.79 16.66 16.62 99.00
28 0 55 19.23 -1 16 29.10 0.039 0.000 19.60 18.45 17.84 17.39 16.89 16.85 16.64 16.43 16.23 16.10 16.09 15.85 15.65 15.52 15.50
29 0 55 28.43 -1 41 13.90 0.040 0.274 21.55 20.00 19.52 99.00 18.79 18.66 99.00 18.12 18.05 18.05 17.99 17.78 17.57 17.57 17.69
30 0 55 44.12 -1 29 2.10 0.040 0.248 21.97 21.15 20.34 99.00 19.68 19.32 19.21 18.72 18.80 18.61 18.66 18.52 18.41 18.18 18.76
31 0 55 10.98 -1 04 51.30 0.040 0.157 20.19 19.59 19.36 19.25 19.11 18.94 19.27 18.80 18.90 18.50 19.01 18.81 18.91 18.79 99.00
32 0 56 05.55 -1 03 22.90 0.040 0.489 20.30 19.38 18.64 18.11 17.75 17.57 17.34 17.19 16.98 16.94 16.85 16.69 16.63 16.42 99.00
33 0 56 57.42 -0 57 34.70 0.040 0.370 20.64 19.90 19.33 18.94 18.47 18.37 18.04 17.90 17.72 17.74 17.55 17.50 17.37 17.30 17.03
34 0 55 25.87 -0 57 01.20 0.040 0.950 21.11 20.91 20.09 19.90 19.64 19.18 19.05 18.85 18.68 18.58 99.00 18.61 18.24 18.34 17.83
35 0 55 37.82 -0 56 01.00 0.040 0.000 20.56 19.97 19.76 19.65 18.80 19.08 18.93 18.82 18.85 18.20 99.00 18.38 17.95 17.78 17.99
36 0 55 19.42 -0 48 38.50 0.040 0.094 21.31 21.56 19.85 19.40 19.12 19.02 18.53 18.78 18.56 18.56 99.00 18.53 99.00 18.24 18.07
37 0 56 38.89 -1 00 48.00 0.041 0.986 22.04 99.00 21.49 99.00 21.46 20.29 19.10 19.33 19.44 99.00 19.78 19.14 18.41 18.69 17.57
38 0 55 14.03 -1 04 08.20 0.042 0.317 99.00 20.56 20.32 19.85 19.59 19.40 18.92 18.88 18.69 18.50 99.00 18.12 17.85 17.96 17.72
39 0 57 23.13 -1 43 33.10 0.042 0.502 21.49 20.88 21.09 99.00 19.81 19.91 19.11 19.29 19.41 19.19 18.91 99.00 18.48 18.70 18.32
40 0 54 39.14 -1 36 02.00 0.042 0.589 19.45 19.11 18.39 17.97 17.87 17.81 17.57 17.47 17.35 17.29 17.34 17.21 17.13 17.02 17.09
41 0 55 23.45 -1 17 22.00 0.042 0.578 21.11 21.40 20.34 19.88 19.84 99.00 18.85 19.46 18.80 18.90 19.29 18.88 18.72 18.61 20.00
42 0 58 03.53 -1 40 35.80 0.042 0.000 21.85 99.00 20.64 99.00 20.02 19.84 19.86 99.00 19.23 19.31 19.31 99.00 18.64 19.04 18.93
43 0 55 58.89 -1 17 49.50 0.043 0.000 21.96 20.36 20.32 19.88 19.53 19.36 19.47 19.78 18.86 19.15 19.11 18.73 18.44 18.39 17.78
44 0 55 17.89 -1 17 10.30 0.043 0.631 19.82 19.04 18.22 17.77 17.24 17.12 16.86 16.68 16.49 16.40 16.34 16.19 16.07 15.98 15.96
45 0 56 59.72 -0 51 02.80 0.043 0.246 21.01 20.32 20.33 20.38 19.23 19.46 19.34 19.09 19.16 19.03 18.98 18.87 18.43 18.35 18.65
46 0 55 05.88 -1 39 30.20 0.044 0.259 21.32 20.34 20.32 99.00 19.57 19.81 19.94 19.23 19.28 19.22 19.13 18.91 18.76 18.76 18.23
47 0 55 13.98 -1 07 30.20 0.044 0.441 21.59 20.81 20.12 19.57 19.28 19.09 18.72 18.72 18.55 18.63 18.60 18.43 18.28 18.01 19.91
48 0 56 29.41 -1 11 41.30 0.045 0.139 20.68 20.45 19.71 19.58 18.92 18.90 18.34 18.43 18.25 99.00 18.03 17.92 17.86 17.69 17.59
49 0 56 27.08 -1 20 53.90 0.045 0.898 20.23 19.16 18.63 18.00 17.66 99.00 17.20 17.08 16.86 16.81 99.00 16.55 16.45 16.33 16.26
50 0 54 39.17 -1 34 32.50 0.045 1.000 19.95 19.17 18.45 99.00 17.53 17.48 17.18 17.08 16.84 16.72 16.74 16.53 16.44 16.29 16.46
51 0 56 07.93 -1 00 52.20 0.046 0.350 21.41 20.11 20.22 19.60 19.25 19.14 19.00 18.75 18.45 18.30 18.06 18.03 17.85 17.75 99.00
52 0 55 09.54 -1 03 03.40 0.046 0.000 21.71 22.22 20.03 20.17 18.87 18.98 18.83 18.77 18.54 18.33 18.53 18.25 18.24 18.09 18.42
53 0 55 03.89 -1 22 40.20 0.047 0.586 21.20 20.56 19.73 19.55 18.96 18.89 18.74 18.40 18.22 18.12 18.39 18.07 17.82 17.94 17.87
54 0 56 46.26 -1 36 13.80 0.048 1.000 20.43 19.82 18.94 99.00 18.06 17.90 17.64 17.44 17.31 17.30 17.14 17.06 16.94 16.84 16.73
55 0 55 44.80 -1 34 49.80 0.048 0.933 20.53 19.94 19.09 99.00 18.13 18.02 17.69 17.55 17.42 17.32 17.29 17.08 16.91 16.95 16.80
56 0 55 50.13 -1 28 38.10 0.048 0.000 20.92 20.52 20.13 20.20 19.69 19.78 19.13 18.81 19.25 19.27 19.69 19.15 19.07 19.33 99.00
57 0 55 17.55 -1 16 47.00 0.048 0.336 22.25 21.60 19.81 19.37 18.78 18.63 18.31 18.07 17.77 17.76 17.56 17.37 17.27 17.19 16.96
58 0 56 17.98 -1 15 00.90 0.048 0.000 22.40 21.16 19.87 19.08 18.68 18.49 17.96 18.05 17.79 17.97 17.58 17.39 17.34 17.20 17.94
59 0 56 10.55 -1 04 04.20 0.048 0.283 22.19 99.00 20.36 20.33 19.68 19.50 19.48 19.06 18.78 18.70 18.91 18.72 18.72 18.55 99.00
Table 3: Catalog of 117 Newly-selected Candidates of Member Galaxies in A119
No. R.A. Decl. fracDeV
60 0 56 59.41 -1 21 51.50 0.048 0.485 99.00 21.11 20.47 20.28 19.69 19.51 19.73 18.99 18.92 18.86 18.92 18.70 18.90 18.40 19.62
61 0 54 30.41 -1 39 21.10 0.049 0.298 20.91 19.41 18.84 99.00 18.07 17.85 17.54 17.42 17.18 17.14 17.18 16.93 99.00 16.78 16.72
62 0 57 12.41 -0 58 28.50 0.049 0.329 20.92 20.73 19.67 19.12 18.77 18.76 18.36 18.68 18.16 18.16 17.99 17.88 17.67 17.81 99.00
63 0 54 53.93 -1 40 43.10 0.050 0.237 21.08 21.88 20.14 99.00 19.41 19.29 18.83 19.10 18.98 18.73 99.00 18.70 18.51 18.58 18.05
64 0 56 06.48 -1 37 54.00 0.050 0.000 21.01 20.27 19.93 99.00 19.37 19.39 19.58 19.55 19.02 18.94 19.03 18.72 18.82 18.35 17.69
65 0 56 12.34 -1 31 50.20 0.050 0.000 21.12 20.05 19.83 99.00 19.27 19.33 19.23 18.99 18.93 18.86 19.02 18.75 18.77 18.77 19.00
66 0 56 13.87 -1 16 24.30 0.050 0.863 21.99 21.02 20.49 21.37 19.80 19.65 19.84 19.86 18.75 19.18 20.27 18.63 18.48 18.79 18.16
67 0 55 10.34 -1 02 42.90 0.050 0.000 22.14 21.08 20.06 19.73 18.80 18.72 18.43 18.61 18.28 18.07 18.35 17.90 17.80 17.70 18.34
68 0 57 55.99 -0 59 55.80 0.050 0.000 20.19 19.39 18.87 18.64 18.28 18.20 17.95 17.92 17.74 17.59 17.71 17.62 17.50 17.48 17.17
69 0 54 43.20 -1 20 05.10 0.051 0.180 20.40 19.72 19.52 19.08 18.94 99.00 19.10 19.38 18.96 18.88 18.72 18.67 18.58 18.66 17.85
70 0 56 07.58 -1 20 38.10 0.051 1.000 19.72 18.90 18.32 17.83 17.35 17.16 16.91 16.79 16.56 16.55 16.51 16.27 16.19 16.06 16.02
71 0 55 15.35 -0 54 59.90 0.051 0.000 21.42 19.98 19.46 19.11 18.51 18.61 18.23 18.42 18.07 18.06 18.16 17.75 17.65 17.65 17.54
72 0 56 35.20 -1 07 10.90 0.052 0.271 21.61 20.42 20.08 19.97 19.36 19.21 18.82 18.64 18.63 18.38 18.58 18.32 18.21 18.34 18.30
73 0 54 44.56 -1 28 19.30 0.053 0.000 20.29 20.02 19.26 18.68 18.57 18.22 17.88 17.83 17.68 17.60 17.63 17.48 17.28 17.25 17.02
74 0 56 34.55 -1 25 46.20 0.053 0.586 20.67 20.06 19.54 19.10 18.69 18.60 18.07 17.99 18.04 17.84 17.89 17.78 17.84 17.55 17.67
75 0 56 53.33 -1 13 24.70 0.053 0.000 21.79 20.44 20.43 99.00 19.44 19.57 19.12 18.92 19.10 18.85 19.18 18.88 18.73 18.62 18.72
76 0 57 13.58 -1 03 16.30 0.053 0.271 20.23 19.39 18.97 18.67 18.38 18.37 18.16 18.18 18.02 17.98 17.99 17.90 17.73 17.82 18.57
77 0 55 33.50 -1 29 00.80 0.054 0.784 20.49 19.77 19.40 18.91 18.55 18.40 18.09 17.97 17.77 17.69 17.66 17.42 17.27 17.31 17.37
78 0 57 05.14 -0 50 24.90 0.054 0.413 22.61 21.81 20.13 19.99 19.25 19.23 18.74 18.80 18.47 18.50 18.60 99.00 18.26 18.39 17.59
79 0 56 34.49 -0 53 35.80 0.056 0.998 21.03 20.41 20.33 19.73 18.85 18.87 18.70 18.41 18.22 18.15 17.93 17.79 17.71 17.47 17.40
80 0 55 40.63 -1 36 18.20 0.057 0.514 20.88 19.97 19.58 99.00 18.75 18.55 18.20 18.18 18.02 17.98 17.94 17.77 17.68 17.62 99.00
81 0 55 37.21 -1 35 30.30 0.057 0.769 19.89 19.22 18.70 99.00 17.82 17.64 17.40 17.22 17.03 16.91 16.91 16.72 16.65 16.57 16.40
82 0 55 31.75 -1 34 57.60 0.057 0.094 20.82 20.22 19.67 99.00 18.95 18.97 18.64 18.61 18.58 18.38 18.68 18.36 18.36 18.44 18.37
83 0 56 29.31 -1 05 56.50 0.057 0.780 20.36 19.47 19.02 18.45 18.14 18.01 17.75 17.57 17.44 17.54 17.30 17.19 17.10 17.01 16.96
84 0 55 05.80 -0 53 40.30 0.057 0.033 20.32 19.71 19.33 18.63 18.31 18.13 17.85 17.68 17.54 17.47 99.00 17.24 17.14 17.02 17.23
85 0 55 39.07 -1 34 49.90 0.058 1.000 20.97 20.24 19.66 99.00 18.80 18.74 18.43 18.42 18.13 17.97 17.93 17.74 17.69 17.62 17.47
86 0 56 59.62 -1 15 54.20 0.059 0.543 20.41 20.24 19.46 18.96 18.50 18.46 18.09 17.88 17.82 17.90 17.68 17.55 17.42 17.43 17.25
87 0 57 45.14 -1 44 54.00 0.060 0.018 20.77 20.20 19.48 19.02 17.93 18.18 99.00 17.38 17.52 18.24 18.41 18.19 18.84 17.70 17.79
88 0 55 40.59 -1 35 41.10 0.060 0.497 21.08 20.17 20.25 99.00 19.83 19.38 19.45 19.51 19.39 19.39 19.53 19.03 18.98 18.73 17.68
89 0 57 10.97 -1 22 35.70 0.060 0.000 20.30 19.65 19.17 18.87 18.52 18.30 18.09 18.05 17.90 17.95 17.81 17.57 17.70 17.41 17.13
90 0 56 08.43 -1 15 16.00 0.060 0.349 21.20 19.83 19.44 18.80 18.54 18.36 18.24 18.12 17.88 99.00 17.70 17.55 17.54 17.38 17.40
91 0 57 24.61 -0 57 49.10 0.060 0.417 21.44 99.00 20.76 20.34 19.93 19.82 19.45 19.31 19.49 19.45 19.18 19.05 18.83 19.05 21.11
92 0 54 50.51 -0 53 35.50 0.060 0.778 22.49 99.00 21.81 21.57 19.86 20.15 19.44 19.31 19.31 19.40 99.00 18.74 18.79 18.55 17.96
93 0 55 18.68 -0 49 27.20 0.060 0.302 20.22 19.77 19.22 18.72 18.66 18.61 18.49 18.44 18.32 18.43 99.00 18.00 99.00 17.96 18.82
94 0 54 39.05 -0 55 47.10 0.060 0.942 22.30 20.81 22.26 23.47 20.19 20.68 20.86 19.55 19.36 19.90 99.00 19.10 19.07 18.75 17.77
95 0 56 45.13 -1 17 59.80 0.061 0.551 20.07 19.55 18.81 18.37 17.91 17.76 17.47 17.32 17.17 17.17 17.08 16.90 16.81 16.75 16.42
96 0 56 49.00 -1 17 32.90 0.061 0.333 20.19 19.55 18.96 18.30 18.03 17.81 17.40 17.28 17.10 17.03 16.86 16.77 16.69 16.59 16.42
97 0 54 55.40 -1 01 06.80 0.061 0.000 21.62 20.46 20.13 19.91 19.19 19.32 18.85 19.37 19.10 19.21 99.00 18.63 18.69 18.64 18.69
98 0 57 00.21 -0 51 02.70 0.061 0.000 20.34 19.60 19.49 19.05 18.47 18.44 17.88 18.10 17.85 17.86 17.78 17.60 17.61 17.41 17.20
99 0 57 04.09 -1 09 06.60 0.062 0.254 20.34 19.80 19.14 18.78 18.25 18.08 17.81 17.68 17.56 17.38 17.40 17.24 17.23 17.07 17.05
100 0 55 10.65 -0 56 07.90 0.062 0.374 21.51 21.35 19.75 19.65 19.09 19.05 18.99 18.84 18.55 18.75 99.00 18.31 18.52 18.21 18.03
101 0 54 49.28 -0 55 02.20 0.062 0.493 21.50 21.05 20.75 20.31 19.56 19.49 19.33 18.66 18.99 18.91 99.00 18.44 18.65 18.26 18.89
102 0 57 28.06 -1 14 59.00 0.063 0.938 21.68 20.72 20.58 20.05 19.50 19.40 18.98 18.72 18.63 99.00 18.37 18.28 18.02 18.18 17.72
103 0 55 00.15 -1 18 42.90 0.063 0.189 21.35 22.01 20.44 19.81 19.62 99.00 20.31 19.75 19.37 19.21 99.00 18.81 19.60 18.86 18.30
104 0 55 36.59 -0 50 42.80 0.063 0.633 20.35 19.13 18.85 18.42 18.20 18.07 17.98 17.74 17.64 17.57 99.00 17.40 17.43 17.26 17.04
105 0 54 49.48 -1 32 33.90 0.064 0.000 99.00 21.45 19.67 19.62 19.42 19.73 18.68 18.98 19.11 20.30 19.88 18.91 18.16 20.15 99.00
106 0 55 57.48 -1 40 26.10 0.064 0.942 20.13 19.37 18.88 99.00 18.61 18.55 18.43 99.00 18.37 18.53 18.56 18.39 18.43 18.58 19.18
107 0 57 14.62 -1 36 04.40 0.064 0.155 21.03 21.53 20.34 99.00 19.94 20.02 19.94 19.01 19.45 19.70 19.53 19.44 19.28 19.59 19.07
108 0 54 38.22 -1 28 35.00 0.064 0.932 21.28 21.34 20.04 19.91 19.88 19.52 19.76 19.46 19.31 19.20 99.00 19.20 19.04 19.27 18.52
109 0 55 30.97 -1 28 38.20 0.065 0.000 21.20 20.40 19.44 19.18 18.91 18.83 18.31 18.50 18.35 18.30 18.23 18.29 18.23 18.19 18.81
110 0 56 28.27 -0 56 41.20 0.065 1.000 19.47 18.76 18.35 17.95 17.80 17.72 17.47 17.25 17.16 17.17 17.12 16.96 16.93 16.91 16.79
111 0 56 00.93 -0 56 26.80 0.065 0.072 21.54 20.16 20.02 19.50 19.40 19.13 18.57 18.73 18.60 18.57 99.00 18.43 18.35 18.34 18.34
112 0 56 40.83 -0 55 20.40 0.065 0.378 21.59 20.64 20.49 20.11 20.00 19.74 19.58 19.17 19.22 18.95 19.51 18.60 19.25 18.71 17.61
113 0 55 49.02 -0 52 37.10 0.065 0.632 21.41 21.02 20.27 19.85 19.41 19.48 19.33 19.34 19.03 18.92 19.12 18.86 18.69 18.88 18.15
114 0 58 02.90 -1 26 15.70 0.066 0.023 20.27 19.58 19.37 19.13 18.85 18.68 18.45 18.35 18.21 18.15 18.19 99.00 18.01 17.91 17.66
115 0 55 55.93 -1 17 50.20 0.066 0.956 20.51 19.79 19.25 18.72 18.39 18.22 17.83 17.72 17.57 17.62 17.54 17.36 17.38 17.18 17.06
116 0 54 50.14 -0 54 58.70 0.066 0.485 20.94 21.06 20.47 19.86 19.17 18.93 18.71 18.41 18.22 18.07 99.00 17.72 17.76 17.61 17.16
117 0 57 10.32 -0 48 57.60 0.066 0.352 22.41 20.33 20.05 19.71 19.51 19.08 18.60 18.61 18.61 18.39 18.77 99.00 99.00 18.28 20.28
Table 3: — Continued.

5 The Properties of the Cluster A119

5.1 Spatial Distribution and Localized Velocity Structure

Based on sample II, we investigate spatial distribution and localized velocity structure of A119. Left panel of Fig. 8 shows contour maps of surface density with smoothing Gaussian window of , superimposed projected distribution of galaxies in sample II. The early-types and late-types are marked with open circles and asterisks, respectively. Density contour for sample II appears to have more significant deviation from spherically symmetry, indicating that A119 is a dynamically complex system with significant substructures.

Three substructures (A, B, and C) shown in Fig. 3 are confirmed in Fig. 8. Result of the -test for sample II is given in Table 4. The probability P() is less than , strongly suggesting a more significant detection of substructure. The bubble clustering in clump A appears to be split into two bunches, which makes the picture of merging along the line of sight clearer. In addition, two bunches of bubbles are newly detected at about 23\arcminsouthwest and northwest of the main concentration. Considering the large uncertainties of estimate, follow-up spectroscopy is needed to confirm these two substructures.

Figure 8: left: Spatial distribution for 355 member galaxies in sample II. The smoothing Gaussian window is =2\arcmin, the contour levels are 0.22, 0.32, 0.42, 0.52, 0.62, 0.72, 0.82, and 0.92 arcmin. open circles for early-type galaxies and asterisks for late-type galaxies, respectively. Right: Bubble plot showing the localized variation for groups of the 9 nearest neighbors in sample II.
Neighbor size Sample I Sample II
() ()
6 14.1% 0.1%
7 14.6% 0.1%
8 13.9% 0.2%
9 7.7% 0.7%
10 8.5% 1.1%
11 9.4% 0.6%
12 11.1% 0.5%
Table 4: -test for member galaxies in samples I and II of A119

5.2 Morphology and Luminosity Segregations

The clustercentric distance and local galaxy density are traditional parameters tracing the environment in a cluster. Projected local galaxy density is commonly defined as , where is the distance from a given galaxy to the ninth nearest neighbor (Dressler 1980). As reviewed by Sandage et al. (2005), morphological classification is the most intuitive tool for extragalactic astronomy. Dressler (1980) investigated the relation between morphology and local galaxy density, so called morphology-density relation, and found that fraction of spiral galaxies decrease with increasing local density for low-redshift galaxy clusters. This relation has been studied by other authors subsequently (Hashimoto & Oemler 1999; Goto et al. 2003). Whitmore et al. (1991, 1993) re-analyzed the samples of Dressler (1980), and argued that the correlation between morphology and clustercentric radius appears tighter than morphology-density relation. Sanroma & Salvador-Solé (1990) and Whitmore et al. (1993) suggested that the global parameter, clustercentric radius , should be more fundamental. Local and global processes in cluster galaxies are generally considered to be two causes of different morphologies. Due to the close relation between local galaxy density and clustercentric radius(Beers & Tonry 1986; Merrifield & Kent 1989), the argument on which parameter is more fundamental in morphology and luminosity segregation is still inconclusive so far.

For checking the presence of luminosity segregation in A119, Pracy et al. (2005) studied the luminosity functions and locations of cluster galaxies in A119 on the basis of their V-band photometry. The information of radial velocities were not taken into account during their sampling. They found that the core radius of a King profile is invariant with intrinsic luminosity. The luminosity functions for member galaxies within three annuli (Mpc, Mpc, and Mpc) are fitted with the Schechter function, and no significant systematic correlation with cluster-centric radius are found. Alternatively, Driver et al. (1998) defined the dwarf-to-giant ratio (DGR) to quantify the luminosity distribution, and found that giant galaxies are more centrally concentrated than the dwarfs in galaxy clusters. In our paper, because of the limited number of member galaxies, we define the faint-to-bright ratio (FBR) to describe the luminosity distribution: FBR , where is the absolute magnitude for the conventional Kron-Cousins band which can be calculated via the equations in Zhou et al. (2003a).

Figure 9: Left: Fraction of late-type galaxies and faint-to-bright ratio (FBR) as functions of clustercentric radius for sample I and sample II, respectively. Right: Fraction of late-type galaxies and faint-to-bright ratio (FBR) as functions of local galaxy density for sample I and sample II, respectively. The width of annuli is 0.5 Mpc, and bin size of local density is log (galaxies Mpc).

Fig. 9 shows the fraction of late-type galaxies and the FBR as functions of clustercentric radius and local density for both samples. For sample I, the late-type galaxy fraction slightly decreases with increasing , which might be due to the strong bias in sample I. As a matter of fact, the spectroscopic redshifts in sample I are contributed by several observations (see Table 2), and the bright early-type galaxies closer to the cluster center have greater probability to be selected as spectroscopic targets. Small number of faint member galaxies are spectroscopically detected in the outskirt regions.

Some faint member galaxies in the outskirt low-density region are selected by our multicolor photometry, which results in a prominent increase of the late-type galaxy fraction and the FBR for sample II in the regions with larger and lower density (see the red points in Fig. 9). The FBR and late-type fraction in sample II appears to increase monotonically with decreasing local density, rather than with increasing clustercentric radius. However, owing to the limited number of member galaxies, significant uncertainties in the late-type galaxy fraction and the FBR can be found for the low-density and outskirt regions in sample II, which will surely reduce the probability of monotonically increasing tendency. Considering the error bars in the right panels of Fig. 9, we apply Monte Carlo simulations to estimate the probabilities of monotonic increase for sample II. As a result, the late-type galaxy fraction has a probability of 31.0% to monotonically increase with the decreasing density, and the probability that the FBR monotonically increases with decreasing density is about 18.8%. Therefore, we may safely conclude that no clear evidences are found for morphology and luminosity segregations in A119. A deep and complete sample of member galaxies is necessary to further determine which environmental indicator is more fundamental in the future study.

6 Star Formation Properties of Cluster Galaxies

The star formation properties of member galaxies in a cluster can help us to understand formation and evolution of galaxies and their host cluster. Thus, This is important to observe the systematic tendency of the star formation properties for the galaxies in a cluster.

With the evolution synthesis model, PEGASE (version 2.0, Fioc & Rocca-Volmerande (1997, 1999)), we investigate the star formation properties of A119. A Salpeter initial mass function (IMF) (Salpeter 1955) is adopted. The star formation rate (SFR) are assumed to be in exponentially decreasing form, , where the time scale ranges from 0.5 to 30.0 Gyr. To avoid the degeneracy between age and metallicity in the model, the same age of 12.7 Gyr is adopted for all the member galaxies in A119, responding to the age of the first generation stars at = 0.0442. A zero initial metallicity of interstellar medium (ISM) is assumed. Firstly, a series of modelled spectra at rest frame (z=0) with various star formation histories are generated by running the PEGASE code. Then we shift them to the observer’s frame for a given redshift, and convolve with the transmission functions of the BATC filters. As a result, we obtain the template SED library for the BATC photometric system. Based on the template SED library, the best fit (in the sense) to the observed SEDs are performed for 238 member galaxies with known spectrocopic redshifts. The SFR time scale (), mean ISM metallicity (Z), and the mean stellar age () weighted by mass and light for each cluster galaxy can be achieved.

Figure 10: Star formation properties, such as the SFR time scale , mean ISM metallicity, and the mean stellar ages weighted by mass and light, for the galaxies with known z values as the functions of local galaxy density.

As we know, early-type galaxies in the field commonly have low star formation rates, whereas late-type galaxies have high star formation activity. This bimodality is modified in dense environments: a higher occurrence of passive spiral galaxies is found in clusters than in the field, whereas star-forming elliptical galaxies are rarer in clusters (Bamford et al. 2009). This suggests that star formation rate couples most strongly to environment, with morphology being only a secondary correlation. Firstly, we attempt to find the tendency of star formation property along the clustercentric radius of A119. However, no any tendencies are found as expected. This suggests clustercentric radius is not a good environmental indicator for A119. An alternative explanation is that local processes (e.g., galaxy-scale interaction) affect star formation activities, rather than the global processes (e.g., ram-pressure stripping within cluster-scale environment). This result proves the correctness of the morphology-density relation pointed out by Dressler (1980) again, which can be well explained in the context of hierarchical cosmological scenario (Poggianti 2004).

Fig. 10 shows the star formation properties as a function of the local galaxy density for 238 member galaxies in sample I. We take as a boundary between the regions with high and low densities. Panel (a) shows that the galaxies in the high-density regions have shorter SFR time scale than those in the low-density regions. Panel (b) shows that the galaxies in high-density regions are more likely to have a higher metallicity of interstellar medium (ISM). It is generally regarded that the galaxies in high-density regions (e.g., cluster core) tend to be more luminous and massive. This trend can be commonly interpreted as luminosity-metallicity relation and mass-metallicity relation(Garnett & Shields 1987). Panels (c) and (d) show that the galaxies in low-density regions tend to possess younger stellar population with shorter mean stellar ages weighted by either mass or light. Variation of light-weighted stellar age is remarkably widespread, particularly in the high-density regions, in contrast to mass-weighted stellar age. A possible explanation is that current SFR in a cluster is mainly contributed by the late-type galaxies in low density regions, and young stellar population has a greater weight in average age calculation. It is reasonable that the light-weighted mean of stellar ages tend to be younger for cluster galaxies.

Figure 11: The SFR time scale and mean ISM metallicities for the galaxies with known z in A119 against magnitude in the BATC band.

It is generally considered that member galaxies in a cluster have same distance modulus, apparent magnitude could reflect their intrinsic luminosity. The SFR time scale () and mean ISM metallicity for the galaxies in sample I are illustrated in Fig. 11, as the functions of apparent magnitude in the BATC band. Fig. 11(a) shows brighter galaxies tend to have shorter SFR time scales. Massive and luminous member galaxies located at high-density region began to fall into gravitational potential well at earlier time, thus their star formation activities have been reduced by some physical processes for a longer time, which results in a short timescale of star formation. Fig. 11(b) gives the variation of mean ISM metallicities with their magnitudes in the BATC band. Fainter member galaxies tend to have lower mean ISM metallicities, while luminous galaxies are likely to have greater metallicities. This is consistent with the ideas that metals are selectively lost from faint galaxies with shallow potential wells via galactic winds (Melbourne & Salzer 2002; Tremonti et al. 2004).

7 Summary

X-ray observations suggest that the nearby cluster A119 is not a regular and well-relaxed cluster. We present our multicolor photometry in optical bands for this galaxy cluster, on the basis of the Beijing-Arizona-Taiwan-Connecticut(BATC) 15 intermediate filters system that covers almost whole optical wavelength domain. We obtain the SEDs of 1376 galaxies brighter than in our viewing field of . There are 368 galaxies with available spectroscopic redshifts, among which 238 galaxies with 10736 15860 are regarded as member galaxies of A119 (sample I).

Based on sample I, both projected distribution and localized velocity structure support the picture that A119 is a dynamically young cluster with some substructures, which is in agreement with the X-ray image. Three potential substructures are confirmed in localized deviation of velocity distribution in the central region of A119. Clump A is found to have a very large velocity dispersion, which supports a merger at the cluster center along the line of sight. Clump C might be a compact group of galaxies which have a bulk velocity of 12966 .

Photometric redshift technique is applied to the faint galaxies without values, and the CM relation for early-type galaxies is also used to constrain the membership selection. As a result, 117 faint galaxies are selected as candidates of member galaxies. An enlarged sample of 355 member galaxies, called sample II, is obtained by combining with sample I. Based on sample II, projected distribution and localized velocity structure are investigated. The result of -test for sample II definitely suggests significant substructures in A119. Three substructures mentioned above are all enhanced in bubble plot.

Subsequently, morphology and luminosity segregations on the basis of sample II are investigated. We define the faint-to-bright ratio to quantify the luminosity distribution, and find that the fraction of late-type galaxy and the faint-to-bright ratio have very small probabilities to monotonically increase with decreasing local galaxies density. No significant evidences for morphology and luminosity segregations are found.

With an evolutionary synthesis model, PEGASE, star formation properties of sample I is studied. Environmental effect on star formation histories is found for these member galaxies. The bright massive galaxies in the high-density region of A119 are found to be more likely to have shorter SFR time scales, higher mean ISM metallicities and longer mean stellar ages, and vice versa. These results can be well interpreted by the existing correlations, such as the morphology-density relation, the luminosity-metallicity relation, and the mass-metallicity relation.

Acknowledgements.
We thank the anonymous referee for his/her invaluable comments and suggestions. This work was funded by the National Natural Science Foundation of China (NSFC) (Grant Nos. 11173016, 10873016, 11073032, 11003021, and 10803007), and by the National Basic Research Program of China (973 Program) (Grant No. 2007CB815403). We would like to thank Prof. Kong, X. and Cheng, F.-Z. at the University of Science and Technology of China for the valuable discussion. This research has made use of the NED, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Funding for the SDSS was provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society. The SDSS web site is http://www.sdss.org.

References

  • Abazajian et al. (2003) Abazajian, K., Adelman-McCarthy, J. K., Agüeros, M. A., et al. 2003, \aj, 126, 2081
  • Abell (1958) Abell, G. O. 1958, \apjs, 3, 211
  • Allen (1976) Allen, D. A. 1976, \mnras, 174, 29P
  • Arnouts et al. (1999) Arnouts, S., et al. 1999, \mnras, 310, 540
  • Bahcall et al. (1988) Bahcall, N. A. 1988, \araa, 26, 631
  • Bamford et al. (2009) Bamford, S. P., et al. 2009, MNRAS, 393, 1324
  • Bautz & Morgan (1970) Bautz, L. P., & Morgan, W. W. 1970 \apj, 162, 149
  • Beers & Tonry (1986) Beers, T. C., & Tonry, J. L. 1986, \apj, 300, 557
  • Beers et al. (1990) Beers, T. C., Flynn, K., & Gebhardt, K. 1990, \aj, 100, 32
  • Bolzonella et al. (2000) Bolzonella, M., Miralles, J.-M., & Pelló, R. 2000, \aap, 363, 476
  • Bower et al. (1992) Bower, R. G., Lucey, J. R., & Ellis, R. S. 1992, \mnras, 254, 601
  • Brunner & Lubin (2000) Brunner, R. J., & Lubin, L. M. 2000, \aj, 120, 2851
  • Bruzual & Charlot (1993) Bruzual, A. G., & Charlot, S. 1993, \apj, 405, 538
  • Buote & Tsai (1996) Buote, D. A., & Tsai, J. C. 1996, \apj, 458, 27
  • Cava et al. (2009) Cava, A., Bettoni, D., & Poggianti, B. M. 2009, \aap, 495, 707
  • Colless & Dunn (1996) Colless, M., & Dunn, A. M. 1996, \apj, 458, 435
  • Cortese et al. (2004) Cortese, L., Gavazzi, G., Boselli, A., et al.  2004, \aap, 425, 429
  • Dale et al. (1998) Dale, D. A., Giovanellt, R., Haynes, M. P., et al. 1998, \aj, 115, 418
  • Dressler (1980) Dressler, A. 1980, \apj, 236, 351
  • Dressler & Shectman (1988) Dressler, A., & Shectman, S. 1988, \aj, 95, 985
  • Driver et al. (1998) Driver, S. P., Couch, W. J., & Phillipps, S. 1998, \mnras, 301, 369
  • Edge et al. (1990) Edge, A., Stewart, G., Fabian, A., & Arnaud, K. 1990, \mnras, 245, 559
  • Fabricant (1993) Fabricant, D., Kurtz, M., Geller, M., & Zabludofe, A. 1993, \aj, 105, 788
  • Fan et al. (1996) Fan, X.-H., Burstein, D., Chen, J.-S., et al. 1996, \aj, 112, 628
  • Feretti et al. (1999) Feretti, L., Dallacasa, D., Govoni, F., et al. 1999, \aap, 344, 472
  • Fioc & Rocca-Volmerande (1997) Fioc, M., & Rocca-Volmerange, B. 1997, \aap, 326, 950
  • Fioc & Rocca-Volmerande (1999) Fioc, M., & Rocca-Volmerange, B. 1999, \aap, 351, 869
  • Furusawa et al. (2000) Furusawa, H., Shimasaku, K., Doi, M., & Okamura, S. 2000, \apj, 534, 624
  • Garnett & Shields (1987) Garnett, D. R., & Shields, G. A. 1987, \apj, 317, 82
  • Geller & Peebles (1973) Geller, M. J., & Peebles, P. J. E. 1973, \apj, 184, 329
  • Geller & Beers (1982) Geller, M. J & Beers, T. C. 1982, \pasp, 94, 421
  • Girardi et al. (1997) Girardi, M., Escalera, E., Fadda, D., et al. 1997, \apj, 482, 41
  • Goto et al. (2003) Goto, T., Yamauchi, C., Fujita, Y., et al. 2003, \mnras, 346, 601
  • Gunn & Stryker (1983) Gunn, J. E., & Stryker, L. L. 1983, \apjs, 52, 121
  • Hashimoto & Oemler (1999) Hashimoto, Y., & Oemler, A. J. 1999, \apj, 510, 609
  • Jones & Forman (1984) Jones, C., & Forman, W. 1984, \apj, 276, 38
  • Katgert et al (1998) Katgert P., Mazure, A., den Hartog, R., Adami, C., Biviano, A., & Perea, J. 1998, \aaps, 129, 399
  • Katz & White (1993) Katz, N., & White, S. W. D. 1993, \apj, 412, 455
  • Kinman & Hintzen (1981) Kinman, T. D., & Hintzen, P. 1981, \pasp, 93, 405
  • Lanzetta et al. (1996) Lanzetta, K. M., Yahil, A., & Fernández-Soto, A. 1996, \nat, 381, 759
  • Liu et al (2011) Liu, S.-F., Yuan, Q.-R., Yang, Y.-B., et al. 2011, \aj, 141, 99
  • Mantz et al. (2008) Mantz, A., Allen, S., Rapetti, D., & Ebeling, H. 2008, \mnras, 387, 1179
  • Melbourne & Salzer (2002) Melbourne, J., & Salzer, J. J. 2002, \aj, 123, 2302
  • Merrifield & Kent (1989) Merrifield, M. R., & Kent, S. M. 1989, \aj, 98, 351
  • Mohr et al. (1995) Mohr, J. J., Evrard, A. E., Fabricant, D. G., & Geller, M. J. 1995, \apj, 447, 8
  • Oegerle & Hill (1994) Oegerle, W. R., & Hill, J. M. 1994, \aj, 107, 857
  • O’Hara et al. (2006) O’Hara, T. B., Mohr, J. J., Bialek, J. J., & Evrard, A. E. 2006, \apj, 639, 64
  • Pan et al. (2011) Pan, Z.-Z, Yuan, Q.-R., Kong, X., et al. 2011, \mnras(accepted)
  • Pearce et al. (2000) Pearce, F. R., Thomas, P. A., Couchman, H. M. P.,& Edge, A. C. 2000, \mnras, 317,1029
  • Pelló et al. (1999) Pelló, R., Kneib, J. P., Le Borgne, J. F., et al. 1999, \aap, 346, 359
  • Peres et al. (1998) Peres, C. B., Fabian, A. C., Allen, S. W., & Johnstone, R. M. 1998, \mnras, 298, 416
  • Piffaretti & Valdarnini (2008) Piffaretti, R., & Valdarnini, R. 2008, \aap, 491, 71
  • Poggianti (2004) Poggianti, B. 2004, Proceedings of “Baryons in Dark Matter Halos”. Novigrad Croatia, 5-9 Oct 2004. Editors: R. Dettmar, U. Klein, P. Salucci. Published by SISSA, Proceeding of Science, p.104.1
  • Postman & Lauer (1995) Postman, M., & Lauer, T. R. 1995, \apj, 440, 28
  • Pracy et al. (2005) Pracy, M. B., Driver, S. P., De Propris, R., et al. 2005, \mnras, 364, 1147
  • Rines et al. (2003) Rines, K., Geller, M. J., Kurtz, M. J., & Diaferio, A. 2003, \aj, 126, 2152
  • Saglia et al. (1997) Saglia, R. P., Burstein, D., Baggley, G., et al. 1997, \mnras, 292, 499
  • Salpeter (1955) Salpeter, E. E. 1955, \apj, 121, 161
  • Sandage et al. (2005) Sandage, A. 2005, \araa, 43, 581
  • Sanroma & Salvador-Solé (1990) Sanroma, M. & Salvador-Solé, E. 1990, \apj, 360, 16
  • Smith et al. (2004) Smith, R. J., et al. 2004, \aj, 128, 1558
  • Stetson (1987) Stetson, P. B. 1987, \pasp, 99, 191
  • Tremonti et al. (2004) Tremonti, C. A., et al. 2004, \apj, 613, 898
  • Ventimiglia et al. (2008) Ventimiglia, D. A., Voit, G. M., Donahue, M., & Ameglio, S. 2008, \apj, 685, 118
  • Way et al. (1997) Way, M. J., Quintana, H., & Infante, L. 1997, arXiv:astro-ph/9709036
  • Wegner et al. (1999) Wegner, G., Colless, M., Saglia, R. P., et al. 1999, \mnras, 305, 259
  • West et al. (1991) West, M. J.,Villumsen, J. V., & Dakel, A. 1991, \apj, 369, 287
  • Whitmore et al. (1991) Whitmore, B. C., & Gilmore, D. M. 1991, \apj, 367, 64
  • Whitmore et al. (1993) Whitmore, B. C., Gilmore, D. M., & Jones, C. 1993, \apj, 407, 489
  • Xia et al. (2002) Xia, L.-F., Zhou, X., Ma, J., et al. 2002, \pasp, 114, 1349
  • Yahil & Vidal (1977) Yahil, A., & Vidal, N. 1977, \apj, 214, 347
  • Yan et al. (2000) Yan, H.-J., Burstein, D., Fan, X.-H., et al. 2000, \pasp, 112, 691
  • Yang et al. (2004) Yang, Y.-B., Zhou, X., Yuan, Q.-R., et al. 2004, \aj, 600, 141
  • Yuan et al. (2001) Yuan, Q.-R., Zhou, X., Chen, J.-S., et al. 2001, \aj, 122, 1718
  • Yuan et al. (2003) Yuan, Q.-R., Zhou, X., & Jiang, Z.-J. 2003, \apjs, 149, 53
  • Zhang et al. (2009) Zhang, Y.-Y.,Reiprich, T. M., Finoguenov, A.,Hudson, D. S., & Sarazin, C. L.  2009, \apj, 699,1178
  • Zhang et al. (2010) Zhang, L., Yuan, Q.-R., Zhou, X., et al. 2010, RAA, 10,1
  • Zhou et al. (1999) Zhou, X., Chen, J.-S., Xu, W., et al. 1999, \pasp, 111, 909
  • Zhou et al. (2001) Zhou, X., Jiang, Z.-J., Xue, S.-J., et al. 2001, \cjaa, 1, 372
  • Zhou et al. (2003a) Zhou, X., Jiang, Z.-J., Ma, J., et al. 2003a, \aap, 397, 361
  • Zhou et al. (2003b) Zhou, X., Arimoto, N., Tanaka, I., et al. 2003b, \pasj, 55, 891
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