CDROM/APJ/V485/P447 Evidence of Substructure in A3558 (Dantas+ 1997) ================================================================================ Evidence of Substructure in the Cluster of Galaxies A3558 Christine C. Dantas, Reinaldo R. de Carvalho, Hugo V. Capelato, and Alain Mazure <1997, ApJ, 485, 447> =1997ApJ...485..447D ================================================================================ Abstract: We investigate the dynamical properties of the cluster of galaxies A3558 (Shapley 8). Studying a region of 1 deg^2 (~3 Mpc^2) centered on the cluster cD galaxy, we have obtained a statistically complete photometric catalog with positions and magnitudes of 1421 galaxies (down to a limiting magnitude of B ~ 21). This catalog has been matched to the recent velocity data obtained by Mazure et al. and from the literature, yielding a radial velocity catalog containing 322 galaxies. We analyze the resulting catalog in search of substructure, using different statistical techniques. This analysis shows that the position/velocity space distribution of galaxies shows significant substructure. A central bimodal core, detected previously in a preliminary study by Dantas, de Carvalho, & Capelato and by an analysis of the X-ray emission map by Slezak, Durret, & Gerbal, is confirmed using the adaptive kernel technique and wavelet analysis. We show that this central bimodal substructure is nevertheless composed of a projected feature, kinematically unrelated to the cluster, plus a group of galaxies probably in its initial merging phase into a relaxed core. The cD galaxy's velocity offset with respect to the average cluster redshift, reported earlier by several authors, is completely eliminated as a result of our dynamical analysis. The untangling of the relaxed core component also allows a better, more reliable determination of the central velocity dispersion, which in turn eliminates the "Beta problem" for A3558. The cluster also shows a "preferential" distribution of subclumps coinciding with the direction of the major-axis position angle of the cD galaxy and of the central X-ray emission ellipsoidal distribution, in agreement with the anisotropic merger scenario described by West. Keywords: catalogs -- galaxies: clusters: individual (A3558) -- galaxies: distances and redshifts -- galaxies: elliptical and lenticular, cD -- galaxies: photometry File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table.dat 75 1421 A3558 Photometric Galaxy Catalogue -------------------------------------------------------------------------------- Byte-by-byte Description of file: table.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- Num Galaxy number 5- 7 I3 h RAh Right Ascension 8-10 I3 min RAm R.A. 11-16 F6.2 s RAs R.A. 17 1X --- --- Blank 18 A1 --- DE- Declination sign 19-20 I2 deg DEd Declination 21-23 I3 arcmin DEm Dec. 24-29 F6.2 arcsec DEs Dec. 30-35 F6.2 mag B Magnitude 36-39 I4 arcsec2 SA Surface area 40-44 F5.2 --- e Ellipticity 45-52 F8.4 mag/arcsec2 SB Surface brightness 53-61 F9.6 --- CI Color Index 62-67 I6 km/s v []? Velocity 68-71 I4 km/s e_v []? Velocity error 72 1X --- --- Blank 73-75 A3 --- Note *Notes -------------------------------------------------------------------------------- Notes for file: table.dat -------------------------------------------------------------------------------- Note: emm = emission line; e+a = emission and absorption lines; g+S = contamination by foreground star; g+g = merged galaxies in projection. -------------------------------------------------------------------------------- ================================================================================ (End) Lee E. Brotzman [ADS] 27-Aug-97