A bulge-disk decomposition is made for 737 spiral and lenticular galaxies drawn from a SDSS galaxy sample for which morphological types are estimated. We carry out the bulge-disk decomposition using the growth curve fitting method. It is found that b
ulge properties, effective radius, effective surface brightness, and also absolute magnitude, change systematically with the morphological sequence; from early to late types, the size becomes somewhat larger, and surface brightness and luminosity fainter. In contrast disks are nearly universal, their properties remaining similar among disk galaxies irrespective of detailed morphologies from S0 to Sc. While these tendencies were often discussed in previous studies, the present study confirms them based on a large homogeneous magnitude-limited field galaxy sample with morphological types estimated. The systematic change of bulge-to-total luminosity ratio, $B/T$, along the morphological sequence is therefore not caused by disks but mostly by bulges. It is also shown that elliptical galaxies and bulges of spiral galaxies are unlikely to be in a single sequence. We infer the stellar mass density (in units of the critical mass density) to be $Omega=$0.0021 for spheroids, i.e., elliptical galaxies plus bulges of spiral galaxies, and $Omega=$0.00081 for disks.
We report the discovery of a large-scale structure of Lyman alpha emitters (LAEs) at z=4.86 based on wide-field imaging with the prime-focus camera (Suprime-Cam) on the Subaru telescope. We observed a 25 x 45 area of the Subaru Deep Field in a narrow
band (NB, lambdaC=7126 A and FWHM=73 A) together with R and i. We isolate from these data 43 LAE candidates down to NB=25.5 mag using color criteria. Follow-up spectroscopy of five candidates suggests the contamination by low-z objects to be ~ 20%. We find that the LAE candidates are clustered in an elongated region on the sky of 20 Mpc in width and 50 Mpc in length at z=4.86, which is comparable in size to present-day large-scale structures (we adopt H0=70 km/s/Mpc, Omega0=0.3, lambda0=0.7). This elongated region includes a circular region of 12 Mpc radius of higher surface overdensity (delta=2), which may be the progenitor of a cluster of galaxies. Assuming this circular region to be a sphere with a spatial overdensity of 2, we compare our observation with predictions by Cold Dark Matter models. We find that an Omega0=0.3 flat model with sigma8=0.9 predicts the number of such spheres consistent with the observed number (one sphere in our survey volume) if the bias parameter of LAEs is b simeq 6. This value suggests that the typical mass of dark haloes hosting LAEs at z simeq 5 is of the order of 10^12 Msolar. Such a large mass poses an interesting question about the nature of LAEs.
